Today marks 10 years since Hurricane Irene struck Cape Lookout, North Carolina, causing 49 direct deaths and spawned several tornadoes prior to landfall.

Storm Synopsis

On August 15th, 2011 a tropical wave exited the west coast of Africa accompanied by a large area of clouds and thunderstorms. 

The wave would soon become a tropical storm and eventually a hurricane, bringing severe impacts along the US East Coast.

The storm’s convection diminished passing south of the Cabo Verde Islands the next day, but it maintained its mid-level circulation.

Thunderstorm activity regenerated as it continued to move westward across the tropical Atlantic and became organized halfway between the Lesser Antilles and west coast of Africa.

A reconnaissance aircraft investigated the system on the 20th, finding surface winds of 45 to 50mph but without a well-defined low-level circulation.

Just before the conclusion of the mission, the aircraft was able to isolate a circulation in the southern edge of the convection, prompting the designation as Tropical Storm Irene in the evening of the 20th.

Throughout the 21st, as it moved west-northwest across the extreme northeast Caribbean Sea, it continued to gain strength as the circulation became larger.

It then made a landfall over St. Croix the evening of that day and over Punta Santiago, Puerto Rico early into the next day.

It became a hurricane shortly after the Puerto Rico landfall.

It passed north of Hispaniola throughout the 23rd, and despite being over warm water and low wind shear, the interaction of Irene’s circulation with the mountains of the Island delayed further intensification.

As it moved away from Hispaniola, it quickly intensified and became a Category 3 Major Hurricane with peak intensity of 125mph and a minimum central pressure of 957mb within the 18 nautical mile diameter eye.

However, it wasn’t the lowest pressure observed from Irene as the pressure was observed while the closed eyewall structure became more fractured.

The dropsonde measured a minimum central pressure of 942mb with now decreasing winds of 105mph.

It then made four landfalls in The Bahamas throughout the 24th and 25th.

The hurricane then continued northward and passed far from the eastern coasts of Florida and Georgia.

And on the morning of the 27th, it made landfall near Cape Lookout, North Carolina with an intensity of 85mph with hurricane winds east of the North Carolina Sounds and Outer Banks.

As it continued north-northeast movement just offshore of the Delmarva Peninsula and made landfall over Brigantine Island, New Jersey in the early morning of the 28th, still being a high-end tropical storm with winds of 70mph.

Later into the day, it made landfall over Coney Island, New York and it moved over Manhattan Island.

Swells over the Mid-Atlantic were observed for a couple of days between the North Carolina and New York landfalls.

It continued north-northeast over New England and became extratropical on the 29th near the New Hampshire-Vermont border.

The next day, it was absorbed by a frontal system in northeastern Canada.

Overview

The system was well observed with 19 Air Force Reserve reconnaissance missions and 16 NOAA reconnaissance missions.

Guzabo Abajo, Puerto Rico, recorded the heaviest rain from Irene at 22.05 inches enough to cause flooding.

There were unconfirmed reports of wind gusts of 115mph in Cat Island, The Bahamas.

A pressure reading of 950.4mb, during the afternoon of the 25th, was observed in Marsh Harbour, in the Island of Abacos, The Bahamas.

Large swaths of 5 to 10 inches of rain along the US east coast was recorded with Bayboro, North Carolina recording the highest amount at 15.74 inches.

Largest storm surge was 7 feet in Oregon Inlet, Marina, North Carolina in the late night of 27th.

It also spawned several tornadoes across the Mid-Atlantic with an EF2 tornado that landed in Columbia, North Carolina.

A total of 49 deaths and damages amounting to $14.2B (2011 value) were recorded.

The name was then retired and got replaced by Irma which suffered a similar fate.

Response and Aftermath

Many people underestimated Irene as a Category 1 hurricane, but the storm produced major damage.

Sustained high winds and major flooding together with storm surges caused more damage than anticipated.

Official forecasts were accurate but the populous was largely caught off guard.

“People just did not think that the impacts from a Category 1 would have been so substantial”

John Cole, meteorologist with the NWS in Newport/Morehead City.

To understand the public perception of the threats posed by Hurricane Irene and find out how people responded to the weather forecasts, the NWS held public meetings in some of the communities hardest hit by the storm.

Meetings during December were held in Dare, Pamlico, and Beaufort counties, where participants were surveyed about their experiences and perceptions.

In addition, Rich Bandy, lead meteorologist at the NWS Newport/Morehead City office, presented comparisons of the forecasts for wind, inland flooding and storm surge with observations during and after the storm.

Coastal flooding caused by storm surge was the main threat were people were not prepared enough for.

The NHC correctly forecasted storm surge will be between 6 to 8 feet as the highest storm surge was recorded at 7 feet.

And major flooding across parts of Carteret, Pamlico, Beaufort and Hyde counties and other areas including the entire barrier island chain north of Cape Lookout, and the Pamlico and Neuse river areas was observed.

Improvements

The NHC improved its warning system with better accuracy and longer lead time for preparation and information decimation.

However, making people evacuate remains a problem as people often don’t want to leave.

The NWS and local governments then used social media to reach more people in addition to the traditional TV news networks and newspapers.

“While social media is a way to reach people who do not rely on traditional media, adoption has been slow because many municipalities do not allow employees to access the sites on work computers. One of the lessons from Irene for emergency communicators has been that policies need to be developed about the use of social media, including how it will be staffed when a crisis occurs.”

Roberta Thuman, Town of Nags Head’s public information office.

Conclusion

While Irene was certainly not the strongest storm of the 2010s, it certainly resulted in significant changes in forecasting and forecasting platforms.

The impacts of Irene will likely be remembered for many years to come, even with the more powerful Hurricane Sandy that occurred one year later.

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Current Information

Potential Tropical Cyclone (PTC) 3 is currently located at 22.9N 92.4W which is about 479 miles (765km) south of Morgan City, Louisiana. According to satellite estimates the storm and a reconnaissance mission, it currently has 35mph (55kph) winds and a pressure of 1008mb (29.74inHg). The storms center is currently exposed and very broad with most of the showers and thunderstorms to the east of it stretching from the Mississippi Delta to Belize signaling this storm will likely be subtropical upon landfall. The storm is officially a tropical disturbance and labeled 03L but it does have a 90% chance of becoming a tropical or subtropical storm in the next 2 days so the National Hurricane Center has begun issuing advisories for this storm as it could make landfall in less than 2 days. It is currently moving north at 9mph (15kph) and is expected to come ashore in Louisiana in the early morning of Saturday. When it does make landfall, the storm will bring very heavy rain as it turns from due north to more northeast. It will then spread more rain to other southeast states before dissipating over North Carolina Sunday afternoon. With landfall about 36 hours away, Tropical Storm Warnings are also in effect for Intracoastal City, Louisiana to the Alabama/Florida Border including Lake Pontchartrain and Lake Maurepas.

Impacts

As all tropical systems go, there will be multiple hazards with this, although most will be pretty minimal. Winds are expected to be around 45mph (72kph) which can break branches of trees and also do light damage to roofs. Storm surge is expected to be up to 3ft. (0.9m) in areas from Intracoastal City, LA to the AL/FL border which will cause significant flooding in low lying areas during high tide. Isolated tornadoes will also be a threat with this storm along the coast on Friday and further inland on Saturday which could cause moderate damage to areas they effect. However, the main threat will be the rainfall. The Weather Prediction Center has put areas of Southeastern Louisiana, Southern Mississippi and Alabama, and Western Florida under a Moderate Risk for flooding meaning numerous flash floods are likely in the region. Widespread totals of 4-8″ are expected in this region, though totals could be as high as a foot in isolated areas. This will cause life-threatening flooding in urban areas and significant rises on creek and rivers which will cause flooding well after the storm has passed. Further northeast over Alabama and Georgia, totals up to 4″ can be expected which can also cause significant rises on small streams and also major flooding in flood prone areas. If flooding occurs, do not drive on flooded roads or go outside and instead move to a higher area immediately. It only takes a few inches of moving water to knock an adult off their feet and only 6″ of standing water for one to lose control of their vehicle. Remember: Turn around, don’t drown.

This is a very dangerous situation in the upcoming days. Stay up to date to your local weather authorities, National Weather Service and National Hurricane Center. Also make sure to Follow Force Thirteen on Facebook, Twitter and YouTube for the latest updates on this system. Be prepared for its arrival and most importantly, be safe.

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Current Setup and Outlooks

Over the past few days moisture has continue to surge into the state of Texas which has brought round after round of severe weather. Today this is once again the case as dewpoints have surged into the 50’s and 60’s over Western Texas while they are in the 70’s in the southeastern and eastern part of the state, but is very dry further up in the atmosphere. Meanwhile the atmosphere is increasingly unstable meaning it is very easy for air to rise and form thunderstorms as for an air parcel to rise it has to be warmer than its environment. The distance between the temperature and the temperature of a rising air parcel is called the Convective Available Potential Energy (CAPE) and is measured in joules per kilogram of air. Current values are about 1000-2000 in this region, but models predict it to skyrocket into the 3000 and even upwards of 4000. This combined with very strong updrafts (winds flowing upwards into the storm) will make a environment very suitable for large and very large hail, likely larger than 2″ in diameter. There is also weak, but rotation in the atmosphere which will support potential tornado development, though not very strong. Because of this a Severe Thunderstorm Watch has been issued for Northeastern New Mexico and Northeastern Oklahoma and Texas and a Tornado Watch has been issued for Eastern Texas.

The Storm Prediction Center has also issued a rare Moderate Risk for Western Texas, including the cities of Lubbock, Abilene and Plainview. This area has a 45% significant chance of hail, meaning that there is a 45% chance of there being a hailstorm within 25 miles of a given point inside the risk area as well as a 10%+ chance of there being a significant hailstorm within the same area. There is also a 10% tornado risk and 15% damaging wind risk. An Enhanced Risk, meaning numerous severe storms are possible, surrounds this risk region and includes areas of Central and Western Texas as well as Southwestern Oklahoma, including Ft. Worth, Amarillo and Midland, TX as well as Ft. Still, OK. Here there is a 30% significant risk for hail and a 15% damaging winds and these areas will also likely receive severe weather. Just east of this region, a 30% wind risk was issued for when this storm turns into a more linear system supporting a more damaging wind threat.

Severe Weather Event

Currently over New Mexico, there has been an increase in clouds and thunderstorms noted. This is signaling that supercells (thunderstorms with rotation) are likely to initiate sooner than expected. The current guidance suggests that over the next few hours, there will be a significant growth in coverage of this event. By 7pm there is expected to be a line of supercells from Del Rio to Dalhart in Texas posing a risk for mainly very large and even giant size hail, but also tornadoes and damaging winds. After this the southern ones will die down while the northern half (north of I-20) will begin to organize into a bow echo, still posing a risk for very large hail. By 11pm these will have fully organized into a line posing more of a risk for damaging winds but also may produce brief tornadoes. further south around this time new storms will have developed around the Del Rio-Laredo region which will move northeast staying just north of and along the I-35 corridor. These will pose a risk for large hail, damaging winds and a tornado or two as by 4am they will move through the San Antonio region. Further north the bow echo is expected to move through Northern Texas and Oklahoma but begin to dissipate around 4-5am just east of I-35.

Flooding Risk

Further east in Eastern Texas and Louisiana, extensive flooding is ongoing and is expected to occur these next few days. Today a Slight Risk for flooding was issued meaning scattered flash flooding events are possible for the far eastern Texas and Southern Louisiana today. Here stalling thunderstorms have produced heavy amounts of rain with widespread totals of 3″ with some areas getting over a foot of rain today. This has prompted two Flash Flood Emergencies for Lake Charles County, LA and Jefferson County, TX. This will make the ground extremely saturated ahead of 2 more waves of storms tomorrow which will bring another 2-4″ of rain across Eastern Texas and another 5″ over Southeastern Louisiana. On Wednesday, a strong complex of storms is expected to form and stall over the I-35 corridor bringing extreme rain with widespread values of 2-6″ with isolated amounts of a foot being predicted. Because of this Eastern Texas is under a Moderate Risk for flooding for both tomorrow and Thursday meaning numerous flash flooding events are likely. Southern Louisiana is also under a Moderate Risk for flooding tomorrow.

This is a very dangerous situation! Keep up to date with your local weather authorities as well as the National Weather Service for any storm information. Go to the Storm Prediction Center’s website for any information on severe weather and the Weather Prediction Center’s website for information on the current flooding risk. Also, subscribe to the Force13 US YouTube channel and follow us on Twitter for the latest video’s and updates on severe weather. Be prepared for these storms and most importantly, be safe.

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In reality, more tornadoes would occur in this one day than any other day in world history and the more people would be killed in tornadoes in this one day from tornadoes than any other day in the previous 79 years.

Morning Weather Outlooks

The Day 1 outlook for April 27, 2011 once again featured a High Risk for severe weather, this time for Northern Alabama, Northeastern Mississippi, Northwestern Georgia and Southern Tennessee. Here a strong squall line from the previous day of storms was expected to move through the region in the morning. This would bring damaging winds and tornadoes as it fed off of the untouched environment and would temporarily make conditions unsuitable for storms. However, the environment was expected to rapidly recover as moisture from the Gulf was expected to surge back into the region and make the atmosphere once again unstable. Convective Available Potential Energy (CAPE) values, a measurement on how easy it would be for air to rise and produce thunderstorms measured in joules per kilogram of air, were expected to be between 2500 and 4000 which is extremely favorable for tornadoes. The only catch was a cap would be in place, or an area in the lower part of the atmosphere where if an air particle were to rise it would be cooler than its environment and sink back down making it unable to produce thunderstorms. This would stop severe weather from happening until the afternoon when a dry line and cold front would interact with this environment. This would cause the cap to explosively break and cause the rapid development of supercells (thunderstorms with rotation making a tornado likely from them). These storms would be not only particularly strong with the potential for 1 or 2 violent tornadoes (tornadoes with 166mph winds or greater) but also allow for any tornadoes to be long-tracked. Supercells that did form would also pose a risk for large hail and damaging winds. The environment and setup looked so good that the Storm Prediction Center (SPC) did something very uncommon. Instead of the usual 30% risk for a tornado within 25 miles of a given point inside the High risk, they upgraded it to a 45% risk for parts of Alabama and Mississippi, above the High risk criteria. This had only been done once which had been issued over 5 years earlier. It was clear the setup was there for a major tornado outbreak and it was just a matter of time before storms initiated.

For the following day of April 28, a Slight Risk was maintained for a majority of the Eastern Coast. Here the previous days event was expected to become a linear system and with that bring a chance of tornadoes to the coast, though these were expected to be more marginal in intensity as CAPE values of 500-1000 would be present, which isn’t the most ideal for tornadoes. Nevertheless, damaging winds also seemed like a possibility but mainly over the Carolina’s and Virginia Coast before the system moved off shore.

Weather Event

The day immediately began with a bang as storms over Louisiana continuing from the previous day began to drop tornadoes across the state. This main line of storms stretched from Monroe, LA to Greenville, MS while a second line stretched east behind that line. The full squall line stretched northward into the Ohio River Valley but the northern section didn’t pose as much of a risk tornado wise but more of a risk for large hail. The southern end over Louisiana, however, posed a damaging, straight-line wind threat which had frequent gusts up to 85mph (137kph) while imbedded tornadoes were touching down, including an multi-votex EF-1 and multiple EF-2 with one wrapping a mobile home frame around a tree. This line of storms began to race across the state and into Mississippi where the main line of storms began to shift north and allow the second line of storms to turn more vertical behind it. At 1:40am the main line of storms stretched parallel to I-55 and was just north of Jackson when the first EF-3 tornado touched down that day. It stayed over mainly rural areas near the Yazoo River but did damage some homes and mobile homes. It later merged with another EF-2 tornado before dissipating.

By 2am the first line of storms had begun to fall apart while the second one became the more dominant storm system. This prompted the issuance of a new Tornado Watch for Alabama and Mississippi and also parts of Tennessee and Louisiana. For the next few hours while the first wave moved north and hit the northern part of Mississippi while the second, stronger wave moved through the central part of the state and spread even more wind damage. At around 2:30am an EF-3 tornado touched down near Europa and tracked for 58 miles before lifting while an EF-2 tracked along side it for 13 miles and killed 1 person. These tornadoes damaged or destroyed many homes and businesses and even tore off a canopy on a gas station. At 3:40am, another EF-2 tornado touched down in northern Mississippi devastating the community of Belmont. By 4am the main line of storms began to enter the state of Alabama and produced 2 long-tracked tornadoes that moved west and north of Tuscaloosa. The first rated EF-2 and the second, which was caught on air by channel ABC 33/40, was rated EF-3. Then another EF-3 hit the town of Coaling, AL near Interstate 20-59 damaging and destroying many homes while a minute later another EF-3 touched down in Cordova causing more damage there. But while this way began its assault on Alabama, a new wave of storms was forming right behind it.

At around 4am CDT a new wave of thunderstorms began developing over Arkansas and Texas in response to a developing low-pressure system. These storms mainly were a hail and damaging wind threat as they began to move northeast and organize. Soon they would become the center of attention for the day’s events. But meanwhile, the main line of storms continued to move through Alabama spreading damaging winds with gusts hitting 90mph. At around 5:48am CDT, a powerful EF-2 tornado hit south of Cullman, AL at Hanceville causing damage to many farms and a school campus killing 1 person. Numerous small tornadoes began touching down after this in Marshall County near Guntersville while a longer EF-2 tracked north of the city until a long-tracked EF-1 killed 1 person as it moved through the northeast part of the state. After this the activity shifted over to Tennessee with numerous tornadoes touching down, though they were generally weak. By 8am the line began to pass over the Appalachians and Georgia where energy was not as present and robust like over the southeast and because of this began to significantly weaken. But the damage had already been done. A long stretch of wind damage was present across Mississippi and Alabama that had hit cities like Jackson, MS, Tuscaloosa, Al and Birmingham, AL. Hundreds of thousands of trees had been blown down, powerlines had been brought down cutting electricity to millions, widespread straight-line winds caused more widespread property damage while 92 tornadoes had touched down causing locally intense damage. 3 people had been killed from the tornadoes with many more from the damaging winds and hail. And with all of this not only were as skycams damaged making it harder to see and broadcast weather conditions, NOAA weather radio transmitters, transmitters that allowed warnings to be immediately broadcast after being issued, had been damaged and made inoperable. With this a quarter of a million people were without power, without their NOAA weather radio broadcasting correctly and were completely oblivious of the upcoming wave of storms as the temperature rose and the skies cleared revealing a beautiful, sunny day.

At 8am a new Tornado Watch was issued for the northern parts of Mississippi and Alabama as a new, smaller squall line began to ravaged the northern parts of the states as the low-pressure system continued to develop over Arkansas and Missouri. This wave continued to bring intense winds through the state of Mississippi and by 11am also Alabama and Southern Tennessee. Over the state a new wave of tornadoes began to ravage areas north of the Tennessee River. These, however, were relatively weak and didn’t cause that much damage compared to the straight-line winds. But at this point, the first hints of what was to come began to be announced by the SPC and it didn’t look hopeful.

At 10:45am CDT a Mesoscale Discussion (MD) was issued for Mississippi where it described the conditions currently present. Clear skies had returned after the main line of storms and with moisture continuing to surge into the region causing dew points to rise by 8-12F in just 2 hours, the environment was once again very unstable with wind shear continuing to increase by astonishing levels. It was prime for tornado development and thus the SPC said that a Particularly Dangerous Situation (PDS) Watch would be issued for the state very soon. This is because attached to the squall line dragging south was a dry line or a line that separates warm, moist air in front of it from warm, dry air behind it. it forces warm to immediately rise and produce thunderstorms which in this case would be supercelluar. This, however, was not expected to happen until the afternoon and be more centered over Alabama and Eastern Mississippi. Shortly after this at 11:05am, a PDS Tornado Watch was issued for almost the entire state of Mississippi as well as small parts of Louisiana and Arkansas. The probabilities for the watch were shocking. There was a greater than 95% chance for 2 or more tornadoes and 10 damaging wind and hail reports while there was a 90% chance for 1 or more significant tornadoes (111mph or 179kph tornado or greater), 1 wind report of 75mph (120kph) or greater and 1 hail stone larger than 2″ (5cm) in diameter. Although the threat was not expected until the afternoon, the SPC did state that “All parameters suggest [that] strong/violent and long-track tornadoes are possible.” During this time a line of thunderstorms developed just east of the Mississippi River in Arkansas and around 12:30pm crossed over into Mississippi. 20 minutes later at 1:05pm, the SPC issued another MD, this time for Alabama stating a similar thing and 30min. later issued another PDS Tornado Watch for Alabama but also a few counties in Tennessee, Georgia and Mississippi where “A classic tornado outbreak situation…[was]…developing.” Here for the first time ever in a watch, all the probabilities were greater than 95%. Never before had this been seen and only once to date after this point (May 20, 2019) has it been seen. But by this point, the new wave of supercells had already produced the first tornado.

At 1:36pm CDT the first tornado of these supercells touched down and moved just south of the city of Oxford destroying many homes and mobile homes. The front would fall silent for about an hour after this while the previous day/morning system began to harass the Northeast producing some severe storms and tornadoes. Despite this the extremely favorable conditions present were becoming clear to all. Meteorologist James Spann went live on TV at 2:00pm to notify the public of the PDS watch just issued along with a developing supercell. When checking the details on the cell, the Significant Tornado Index, an index to show how likely a significant tornado is, was at 12.6; a number so high that Spann had never even seen something like it on a scale that he thought went to 10. At the Weather Channel, their metric used to measure tornado likelihood called the Tornado Condition Index (TORCON) maxed out at 10/10 for the first time in its history. But by 2:30pm attention shifted back to the Southeast as the cap began to break. At this time a tornado touched down near the town of Philadelphia, MS and immediately intensified into a powerful EF-5 tornado. It stayed over rural areas but caused extensive ground scouring (removal of grass and dirt) of up to 2ft. (0.6m) deep and even removed asphalt from a road. 3 people were killed in it as it stayed away from populated areas. But just 10min. after this tornado touched down, a large and multi-vortex tornado (meaning there were multiple funnels inside the main one) touched down near the city of Cullman, AL and gave the city a direct hit. Many well-built buildings were destroyed and the downtown was hit directly. Churches, schools and even the courthouse were all hit and all were badly damaged. The tornado remained on the ground and moved just north of Arab where it swept away a brick home. 6 people were killed in the tornado as the SPC began to take note of the situation.

At 2:56pm CDT as the Cullman tornado was still on the ground, the SPC issued another MD stating that “an extremely dangerous/life threatening situation continue[d] to unfold” in the area. They once again reiterated the conditions present and also said that scattered supercells were likely to continue forming in the region and that the threat for long-tracked/strong and possible violent tornadoes were still likely. They also issued a new PDS Watch for Central and Western Tennessee as supercells began to head northeast to that part of the state. The probabilities were not as high as the previous watches, but still featured a 90% risk of 2 tornadoes and 80% chance of a significant tornado. A couple minutes after this watch was issued a powerful EF-3 touched down in Mississippi and would remain on the ground for almost an hour destroying communities in New Wren, Anchor and Houston killing 4 people.  but it was the tornado that touched down right afterwards that gained everyone’s attention.

A powerful touched down at 3:00pm CDT just south of Hamilton, AL. It quickly went on to hit the city of Hackleburg where mass destruction occurred. well built homes were swept away, a school was heavily damaged, asphalt was torn out of roads, trees were debarked and cars were thrown long distances. The tornado continued to move northeast while behind it, the supercell that produced the New Wren tornado dropped a second, more violent tornado at around 3:42pm CDT. This tornado rapidly intensified into an EF-5 and immediately hit the city of Smithville 5 min. later. Numerous homes in the city were swept away including one which was so aggressively picked up that the foundation was lifted partially out of the ground. 16 people were killed in the city. At the same time hundreds of miles to the south, another tornado touched down in Tuscaloosa County, but the tornado was relatively weak as it passed through the north side of the county. Meanwhile back north, the tornado that devastated Hackleburg devastated another city: Phil Campbell. Houses in the city were swept away, a church was completely destroyed and swept away while 3 others sustained significant damage. The tornado continued to just outside of the city where the worse damage was observed. Vehicles were thrown and mangled to the point that they were no longer recognizable and brick houses were completely swept away with their debris thrown hundreds of yards. The tornado continued to move northeast and devastated the community of Mt. Hope. Here a restaurant was destroyed with just a pile of debris left and a part of the foundation broken. The Smithville tornado also crossed into Alabama but significantly weakened to an EF-1. Further to the south, another tornado had crossed into Alabama where it severely damaged a home made out of cinderblock at EF-3 strength but began to lose steam as another cell to its south began competing with it. Although it looks like the tornado threat was weakening, everyone knew this was just the beginning. In fact, it was about to get much worse and there was even another wave of supercells behind this one.

At 4:05pm the Hackleburg tornado hit the city of Moulton at EF-4 intensity destroying many houses in the town. Also, at this time the supercell that produced the Cullman tornado produced another multi-vortex tornado where it immediately intensified into an EF-4 passing north of Pisgah and Rosalie where it destroyed many homes. It then passed north of Flat Rock as it completely swept away a farmhouse and killed many animals. Meanwhile the Smithville tornado intensified to an EF-3 and ravaged mobile homes and farm houses in the region killing 7 more people. It continued north of Hamilton and dissipated at 4:23pm CDT after killing 23 people.

Further south, the weak tornado in northern Tuscaloosa County strengthened and crossed into Fayette County where it reached EF-3 strength and destroyed a mobile home and displaced its debris. It then weakened back into an EF-1. Meanwhile the EF-3 tornado to the south succumbed to the new supercell forming. This new cell began intensifying and put Tuscaloosa County back under the gun. Back north the Hackleburg tornado that was still on the ground and crossed the Tennessee River where it hit the city of Tanner which was hit by not 1, but 2 F-5’s in the 1974 Super Outbreak. Here the city had been devastated with several foundations being wiped clean at possible EF-5 intensity. It then weakened back to an EF-3 as it hit the communities around Harvest doing more damage. It would continue to gradually weaken and dissipated almost an hour later at around 5:30pm CDT. 72 people were killed in the 132 mile track and over $1B in damages was done. It was the deadliest, longest and second costliest tornado of the outbreak.

Besides this tornado the bulk of the activity began to shift further south. The tornado in Fayette County strengthened into an EF-2 and passed just south of Oakman damaging many homes before strengthening into an EF-3 causing heavy damage to a cinder block home. It then hit the city of Cordova at that intensity sweeping away many homes and damaging many others. Back south over Greene County, the supercell there finally dropped large multi-vortex tornado that began moving toward Tuscaloosa County and more majorly, the city of Tuscaloosa itself.

Meanwhile after devastating the city of Cordova, the tornado here intensified into an EF-4 and began to destroy and throw many vehicles long distances. It weakened back to an EF-3 and passed just south of Sipsey destroying many more homes. Back North, a new tornado touched down very close to the path of the Flat Rock tornado. The tornado touched down at 5:05pm and strengthened into an EF-2 tornado when it hit the city of Stevenson causing significant damage before hitting the airport and reaching EF-3 intensity. Here several truss towers were bent and flattened. It went over rural areas where it reached EF-4 intensity and destroyed a cinder block home leaving just a pile of rubble behind. Back south, Channel WVUA in Tuscaloosa showed the tornado in Tuscaloosa County hit the city of Tuscaloosa head on as their power went out and meteorologist Richard Scott became visibly nervous but still remained calm in his speaking. The storm caused major devastation. Homes were completely destroyed and some were swept way with even well-built apartment buildings being destroyed. This tornado was also caught on air by channels CBS 42 and ABC 33/40 with meteorologist James Spann saying “all you can do is pray” as the tornado began to rip through town. 44 people were killed in the city before it weakened and moved through a densely wooded area debarking and uprooting trees producing a scar that can still be seen to this day.

Back north the Stevenson tornado continued to move through more rural areas and flatten many houses before crossing into Tennessee and weakening into an EF-2. It dissipated around 5:30pm CDT leaving the Tuscaloosa and Cordova tornadoes the lone violent tornadoes active. The Cordova tornado restrengthened back to an EF-4 and destroyed 2 cinder block houses before fluctuating between EF-2 and EF-3 for the rest of its life. But back over Mississippi, a new, strong EF-2 tornado touched down near Raleigh, and began to steadily intensify into a violent EF-4 destroying many mobile homes. Around 6pm the tornado entered Jasper County in Mississippi where it destroyed many mobile homes and frame houses and debarked trees. Meanwhile the Cordova tornado dissipated after traveling 127 miles for over 2 hours and killing 13 people. Meanwhile the Tuscaloosa tornado slammed into the northern suburbs of Birmingham causing heavy damage and destruction at EF-4 intensity. The tornado quickly dissipated after this but not after killing 64 people and also doing over $1B in damages and becoming the costliest tornado of the outbreak. This left the Raleigh as the sole violent tornado while 2 other EF-3 were also on the ground — One in Northwest Alabama that stayed over forest areas but did sweep a building off its foundation, and a long-tracked one just southwest of the Tuscaloosa cell that also impacted very wooded regions, but also the town of Eoine where it caused heavy damage or destroyed many houses and even destroyed the fire department. But the amount of tornadoes down would quickly change as previous supercells refused to give up so early.

At 6:19 pm the supercell that had produced the Philadelphia EF-5 and Cordova EF-4 dropped another tornado which quickly intensified into an EF-5 as it hit the city of Rainsville, AL. Here businesses were completely destroyed and houses were swept away. One particular house had its stone structure swept away and a concrete pillar so aggressively pulled up that its concrete foundation was damaged. Roads were also scoured and it even broke a concrete porch in half. It then skimmed the city of Sylvania and ripped a sidewalk out of the ground as well as destroy a church and many other homes in the region. It later crossed into Georgia as an EF-1 before dissipating at 6:55pm CDT with a final cost of 25 lives. Meanwhile the Tuscaloosa supercell produced another tornado at 6:28pm CDT that intensified into an EF-3 as it moved through rural areas while leaving just the interior walls left in houses. It strengthened into an EF-4 as it skimmed the northern part of Ohatchee as it destroyed every house in sight and even sweeping some away. It weakened after destroying 256 houses to an EF-3 as it moved near Wellington and through Piedmont. It then moved through rural areas of Georgia before dissipating after tracking for almost 100 miles and killing 22 people in just over an hour and 45 minutes.

In Mississippi the tornado there weakened from an EF-4 and hit the city of Rose Hill as an EF-3 causing heavy damage in the city. It then moved south of the city of Enterprise and intensified into an EF-4 just east of the city destroying and sweeping away a home under construction but almost complete. It weakened back to an EF-3 as it crossed into Alabama around 7:30pm CDT after traveling for 67 miles. It quickly sped through Alabama as an EF-2 and dissipated after traveling for 122 miles but only killed 7 people. But before the Enterprise and Ohatchee tornadoes dissipated, the Philadelphia tornado supercell would drop another EF-4.

At 7:15pm CDT, 20 minutes after the Rainsville tornado, the supercell dropped a large and powerful multi-vortex tornado which quickly intensified to an EF-3. It hit the city of Ringgold, GA which sat comfortably on Interstate 75. This allowed for a hotel and several restaurants and gas stations to be partly destroyed by the tornado. It then moved through the residential region where it strengthened into an EF-4 as many homes were destroyed and some were swept away. It then crossed into Tennessee where the community of Apison was also obliterated at EF-4 intensity while Cleveland was skimmed to the south and east. It continued on its trajectory killing 20 people before dissipating at 8:07pm CDT, almost an hour later.

While the event began winding down, 2 more EF-4 occurred in Southern Tennessee. The first occurred at 6:35pm CDT and was produced by the same cell that produced the Cullman tornado. However, it mainly stayed in the forested regions of the mountains and didn’t cause a significant amount of damage minus uprooting and debarking thousands of trees and ripping a TV station transmitter right out of its concrete base. Meanwhile further east at just after 8pm, another EF-4 tornado touched down and moved just south of Pikeville where houses were completely destroyed as farm vehicles being mangled and being thrown with cars. 4 people were killed in it in this region. 5 minutes later the last EF-4 tornado touched down in Southern Alabama. It was an EF-3 for a lot of its life at the beginning passing near the cities of Central and Eclectic. It strengthened into an EF-4 when it began to ravage the Lake Martin region, completely destroying houses on the lake leaving nothing left but the basement. It then moved near Dadeville where another 2 houses were destroyed. it continued and destroyed a few more houses before lifting an hour later. 7 people were killed in this tornado.

After this point the threat began to die down. storms began to organize into a large linear system stretching from Southern Alabama to Kentucky. At 8:20pm CDT a tornado of the Tuscaloosa, AL tornado supercell touched down in Northern Georgia as an EF-3, though it mainly stayed over rural areas and missed major cities. An hour later at 9:30pm CDT the final tornado produced by the supercell touched down in a wooded area in the northern part of the state killing 2 and being rated EF-3. The final major tornado of the Philadelphia tornado touched down in Georgia and destroyed many houses killing 6.

Meanwhile in the Northeast and Mid-Atlantic, the low-pressure from the morning squall line began to produce isolated storm systems in the area. At 1:25pm EDT, a Tornado Watch was issued for Virginia, North Carolina and small portions of West Virginia and Maryland for this threat, though few storms ended up forming. 2 hours later another Tornado Watch was issued for New York, Pennsylvania and a small portion of West Virginia for a developing thunderstorms. Storms would form, but only 2 tornadoes would touch down in the regions. At 6:15 EDT, a new Tornado Watch was issued for Virginia, North Carolina and Maryland as isolated supercells rapidly developed. 11 tornadoes touched down in Virginia (along with 1 in West Virginia) including an EF-2 that destroyed 5 buildings/mobile homes and damaged 20 others killing 1 person. Watches were also issued for the Midwest and Kentucky, but widespread storms failed to develop and only 4 tornadoes touched down, though 2 EF-1’s in Kentucky did cause some moderate damage. By 11pm CDT, things began to wind down and at 11:56pm CDT the last tornado lifted.

Never before had there been a day so active like this one. 212 tornadoes touched down this day including 11 EF-4’s and 5 EF-5’s. 9 of these violent tornadoes were produced by 3 supercells: the Philadelphia (4), Cullman (3) and Tuscaloosa (2). More tornadoes occurred this day than ever before in world history while it comes in third of most violent (EF-4 and EF-5) tornadoes behind the Palm Sunday Outbreak of 1965 and 1974 Super Outbreak. It is also only the second day in history to have more than 1 EF-5 occur during it (other being April 3, 1974). 316 people were killed this day including 270 in Alabama alone in the state’s deadliest outbreak. This made it the deadliest outbreak in American history. over $10B in damages was also done making it the costliest tornado outbreak in U.S. history. The storms would move on to the East Coast where on April 28, it would be there turn to feel the brunt of the tornadic activity, but be overshadowed by the previous day.

April 27, 2011 will live long in the minds of the weather community and south as one of the worst weather outbreaks in US history 10 years ago today.

Sources:

https://www.spc.noaa.gov/cgi-bin-spc/getacrange.pl?date0=20110426&date1=20110427&csrf=61900d0263b3a25d33ad14a43279d1a7552b2dbb

https://www.spc.noaa.gov/exper/archive/event.php?date=20110427

https://mesonet.agron.iastate.edu/current/mcview.phtml?prod=usrad&java=script&mode=archive&frames=300&interval=5&year=2011&month=4&day=27&hour=0&minute=0

https://mesonet.agron.iastate.edu/current/mcview.phtml?prod=hunrad&java=script&mode=archive&frames=300&interval=5&year=2011&month=4&day=27&hour=0&minute=0

https://gis.ncdc.noaa.gov/maps/ncei/radar

https://en.wikipedia.org/wiki/2011_Super_Outbreak

https://en.wikipedia.org/wiki/List_of_tornadoes_in_the_2011_Super_Outbreak

https://www.youtube.com/watch?v=J8uSIQLftME

https://www.youtube.com/watch?v=EGrErqGrtjw&t

www.youtube.com/watch?v=FE6lHka1jqc&t

www.youtube.com/watch?v=ElZZNvNdhks&t

www.youtube.com/watch?v=Ftz5UL8S2Ms&t

Tornado Archive Data Explorer

The post Remembering the 2011 Super Outbreak: April 27 “An Extremely Dangerous/ Life Threatening Situation” appeared first on Force Thirteen.

Morning Weather Outlooks

After reviewing the weather model data and looking at the setup, the Storm Prediction Center (SPC) issued a rare High Risk for severe weather meaning a tornado outbreak is expected. The risk initially was for Northeastern Texas, Southeastern Oklahoma, extreme Northwestern Louisiana and Southern Arkansas, but was later expanded to include Southwestern Tennessee and Northwestern Mississippi. Here moisture flow from the Gulf had created even more instability (meaning it would be easier for air to rise and produce thunderstorms than before) than the previous day and temperatures across that region began to soar into the 80’s and 90’s Fahrenheit (upper 20’s to low 30’s Celsius) and dew points rose into the 70’s Fahrenheit (low to mid 20’s Celsius) making forecasted CAPE values (Convective Available Potential Energy measured in joules per kilogram which is a measurement of how unstable that air is/how easy it is for air to rise) shoot into the 3000-4000 range, extremely high and favorable for tornadoes. Meanwhile wind shear (winds blowing in different directions and speed with height) continued to strengthen and support rotation. because of this, the SPC predicted widespread supercells (a thunderstorm with rotation and the potential to produce a tornado) would form near the AR/TX border and rapidly produce potentially strong (EF-2 to EF-3) tornadoes. Models then suggested that a second wave of supercells would form later in the evening as the conditions continued to get move favorable but this time these storms would form over Northern TX/OK and have a higher chance of producing strong tornadoes. Once these moved west, they would enter a more favorable environment which after this either, 2 solutions emerged: 1. The storms would remain discrete and produce strong or even violent tornadoes (EF-4+, the highest ratings) or 2. they would organize into a powerful bow echo and blast the region with intense winds.

For the Day 2 (April 27) outlook, a Moderate Risk was still in place for the “Potential for a significant/widespread severe weather event — including the possibility of a tornado outbreak…” mainly focused over Tennessee but also for Northern Alabama, Northeastern Mississippi and Eastern Kentucky, where the Moderate Risk was in place. Here the previous days weather system would still be going on and move through the region but behind it, an extremely unstable air mass would be ushered in which as a new storm system arrived would support significant tornadoes (EF-2+) but because of the environment any tornadoes that occurred would have the high potential of being long-tracked. North of this region the storm system was likely to produce a damaging wind event so therefore the risk was expanded northward toward Lake Erie and included parts of Ohio, Indiana, West Virginia, Pennsylvania, and Virginia. The only uncertainty was that if additional storms formed before the main event, they would hinder destabilization and make it unsuitable for intense storm development.

For the Day 3 (April 28) Outlook, the previous days storms were expected to organize into a linear system and move onto the east coast where a Slight risk was issued. Here the environment was not quite as favorable for storm development but 1000 CAPE was still present which was plenty for tornadoes.

Weather Event

30 minutes after the clocked chimed midnight, the first tornado of the day touched down associated with the previous day’s storms. An intense bow echo stretched from Greenville, MS to Tupelo, MS northward toward Evansville, IN with the most intense part in Tennessee. Here imbedded tornadoes in the line were occasionally touching down. 4 tornadoes touched down in the next 30 minutes before a powerful EF-3 hit an army base near Phil Campbell, KY destroying a building and damaging 3 others before lifting 3 minutes later. Despite this tornado and an EF-2 that hit a rural area in Indiana, the tornadoes were relatively weak. Things were silent for the next few hours until another bow echo from the previous day hit the Gulf Coast producing 2 more EF-1 tornadoes an hour apart which both hit Mississippi. After this storms fell quiet for 6 hours as the main events began taking shape.

The first watches issued this day were associated with the previous low-pressure system which was now over the Great Lakes with a front that stretched across the Appalachians. Ahead of this front was a relatively favorable environment for storms prompting 2 Severe Thunderstorm Watches for New York, Pennsylvania, Virginia and West Virginia. Damaging winds were rampant and 2 tornadoes also occurred. A few hours later at 2:05pm CDT, a Tornado Watch was issued for parts of Michigan, Indiana and Ohio as another part of the low entered a relatively favorable environment here as well. Only a few cells ended up forming, though one weak tornado did touched down in Michigan.

Back over the Southeast, the SPC continued to monitor conditions over the High risk region and before any storms popped up on radar the SPC issued a Particularly Dangerous Situation (PDS) Tornado Watch at 1:45pm CDT for parts of Texas, Louisiana and Arkansas. The watch included a greater than 95% chance of 2 or more tornadoes and a 90% chance of one or more significant tornadoes within 25 miles of a given point inside the watch. Storms began to slowly form and intensify in this region, mainly along a line from southeast of Dallas, TX to west of Memphis, TN. At 3:05pm CDT as storms were still intensifying, a second PDS Tornado Watch was issued for parts of Arkansas, Mississippi, Tennessee and 3 other states. But even after this it took another 2 hours before storms began to become tornadic and more widespread but even then they were generally weak. But the SPC did issue 2 more Tornado Watches, one for Texas and Louisiana directly south of the first PDS watch and one for Arkansas and Oklahoma north of the PDS watch.

Just before 4:00pm CDT, the SPC issued a Mesoscale Discussion  to discuss what is current situation and what was expected. The environment had ended up not becoming as favorable as expected. The 3000-4000 CAPE was mainly present over Eastern Texas while CAPE values were around 2000-2500 across Southern Arkansas, which was still plenty for tornadic development but potentially not to the degree as expected. But as wind shear increased through the night, “…the tornado threat /including the possibility for strong tornadoes” was “expected to increase toward/after dark.” This would indeed be the case, but not for the region originally predicted.

By 6pm CDT storms had taken up a fish hook shape from Memphis, TN to Fayetteville, AR to Dallas, TX to Lufkin, TX back north to Texarkana, AR as discrete cells. Although few tornadoes were touching down, these storms were dropping large hail and bringing damaging winds. Just after 7pm CDT a cell did produce an EF-2 tornado on the Texas side of the TX/LA border. This 10min. tornado caused some damage to a metal roof and downed many trees before dissipating. This tornado kicked off a new wave of activity as discrete cells in Texas began to intensify and move east over Louisiana. About 40 minutes after this initial tornado, a new, large EF-2 tornado touched down near the TX/LA and stayed on the ground for 42 miles and about 55 minutes. It mainly hit rural areas passing just south of Shreveport, LA but did damage many homes and a mobile home and destroyed many trees, injuring 2 people.

As the night progressed the storms over Louisiana became a powerful bow echo and continued to move east producing damaging winds and tornadoes while storms over Arkansas fanned out and became a disorganized mess over Mississippi, Tennessee and Kentucky while new storms began to fire up over Texas. This prompted the SPC to issue 3 new watches, first was a new PDS Tornado Watch issued at 9:35pm CDT for Louisiana, Arkansas and Mississippi also with a greater than 95% chance for 2 or more tornadoes. At 9:45pm CDT a Tornado Watch was issued for the developing storms over Texas associated with this system and at 10:00pm CDT a Tornado Watch was issued for the northern part of the line in Arkansas, Tennessee and Kentucky. This part of the line no longer posed a significant tornado threat but was mainly now a damaging wind threat. By 12am, though, the main bow echo over Louisiana had crossed into Mississippi and showed no signs of weakening. At around 11pm CDT it produced its last tornado for the day but continued to produce damaging winds across the south, threatening to cut power to millions as the area braced for what the next day would bring.

All in all, 55 tornadoes had touched down on April 26 including 4 EF-2 and 1 EF-3. This brought the total amount of tornadoes of the outbreak to 97 with 8 EF-2 and 2 EF-3. Despite the number of tornadoes that occurred, most of them missed the High risk area and occurred in Louisiana, just south of the risk. The bow echo of storms continued through the night and it would be this event that would begin the next 24 hours of almost non-stop activity of one of the worst weather days in American history:

April 27, 2011

Sources:

https://en.wikipedia.org/wiki/List_of_tornadoes_in_the_2011_Super_Outbreak

https://www.spc.noaa.gov/exper/archive/event.php?date=20110426

https://www.spc.noaa.gov/products/outlook/archive/2011/day2otlk_20110426_0600.html

https://www.spc.noaa.gov/products/outlook/archive/2011/day2otlk_20110426_1730.html

https://mesonet.agron.iastate.edu/current/mcview.phtml?prod=usrad&java=script&mode=archive&frames=600&interval=5&year=2011&month=4&day=26&hour=0&minute=0

https://gis.ncdc.noaa.gov/maps/ncei/radar

The post Remembering the 2011 Super Outbreak: April 26 “The Tornado Threat /Including the Possibility of Strong Tornadoes/ Expected to Steadily Increase” appeared first on Force Thirteen.

Morning Weather Outlooks

People in the Deep South and the nation woke to see something shocking: 3 Moderate Risk days were issued back-to-back for the Days 1, 2 and 3 outlooks. This was only indicative that a major tornado outbreak would be taking place that day and would potentially be one of historic proportion. The Day 1 outlook for April 25 featured a Moderate Risk for severe weather which included Central and Southern Arkansas, Northeastern Texas, Southwestern Oklahoma, Northern Louisiana, Northwestern Mississippi and Western Tennessee. Here a complex weather scenario was in the making. When the outlook was issued an intense bow echo was moving through the region. Traditionally, the bow echo would eat up the energy in place and make conditions behind it unsuitable for thunderstorm development. But in this case, unstable air (air that would support the development of thunderstorms) from the Gulf would continue to surge into the region meaning that the developing low-pressure system behind the bow echo would have ample moisture to feed off of. Attached to the low-pressure system was a dry line which as it sounds, separates warm, moist air in front of it and warm, dry air behind it. The dry air forces the moist air to rise and rapidly produce thunderstorms and because of strong wind shear (winds blowing in different directions at different speeds in different altitudes of the atmosphere) would promote supercells and tornadoes, which according to the SPC could be strong (EF-2 to EF-3) with large hail and damaging winds also being hazards. These storms would form in Texas and Oklahoma and then sweep east into Arkansas.

For the Day 2 (April 26) outlook, the SPC also issued a Moderate Risk for a similar area. The outlook initially included Southern Arkansas, extreme Northeastern Texas, Northwestern Mississippi and Western Tennessee but was later expanded to include all of Northern Mississippi and more of Western Tennessee. Here the SPC stated that a ”Complex — but potentially significant/dangerous — severe weather event is unfolding for this area…” as the remnants of the previous days storms would likely be still ongoing in the region. But as the day drew on, moisture was expected to continue to move into the region while shear was expected to strengthen even more which would make a “substantial tornado threat” likely to evolve in the region as a new low-pressure system developed. Very large hail (and damaging winds would also still be likely.

The following day, April 27, the Day 3 outlook also featured a rare moderate Risk but this time mainly for Northern Alabama, Central and Eastern Tennessee and Eastern Kentucky. Here a “…potentially very significant severe weather…” day seemed to be on tap like the 2 previous days but with a more complex setup. Severe storms would once again be ongoing from the previous day which would bring a chance for strong and severe damaging winds to the risk area. On the back end of this, a very unstable air mass would arrive as shear would continue to increase and support rotation. This would support strong tornadoes and damaging winds that as a new low-pressure system interacted with it, were expected to be centered over Tennessee. For the D4 outlook, no areas were assigned as the SPC wasn’t sure when the front from April 28 would arrive with some models moving it fast before suitable conditions arrived for severe weather while some were slower and allowed for a more major severe weather event.

Weather Event

As April 25 began over Arkansas, the lingering bow echo from the previous day continued to move through the state but had weakened below severe limits and didn’t really pose a threat. Meanwhile over Texas, lingering supercells began to redevelop into a bow echo as it moved over Southern Oklahoma at around 5am CDT. This prompted the first Severe Thunderstorm Watch of the outbreak to be issued for parts of Texas, Oklahoma, Louisiana and Arkansas. The line continued to speed east through the morning blasting most of Arkansas with intense winds. But at 9:05am CDT on the southern end of this system, a small funnel touched down over Hempstead County, Arkansas. The tornado would last 8 minutes before lifting and get an EF-0 rating. This tornado would be the first tornado of the outbreak and begin the next 3 days of horror.

Behind this line of storms over Oklahoma and Texas, the dry line did begin to interact with the environment as expected and as early as 10am began to produce thunderstorms around the Tulsa, OK region. These storms began to expand southwest in coverage and began to organize into two lines, one stretched from Muskogee, OK to Ardmore, OK while one in front of it stretched from Waco, TX to Fayetteville, AR. At 11am the first Tornado Watch of the outbreak was issued for Texas, Arkansas and Oklahoma ahead of these storms. These lines moved northeast: the one over Oklahoma organized into a squall line while the one in front stayed more discrete. Tornadoes during this time were mainly isolated to Texas and were weak and brief.

Around 12pm CDT, the two lines of storms began to combine as thunderstorms filled in the holes between them and turn more discrete. But a few hours later a new squall formed right behind the main line. At 3:25pm, the first line of storms stretched from Tyler, TX to Hot Springs, AR and consisted of discrete cells. Behind this line, a squall line of storms posing a risk for damaging winds stretched from Ft. Worth, TX to Fayetteville, AR. This setup prompted the SPC to issue a Particularly Dangerous Situation (PDS) Tornado Watch for most of Arkansas but also Louisiana and Texas meaning a very dangerous tornadic situation was developing and persons in the region should take extra caution.

The squall line began to move faster than the discrete cells and the two lines began to combine. But before all cells had been consumed, two cells dropped two EF-2 tornadoes in Garland Country, AR that caused heavy damage to many communities there including Sunshine and Lake Ouachita injuring 19. After a lull of intense tornadic activity, a new fast-moving cell formed and at 6:07pm CDT dropped a powerful EF-3 tornado that once again tore through communities in Garland County, AR destroying 25 houses and numerous mobile homes killing 1 person as well as blowing down hundreds of trees. This tornado lifted but it then the supercell dropped another large EF-2 tornado that began barreling toward the city of Vilonia, AR, just north of Little Rock. This prompted the first Tornado Emergency of the outbreak as the town was hit head on. It first destroyed a mobile home park where four deaths occurred before roaring through the city and causing immense damages to homes and businesses. 34 houses and 62 mobile homes were destroyed. Because of advanced warning time, only 4 people died and 16 were injured. Meanwhile, another part of the same cell moved through the northwest side of Little Rock, detached itself from the cell and at 7:46pm CDT dropped another significant tornado. It damaged planes at an air force base and also damaged parts of a school in the region before lifting just 8 min. later.

Over Arkansas, the two lines combined into one intense bow echo that began to move through the state. The SPC issued a new PDS Tornado Watch at 4:50pm for Tennessee, Arkansas and small parts of 4 other states ahead of the front, though few tornadoes occurred in those regions. Meanwhile, 2 cells had detached themselves from the main line of storms and moved southeast across Eastern Texas, moving from just south of Dallas/Ft. Worth to the Louisiana/Texas border. they were very isolated but did produce about 15 EF-0 and EF-1 tornadoes in the state.

By midnight as the bow echo moved through Tennessee and Kentucky, the tornado threat ended. That day 42 tornadoes had touched down across 6 states including 4 EF-2 and 1 EF-3. 5 people were killed and 59 were injured. The line of storms continued into the next day, but this had only been a small taste of what was to come. April 26 would be would end up being a more intense day than this.

Sources:

https://en.wikipedia.org/wiki/List_of_tornadoes_in_the_2011_Super_Outbreak

https://en.wikipedia.org/wiki/2011_Super_Outbreak

https://www.spc.noaa.gov/exper/archive/event.php?date=20110425

https://www.spc.noaa.gov/products/outlook/archive/2011/day2otlk_20110425_0600.html

https://www.spc.noaa.gov/products/outlook/archive/2011/day2otlk_20110425_1730.html

https://www.spc.noaa.gov/products/outlook/archive/2011/day3otlk_20110425_0730.html

https://www.spc.noaa.gov/products/exper/day4-8/archive/2011/day4-8_20110425.html

https://mesonet.agron.iastate.edu/current/mcview.phtml?prod=usrad&java=script&mode=archive&frames=300&interval=5&year=2011&month=4&day=25&hour=0&minute=0

https://gis.ncdc.noaa.gov/maps/ncei/radar

The post Remembering the 2011 Super Outbreak: April 25 “Potentially Significant/Dangerous — Severe Weather Threat is Unfolding” appeared first on Force Thirteen.

It was one of the country’s worst tornado outbreaks. 178 tornadoes had hit 16 states causing $2.1B in damages and killing 45 people in the deadliest outbreak since 2008. Entire communities had been affected with many large cities such as Jackson, MS, Raleigh, NC and Fayetteville, NC being especially hard hit. AccuWeather even stated that the outbreak was the largest number of tornadoes in a 3-day period in history. Surely this had to be the worst outbreak of the year, something like this wouldn’t happen for a while. Therefore, there was no need to panic and people went on with their lives helping clean up and begin repairing damaged areas. Little did people know this was just a taste of the horrors that would occur that tornado season, it was about to be much worse.

On Tuesday April 19, 2011, just 3 days after the April 14-16 tornado outbreak, the SPC stated on their day 4-8 outlook that a more amplified weather pattern seemed to be on tap for the Southeast on April 25 and 26 (days 7 & 8 on the outlook). When one goes more than 3 days out on model runs, very low congruency begins to occur. Because of this the SPC, with Day 1 being the day the outlook is issued (meaning it would be April 19 this day), bunches the Day 4-8 outlooks into one map and only issues a severe weather risk when there is a 30% probability of severe weather for an area which is very rare. During this day on this outlook, there wasn’t enough certainty to justify a risk so it was left with “Predictability Too Low” meaning just that.

On Wednesday, April 20, the SPC once again said that a very active pattern was likely over the Southern US in the coming days, though there wasn’t enough confidence to add a 30% risk. They stated that the main threat would probably be on the 25th to 28th (Monday-Wednesday) which would be widespread while a more limited event on the 24-25th but they stressed that there was still ample uncertainty on the event. Unknown to them, this forecast would become extraordinarily accurate in the coming days.

The following day on April 21, a 30% risk was added on the Day 5 (April 25) outlook for the ArLaTex region as well as for Eastern Oklahoma and Southwestern Missouri. The setup was that a weather system would pull moisture north into the Gulf Coast states which would make an unstable environment (meaning it would be very easy for thunderstorms to form in the area) that a cold front would interact with causing warm air to rapidly rise and form thunderstorms capable of producing severe storms, which as defined by the National Weather Service is thunderstorms which produce 58mph wind gusts or greater and/or hail the size of quarters (1″ in diameter) or larger and/or a tornado. These storms were likely to be very widespread that day. For the following 2 days, the SPC stated that “A relatively widespread/multi-round severe weather threat” was expected. There was still lingering uncertainty on where it would be which limited predictability and thus no highlighted areas were given.

On April 22, another 30% risk was added for Day 5 (April 26) while the one for Day 4 (April 25) remained. They were both for similar areas centered over Arkansas but included areas of Eastern Texas, Northern Louisiana and Western Oklahoma with the Day 5 risk including extreme Western Tennessee and Mississippi. The first weather system was expected to have an enhanced tornado threat while the following a day a second weather system would likely bring another threat for severe weather over the same area with a similar threat. On April 27, the threat was harder to tell so no area was marked.

On Saturday, April 23, the SPC issued a Slight risk for severe weather for April 25. For the Day 1-3 forecasts there is usually more certainty to what to expect so the SPC will issue risks dependent on that threat which include a Slight risk (scattered severe storms are possible), a Moderate Risk (widespread severe storms are likely) or a High Risk (a tornado outbreak is expected). On the Day 1 and 2 outlooks the SPC also included a General Thunderstorms risk (thunderstorms, but no severe weather, are possible). The Slight Risk was mainly focused over the ArLaTex region and Eastern Oklahoma. Here a similar severe threat to that of April 14 was developing which included the risk for mainly large hail but also damaging winds and tornadoes. Meanwhile a 30% risk was added for both Day 4 (April 26) and Day 5 (April 27). Day 4 was similar to that of Day 3 with a threat mainly in the ArLaTex region but also extended to cover almost all of Arkansas and part of the Lower-Mississippi River Valley. Here, as instability was expected to continue to increase, large hail would once again be the main threat as well as damaging winds and tornadoes. But April 27 seemed to be the main day for the event. Here a large 30% risk spanned from the Gulf Coast to the Ohio River Valley and from the Mississippi River to the Appalachians. With ample destabilization a tornado environment seemed prime for this region. Past these day models diverged on what the front would do over the Mid-Atlantic states so no area was added. However, things would come into place the following day, April 24. This day a powerful weather system would begin forming and be the preshow the upcoming historic outbreak.

April 24

Morning Convective Outlooks

Models began to come in better agreement on what to expect for the following day of April 25. Because of this, the SPC issued a rare Day 2 Moderate Risk for a “Potentially significant severe weather event…with potential for strong tornadoes in addition to very large hail and damaging winds.” This Moderate Risk was over mainly over Arkansas but also parts of Southern Missouri. Here strong southerly flow was expected to make the environment very unstable and with strong, rotating winds in the atmosphere, it made conditions prime for tornado development. As the night progressed the threat was expected to turn more into a bow echo/more linear shifting the threat to more of a damaging wind threat with isolated tornadoes.

Here, some basic thermodynamics should be understood. For thunderstorms to form, warm air needs to be able to rise and form clouds. For something to rise it needs to be warmer/less dense than its environment. Air is the same way and to form thunderstorms must be always warmer than its environment through the atmosphere. The warmer an air parcel is to its environment, the easier it is to rise and form thunderstorms. This is called instability and how warm an air parcel is compared to its environment is called the convective available potential energy (CAPE) and is measured in joules per kilogram of air. For April 25, CAPE values were expected to be as high as 2000 but the estimate grew to 2500 that afternoon

For April 26 the SPC also stated that a “Complex — but potentially significant — scenario appears to be unfolding…” mainly across Arkansas, Northern Mississippi and Western Tennessee. Here moisture would continue to surge into the region and interact with a new weather system and a cold front. As wind shear (winds blowing in different directions and speed with height) would be strong and support rotation. As the cold front interacted with the environment, severe thunderstorms and tornadoes would rapidly form, with some tornadoes being quite strong. For April 27, the risk area hadn’t really changed but they expected the cold front from the previous to sweep through the region. Afterwards moisture would continue to surge into the region and with strong rotation, a “substantial severe weather” threat would be likely. damaging winds and hail as well as isolated tornadoes would be likely. Past this it became more uncertain so no area was marked.

Weather Event

A new low-pressure system began to develop over the Southern Rockies. This new low-pressure system began to produce powerful thunderstorms over Oklahoma and Texas prompting two Severe Thunderstorm Watches. These storms stretched on a line from Abilene, TX northwest toward just south of Tulsa, OK. They quickly became severe and began dropping large hail across the region. Just east of Abilene, thunderstorms began to suddenly become supercells (a thunderstorm with rotation that could form a tornado) and drop several tornadoes, including one that was reported to be a multi-vortex tornado. But as the night progressed, the storms over Texas began to weaken and dissipate while the ones over Oklahoma organized into a linear system and began to plow through Northern Arkansas. The low-pressure system continued to take shape and move north-west over Kansas. Meanwhile moisture was surging into the lower Mississippi River Valley and shear continued to rotate and strengthen.

The stage was set for the largest tornado outbreak in the history of the world.

Sources:

https://www.weather.gov/ffc/20110427_svrstorms

https://en.wikipedia.org/wiki/Tornado_outbreak_of_April_14%E2%80%9316,_2011

https://www.spc.noaa.gov/exper/archive/event.php?date=20110415

https://www.spc.noaa.gov/products/exper/day4-8/archive/2011/day4-8_20110419.html

https://www.spc.noaa.gov/products/exper/day4-8/archive/2011/day4-8_20110420.html

https://www.spc.noaa.gov/products/exper/day4-8/archive/2011/day4-8_20110421.html

https://www.spc.noaa.gov/products/exper/day4-8/archive/2011/day4-8_20110422.html

https://www.spc.noaa.gov/products/outlook/archive/2011/day3otlk_20110423_0730.html

https://www.spc.noaa.gov/products/exper/day4-8/archive/2011/day4-8_20110423.html

https://www.spc.noaa.gov/products/outlook/archive/2011/day2otlk_20110424_0600.html

https://www.spc.noaa.gov/products/outlook/archive/2011/day2otlk_20110424_1730.html

https://www.spc.noaa.gov/products/outlook/archive/2011/day3otlk_20110424_0730.html

https://www.spc.noaa.gov/products/exper/day4-8/archive/2011/day4-8_20110424.html

https://gis.ncdc.noaa.gov/maps/ncei/radar

https://mesonet.agron.iastate.edu/current/mcview.phtml?prod=usrad&java=script&mode=archive&frames=600&interval=5&year=2011&month=4&day=24&hour=0&minute=0

https://www.spc.noaa.gov/exper/archive/event.php?date=20110424

The post Remembering the 2011 Super Outbreak: April 14-24 “A Relatively Widespread/Multi-Round Severe Threat is Expected” appeared first on Force Thirteen.

Current Information

As for 11am PHT (11pm EDT), Surigae was located at 10.9N 130.8E or about 544km (338mi) from Bising or about 549km (341mi) from Surigao both of which are on Mindanao Island. Winds are estimated to be at 233kph (145mph) making it a powerful category 4 hurricane with a pressure of 936mb moving WNW at 24kph (15mph). This storm was actually not expected to intensify this quickly as yesterday at this time the storm was expected to be a category 2 in 24 hours but it has since exploded in intensity becoming a category 2 12 hours later and steam rolling for the next 12 hours to becoming a category 4. Further strengthening is expected and this storm will likely become a Super Typhoon with in next few days. After this the storm is expected to slow down in speed and intensity before moving to the Northeast and losing tropical characteristics.

Uncertainty in Track

Models are in strong disagreement of what this storm will do. The GFS has the most central forecast and shows the storm brushing the coast of the Central Philippines while delivering hurricane force winds before turning east and heading out toward sea. Meanwhile the EURO is the most aggressive model showing the storm also deliver hurricane force winds to the coast but then moving North and making a powerful landfall on Luzon Island near areas already affected by Typhoon Goni just over 5 months ago. This would have major affects including possibly major hurricane force winds and heavy rain as it shows the stalling there for over 24 hours. The CMC and ICON are the exact opposite and instead shows tropical storm force winds affecting the Central Philippines before the storm curves East and out to sea. Finally, he NAVGEM has a similar solution to that of the EURO but shows an overall weaker system which should be watched closely.

In conclusion, Surigae is expected to be a very powerful typhoon in the coming days. Although the track forecast is uncertain, the intensity forecast is not. Persons along the whole eastern Philippine’s should watch this storm and prepare for potential tropical storm and hurricane impacts. Listen to local weather authorities for the latest details and follow Force 13 and Force 13 Philippines for up-to-date information. Be prepared and most importantly, be safe.

The post Surigae Rapidly Intensifies into a Category 4 Typhoon, Potential Impacts in The Philippines appeared first on Force Thirteen.