Watch our official 100K Milestone video here with an introduction and presentation by our founder, Nathan Foy: https://www.youtube.com/watch?v=oNaOGccTzmc

The post Force Thirteen’s 100K Milestone appeared first on Force Thirteen.

Five years ago today, on August 25th 2017, Major Hurricane Harvey ended the twelve-year US major hurricane landfall drought, bringing devastating impacts across parts of Texas and Louisiana during the 2017 Atlantic Hurricane Season.

A historic storm, Harvey made landfall near Rockport, TX as a powerful category four hurricane with winds of 130mph, and a pressure of 934 millibars at 10pm CDT on the 25th.

Despite Harvey’s impressive intensity, the greatest threat from the storm became record-setting rainfall, which resulted in incredible totals, as some areas recorded fifty inches of rain.

As of 2022, Hurricane Harvey still remains as one of the costliest natural disasters in US history, with a price tag estimated at $134 billion.

Sadly, 89 lives were lost during the disaster.

Five years later, the storm serves as a poignant reminder of the power of mother nature, as well as the inevitability of natural disasters.

Storm Synopsis

Despite most, if not all, damages caused by Hurricane Harvey being located in Texas, Louisiana and surrounding areas, Harvey developed over 2,500 miles away from the coast of Texas, developing from a tropical wave in the main development region on August 18th.

As a weak tropical storm, the storm moved west and made two landfalls, one in Barbados and the other in St. Vincent island, both as a moderate tropical storm.

Minor impacts were dealt to the islands as the storm continued to drift west, eventually dissipating into a remnant low on the 19th.

For four days, the remnants of Harvey continued to drift west, crossing the Yucatan on the 22nd and 23rd.

As the storm crossed, the National Hurricane Center marked the possibility of redevelopment from the disturbance as it entered the Gulf of Mexico.

As the storm re-emerged off of the coast of the Yucatan, the storm slowly began to recover tropical storm characteristics, and gained Tropical Storm status during the early hours of the 24th, with a forecasted tropical storm landfall in Texas.

However, Harvey had other plans, and began to rapidly intensify on the 24th, quickly becoming a hurricane during the afternoon, only 12 hours after it had regained tropical storm status.

Intensification of the storm continued further, as the storm gained major hurricane status the next day on the 25th, hours prior to landfall.

Harvey’s rapid intensification stage is of great note, as the storm continually intensified up until the landfall in Rockport, Texas, a relative rarity of tropical systems.

Government officials and media outlets, including Force Thirteen began emphasizing the dangerous nature of the storm, as Hurricane Watches and Warnings were put in place, as evacuation orders were mandated by state and local officials.

As a whole, Force Thirteen held over thirty hours of coverage from Harvey’s redevelopment to the devastating impacts as the storm trudged through Texas.

However, as Harvey made landfall, it became apparent; if it had not been, that the storm would be historic.

Harvey’s intense wind field delivered catastrophic damage across South Texas, resulting in significant structural damage and tree damage for towns in the eyewall, such as Port Aransas and Rockport.

Despite intense winds, the greatest threat from the storm ultimately proved to be flooding rains, which exceeded over five feet in some locations as the storm stalled over Central Texas.

As a result of two to three feet of rain, significant flooding occurred, resulting in the damage of over 200,000 homes and businesses.

Ultimately, Hurricane Harvey is considered to be a historic hurricane for a multitude of reasons, from its incredible intensification to the heart-breaking damages occurred by the storm’s wrath in Texas and Louisiana.

Harvey was ultimately retired from the naming list, being replaced with Harold which will be used in 2023.

Five years on, Harvey is still a fresh memory in the eyes of many Texans, and will be for many years to come.

Force Thirteen’s Report

For more in-depth information, you can watch Force Thirteen’s full report on Hurricane Harvey using this link: https://youtu.be/pk6k9kMfGVk

The post Remembering Hurricane Harvey Five Years Later appeared first on Force Thirteen.

On this day in 2012, Intense Tropical Cyclone Funso peaked in the Mozambique Channel.

Unofficial Force Thirteen analysis indicates Funso’s peak to have been with winds of 145 mph (1-min sustained) and a pressure of 925 hPa (mbar).

Funso was the first storm since Cyclone Jokwe (2008) to impact Mozambique, and was the strongest tropical cyclone of the 2011-12 Southwest Indian Ocean Cyclone Season.

Cyclone Funso is remembered primarily due to its erratic track in the Mozambique Channel.

The cyclone had also came to a crawl at one point prior to peak and spent several days meandering off the coast of Mozambique.

Even though Funso never made landfall, over three million people were still affected by the storm’s gale-force winds.

A total of 12 lives were lost in the Zambezia Province, and further impacts were also recorded in the Inhambane Province.

The Movene River, the main water source for residents of Maputo, had risen at a substantial rate.

Funso is also responsible for providing flooding across the Incomati River.

In neighboring Malawi, heavy rainfall was also recorded.

Two rivers exceeded their banks causing floods that destroyed roads and bridges between Blantyre and Nsanje.

This resulted in at least 30 villages becoming isolated.

Cyclone Funso continued a series of flooding events that had been occurring throughout Southern Africa in 2012.

The flooding itself had begun with an enhanced monsoon, but then, Tropical Storm Dando struck the country and worsened the flooding by a large margin.

When Cyclone Funso stalled off the coast, the flooding was prolific enough to unfortunately claim the lives of up to 40 people.

Funso also became one of the first storms to be animated by Force Thirteen – With this animation coming out almost 10 years ago!
Watch Here: https://youtu.be/e-jWU7In2VQ

The post On This Day – January 25th: Cyclone Funso appeared first on Force Thirteen.

Hurricane Sandy will be remembered for decades as a very unusual storm, with its huge size and disputed tropicality all the way back to its passage near the Bahamas.

Of course, it cannot be forgotten that the storm also made a hurricane landfall on Jamaica and a major hurricane landfall in Cuba, before it devastated the northeastern United States.

It will also be remembered in meteorological circles for the National Hurricane Center’s paralysis in issuing watches and warnings beyond North Carolina, due to the storm’s transition to extratropical status.

This pedantry caused much confusion in the wider world, and one could suggest that many at the NHC were desperate to make exceptions, but protocol at the time didn’t allow it.

We know of course that these rules were changed after Sandy, and the National Weather Service had out all the relevant warnings relating to an extratropical cyclone when it made landfall.

Awareness and Criticism

High Wind Warnings and Flood Warnings littered the Mid-Atlantic and the northeast, but some still didn’t take it as seriously as they would a hurricane watch or warning.

Hurricane Sandy’s enormous wind-field caused maximum impact when it made landfall in New Jersey, with impacts extending over many adjacent states and beyond to the whole region, with damages reaching around $75 billion – the second highest ever total at the time behind Hurricane Katrina.

Meanwhile in the United Kingdom, mute one-man show Nathan Foy was scheduled to have a Monday-Friday vacation in the south of England during the storm.

Early updates were created easily and efficiently, even though by today’s standards they are pretty poor. Internal communications also reveal that Nathan criticised the British news media for publicising Hurricane Sandy as “Frankenstorm”.

“Oh for goodness sake. Now the British news agencies are calling Sandy “Frankenstorm”, coined by the American media. They named storms since 1950 for a reason. The name’s Sandy!”

But a point of realisation came about where it was becoming plain that this would be a severe impact whether tropical or not, and that he would have to either sit out the vacation or sit out Sandy.

A Holiday Cut Short

Things got worse when Sandy reached Category 2 hurricane status as it started to execute its terminal turn towards the United States in the subtropics.

Landfall was slated for Monday evening, October 29, right around the time that Nathan and company would be settling in after driving six hours across the country.

The journey began at 12:15pm, and ended at 5:30pm, with good traffic along the way. At this point, Hurricane Sandy was now 8 hours from landfall.

And so, the source of the below photo comes from hurriedly setting up the computer in an isolated cabin in Cornwall, to produce the biggest update of Hurricane Sandy’s life – the one where it was about to make landfall and unleash its widespread damage and storm surge.

The video was made as normal on the computer, however the only free power point was along a wooden bench, with no desk for a monitor.

Making the video was only one part of the project, however, as the cabin had no internet reception.

Nathan was also prepared for this, and had to rush a laptop across to the community hub of the holiday park and use their Wi-Fi to upload the video, after transferring the video via a memory stick.

The vacation in general was a damp squib, with Hurricane Sandy getting in the way and the accommodation having poor heating.

Nathan and his family headed back home on October 31, only three days into the five day trip.

Links:

The video that was produced from the holiday cabin:
https://youtu.be/7Z24AvnOn20

The Track of Hurricane Sandy (created in 2020):
https://youtu.be/ASr7Vrb04lc

The post 9 Years Since the Hurricane Sandy Kerfuffle appeared first on Force Thirteen.

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.

The post Major Hurricane Irene: A Decade Later appeared first on Force Thirteen.

It’s been 13 years since Typhoon Frank (Int’l name Fengshen) brought catastrophic damage to the Philippines, and caused the sinking of the M/V Princess of the Stars on June 21st, 2008, off the coast of central Sibuyan Island, Romblon Province.

The storm peaked as a 195 kph (120 mph) typhoon with minimum central pressure of 960 millibars and caused torrential rain that led to widespread flooding, forcing people onto their rooftops and seek refuge in public shelters.

Storm Synopsis

Fengshen formed east of Mindanao on June 18th and was designated as Tropical Depression 07W and received the local name “Frank.”

It slowly moved northwest and intensified as Tropical Storm “Fengshen” in the 19th.

The storm then moved West-Northwest and intensified into a Typhoon before making landfall in Llorente, Eastern Samar and continued to intensify after landfalls over Biliran.

Moving into the Visayan and Capiz Seas, Frank peaked as a Category 3-equivalent Typhoon.

It then moved North-Northwest and made landfall over Romblon and made its last landfall in the Philippines over the Quezon Province.

Frank then weakened to a Tropical Storm as it emerged into the South China Sea, made landfall near Hong Kong, and became a remnant low and then dissipated by June 27th.

The Aftermath

Frank caused ₱13.525 billion ($327 billion) in damages with 557 people dead, 87 missing, and 826 injured in the wake of the storm (excluding the fatalities on M/V Princess of the Stars).

The storm affected about 4.8 million people and caused 326,321 partially/totally damaged homes.

The name “Frank” was retired and was replaced by Ferdie. The WMO Typhoon Committee did not retire the international name Fengshen.

M/V Princess of the Stars

The ferry M/V Princess of the Stars deported from Manila on June 20th, even though Frank already made landfall over Samar Island.

It was permitted to sail because “it was large enough to stay afloat in typhoon’s periphery.”

With the unexpected movement of the storm, the ferry sailed into the eye of the storm.

By 12:55PM PHT, the ship sent a distress signal, then the ship lost radio contact.

A total of 814 people dead and missing and only 56 known survivors.

A months long body recovery operation took place, where only 312 bodies have been recovered.

A full report of Typhoon Fengshen can be found here:
https://reliefweb.int/sites/reliefweb.int/files/resources/AF08756A504E59A48525749700629D7A-Full_Report.pdf

Article written by Justine, formatted by Preston Schenk.

The post Remembering Fengshen: 13 Years Later appeared first on Force Thirteen.

Mount Pinatubo erupted multiple times from 1991 and 1992, causing one of the most historical and devastating volcanic eruptions of the 20th century, coupled by a typhoon that further amplified its devastation.

But how did people find out that it was a volcano?

How did people respond to the impending volcanic threat?

How often can this type of eruption occur?

And what can we learn from this monster of a volcano?

It all started back in early 1991 where the indigenous Aeta Negrito tribal communities lived on the slopes of Mount Pinatubo.

The Aetas believed that one of their deities, Apung Malyari, lives in Mount Pinatubo, and they felt that it was their duty to guard the mountain.

First Signs

On August 3rd, 1990, 2-3 weeks after the 1990 Luzon earthquake that struck Cordillera and devastated many people’s livelihoods, ground fracturing and steam emissions were reported by residents of Sitios Tarao and Yamut on the upper slopes of Mount Pinatubo.

This event signalled magmatic or hydrothermal activity yet no one thought that this would lead to an eruption at the time.

On March 15th, 1991, the Aetas, on the lower north-western flank of Pinatubo, felt earthquakes that could have originated from Mount Pinatubo.

Then in the following month of April 2nd, steam explosions, coming from the mountain, were witnessed by many within the tribal community.

Two days later on April 4th, Sister Emma Fondevilla of LAKAS reported these explosions to the Philippine Institute of Volcanology and Seismology (or PHIVOLCS); she also reported felt earthquakes and a strong sulfur odor during and after the explosions.

The series of explosions and the strong sulfur odor caused some residents of villages at the northwest, west, and southwest slopes of the volcano to evacuate voluntarily.

PHIVOLCS began to become more concerned regarding these reports, but could they trust the accounts of a people who believed in make believe deities living in the mountain?

Punongbayan’s Assessment

PHIVOLCS, under the guidance of one of the world’s best volcanologists Raymundo Punongbayan, deployed scientists to install seismographs near Mount Pinatubo to determine whether these accounts were true.

In the first 24 hours after the seismographs were deployed, more than 200 small and high-frequency earthquakes were recorded.

These were not your average tectonic earthquakes, these were volcanic earthquakes.

On April 7th, PHIVOLCS stated that Mount Pinatubo was a volcano and that its condition was unstable.

A 10 km danger zone around Pinatubo’s summit was created.

Around 5,000 indigenous Aetas were evacuated from the volcano due to the enforcement of the danger zone, yet some stayed as they felt that leaving would be like betraying their deity, Apung Malyari.

Frequent Earthquakes and Reconnaissance

Throughout the months of April and May, around 30-180 high frequency earthquakes occurred per day and the volcano’s condition remained unstable.

Around late April, a team from the USGS joined PHIVOLCS at an apartment in Clark Air Base.

This apartment would later be known as the Pinatubo Volcano Observatory (PVO).

Reconnaissance was sent by the PVO to look at the magnitude of past eruptions and this provided an insight into the behavior of Pinatubo: large explosive eruptions separated by repose periods lasting millennia.

Three most recent major eruptions happened around 500, 3k, and 5.5k years ago.

Daily bulletins and special advisories were provided about Pinatubo throughout the entirety of the unstable condition of the volcano.

Alert Levels and Magma Activity

On May 13th, 1991, PHIVOLCS released Alert Levels for Pinatubo, which they have done for other volcanoes like Taal.

These Alert Levels range from 1-5, depending on the activity of the volcano.

Alert Level 2 was issued on the same day, meaning probable magmatic intrusion that could eventually lead into an eruption.

The 10 km danger zone was reiterated with this Alert Level being raised.

The earthquakes around the volcano remained relatively shallow and less than Magnitude 2.5.

These earthquakes were too small to be felt except by people near the areas where the earthquakes were.

Meanwhile, sulfur dioxide emissions began rising near the summit from 500 tonnes/day on May 13th to more than 5,000 on May 28th.

The data at the time suggested that the magma beneath Pinatubo was going in a more shallow area sufficient for substantial degassing of toxic volcanic gas.

An electronic tiltmeter was installed on the eastern flank of the volcano during late May.

The month of June arrived and on June 1st, a second swarm of shallow earthquakes was recorded around the area of fuming vents.

These earthquakes signalled rising magma trying to forcefully open a conduit between Pinatubo’s magma reservoir underneath and the surface.

The rate of SO2 emissions had also dropped from 1,800 tonnes/day on May 28th, to 260 on June 5th.

This may have signalled that the passages where the gases were getting out of were getting sealed, and that rapidly increasing pressurization and an imminent explosive eruption might ensue.

On the evening of June 3rd, a small explosion rocked Pinatubo with an increasing level of unrest characterized by increasing seismicity beneath the vents, harmonic tremor, minor emission of ash, and a gradual outward tilt on the tiltmeter in the volcano’s eastern flank.

After 2 days, Alert Level 3 was raised for Mount Pinatubo signalling that an eruption is possible within 2 weeks.

The 10 km danger zone was still maintained for the volcano.

The electronic tiltmeter on the eastern flank of Mount Pinatubo had accelerated outward tilt at noon June 6 along with increased seismicity until June 7 when increased emission generated a column of ash and steam around 7 to 8 km high.

After that, seismicity had decreased and the accelerated outward tilt had stopped.

PHIVOLCS then announced Alert Level 4 which meant that an eruption was possible within 24 hours.

The danger zone was extended to 20 km and included more civilians to be evacuated.

The outward tilt and the shallow seismicity suggested that a shallow conduit was being developed in order to be transported to the surface.

This was confirmed when witnesses the next morning saw a 50m-100m diameter lava dome northwest of the summit.

Aerial observations, despite extremely poor visibility due to venting steam and tephra, indicated that the lava dome had kept expanding until June 11.

Volcanic Escalations and Military Evacuations

The south-eastern section was destroyed by vertical eruptions on June 12-14.

The dome margin, despite destruction, had continued to expand westward.

The last time it was seen (June 14, a day before the cataclysmic and climactic eruption), the dome was flat-topped and spanned the upper Maraunot River valley.

This expansion may have been caused by continued extrusion or post-extrusion flowage as the dome lava continued to move downwards under gravity.

The period from June 8 to early June 12 was marred with increased ash emissions from Pinatubo, more swarms of shallow earthquakes beneath the dome, and continued episodes of harmonic tremor.

The wind carried the ash plume westward.

At times, dilute ashy density currents flowed down the upper Maraunot valley.

These dilute ashy density currents resembled ash clouds commonly associated with pyroclastic flows, but they never coincided with seismic explosion signals nor had any recognizable flowage deposits marking their tracks.

PHIVOLCS, seeing the continued escalation of volcanic unrest and observation of these dilute ashy density currents had prompted them to raise Alert Level 5 on June 9th meaning that an eruption was in progress.

On June 10th, 14.5k American military personnel and other relatives had evacuated Clark Air Base and travelled to Subic Bay Naval Base.

All remaining aircraft except 3 helicopters had also left Clark in the same day.

Around 1.5k American and nearly the same amount of Filipino troops had remained behind to provide base maintenance and security.

The PVO had remained the base however moved their headquarters to a building 25 km away from the summit near the east end of Clark Air Base.

They had continued monitoring Pinatubo’s unrest from there.

Tremors and Eruptions

A large burst of intense seismic tremor had occurred on June 12 at 3:10AM.

High magnitude tremor persisted for around 40 minutes.

Although the magnitude gradually had decreased, it had returned back to background level more than 2 hours after it began.

A small eruption signal with an onset time of 3:41AM (noting that seismic-drum records had recorded uncorrected local time) had been embedded in the tremor episode.

No tephra fall was reported during this signal, however this could have coincided with increased ash emission.

As the sun rose, a plume of steam and ash had been rising 3 kilometers above the volcano, higher than what had been observed during the past few days.

Aerial observations had shown that small pyroclastic flows had coursed down the uppermost Maraunot and O’Donnell drainages which had spawned small lahars.

Meanwhile in the Philippine Sea, a Tropical Cyclone Formation Alert had been issued for a tropical disturbance that would later be known as Typhoon Yunya.

A major explosive eruption had occurred at 8:51AM.

Seismicity had increased in just a few seconds from a low-amplitude tremor to a high-amplitude signal that had saturated records of all seismic records.

The high-amplitude signal and rise of the eruptive column had began simultaneously.

Ash from this eruption had been transported southwestward past communities north of Subic Bay, and a small pyroclastic flow travelled northwest from the vent in the headwaters of the Maraunot River.

This was the first and the longest out of four eruptions that had been occurring from June 12-14, 1991.

The others had occurred at 10:52PM at the same day, 8:41AM at June 13, and 1:09PM at June 14.

Ground-based observers at Poonbato had reported seeing pyroclastic flows at each of the 3 daytime eruptions and low tephra plumes have been seen over the vents following the 8:51AM June 12 and the June 13 eruptions.

Explosion plumes seen from the air along the upper 5 km of the Maraunot River valley after the 8:51AM June 12 eruption provided indirect evidence of new pyroclastic-flow deposits, but poor visibility prevented direct observation of the deposits themselves.

Another observation flight shortly before the 1:09PM June 14 eruption documented new pyroclastic-flow deposits in the upper Maraunot valley.

Later ground-based observations about 3.5 km downstream from the position of the 1991 dome showed deposits of only two pyroclastic flows beneath the June 15 deposits in the Maraunot valley.

The Danger Zone Extension

On June 14, the danger zone had been extended to 30 km and the number of evacuees had increased to 85k.

600 of the 1.5k remaining American soldiers at Clark Air Base had been evacuated.

North-easterlies had prevailed during the eruptions which had caused tephra to fall southwestward across Subic Bay and nearby communities.

No tephra had been recorded in Clark Air Base.

Unlike the initial eruption at 8:51AM on June 12, the eruptions at 10:52PM on June 12 and 8:41AM on June 13 were preceded by 2-4 hour swarms of long-period earthquakes which made it easier for the PVO to issue explicit warnings in advance.

The resumption of this pattern during the evening of June 13 had suggested that another eruption would be imminent however none occurred as expected.

The pattern had changed to one where long-period earthquakes had continued hour after hour.

A sequence of 13 explosive eruptions began shortly after the 1:09PM eruption on June 14 and continued for nearly 24 hours.

These became more closely spaced as time progressed and apparently reflected pyroclastic-surge production.

Tropical Cyclone Yunya

Meanwhile, Yunya had rapidly organized and became a Category 3 typhoon east of Luzon.

However, strong wind shear had continued to weaken this small system and once it made landfall, it became a minimal typhoon and weakened into a tropical storm once land interaction occurred.

Deteriorating weather conditions related to the approach of Typhoon Yunya obscured the view of Mount Pinatubo from Clark Air Base so that only one of these events (at 5:55AM June 15) was seen directly from Clark.

Several were seen, however, by observers to the northwest at Poonbato and to the north at Camp O’Donnell.

In addition, two night eruptions (11:20PM on June 14 and 1:15AM on June 15) were recorded by an infrared-imaging device at Clark Air Base.

All views were of large pyroclastic density currents sweeping the volcano’s flanks.

The Big Event

The cataclysmic and climactic eruption occurred at 1:42PM and had initiated continuous high-amplitude tremor and had initiated 9 hours of atmospheric pressure variation and ash with pumice fragments as large as 4 cm in diameter that was falling at PVO.

A 40-km wide danger zone had been in place, the highest that has ever been placed by PHIVOLCS during the 1991 Mount Pinatubo eruption- This included 17 towns.

The PVO team and the rest at Clark Air Base were forced to evacuate at around 3:00PM in pitch black darkness.

Large earthquakes had occurred varying from Magnitude 4.3 to 5.7. These earthquakes may have recorded caldera formation.

There have been 29 of these earthquakes within the first 6 hour period of the eruption.

The eruption cloud expanded to 400 kilometers wide at around 3:55PM and shadow measurements around the white clouds suggest that the altitude was about 25 kilometers at the eastern edge and 34 kilometers at the center.

Mount Pinatubo’s present caldera had formed from around 4:30PM when volcano-tectonic activity had increased to 10:30PM when the climactic eruption ended.

The PVO team went back to Clark Air Base and re-established seismic monitoring at June 16.

The seismicity of the volcano had decreased for the next 2 months.

The climactic eruption left open a vent system where ash kept billowing in the caldera for another month.

Plumes at times reached 18 to 20 kilometers tall. Winds caused significant ashfall, especially southwest and northeast of the new caldera.

Alert Levels have been downgraded gradually from Alert Level 2 as the volcano was reeling from its climactic eruption.

Disruption

Mount Pinatubo’s lahars have caused severe economic and social disruption.

It has kept striking Central Luzon during the SW monsoons of 1991 and 1992.

Numerous secondary explosions occurred during the 1991 and 1992 monsoon seasons from the interaction of water with hot pyroclastic-flow deposits.

A lava dome formed within the new summit caldera from July through October 1992.

Its emplacement was heralded by increasing earthquakes and tremor in early July.

By July 9, explosions near the center of the caldera lake had built a low pyroclastic cone that was about 70 to 100 m across and extended 5 m above the lake surface.

Alert Level 3 was raised by PHIVOLCS with a 10-km danger zone.

Lava extrusion had ensued, by July 14, a lava dome was about 5 to 10 meters high and 50 to 100 meters in diameter which had grown in the pyroclastic cone that had widened to 150 meters.

Alert Level 5 was raised while maintaining the 10-km danger zone.

By July 23, the lava dome had buried the pyroclastic cone.

Dome growth continued through October marked by the formation of a succession of extrusive lobes and accompanied by intense swarms of shallow earthquakes.

A sharp drop in seismicity in October 31 had marked the end of the 1992 lava dome growth.

The Alert Level was downgraded to 2 on December 9th of 1992, maintaining the 10-km danger zone.

In Summary

The 1991 eruption of Mount Pinatubo was the world’s largest in more than half a century and probably the second largest of the century.

Its roughly 5 km3 of erupted magma is an order of magnitude greater than the volume of magma erupted in 1980 from Mount St. Helens but is smaller than the 13+-3 km3 of ignimbrite and fall deposits from the 1912 eruption of Novarupta, Alaska.

Pinatubo measured VEI 6 on the Volcanic Explosivity Index.

Usually eruptions like what happened with Pinatubo happen every 50-100 years.

Due to the volcanologists’ efforts to get people to safety, thousands of lives have been saved from what could have been a very worse fate.

Unfortunately hundreds have still perished due to the raining ash and toxic gas around the volcano.

We can learn to continue improving our response to future eruptions by keeping track of the activity of active volcanoes, listening to our local volcanology agency, and preparing for the worst.

Article written by Zenitsu on April 15th, 2021 at 17:54 UTC.

The post Remembering Mount Pinatubo 30 Years Later appeared first on Force Thirteen.

This January has been a fairly active month compared to climatology in cyclone activity, with cyclone development spreading across all three Southern Hemisphere basins: Southwest Indian Ocean, Australian Region, and the South Pacific.

Southwest Indian Ocean

The Southwest Indian Ocean saw the formation of one cyclone, Cyclone Eloise.

Eloise formed on January 14 well to the east of Madagascar, eventually impacting the island as a mid-strength tropical storm.

After clearing the island, Eloise quickly strengthened on its approach to Mozambique, peaking as a Category 2 equivalent storm as it made landfall in Beira with 1-minute winds near 105 mph and 10 minute winds near 90 mph.

Eloise weakened as it moved inland over Africa, dissipating on January 25.

Eloise caused severe damage in Mozambique, with at least 21 deaths reported.

Weather stations in Beira recorded 25cm (10 inches) of rain within 24 hours.

Several rivers burst their banks, causing roads to become submerged in floodwaters.

Additionally, Eloise caused damage and flooding to South Africa, Eswatini, and Zimbabwe, as it weakened across southern Africa.

Australian Region

In the Australian Region, activity was unusually high with the JTWC designating six cyclones: Imogen, Joshua, Kimi, Lucas, 08U, and 12U.

The first four were also classified by the Bureau of Meteorology, the last two being tropical lows by their estimates.

The most notable storms this month in the Australian Basin were Kimi, Lucas and 12U.

With a lifespan ranging from the 16th to the 19th of January, Kimi took a short but unpredictable track in the middle of the month, peaking with both 1 and 10-minute winds of 65 mph.

Despite its proximity to land, no impacts have been reported.

Lucas was the strongest storm to form in the Australian basin this month, peaking at 75 mph in 1-minute winds and 70 mph in 10-minute winds over the South Pacific.

The cyclone formed on January 25, and crossed over into the South Pacific basin on February 1.

Shortly thereafter, Lucas made landfall over New Caledonia as a weakened storm, dissipating on February 3.

Damages are currently unknown, and no deaths have been reported as a result of Lucas.

12U was a very unusual storm that took a winding track along the northern coastline of West Australia, forming over land on January 30 and staying over it for 5 days while maintaining its strength as a tropical depression.

It finally attained tropical storm strength as it approached the coastline and peaked as a 40 mph storm, however it began extratropical transition shortly thereafter and dissipated on February 5.

South Pacific

For the South Pacific Basin, activity was limited to two systems, Ana and Bina.

Ana formed on January 26 northeast of Port Vila, Vanuatu, and began to gradually strengthen.

After several days, Ana made landfall over Viti Levu, Fiji as a Category 1 storm on the SSHWS and a Category 3 on the Australian scale, peaking with 75 mph winds in both scales.

After clearing Fiji, Ana weakened significantly, dissipating on February 3.

Damages from Ana are unknown, with one person confirmed dead and five others still missing as of February 7.

Bina also took a similar track to Ana from January 29-31, with its remnants making landfall just after its dissipation.

Bina peaked with 10-minute winds of 40 mph and 1 minute winds of 50 mph. No significant impacts to land were reported as a result of Bina.

Force Thirteen produces regular updates on our Twitter page and YouTube channel.
Our Cyclone Monitoring Homepage also provides updated graphics and info on cyclones around the world.

The post January 2021 Worldwide Cyclone Summary appeared first on Force Thirteen.

Cyclogenesis

When Odette formed, the depression was still quite small and weak. Weathermodels were suggesting a potential heavy-storm forming from it. On the 25th of December, As the occluded front started spiraling very tightly, the winds got accelerated. Over the next seven hours, she deepened incredibly fast. Creating a strong, but local windfield. This would then aim at the NW of Belgium and the entire province of Zeeland. Cyclogenesis is the process of the formation of an extratropical cyclone and occurs when a warm and a cold front meet. These can start to occlude and form a low-pressure system. A select few of those actually become windstorms.

(Figure 1) A small storm-depression which has formed in the North Sea and has been given the name “Odette” by KMI   Charts: @KNMI

Landfall of the storm

On the 26t-27th of September Odette made landfall in the Netherlands, with the full windfield on Zeeland and northwest Belgium. As Odette came ashore, gusts were reported of over 110 km/h. The winds blew on the coast with such a force, that the whole dune was blown on land and whole parts of beaches were slammed away. (See figure 3). KMI issued a code orange for the coast and West-Vlaanderen. With gales topping the 11 Beaufort, it made the storm earn the title of a very heavy storm. Whole parts of beaches were swept away by the sea. In Hoek van Holland (Netherlands), a wind gust of 114 km/h was reported. In Zeeland, the storm had sustained Beaufort 10 for two hours long. Making it a heavy storm for the Netherlands. The damage caused by Odette was massive because the incredibly strong winds at the low level forced them into a very small area. Due to the English Canal, the Venturi Effect took place. Because of the narrower space to move through, the air got crushed into itself and forced to flow faster. This caused stronger winds in the areas directly impacted. The total damage estimate is still unknown.

(Figure 2) Odette causing a huge swell of the Belgian coast. Photo: @Belga

The Damage

After Odette ravaged through northwestern Belgium and Zeeland, Netherlands, the true extent of the damage became clear. Whole parts of the beach swept away, small beach-houses destroyed. destroyed sailing yachts and small boats, sand blew off the beaches and onto roads of the cities and villages. Trams cannot move due to the sand and cars that are completely buried in the sand. The following set of photos depicts the damage Odette caused.

(Figure 3) Sand has blown all over the road and railway between Oostende and Westende (Belgium)   photo: @Belga
(Figure 4) Cars buried beside the tram line between Oostende and Westende (Belgium)                photo: @Belga

(Figure 5) Small beach houses destroyed by storm Odette  Photo: @Belga
(Figure 6) Dike of Oostende after storm Odette                     Photo: @Belga

Author: Alex R (17 years old Climate Physics Enthusiast, future UU Physics and Climate Physics student)

Date of publishing: 26th of December 2020

The post Windstorm Odette (23-26 September 2020) appeared first on Force Thirteen.

Pongsona was first noticed by the Japan Meteorological Agency on December 2, 2002, and designated as a tropical depression near Pohnpei. It was later designated by the Joint Typhoon Warning Center as 31W, and will later be upgraded to a tropical storm in the next day, being named Pongsona. Pongsona moved to the west due to a ridge, and became a typhoon on December 5.

Pongsona then continued to intensify until it reached its peak intensity on December 8, with winds of 150 mph with a minimum pressure of 910 millibars. The storm then later made landfall on Guam at 05:00 UTC, and then later, the northern part of the system crossed over Rota. The storm then turned to the north-northwest due to a subtropical ridge near the northern Mariana Islands. Pongsona will later then undergo an eyewall replacement cycle, a cycle that will be completed on December 11, 2002.

Pongsona brought destruction to both Guam and Rota, with extensive damage being seen when Guam was inspected after the storm. The island immediately was declared a “major disaster area”, allowing aid to come in the island. In total, the storm got 1 dead indirectly, and caused $370 million 2002 US dollars in damages; if adjusted with inflation, it’s $465.4 million USD on 2020 currency.

Typhoon Pongsona maintained a 65 km (40 mi) wide eye upon crossing the northern portion of the island of Guam; the Andersen Air Force Base was in the eye for two hours. Sustained winds from the typhoon peaked at 232 km/h (144 mph) with gusts peaking at 278 km/h (173 mph); gusts of at least 160 km/h (100 mph) affected the entire island. The lowest pressure on the island was 935 millibars (27.61 inHg), making Pongsona the third most intense typhoon to strike Guam; it is behind only a typhoon in 1900 (926 mbar, 27.34 inHg) and Typhoon Karen of 1962 (932 mbar, 27.52 inHg).

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