Cyclone Idai Remains a Big Threat to Mozambique

Cyclone Idai, still located in the Mozambique Channel, is now an Intense Tropical Cyclone with maximum 1-minute sustained winds of 120mph (195kph). With 6 other ITCs forming so far this season, the 2018-19 Southwest Indian Ocean cyclone season has now produced more ITCs than any other season previously, surpassing the 2006-07 season.

Idai’s center is currently situated about 95mi off the coast of Madagascar, delivering intermittent squalls with heavy rainfall and gusty winds, along with rough seas. Idai was rapidly strengthening earlier today, strengthening from 80mph to 120mph in 18 hours, but has since leveled off and has potentially weakened slightly. This is most likely due to upwelling, as the storm has been sitting over the same general waters for about 2 days due to weak upper-level steering currents. As a result, convective tops have cooled and the eye has become less defined with time.

Idai at 2045 UTC 11 March west of Madagascar. (RAMMB)

The storm has slowly begun to move towards the southwest as a ridge to the south begins to build once more. As the storm moves away from the Madagascan coastline, it will begin to encounter a more favorable environment, featuring warmer ocean waters and low wind shear. The only potential hinderance to the storm could be dry air brought in off the African Continent, which could disrupt the inner core. Intensification over the next several days is likely to be gradual as a result as Idai moves towards the west. By Thursday, the cyclone is likely to make landfall along the central Mozambique coast north of Beira as a category 3 cyclone with winds of between 120mph (195kph), after peaking as a moderate category 4 cyclone. Afterwards, the storm would move inland and weaken, but some longer-range forecast models indicate it could reemerge over the Mozambique Channel and possibly restrengthen as it dives southwards, but this would not occur for another week.

JTWC forecast track and intensity for Idai as of 1800 UTC March 11.

If Idai were to make landfall as the forecast indicates, then it would rival some of the strongest storms to ever impact the country. Along the immediate coastline to the south of the center, high storm surge on the order of 5 to 8 feet (~1.5-2.5 meters) could occur in some areas. This would inundate multiple coastal structures and cause flooding well inland. Strong winds will likely knock out power and down trees across a wide swath of land. However, heavy rainfall and flooding are the primary threats. In most locations, rainfall totals could exceed 25cm, with isolated areas possibly receiving 40-50cm. This can create flash flooding that is both dangerous and life-threatening. The primary areas of concern are areas in and around central Mozambique, but surrounding areas should watch out for possible impacts by this weekend.