Madagascar Braces for Extreme Rains From Category 2 Tropical Cyclone Enawo

Dangerous Category 2 Tropical Cyclone Enawo was plowing westwards at 6 mph on Monday morning towards Madagascar, and is expected to make landfall on the island on Tuesday morning. The storm is passing over waters of 29°C—approximately 0.5°C above average in temperature—and is an unusually wet storm, with amounts of water vapor near the very high end of what is observed in tropical cyclones (precipitable water values up to 3.0 inches.) Recent runs of the HWRF model (Figure 2) have shown some very worrisome amounts of rain falling on heavily populated regions of Madagascar, and Enawo has the potential to be a top-five most damaging storm in the island’s history. With warm waters, moderate wind shear of 15 - 20 knots, and plenty of moisture available, intensification into a Category 3 storm appears likely on Monday afternoon and evening, before interaction with land knocks the intensity of the storm back to Category 2 at landfall on Tuesday.


Figure 1. Visible MODIS image of Enawo taken at 10:10 UTC (5:10 am EST) Monday March 6, 2017. At the time, Enawo was a Category 2 storm with 105 mph winds. Image credit: NASA.

According to the 7 am EDT (12 UTC) Monday bulletin from the official cyclone forecasting agency for the Southwest Indian Ocean, Metro France on La Reunion, Antongil Bay in northeast Madagascar is likely to undergo a significant storm surge of 3-4 meters (10-13 feet) near Maroantsetra, but only 1 meter south of Antalaha.


Figure 2. Predicted storm-total rainfall amounts for Tropical Cyclone Enawo from the 06 UTC Monday (1 am EST) March 6, 2017 run of the HWRF model. Rainfall amounts in excess of 16 inches (orange colors) are expected in many areas of Madagascar, with 4 - 8” expected near the capital of Antananarivo (population 1.6 million).

Enawo is the strongest tropical cyclone in the Southern Hemisphere so far in 2017. It has been an unusually quiet tropical cyclone season in the Southern Hemisphere this year, as we discussed in detail in a February 28 post.

Madagascar’s cyclone history
According to NOAA’s Historical Hurricane Tracks website, Madagascar has been struck by twelve major (Category 3 or stronger) tropical cyclones since 1983. The deadliest of these was Tropical Cyclone Gafilo, which hit the island on March 7, 2004, as a Category 4 storm with 150 mph winds. Gafilo killed 363 people; damage was estimated at $250 million, the fifth costliest natural disaster on record in Madagascar. The island’s costliest storm was Tropical Storm Emilie, which caused devastating flooding on February 1, 1977 of $1.4 billion (2017 dollars.) The strongest cyclone to hit Madagascar was Cyclone Hary, which brushed the northeastern coast of the island on March 10. 2002, as a Category 5 storm with 160 mph winds. Hary was a small storm, and caused four deaths and relatively little damage in Madagascar.


Figure 3. Tracks of all major (Category 3 and stronger) tropical cyclones to make landfall in Madagascar, 1983 - 2016. Image credit: NOAA’s Historical Hurricane Tracks website.

There is an enhanced risk of severe weather over Missouri and portions of neighboring states on Monday afternoon, and Bob Henson plans to have an update on this potential in a post later today.

Jeff Masters