Tropical Cyclone Giovanna powered ashore along the east coast of Madagascar as a destructive Category 3 storm with 125 – 130 mph winds at 22 UTC last night. Winds at the coastal city of Tamatave, 70 miles north-northeast of where the center came ashore, peaked at 52 mph, gusting to 71 mph. Giovanna is moving west across the island at 17 mph, and passed just south of the capital of Antananarivo as a Category 1 storm at 8 am local time Tuesday morning. The eyewall missed Antananarivo , and the peak winds in the city were 38 mph, gusting to 55 mph. Microwave satellite imagery from the Navy Research Lab in Monterrey showed that Giovanna had rainfall rates of up to one inch per hour at landfall, and it is likely that the storm dumped 5 – 10 inches of rain along much of its path. The heaviest rains fell on deforested mountain slopes that drain into some of the most densely populated regions on the island, so major flood damage is likely. Heavy wind and storm surge damage undoubtedly occurred where the core of the storm hit the island, as well.

Figure 1. Visible image from NASA’s Terra satellite of Tropical Cyclone Giovanna over Madagascar, taken at 7:15 UTC Tuesday February 14, 2012. Seven hours previous to this time, Giovanna was a Category 2 storm with 110 mph winds, but had probably weakened to a Category 1 storm by the time this picture was taken. Image credit: NASA.

The forecast
Passage over the rugged terrain of Madagascar has significantly weaken Giovanna, and the cyclone will move into the Mozambique Channel between Madagascar and Mozambique as a tropical storm later today. Latest computer model forecasts from the GFS and ECMWF models suggest Giovanna may reintensify over water, and swing around and pass very close to the south tip of Madagascar early next week. Meanwhile, Madagascar must also keep an eye on Tropical Cyclone Thirteen, which is gathering strength over the waters to the east of the island, and is on a course that will bring it close to Madagascar this weekend.

Figure 2. Microwave satellite image of Tropical Cyclone Giovanna taken at 02:44 UTC Tuesday, February 14, 2012. The cyclone was still a well-organized Category 2 storm at this time, five hours after landfall. Image credit: Navy Research Lab, Monterrey.

Jeff Masters