September 15, 2013 - Tropical Storm Humberto (09L) off West Africa
On September 11, 2013 Tropical Depression 09L had strengthened enough to become the first storm of the year to reach hurricane status over the eastern Atlantic Ocean.
The depression strengthened to tropical storm strength on September 10, then received the name of Hurricane Humberto at the first report of the National Hurricane Center (NHC) the next day. At that time the hurricane was located about 310 mi (500 km) west northwest of the southernmost Cape Verde Islands and carried maximum sustained winds of 75 mph (120 km/h).
Humberto’s winds peaked at 85 mph (137 km/h) later that same day, and continued at that strength through September 12 before the storm began to weaken. By the morning of September 13 local wind shear was having its effect on the storm, and Hurricane Humberto’s winds had begun to diminish. By 1500 UTC (11:00 a.m), Humberto had weakened to tropical storm status, with maximum sustained winds of 65 mph (105 km/h).
On September 14, Humberto had reached post-tropical cyclone status, with winds at 40 mph (65 km/h). According to the NHC, that morning the storm maintained a large and well-defined circulation, but had been without organized deep convection for at least 24 hours. They predicted that very strong wind shear, dry air and a track over marginally warm sea surface temperatures could result in a spin-down of the storm during the next day or two. However, Humberto may later regenerate into a tropical cyclone as it moves over warmer water and away from the wind shear.
The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite captured this true-color image of the strengthening storm on September 10, as it was nearing hurricane strength. Near that time Tropical Storm Humberto carried maximum sustained winds near 65 mph (100 km/h) and was located west of the Cape Verde Islands. It was moving west northwest, away from the islands, and stayed over open water through September 14.