On March 15th, 2007, the northeastern coast of Madagascar suffered a direct hit from Indlala, a powerful Category 3 cyclone packing sustained winds estimated at more than 100 mph. The storm made landfall near the coastal town of Antalaha Thursday morning local time. The island nation is still in the process of recovering from its brush with Cyclone Favio back in February.

Indlala started out as a tropical disturbance on the 6th of March 2007 in the central Indian Ocean about 500 miles southeast of Deigo Garcia in the Chagos Archipelago. Over the next few days, this disturbance continued on in a generally west-southwest direction before organizing into a tropical depression on the 10th. During the overnight hours of the 11th, the depression strengthened into Tropical Storm Indlala. By now the system was about 520 miles east-northeast of Madagascar and headed directly for the island. The storm continued to gain strength on the 12th, and by the early morning hours (local time) of the 13th it had become a Category 1 cyclone with sustained winds estimated at 70 knots (81 mph).

The Tropical Rainfall Measuring Mission (TRMM) satellite was placed into low-earth orbit in November of 1997 with the primary mission of measuring rainfall from space; however, it has also proven to be a valuable platform for monitoring tropical cyclones, especially over remote parts of the open ocean. TRMM captured this image of Indlala as it was nearing Madagascar as a Category 1 cyclone. The image was taken at 01:34 UTC (5:34 am local time) on 13 March 2007. It shows the horizontal distribution of rain intensity looking down on the storm. Rain rates in the center of the swath are from the TRMM Precipitation Radar (PR), while those in the outer portion are from the TRMM Microwave Imager (TMI). The rain rates are overlaid on infrared (IR) data from the TRMM Visible Infrared Scanner (VIRS). TRMM shows that Indlala is a fairly well-organized storm. Although the eye is not completely closed as evidenced by the lack of eyewall in the eastern semi-circle (note the incomplete innermost ring), the storm does exhibit excellent banding in the surrounding rain field, which is visible by the tightly-curved bands of moderate (green areas) to heavy (red ares) rain spiraling in towards the center, and is indicative of a well-formed circulation.

Indlala maintained intensity during the day on the 13th as it continued on a course towards to the northeastern coast of Madagascar. However, during the early morning hours of the 14th, the storm entered a rapid deepening cycle and began to intensify quickly. By 10:00 am local time (6:00 UTC) on the 14th, Indlala was packing sustained winds of 100 knots (115 mph). The next TRMM image was taken at 10:29 UTC (2:29 pm local time) 14 March 2007 and shows the powerful cyclone as it was bearing down on the island. The overall rain field is now very symmetric as a result of Indlala's strong circulation with rain bands wrapping completely around the storm. The TRMM PR shows areas of intense rain (dark reds) wrapping around the storm in a large coherent band north of the center. This feature is actually part of a double eyewall structure.

The next image shows a unique 3D perspective of Indlala using data collected from the TRMM PR from the same overpass as the previous image. Higher radar echo tops are indicated in red. The areas of intense rain in the previous image are associated with deep convective towers both in the innermost eyewall and in the large surrounding rain band, which is actually a developing outer eyewall (note how this outer ring of higher tops almost completely surrounds the inner part of the storm). This type of double eyewall structure only occurs in mature, intense tropical cyclones. Given time, the outer eyewall will constrict and eventually replace the inner eyewall. The area of deep convection near the center has tops approaching 15 km. Deep convective towers near the storm's center can be a precursor to future strengthening. They indicate that large amounts of heat are being released into the storm's core. This heat is known as latent heat is what drives the storm's circulation. Indeed Indlala continued to strengthen after these images were taken. At the time of these images Indlala was a Category 3 cyclone with maximum sustained winds estimated at 100 knots (115 mph) by the Joint Typhoon Warning Center.

Click to see a very large Quicktime(42mb) 3-D "flyby" animation of INDLALA.

TRMM is a joint mission between NASA and the Japanese space agency JAXA.
Images produced by Hal Pierce (SSAI/NASA GSFC) and caption by Steve Lang (SSAI/NASA GSFC).