After the immense devastation brought by Hurricane Katrina, all eyes are on Hurricane Rita as it passes the Florida Keys and threatens the Gulf of Mexico. The Tropical Rainfall Measuring Mission (TRMM) satellite is one of a number of satellites being used to monitor Hurricane Rita and storms like it. Launched back in November of 1997 to measure rainfall over the Tropics, TRMM has proven itself to be a valuable platform for observing tropical cyclones, which include hurricanes and typhoons.

Rita formed from a tropical disturbance east of the Turks and Caicos Islands into a tropical depression (TD#18) on the evening of the 17th of September 2005 (local time). The system moved west through the Caicos and strengthened into a tropical storm on the afternoon (local time) of the 18th before entering into the southern Bahamas. This first image was taken by TRMM at 15:57 UTC (11:57 am EDT) on 19 September 2005 as Rita was passing through the southern Bahamas. The image shows the horizontal distribution of rain intensity within Rita as obtained from TRMM's sensors. Rain rates in the center part of the swath are from the TRMM Precipitation Radar (PR), the only radar capable of measuring precipitation from space. The PR can provide fine resolution rainfall data and details on the vertical structure. Rain rates in the outer swath are from the TRMM Microwave Imager (TMI). The rain rates are overlaid on infrared (IR) data from the TRMM Visible Infrared Scanner (VIRS). At the time of the image, Rita was a tropical storm with maximum sustained winds reported at 55 knots (63 mph) by the National Hurricane Center (NHC). A well-defined closed eye is not visible in this image as Rita is still in the process of organizing. However, there is evidence of banding in the rain features southwest and northeast of the center (green and blue arcs), and an area of heavy rain is present on the southwest side of Rita's center (red area).

The second image, which was taken at the same time, shows a 3D perspective of Rita courtesy of the TRMM PR. The 3D isosurface (defined by the 15 dBZ echo intensity) is color-coded to show the vertical height of precipitation-sized particles within the storm. An immense tower (in red) reaches up to 17 km near the center and is associated with the area of heavy rain shown in the previous image. Tall towers are often a sign of future intensification. As water vapor condenses into tiny cloud droplets, heat is released. This heat, known as latent heat, is what drives the storm's circulation. It is most effective when it occurs near the center of the storm. The cloud droplets form into rain, which can be detected by the radar.

The last image was taken at 08:28 UTC (4:28 am EDT) on the 20th of September as Rita was passing through the Florida Straits. Although the center of Rita does not fall within the PR swath, it is obvious from TRMM that Rita is becoming better organized. A ragged eye is present surrounded by areas of moderate rain (green areas) with good banding in the outer rainbands, all signs that the storm's circulation is improving. Rita was still a tropical storm at the time of this image with sustained winds of 60 knots (69 mph), but by early afternoon the same day, Rita would become a Category 2 hurricane as it passed south of the Florida Keys headed for the Gulf of Mexico.

TRMM is a joint mission between NASA and the Japan Aerospace Exploration Agency (JAXA).

Images produced by Hal Pierce (SSAI/NASA GSFC) and caption by Steve Lang (SSAI/NASA GSFC).