On Sunday August 27, 2006, near the one-year anniversary of Hurricane Katrina, Ernesto became the first storm of the Atlantic season to reach hurricane intensity while passing through the central Caribbean. Ernesto did not maintain hurricane intensity for long, however, and was soon downgraded back to a tropical storm after nipping the southwestern tip of Hispaniola.

Ernesto formed from an easterly wave that had propagated westward across the Atlantic and into the Caribbean. After passing through the Windward Islands, convective activity and organization within the wave increased, and a tropical depression, TD #5, formed on the 24th of August northwest of Grenada.

This first image on the left above shows TD #5 in the southeastern Caribbean soon after it had formed. The image was from data obtained at 0241 UTC 25 August 2006 (10:41 pm EDT 24 August 2006) by the Tropical Rainfall Measuring Mission (or TRMM) satellite. With a suite of active and passive sensors, TRMM is designed to measure rainfall from space. The image shows instantaneous rain rates associated with areas of convection within the depression. Rain rates in the center swath are from the TRMM Precipitation Radar (PR), while those 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). Scattered areas of light (blue) to moderate (green) rain with little evidence of organization reveal that the system is still in its early stages of development. TD #5 continued to slowly develop and became Tropical Storm Ernesto the next day, August 25th (local time). As the system tracked off to the west-northwest, it encountered southwesterly winds aloft, which inhibited the storm from gaining much strength despite sufficiently warm sea surface temperatures. The next image on the right above from TRMM was from data obtained at 1134 UTC (7:34 am EDT) 26 August as Ernesto was passing south of the Dominican Republic. At this time intense areas of rain are present within the storm (red areas) and indicate areas of active convection. However, Ernesto still does not have a visible eye nor a particularly well-developed circulation that can be identified in the rain field.

The next image on the right was obtained at the same exact time as the previous image and gives a 3D perspective of the storm from the TRMM PR. The view is to the north. TRMM reveals several deep convective towers (shown in red) that top out over 15 km. These are associated with the heavy rain in the previous image. Such towers can be an indication of future intensification when they occur near the center of the circulation. However, Ernesto did not respond to the deep convection as a result of inhibiting wind shear and instead remained at minimal tropical storm intensity. At the time of these last two images, Ernesto's maximum sustained winds were reported at 40 knots (46 mph) by the National Hurricane Center (NHC).

Ernesto continued to encounter southwesterly shear aloft as it moved into the central Caribbean. The storm then took a jog to the north and assumed a more northwesterly track taking it in the direction of southwestern Haiti. The next image from TRMM was from data obtained at 0224 UTC 27 August (10:24 pm EDT 26 August) as Ernesto was approaching Haiti. Although the center of the storm does not fall within the PR swath, the rainfall pattern from TRMM confirms that the rain and associated convection are still confined to the eastern side of the storm as the result of the impending wind shear. At the time of this image, Ernesto's sustained winds were up slightly to 50 knots (58 mph).

During the night of the 26th, the shear across Ernesto finally relaxed, allowing the storm to intensify into a Category 1 hurricane. By this time, however, it was already very close to southwestern Haiti. Ernesto crossed the southwestern tip of Haiti on the afternoon of the 27th, causing it to weaken back into a tropical storm. Ernesto then continued on to the northwest where it made landfall in southeastern Cuba on the morning of the 28th. After crossing Cuba, a rather disorganized Ernesto re-emerged over the warm water of the Florida Straits and headed for south Florida. Fortunately, Ernesto had little time to strengthen and made landfall during the night of the 29th at the southern tip of Florida after passing through the upper Keys as a weak tropical storm.

The final image on the right from TRMM was taken 0254 UTC 30 August (10:54 pm EDT 29 August) and captures Ernesto just as the center was making landfall on the coast of south Florida. Most of the rain shield (broad blue arc) is well ahead of the center of circulation. The center itself is rather devoid of rain (note the patch of light rain in blue near the southern tip of the peninsula). At landfall, NHC reported that Ernesto's maximum sustained winds were 40 knots (46 mph). Initial reports indicate only minimal damage from the storm in Florida. Ernesto, however, is expected to continue to make its way up the eastern seaboard and could regain some strength over the western Atlantic if it follows the projected path. The biggest impact from the storm could be in the form of heavy rains if as expected it merges with an approaching frontal system later in the week.

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).