As the climatological height of the Atlantic hurricane season draws near, the second Category 5 hurricane of the year has just made landfall. Almost two weeks to the day since Hurricane Dean, the first Category 5 storm of the season, made landfall in the Yucatan Peninsula, Hurricane Felix came ashore on the northeast coast of Nicaragua with sustained winds of 160 mph.

The Tropical Rainfall Measuring Mission (or TRMM) satellite captured this unique series of images, which chronicle the development of Felix from an unnamed disturbance to a powerful hurricane. Launched back in November of 1997, TRMM is armed with an array of passive and active sensors designed to measure rainfall and its structure from space. It has proven itself to be an excellent platform for observing tropical cyclones. The first image was taken by TRMM at 06:10 UTC (2:10 am EDT) on the 28th of August 2007 and shows the horizontal pattern of rain associated with a tropical disturbance located midway between the coast of Africa and the Lesser Antilles. At this stage, there is no evidence of a circulation. The system does not yet show any signs of organization and is best described as a loose cluster of storms with mostly light to moderate rain (blue and green areas, respectively) associated with a tropical easterly wave propagating away from Africa. Rain rates in the center of the swath are from the TRMM PR, and those in the outer swath come from the TRMM Microwave Imager (TMI). The rain rates are overlaid on infrared (IR) data from the TRMM Visible Infrared Scanner (VIRS).

The second image was taken two days later at 15:45 UTC (11:45 am EDT) on the 30th. Not unlike the first image, the disturbance still shows no signs of organization other than that the area of associated rain is somewhat more consolidated. It would be another full day before the disturbance developed a closed circulation, identifying it as a tropical depression (TD #6, the sixth tropical depression of the season). At this point, the system was already approaching the Windward Islands just 180 miles to its west. Over the next day, TD #6 continued to organize and gather strength. By midday on September 1st, it had become a tropical storm and was given the name Felix.

This next image shows Felix just after being named a tropical storm. It was taken at 15:30 UTC (11:30 am EDT) on 1 September. The organization is now clearly evident with rain bands spiraling around a central point (arcs of green and blue denoting moderate and light intensity rain, respectively). This central point is associated with an area of low pressure and marks the center of the storm's circulation. At the time of this image, sustained winds were reported at 55 knots (63 mph) by the National Hurricane Center (NHC) based on aircraft reports. At this stage, warm sea surface temperatures and low atmospheric wind shear made conditions ideal for continued development. As a result, Felix steadily intensified, becoming a hurricane later that same day. A deep-layer ridge to the north of the system continued to steer the system due west. This put Felix on track parallel to but south of that previously taken by Dean. Dean moved pretty much due west through the northern Caribbean, while Felix moved due west through the southern Caribbean.

By daybreak on the 2nd, Felix was up to Category 2 intensity with sustained winds of 85 knots (98 mph). Felix then underwent a period of rapid deepening and quickly intensified. By nightfall, Felix was a very powerful storm, a Category 5 storm with sustained winds of 145 knots (167 mph). This next image from TRMM was taken at 15:13 UTC (11:13 am EDT) on the 3rd and shows Category 5 Felix as it was moving due west through the western Caribbean in the direction of Nicaragua. The storm is very compact and tightly wound with good banding and sharply curving rain bands. However, the storm is a little asymmetric as evidenced by the larger amount of heavy (dark red areas) to moderate rain being north and east of the center. In fact, Felix underwent a period of weakening after this image was taken.

The final image was taken at 06:04 UTC (2:04 am EDT) on the 4th and shows Felix bearing down on the coast of Nicaragua. Felix had regained its Category 5 status and winds were back up to 135 knots (155 mph). The eye is very small, and the center is well-defined. Intense rain occupies the western eye wall (dark red arc), and tightly-curved concentric rain bands surround the center, indicating a very intense circulation. Felix is a small storm. As such, it is can change intensity fairly quickly in response to environmental conditions. The storm is expected to quickly weaken over land. The last great hurricane to impact the region was Hurricane Mitch back in 1998. Mitch killed over 11,000 people in Central America with thousands more missing mostly as a result of massive flooding.

Click to see a 3-D Flyby animation of TRMM PR 15dBZ Isosurface

The image above is a color contoured perspective 3-D image of the rainfall that occurred over Central America during the period from August 30 to September 6, 2007 when hurricane Felix traveled across the Caribbean and into Central America. All of the precipitation isn't due to hurricane Felix. For example the heavy precipitation over Costa Rica is caused by the Inter-Tropical Convergence Zone (ITCZ). This image was made using TRMM based merged satellite micro-wave and Infrared data (3B42).

TRMM is a joint mission between NASA and the Japanese space agency JAXA.

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