It didn't take very long for the 2006 Atlantic hurricane season to get underway with the early arrival of Tropical Storm Alberto over the weekend. Alberto became the first tropical storm of the season on Sunday morning, the 11th of June 2006 in the south-central Gulf of Mexico. On average the first named storm of the Atlantic season forms by the beginning of July. Typically only one out of every four seasons has a named storm this early. Last years incredible hurricane season also began early when Tropical Storm Arlene formed on the 9th of June.

Alberto began as a tropical depression on the morning of 10 June 2006, having formed from an area of low pressure over the northwestern Caribbean. This depression moved generally northwestward through the Yucatan channel between western Cuba and the Yucatan peninsula and into the south-central Gulf of Mexico. The system was rather poorly organized as a result of rather strong southwesterly wind shear that resulted in an ill-defined and elongated center of circulation. Nonetheless, based on hurricane hunter aircraft and ship reports of stronger winds, the system was upgraded to a tropical storm and given the name Alberto by the National Hurricane Center (NHC) at 11:00 am EDT on the 11th. A trough of low pressure over the eastern US then began to steer Alberto more towards the north and eventually the northeast.

The Tropical Rainfall Measuring Mission satellite (known as TRMM) was placed into service in November of 1997. From its low-earth orbit, TRMM has been providing valuable images and information on tropical cyclones around the Tropics using a combination of passive microwave and active radar sensors, including the first precipitation radar in space. This set of images was taken at 19:42 UTC (2:42 pm CDT) 11 June 2006 soon after Alberto had become a tropical storm. The first image shows the horizontal distribution of rain intensity (top down view) as viewed by the TRMM satellite. Rain rates in the center swath are from the TRMM Precipitation Radar (PR), and 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). A tropical storm symbol marks the center of Alberto. TRMM confirms that Alberto was poorly organized. The low-level center of circulation (denoted by the tropical storm symbol) is displaced well to the southwest of the heavier rain areas (darker red and green areas). In fact, there is essentially no rain in the immediate vicinity of the low-level center. This highly asymmetric structure is a result of wind shear. At the time of this image, Alberto was a weak tropical storm with maximum sustained winds of 45 mph.

With its ability to look at precipitation structures in the vertical, the TRMM PR was able to provide this second image, a 3D depiction of Alberto. This image is concurrent with the previous image. The PR shows a couple of tall towers (red surfaces) approaching 15 km that are associated with heavy rain areas well away from the low-level center. The presence of such towers can be an indication of intensification when they are near the storm's core, which at the time was not the case with Alberto.

After these images were taken, however, the inhibiting wind sheer decreased, allowing Alberto to become better organized. The circulation center reformed closer to the convection, and on the 12th of June Alberto strengthened to a strong tropical storm with maximum sustained winds reported at 70 mph by NHC, just below hurricane strength. The system is continuing to track off to the northeast towards the northeastern Gulf coast of Florida where a hurricane watch is in effect.




(CLICK TO SEE) ALBERTO BRINGS HEAVY RAIN, DROUGHT RELIEF TO SOUTHEAST
JUNE 10-14, 2006

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).