Tropical Storm Debby forms; a threat to United States Gulf coast
An area of low pressure over the Gulf of Mexico has sufficient organization of tropical storm; therefore, the National Hurricane Center (NHC) designated Invest 96L as Tropical Storm Debby, the fourth storm of the 2012 Atlantic season. In addition, it is the earliest fourth tropical cyclone in the Atlantic basin on record, surpassing Hurricane Dennis in 2005, which became a tropical storm on July 5. Latest NHC advisory states that Debby has maximum sustained winds of 50 mph and minimum pressure of 1001 mbar. Recent satellite image depicts that Debby has a well-defined surface center, but the convection, which is an activity of showers and thunderstorms, remains toward the east of the center due to both moderate wind shear and little dry air affecting the system. This wind shear is generated from an upper-level low to the west of Debby. However, Debby is over warm sea surface temperature of 28°C, which should help the system to slowly organize and strengthen.
Figure 1. Afternoon visible satellite image of Tropical Storm Debby over the Gulf of Mexico.
Forecast for Debby
Debby is predicted to move slowly northward over the next 12 - 24 hours. After that, however, the forecast track of Debby remains somewhat complex. Many models, including the ECMWF, UKMET, and NOGAPS, forecast Debby to move westward and make landfall on South Texas by a high pressure ridge building over the southern United States. Other models, including the GFS, predict the cyclone move east-northeastward and make landfall on the western coast of Florida by the trough of low pressure moving eastward over the United States East Coast. Since most models predict Debby to move westward, this will likely be the cyclone’s expected path as shown in NHC’s official forecast track.
The environmental conditions in Debby are forecasted to remain relatively favorable over the few days. Wind shear is predicted to lessen slightly as the upper-level low moves southwestward away from Debby. Sea surface temperatures in the Gulf of Mexico are expected to remain warm at 28°C. These favorable conditions should allow Debby to gradually strengthen, and at least become a strong tropical storm. None of the models forecast Debby to become a hurricane in the next few days; however, it is possible that Debby may become a hurricane, if it can linger around favorable conditions longer than it is anticipated.
Interests along the United States Gulf coast, especially Texas and Louisiana, should monitor the progress of Debby over the next several days, and prepare for the storm’s impact, including tropical storm-force winds, heavy rains, and storm surge.