NOAA said Tropical Depression 9 was forecast to become a hurricane and reach the U.S. Gulf Coast on Friday night. The Tropical Storm Isaias forecast puts southeast Louisiana through the Florida Panhandle on alert as the system organizes in the western Gulf of Mexico.
The NOAA/NWS National Hurricane Center designated the system at 5 p.m. EDT Tuesday and predicted steady strengthening. It was expected to become a tropical storm on Tuesday night, then reach the coast at hurricane strength by Friday night.
TD 9 and the western Gulf
Satellite and radar imagery on Tuesday showed the disturbance gaining spin as surface pressures fell. Winds aloft were already affecting the system, with strong wind shear at 15 to 20 knots, or 17 to 23 mph, even as sea surface temperatures across the Gulf were the warmest on record for that point in October.
Those waters along the path were running between 30 and 31 degrees Celsius, or 86 to 88 degrees Fahrenheit. Climate Central said human-caused warming has made readings like that several hundred times more likely over the western Gulf.
92L and northwest Yucatan
Forecast models generally agreed on a curving track across the Gulf, but they split on timing and intensity. Most models kept 92L far enough northwest of the Yucatan Peninsula to avoid major impacts there, though Celestún and Progreso in northwest Yucatan could get a few hours of squally weather on Thursday.
Models were also fairly close on the future Isaias path after it passed by the Yucatan. They pointed it northward toward the central U.S. Gulf Coast, while disagreeing on whether it would arrive before a more favorable southwest wind pattern or a more hostile wind-shear setup took hold.
NOAA Gulfstream-IV flights
The NOAA Gulfstream-IV jet was scheduled to sample the environment around the disturbance on Tuesday evening. The first hurricane hunter flights were scheduled to begin Wednesday morning, giving forecasters another look at whether the system can strengthen fast enough before conditions change.
For residents from southeast Louisiana to the Florida Panhandle, the practical step is simple: watch the forecast closely through Friday night and be ready for a stronger system than TD 9 was on Tuesday afternoon. The next data from the Gulfstream-IV and the aircraft flights should narrow the track and intensity question before the storm reaches the coast.
