UPDATE (9AM MONDAY) -- T.D. #9 is still dealing with a less than ideal environment for strengthening with northwesterly wind shear caused by an upper level low pressure off the South Carolina coast blowing developing thunderstorms away from the center of circulation. Storms need to develop on top of the circulation for it to intensify and so far that isn't happening. Despite this, strengthening to a tropical storm is expected within the next day or so.
My thinking has not changed regarding impacts on SWFL. It will move northwest into the Gulf then turn north then northeast as high pressure to the north weakens and allows the storm to escape toward the Atlantic. Greater coverage of showers and storms can be expected through mid-week with locally heavy rainfall and localized flooding being the main threat.
-Chief Meteorologist Derek Beasley
The National Hurricane Center upgraded former Invest 99L to Tropical Depression #9 Sunday afternoon. After a lengthy struggle to strengthen due to the presence of wind shear and dry air, the future of the former tropical wave now looks promising as it tracks into the Gulf of Mexico on Monday.
While Hurriane Hunters investigating the system on Sunday found wind speeds of 35 mph within the area of low pressure and a better defined center of circulation, it appears that Tropical Depression #9 is still highly disorganized near the Florida Keys. As of Sunday afternoon, the system was moving westward at 9 mph.
The latest forecast from the National Hurricane Center shows that there is still considerable uncertainty in the eventual track and intensity of this system. At this point, some models are showing that a tropical storm could form in the Gulf of Mexico as early as Monday as the system moves into an environment more favorable for strengthening. After meandering in the Gulf through the middle of the week, TD #9 could steer northeastward towards the Big Bend of Florida, making landfall near the area sometime late this week. If TD #9 is able to strengthen into a tropical storm, it would inherit the name Hermine or Ian depending on if it can beat Tropical Depression #8 to tropical storm status.
Southwest Florida will see minimal impacts from TD #9 with locally heavy rainfall the main threat. Rain will be possible at any time of the day and coverage will be highest Monday and Tuesday. Models are projecting rainfall estimates could be as much as 3 to 5 inches in spots with this system, which can create a localized flash flooding threat as heavy downpours move over the same areas.