Wednesday brought no new developments in the evolution of the tropical disturbance labeled Invest 99L. For the second straight day, aircraft reconnaissance failed to find evidence of a closed surface cyclonic circulation.
However, it did find tropical storm force winds at flight level, around 5,000 feet. By Wednesday evening the disturbance was looking ragged, with a possible mid-level circulation north of Puerto Rico moving towards the west-northwest.
For the Leeward and Virgin Islands some squalls brought gusts up to tropical storm strength – 39 MPH in Tortola and 54 MPH in St Marteen. In Puerto Rico the rain was far from a big problem, with about one inch accumulating. Higher amounts were observed in the Dominican Republic, but I would argue that these were not directly linked to Invest 99L.
With any signs of turning limited to the Atlantic waters north of the Antilles, it’s clear that the thunderstorm burst further south that threatened to take over on Tuesday night as the main “centroid” simply never materialized.
So the disturbance hasn’t had to interact with land quite as much. The good news is that, despite this, the system has not gained any strength. Late Wednesday there appeared to be some wind shear impacting 99L as well.
With that in mind, the National Hurricane Center dropped the chance for development in the short term to 50 percent, while keeping the probability that a depression or storm will form over the Bahamas by the weekend to 80 percent. This is in line with my idea that we won’t have a clear notion of what to expect until after the disturbance passes the Turks and Caicos Islands.
Not only will the wind shear diminish to about 10 knots by then, but the water temperatures across the Bahamian archipelago are bathtub warm – in the mid to upper 80s, and even near 90 degrees in the northern Bahamas and the Gulf Stream. This is jet fuel for a tropical system, especially if it’s already a named tropical storm.
What will this entity be once it enters the southern Bahamas? There is still enormous uncertainty. Which means there’s even more uncertainty as to what this system could be if and when it reaches the Florida area.
While almost all models bring some form of tropical cyclone to Florida between Sunday and Monday, many now keep it rather weak – like a depression or tropical storm. As a weaker cyclone, it’s possible that a track further to the south might be expected, either across the southern tip of the peninsula or the Upper Florida Keys, then entering the Gulf of Mexico.
If a storm does develop, would It remain weak? I worry about the chance that it could become stronger. A hurricane? Possibly. A major hurricane? Not impossible given the sea surface temperatures in the Bahamas.
Now, "not impossible" doesn’t exactly convey a message of imminent danger. And there is not imminent danger. But given where Invest 99L or future Hermine is forecast to track through, I want you to be aware that **I’m telling you there’s a chance**.