Invest 99L Could Pass Through South Florida

Posted at 11:40 AM, Aug 24, 2016
and last updated 2016-08-25 09:24:26-04

There is still a concern that Invest 99L has the potential of passing through South Florida and move into the Gulf.

What The Models Show for Invest 99L

The European computer model has been consistent the past few runs (since late Monday) of the storm tracking through the southern Bahamas then turning due west across south Florida into the eastern Gulf. The GFS (US Model) has been the least consistent, going from really ramping the storm up to showing nothing at all developing and flip-flopping on its forecast track. I am not convinced the GFS has a firm handle on what will happen with Invest 99L. The European model was the first model to jump on board with developing Earl last month. The ensemble models from the GFS agree more with the Euro in steering the storm around a large dome of high pressure in the upper atmosphere, the same high pressure that has brought record heat to Southwest Florida the last couple of days.

Invest 99L Still Has To Move Through The Greater Antilles

The disturbance still has to move through the Greater Antilles over the next day or so and it is during this time it will be subjected to dry air and the potential for land interaction. The disturbance is experiencing some 30 kt wind shear on the north side but as it moves closer to the Bahamas the shear should lessen and become more favorable. This combined with very warm water over this area could lead to gradual organization of the system into a depression and potentially Tropical Storm Hermine. The overall satellite presentation is looking more and more organized as just a few days ago it didn’t have any thunderstorms associated with it at all. Recon is scheduled to fly into the storm this morning at 11 AM to get a better idea of where a center may be trying to form if it hasn’t already and get an idea of the inner workings of the disturbance.

Keeping An Eye On Invest 99L


  1. The storm moves into a more favorable environment and slowly develops through the end of the week into this weekend.
  2. A northwest track with an abrupt turn toward the west into the eastern Gulf. This potentially could take it through the Straits or a portion of South Florida. The high pressure dome forecast to develop over the Mid-Atlantic states should keep the system from escaping into the Atlantic. It will have no choice but to turn westward under and around that high pressure ridge. All of the dynamical models agree that there will be a strong mid-Atlantic ridge in place.


  1. Timing: The Euro is fastest bringing the storm toward south Florida by Sunday through Monday. Other models are a tad later.
  2. Eventual Strength: Much of this depends on how quickly it can fight off the dry air, avoid land interaction with Hispaniola and take advantage of the hot water in the Bahamas. The next few days will be critical. I am reasonably confident that the storm should be no stronger than a tropical storm as it moves through or near south Florida although there is still a chance it won’t organize into much more than a depression. Then there is also the chance it could really get under favorable conditions and ramp up quickly. Forecasting intensities of tropical storms/hurricanes is notoriously difficult as there are many factors in play that determine this

We still have a few days to watch this, but keep in mind, this system will likely not get its act together until it is close to South Florida, leaving you little time to prepare regardless of what it does. What’s the worst we could see? Strong winds and very heavy rainfall for a window of 24 hours. There is also the potential for tornadoes in the rain bands on the east side of the storm if we happen to get into a favorable position in Southwest Florida with respect to the storm. Best case scenario for us would be a weaker system, a little rain and some wind and it waits until it gets well into the Gulf (we don’t want that scenario either for our neighbors to the north and west). I will continue to post updates often as needed throughout the coming days.