UPDATE THURSDAY 5 PM: The National Hurricane Center began issuing advisories on what they call Potential Tropical Cyclone Nine (or “PTC Nine”). This nomenclature is used when a system is likely to produce tropical storm conditions near land - in this case, the Bahamas - but has yet to be officially classified as a tropical storm.
PTC Nine was located 310 miles south of Freeport on Grand Bahama Island, per the 5 pm update. The disturbance was moving northwest at 8 mph. A Tropical Storm Warning was issued for the northwestern Bahamas, including Abacos, Berry Islands, Bimini, Eleuthera, Grand Bahama Island, and New Providence.
Forecasters at the National Hurricane Center have noted “greater than normal” uncertainty with PTC Nine, largely due to the absence of a well-defined center of circulation. In their first publicized key messages for PTC Nine, Floridians were urged to stay informed of future updates because the system could bring tropical-storm-force winds and rainfall to portions of the peninsula this weekend.
The original story posted earlier Thursday is below...
A strong tropical wave over the southeast Bahamas is on track to become a depression on Friday and Tropical Storm Humberto over the weekend.
The National Hurricane Center has increased the chances of tropical cyclone development to 70% over the next two days and 80% over the next five days. The tropical wave could develop anywhere from the eastern Gulf of Mexico to the western Atlantic based on its forecast from Thursday afternoon.
NHC continues to monitor a disturbance in the Bahamas that is likely to become a tropical depression or storm in the next day or two as it moves northwestward. Interests in the central and NW Bahamas and Florida should monitor its progress https://t.co/tW4KeFW0gB #95L pic.twitter.com/dxGaWhbDDt
— National Hurricane Center (@NHC_Atlantic) September 12, 2019
There are considerable differences between the most reliable models where the tropical wave will go and how strong it may get. The U.S. global model is forecasting a weaker system moving across Florida late Friday into Saturday before heading toward the central Gulf Coast Sunday evening. Meanwhile, two models run in Europe — the UKMET and ECMWF models — have made a significant change and show a stronger tropical storm forming near the Atlantic coast of Florida this weekend.
If the ECMWF and UKMET models are correct, the storm is likely to be slow-moving and at least some fringe effects — in the form of high surf and rip currents — may spread northward toward Georgia and the Carolinas toward next week. However, this is highly uncertain and subject to additional change.
Another tropical wave near the Cape Verde Islands has a chance to develop next week as it heads toward the Caribbean. The National Hurricane Center says there is a 40 percent chance a depression could form. It is far too soon to know if there will be any effects over the U.S. mainland from this tropical system. If there are any, those effects would be more than a week away.