The most active part of the hurricane season often begins in August. Right on-cue, at least one tropical system is likely to form in the Atlantic by the upcoming weekend.
Forecasters at the National Hurricane Center now say there’s a 70 percent chance that Invest 96L, a tropical wave in the eastern Atlantic Ocean, will become a tropical depression or storm within the next five days.
System Near Florida Only a Rain-Maker
A tropical wave moving through Hispaniola Wednesday night is forecast to reach the southeastern Bahamas and Cuba on Thursday before moving over or close to Florida over the upcoming weekend.
The wave already produced areas of heavy rain over Hispaniola, Puerto Rico, and the Virgin Islands Monday and Tuesday. As it moves to the northwest, tropical downpours will increase over the Bahamas and portions of central and south Florida this upcoming weekend.
In anticipation of the heavy rain this weekend -- including the Tampa Bay area -- NOAA’s Weather Prediction Center has issued a “marginal risk” for flash flooding over much of South Florida on Friday. Slow-moving storms may produce as much as 4 or 5 inches of rain there in a few spots according to some computer models. Areas that receive this much rain are vulnerable to flash flooding.
The National Hurricane Center says there is a “low chance” this tropical wave could become a tropical depression east of Florida or South Carolina this weekend. So far though, strong winds high in the atmosphere have prevented the tropical wave from growing any stronger. These winds may weaken some over the weekend, and this may eventually encourage the formation of a depression, but it is unlikely this will happen. Heavy rain is anticipated regardless of whether the tropical wave becomes a depression or named storm.
Stronger Wave Brewing in the Atlantic Ocean
Farther east, an even stronger tropical wave is moving through the deep tropics a few hundred miles southwest of the Cape Verde Islands. Strong upper-level winds (or wind shear) have prevented it from becoming a depression so far, but global model simulations suggest that’s about to change this weekend.
The National Hurricane Center says there is a 70 percent chance of tropical cyclone formation from this wave in the next five days, when wind shear is expected to relax as it moves westward in the general direction of the Lesser Antilles. Both the U.S. global model (GFS) and the European global (ECMWF) — widely considered to be two of the best models in the tropics — predict the tropical wave to become a depression or named storm sometime this weekend. The tropical system should move west-northwestward and could be close to the Leeward Islands on Monday or Tuesday of next week, if current trends hold. Vacationers and residents of those areas are urged to monitor future forecasts regularly in the coming days.
It is way too soon to say whether this tropical system – which would be named Chantal – will affect the United States. Longer-range computer models are forecasting a pattern that favors a trough of low pressure over the eastern United States and a weaker western flank of the Bermuda-Azores high. Such a pattern often causes developing tropical storms and hurricanes to curve out to sea. Whether this pattern holds next week is not clear and for this reason alone, it’s important to occasionally monitor forecasts of this developing system.