Tropical Storm Dolly Forms, Tracking Toward the Northeast Caribbean

Tropical Storm Dolly has formed over the south-central Atlantic and is heading toward the Leeward Islands this weekend, though hostile wind shear and dry air could weaken or even dissolve the storm before it arrives.

Dolly Targets the Leeward Islands With Rain and Rough Seas

Dolly developed from a tropical wave that grew better organized over the south-central Atlantic, and is expected to approach the Leeward Islands this weekend with downpours and gusty squalls. The name has no connection to the recent passing of the country music star; Atlantic storm names are set years in advance from a rotating list.

At a minimum, the storm is forecast to bring locally drenching showers, gusty thunderstorms and choppy seas to the Leeward Islands and possibly the northern Windward Islands. Rainfall of 1 to 4 inches is expected from the Leewards through Puerto Rico, Hispaniola and Cuba, with mountainous terrain capable of enhancing totals in some spots and an isolated maximum of 12 inches possible. Those islands rely heavily on seasonal rainfall for their year-round water supply, so the rain could bring some benefit even as it raises flash flooding risk.

Dolly isn't expected to be a major wind producer in the northeast Caribbean, though gusts as high as 60 mph in isolated thunderstorms could still down trees and knock out power in spots.

Wind Shear and Dry Air Could Weaken Dolly Before It Reaches the Islands

An area of dry air has developed just west of Dolly, and a belt of disruptive wind shear awaits near the Leeward Islands, both of which could sap the storm's intensity as it approaches. A poorly organized Dolly could struggle to produce much more than a couple of inches of rain.

This year's slow tropical development has been driven largely by a strong and still-strengthening El Niño, which is fueling persistent wind shear across the Caribbean and, at times, into the Atlantic's Main Development Region. Combined with dry, dust-laden air from the Sahara, the pattern has made conditions broadly hostile for tropical development across the basin this season.

It's possible Dolly could weaken significantly or dissipate entirely over the Greater Antilles. But if the storm survives its encounter with the islands, conditions become more favorable for redevelopment off the southeast U.S. coast, since wind shear is expected to be lower and ocean waters warm enough to support renewed strengthening near the Bahamas by the middle to end of next week.

What's Next

This season has produced only four named storms so far, Arthur, Bertha, Cristobal and Dolly, and has yet to generate its first hurricane, well behind the typical pace where the season's first hurricane usually forms by late July. Forecasters say the strong El Niño pattern could make the back half of the season less active than usual overall, though Dolly's potential redevelopment near the Bahamas remains a storyline worth watching for the southeastern U.S. into next week.

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