Tropical storm Ernesto forecast to become hurricane by Monday in Caribbean


Tropical storm Ernesto at 1:30 p.m. (NOAA)

Since yesterday, its intensity has remained steady, with maximum sustained winds of 50 mph. Its current positions is about 90 miles west of St. Lucia and its moving almost due west at 21 mph. As the center crossed St. Lucia, sustained winds reached 41 mph with a gust measured at 63 mph.

The Windward islands are now clearing out and all watches and warnings for Ernesto have been dropped.

Track forecast

It may be several days before Ernesto again threatens any landmass or populated island. Its forecast track keeps it over the open sections of the eastern Caribbean sea through early Sunday. During the day Sunday, it’s likely to pass sufficiently far south of Jamaica to spare it from a direct hit. But the island lies within the storm’s cone of uncertainty so a small northward jog could - at the very least- bring some of the storm’s bands inland.


Official track forecast for Ernesto (National Hurricane Center)

AFTER [2 OR 3 DAYS] TRACK MODELS DIVERGE CONSIDERABLY AND SOME MODELS KEEP ERNESTO ON A MORE WESTWARD TRACK...WHILE ANOTHER GROUP TURN THE CYCLONE MORE TO THE NORTHWEST...

In other words, the storm could strike the Yucatan Peninsula (or even locations slightly south) or turn into the Gulf of Mexico as I discussed yesterday.

Intensity forecast

The storm remains somewhat ragged and disorganized and is unlikely to strengthen in the very near term. While there’s a fairly well-defined low level circulation, the storm lacks concentrated convection near the center.

With wind shear forecast to weaken, conditions are likely to become more favorable for intensification, especially as the storm reaches the central and western Caribbean where ocean heat content is high.

About half of available forecast models project the storm will reach hurricane intensity in 60 to 72 hours (Monday) and two-thirds by 108-120 hours (Wednesday).

Intensity forecasts contain significant uncertainty, so stay tuned for updates.

Elsewhere in the tropical Atlantic

* A disturbance near southern Florida is showing some early signs of organization. Writes University of Miami researcher Brian McNoldy:

This system is crawling to the northwest at about 5kts, and conditions are favorable for slow additional development. The SST is 29C, and although the vertical shear is relatively strong now (~20kts), it should decrease to under 10kts by tomorrow.

Models have not been run on this yet, and there is not an official forecast from NHC yet, but certainly expect increased chances of very heavy rain in southern Florida and western Bahamas this weekend.

Officially, the National Hurricane Center gives the system a 20 percent of becoming a tropical depression or storm in the next 48 hours.


Three centers of tropical activity in the Atlantic (National Hurricane Center)
Jason is currently the Washington Post’s weather editor. A native Washingtonian, Jason has been a weather enthusiast since age 10.
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