Atlantic Tropical Weather Discussion

SPECIAL FEATURES

Western Atlantic Gale Warning: A recent scatterometer satellite pass confirmed winds to gale force south of Bermuda, between 1024 mb high pressure centered north of Bermuda near 37N65W, and 1008 mb low pressure near 26N64W. Gale-force winds are noted near 30N65W. Strong to near-gale force winds are noted from 27N to 31N between 55W and 70W, with associated seas ranging from 8 ft to 12 ft. Scattered showers and isolated thunderstorms are also active in this area. Environmental conditions could support this system gradually acquiring subtropical characteristics through this weekend while it moves slowly eastward over the western and central subtropical Atlantic. Chances of this development remain low through 48 hours, and medium through the next seven days. Regardless of such development, the area of winds and seas will expand as the low shifts eastward, with gale force wind and very rough seas will expand eastward north of 25N reaching as far east as 45W by early Mon. Winds and seas start to diminish thereafter, as environmental conditions are forecast to become unfavorable for further development. Please read the latest High Seas Forecast issued by the National Hurricane Center at website: https://nhc.noaa.gov/text/HSFAT2.html

Heavy Precipitation across Central America: Deep-layer troughing over the northwestern Caribbean extends southwestward across northern portions of Central America and into the tropical eastern Pacific. This feature will interact with enhanced low- level moisture and onshore flow south of the monsoon trough over the next several days. This will favor heavy precipitation developing across Central America starting today and lasting through at least Friday. The heaviest precipitation is expected across Nicaragua and Costa Rica, with the bulk of precipitation occurring through Thursday. Heavy rainfall may lead to life- threatening flash flooding and landslides. Please refer to your local weather agency and the International Desk at the Weather Prediction Center for more details.

MONSOON TROUGH/ITCZ

The monsoon trough reaches the Atlantic from 11N15W to 09N18W. The ITCZ extends from 09N18W to 08N35W to 10N55W. Scattered to numerous moderate convection is noted from 04N to 10N between 25W and 45W.

GULF OF AMERICA

A stationary front reaches from Gulfport, MS to Tampico, Mexico. 1015 mb high pressure is over the eastern and central Gulf, centered near 25N88W. This pattern is supporting light breezes and 1-3 ft seas across the basin.

For the forecast, a frontal boundary extends across the NW Gulf. The front will weaken and dissipate overnight. Moderate northwest to north winds prevail west of the front. The next cold front is expected to move across the Gulf waters this weekend. NW winds to gale force are expected in the SW Gulf Sun night and Mon. Fresh to strong north winds will develop west of the front and west of 93W on Sun, with moderate north to northeast winds elsewhere behind the front.

CARIBBEAN SEA

A cluster of thunderstorms is active south of Jamaica near Pedro Cay. Scattered thunderstorms are active across the southern approaches to the Windward Passage. Broad 1008 mb low pressure near Grand Cayman Island is along a surface trough at 82W from 15N and 21N. This pattern is supporting light breezes and 1-3 ft seas across the basin.

For the forecast, a weak pressure gradient across the area is supporting moderate trade winds, along with moderate seas, over the central and eastern Caribbean. Light to gentle winds and slight to moderate seas are over the western Caribbean. The pressure gradient will further loosen across the area tonight. This will diminish the moderate trades across the central and eastern Caribbean through the forecast period.

ATLANTIC OCEAN

Please see the Special Features section for information on a Gale Warning in the western Atlantic.

Elsewhere, a cold front reaches from 1004 mb low pressure near the Azores to 30N31W to 26N40W, then stationary to 27N50W. Farther south, a trough reaches from the Cabo Verde Islands to 11N35W. This pattern is supporting gentle to moderate breezes and 4-6 ft combined seas in N swell.

For the forecast west of 55W, the low pressure will track slowly east-northeastward during the rest of the week and the weekend. An area of strong to gale-force winds, and rough to very rough seas, peaking near 14 ft, has developed north of the low pres and will expand eastward through Sun, impacting the waters mainly north of about 27N. The gale-force winds will likely be north of 29N through the end of the week. Elsewhere, a weakening cold front will move across the waters between Florida and 75W Fri and Fri night, then dissipate Sat and Sat night.