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Special Features

Atlantic Large Swell Event: Northerly swell generated from a storm force low over the Atlantic waters north of the discussion area will generate rough to very rough seas over the western Atlantic through this weekend. Seas in excess of 12 ft and greater, with period of 12-14 seconds will continue to spread southeastward today, covering the waters north of 25N between 43W and 70W by tonight. The swell will then start to subside over the discussion waters allowing for seas to drop below 12 ft Sun night. Seas with this swell will peak near 18 ft over the waters north of about 30N between 50W and 65W today.

Please read the latest HIGH SEAS FORECAST issued by the National Hurricane Center at website - https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml for more details.

Tropical Waves

A far eastern Atlantic tropical wave has its axis near 22W from from 02N to 15N moving westward around 10 kt. Scattered moderate convection is noted from 08N to 11N between 21W and 24W.

A central Atlantic tropical wave has its axis near 37W from 02N to 10N, moving westward at 10 to 15 kt. No significant convection is evident near this tropical wave.

An Atlantic tropical wave has its axis near 51W from 04N to 18N, moving westward at 15-20 kt. A scatterometer satellite pass from 13 UTC indicated the system lacks a closed circulation, but strong to near-gale force winds were observed along a sharp surface trough along the wave axis, mainly from 12N to 15N. A concurrent Sentinel-3B altimeter pass confirmed seas of at least 8-9 ft near the core of strongest winds. Invest AL98 has been opened to monitor this wave. Environmental conditions appear marginally conductive for slow development over the next couple of days as the system moves quickly westward at 20 kt, crossing the Windward Islands and entering the Caribbean Sea by early next week. By the middle of next week, the system is expected to slow down over the central Caribbean Sea, where environmental conditions could become more favorable for further development. Regardless of development, this system is expected to bring heavy rainfall and gusty winds to the Windward Islands Sun and Sun night.

An Atlantic tropical wave has its axis near 59W south of 16N, moving westward near 15 kt. A scatterometer satellite pass from 1330 UTC indicated fresh to strong winds near the wave axis from 10N to 12N. Numerous moderate to isolated strong convection is noted from 06N to 13N between 56W and 62W.

Monsoon Trough/ITCZ

The monsoon trough enters the Atlantic near 13N16W and extends southwestward to near 05N30W. Segments of the ITCZ extend from 05N30W to 05N36W, and from 05N40W to 03N50W. Other than the convection discussed in the Tropical Waves section above, no significant convection is ongoing along the monsoon trough and ITCZ at this time.

Gulf Of America

A few showers and thunderstorms are active off the central Louisiana coast, south of a coastal trough reaching from off Morgan City, Louisiana to off Port Connor, Texas. 1020 mb high pressure is centered off Cape Hatteras, NC. South of the high pressure, a plume of moderate E to SE winds with 4 to 5 ft seas extends from the Straits of Florida to near the mouth of the Mississippi River. The moist, convergent flow is supporting the showers and thunderstorms off Louisiana. Light to gentle breezes with 1 to 3 ft seas are noted elsewhere.

For the forecast, locally fresh S to SE winds will occur into Sun east of 90W, including through the Florida Straits, as high pressure builds over the western Atlantic. A cold front will move into the northwestern Gulf Sun morning and move southeastward over the basin through Mon. Moderate N to NE winds are expected north of the cold front, and locally fresh winds will be possible north of 26N into Mon morning. High pressure is slated to develop over the basin in the wake of the front, leading to gentle to moderate winds and slight seas over the Gulf early next week.

Caribbean Sea

Convergent easterly flow and lingering moisture from an old trough are supporting scattered showers and thunderstorms across the northwest Caribbean this morning, mainly north of 18N. Convergent trade wind flow is also supporting a few showers and thunderstorms across the far southwest Caribbean between Panama and Nicaragua. Farther east, an upper trough is supporting a few showers and thunderstorms across the south-central Caribbean off northeast Colombia and northwest Venezuela. Scattered showers and thunderstorms are impacting southern Windward Islands from St Vincent to Grenada, ahead of the approaching tropical waves. Clusters of these thunderstorms are training in lines from east to west, and could bring heavy rainfall to these islands. Moderate SE winds and 2 to 4 ft seas are noted over the eastern Caribbean, and gentle E to SE breezes and 1 to 3 ft seas are noted elsewhere.

For the forecast, moderate to fresh E winds and moderate seas are expected over the south-central and eastern basin tonight through Sun as high pressure builds over the western Atlantic. Locally strong winds will be possible in the Gulf of Venezuela on Sun. A long period N swell will lead to rough seas through the Atlantic passages and over the waters east of the Lesser Antilles Sun into early next week. Looking ahead, a tropical wave located in the central Atlantic will move westward this weekend, entering the eastern Caribbean Sun night. Environmental conditions appear marginally conductive for slow development over the next couple of days. By the middle of next week, the system is expected to slow down over the central Caribbean Sea, where environmental conditions could become more favorable for further development. Regardless of development, fresh to strong winds and rough seas will accompany this wave as it moves over the eastern and central Caribbean early next week. This system has a low chance of tropical development within the next 7 days.

Atlantic Ocean

Please refer to the Special Features section for further details on a large swell event that will impact some sections of the north-central waters through the weekend, and details about the tropical wave/Invest AL98W near 50W.

A cold front extends from 31N48W to southern Bahamas and Turks and Caicos Islands, west of 1021 mb high pressure near 27N37W. Scattered showers and thunderstorms are active within 150 nm east of the front. Fresh to strong W to NW winds are west of the front to 65W, north of 25N. Fresh to strong SW winds are also evident within 240 nm east of the front, north of 25N. Seas are in excess of 8 ft north of 23N between 40W and 75W. Outside of the area of winds and seas associated with Invest AL98 described in the Special Features section, moderate to fresh NE to E trade winds and 5 to 7 ft seas are noted south of 20N, with gentle to moderate breezes and 4 to 6 ft seas elsewhere.

For the forecast W of 55W, the front will progress northeastward this weekend. Fresh to strong W to NW winds are expected in the wake of the front north of 27N and east of 65W through Sun morning. Widespread rough seas associated with this storm system will continue north of 20N and east of 77W through tonight, with rough seas expanding southeastward through the Greater Antilles Atlantic Passages on Sun. Very rough seas in excess of 12 ft are expected north of 25N and east of 72W through Sun afternoon. Rough seas will slowly subside from west to east Sun into early next week. Elsewhere, moderate to locally fresh E to NE winds will occur over the Bahamas and through the Florida Straits through Sun morning as high pressure builds over the western Atlantic this weekend. Looking ahead, a series of cold fronts are slated to push off the coast of the southeastern United States early next week, leading to increasing N winds offshore of Florida.

Posted 4 hours ago by NHC Forecaster Christensen