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Monsoon Trough/ITCZ

The monsoon trough enters the Atlantic Ocean through the coast of Guinea-Bissau near 12N16W, then continues southwestward to near 07N20W. The ITCZ extends from 07N20W to 04N30W to 00N50W. Clusters of moderate to strong convection are noted over parts of Guinea, Sierra Leone and Liberia. Scattered moderate convection is observed from the Equator to 05N between 30W and 50W, and from 06N to 10N between 50W and 55W.

Gulf Of America

Smoke from agricultural fires over SE Mexico is affecting the western Gulf. The smoke mixes with haze to create a smoky atmosphere. Durante this time of the year, dense smoke can be seen over the NW Caribbean, including the Gulf of Honduras, and in the Gulf of America reducing visibility for mariners. Otherwise, a ridge remains in control of the weather pattern across the Gulf waters supporting moderate to fresh SE winds and seas of 4 to 6 over the western half of the basin. Gentle to moderate SE winds and seas of 2 to 4 ft are noted E of 90W. Lighter winds and lower seas are observed across the coastal waters of W Florida. Dry sinking air aloft is suppressing any deep convection from developing over the basin.

For the forecast, the pressure gradient between high pressure over the eastern Gulf and relatively lower pressure in Texas and in eastern Mexico will maintain moderate to fresh SE winds and moderate seas across the western Gulf through early Tue evening. Pulsing fresh to locally strong E winds are likely each afternoon and evening, north of the Yucatan Peninsula as a trough develops daily and drifts westward. Smoke from agricultural fires in southeastern Mexico is leading to hazy conditions over the western Gulf zones.

Caribbean Sea

The pressure gradient between high pressure of 1027 mb located over the central Atlantic near 32N47W and relatively lower pressures in the Caribbean and northern South America is maintaining moderate to fresh trades across the east and central Caribbean, including the Gulf of Honduras. Gentle to moderate winds prevail elsewhere. Seas are 4 to 6 ft across the east and central Caribbean, 3 to 5 ft in the Gulf Honduras, and 1 to 3 ft elsewhere, including in the lee of Cuba and the Windward Passage.

An upper-level trough extends from the Atlantic across Hispaniola into the central and SW Caribbean. A diffluent pattern aloft, ahead of the trough is helping to induce convection over Hispaniola, Puerto Rico and the US/UK Virgin Islands. The upper- level trough will move eastward during the weekend. A cut-off low is forecast to develop along the trough axis N of Puerto Rico on Sat. This will continue to enhance the developing of showers and thunderstorms over the NE Caribbean over the next couple of days.

For the forecast, fresh to locally strong E to SE winds will pulse in the Gulf of Honduras late in the afternoons and at night through next week. Moderate to fresh trades along with moderate seas over the south-central part of the basin will continue through tonight. Similar conditions are expected in the lee of Cuba and near the Windward Passage on tonight and Sat night. Moderate to fresh trades and rough seas will persist over the Atlantic waters near and east of the Lesser Antilles through Sun night. Looking ahead, increasing trades along with building seas are expected across the eastern part of the basin beginning Sun night. These conditions are forecast to shift westward across the central part of the region and to the southwestern Caribbean around the middle of next week.

Atlantic Ocean

The aforementioned upper-level trough is also helping to induce an area of showers, with embedded thunderstorms, roughly between 60W and 68W. A surface trough is analyzed in this area and runs from 27N65W to 20N68W. Farther E, another surface trough/former cold front extends from 31N23 to 25N35W to 25N50W. A narrow band of mainly low clouds, with possible showers, is associated with this system. Gentle to moderate NE winds are in the wake of the trough, with seas of 5 to 7 ft. High pressure of 1027 mb located over the central Atlantic near 32N47W dominates the remainder of the Atlantic forecast waters. Its associated ridge extends westward toward the Bahamas and Florida. An area of fresh to locally strong trades are noted S of 22N between 40W and 60W due to the pressure gradient between the high pressure to the N and lower pressures in the vicinity of the ITCZ. Seas are 6 to 9 ft within these winds. An area of moderate to fresh N to NE winds is near the coasts of Mauritania and Western Sahara, where seas are in the 4 to 6 ft range. Elsewhere, gentle to moderate winds and moderate seas prevail.

An early surge of Saharan dust is noted across the tropical Atlantic reaching the Lesser Antilles. The Saharan Air Layer (SAL) activity usually ramps up in mid-June, peaks from late June to mid-August, and begins to subside after mid-August.

For the forecast west of 55W, broad high pressure over the central Atlantic extending westward to across Florida will change little through early next week controlling the wind flow pattern over the region. A weakening cold front will stall just N of 31N and W of 70W late in the weekend. In the long term, fresh southerly winds are expected to develop over the far western waters starting late Tue in advance of a cold front that will be moving across the southeastern U.S. These winds may become fresh to strong, south to southwest in direction, during the middle of next week. Moderate to fresh NE to E winds will pulse north of Hispaniola and in the Windward Passage each night into next week.

Posted 4 hours ago by NHC Forecaster Gr