Tropical Waves

A new far eastern Atlantic tropical wave is analyzed near 17W based on satellite imagery and on model diagnostics. It is moving westward near 15 kt. Satellite imagery shows an ill-defined mid- level cyclonic circulation near 11N17W. Increasing scattered showers and thunderstorms are west of the wave to near 21N from 08N to 10N.

An eastern Atlantic tropical wave has its axis along 37W south of 21N moving westward at 15 to 20 kt. Increasing scattered moderate convection is within 150 nm either side of the wave from 08N to 09N and from 12N to 14N.

A central Atlantic tropical wave has its axis along 48W south of 19N moving westward at 15 to 20 kt. Increasing scattered moderate to isolated strong convection is east of the wave to near 45W and from 10N to 13N.

A central Caribbean tropical wave is along 72W south of 19N. It is moving westward at about 15 kt. No significant convection is occurring with this wave.

A western Caribbean tropical wave has its axis along 87W south of 20N to inland Central America, and reaches farther south to the eastern Pacific Ocean. It is moving westward at around 15 kt. Scattered moderate convection has recently formed over the northwest portion of Honduras and near its coast behind the wave.

Monsoon Trough/ITCZ

The monsoon trough enters the Atlantic near 18N16W and continues southwestward to 10N22W, then to 12N30W to 11N40W and to 10N49W, where it transitions to the ITCZ to 10N55W and to 10N60W. Outside of convection associated with tropical wave, scattered moderate to isolated strong convection is within 60 nm south of the trough between 32W-35W. Scattered moderate convection is south of the trough from 06N to 10N between 29W-33W.

Gulf Of America

A mid to upper-level trough stretches from southeastern Georgia to the NE Gulf and to the northern Yucatan Peninsula. A mid-level low is near 27N86W. To the southwest of these features, broad mid to upper-level anticyclonic flow covers the basin south of about 27N. Plenty of instability is in place over most of the eastern Gulf providing favorable conditions for the trough and low to aid in the development of additional showers and thunderstorms over the NE Gulf through Sat as a couple of shortwave troughs swing eastward across this same part of the Gulf.

Otherwise, relatively weak high pressure across the supported by a 1017 mb high center at 26N91W is providing for generally light to gentle anticyclonic winds throughout, except for fresh to strong NE winds west of the Yucatan Peninsula due the pressure gradient associated with a trough. Seas are generally 3 ft or less.

For the forecast, the aforementioned weak high pressure centered over the central Gulf will prevail over the basin through early next week. A weak pressure pattern will support mostly gentle to moderate winds and slight to locally moderate seas across much of the basin. A surface trough will generate fresh to locally strong winds north and west of the Yucatan Peninsula in the early evenings. These winds will spread westward away from the peninsula at night as the trough migrates into the SW Gulf.

Caribbean Sea

See Tropical Waves section above for information on convection across the basin.

The pressure gradient between weak high pressure centered S of Bermuda and low pressure over northern Colombia is supporting fresh to strong trades over the south- central basin between 69W and 75W, with moderate to fresh trades elsewhere, except gentle over the NW basin. Seas are moderate, except 7 to 9 ft in the south-central portion as noted in overnight satellite altimeter data passes. Slight sea state over the northwest part of the sea.

Isolated showers and isolated thunderstorms are noted south of 14N east of 70W.

For the forecast, the pressure gradient associated to relatively weak high pressure over the western Atlantic will continue to sustain fresh to strong trade winds and rough seas across the south-central Caribbean through much of the forecast period. Moderate to fresh trades and moderate seas will prevail over the north- central and eastern Caribbean through the weekend and into early next week. A tropical wave will move across the tropical Atlantic and into the far eastern Caribbean early next week enhancing the trade wind flow across those waters. Elsewhere, moderate or lighter winds and slight to moderate seas are expected.

Atlantic Ocean

See Tropical Waves section for information on convection in deep tropics.

A weak 1018 mb low is just north of the area near 33N51W, with a trough extending southwestward to another weak low of 1017 mb near 30N56W. The trough continues from this low to near 27N65W. Scattered thunderstorms are along and near the trough and 1017 mb low from 27N to 30N between 55W and 58W. Isolated showers and thunderstorms are present elsewhere north of 25N between 55W and 78W. The remainder of the basin remains under the influence of subtropical ridging, generally allowing for moderate or weaker winds and seas, except for a belt of moderate to fresh trades between 12N and 22N, where seas are 5 to 7 ft. Fresh to locally strong north to northeast winds prevail across the northeastern waters from the Canary Islands southward to near 18N and east of about 22W. Seas over those waters are 6 to 9 ft.

For the forecast west of 55W, the weak pressure gradient in place will support mostly light to gentle winds over most of the waters north of 23N going into early next week. Moderate to fresh trades are expected south of about 23N, especially off northern Hispaniola through the period. These trades may pulse to fresh to strong speeds off northern Hispaniola at night through most of the forecast period. Meanwhile, the northern portion of tropical wave is expected to move through the eastern portion of the area early next week enhancing the trades some.

Posted 0 minutes ago by NHC Forecaster Aguirre