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Atlantic Tropical Weather Discussion

AXNT20 KNHC 121728

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1805 UTC Tue Dec 12 2017

Tropical Weather Discussion for North America, Central America
Gulf of Mexico, Caribbean Sea, northern sections of South
America, and Atlantic Ocean to the African coast from the
Equator to 32N. The following information is based on satellite
imagery, weather observations, radar and meteorological analysis.

Based on 1200 UTC surface analysis and satellite imagery through 
1545 UTC.


The monsoon trough meanders along the SW African coast of the 
Gulf of Guinea, before exiting the coast near 05N90W to near 
06N13W. The Intertropical Convergence Zone extends from near 
06N15W to 07N20W to 04.5N31W to 03N46W to the coast of far NE 
Brazil near 02N51W. Scattered moderate isolated strong 
convection is from 03.5N to 07N between 18W and 52W.


A surface ridge continues across all but the northern Gulf this 
morning, anchored by a 1027 mb high centered offshore of eastern 
Mexico near 22N96W. Gentle to moderate anticyclonic winds are 
noted across central and SE portions of the basin late this 
morning. Meanwhile fresh to strong N to NW winds are occurring 
across NE portions on both sides of a dry cold front moving into 
the N Gulf waters, where a 1524 UTC ASCAT pass showed NW winds 
around 25 kt across the SE Louisiana and Mississippi coastal 
waters. Current buoy data indicates seas across NE portions have 
built to 6-9 ft. The front is forecast to sweep ESE across the N 
half of the basin through tonight and become strung out W to E 
along about 24N Wednesday morning. Fresh to strong NW winds will 
dominate the NE Gulf behind the front. Weak high pressure will 
quickly replace the dissipated frontal trough through Thursday.

A quasistationary frontal boundary persists across the central 
and SW Caribbean this morning, from near the E end of Cuba 
across the W coast of Jamaica to W central Panama. Morning 
satellite imagery suggest the front is drifting W to the S of 
Jamaica. Broken to overcast multi-layered clouds prevail to the 
W of the front from beyond the Bahamas to Panamas and Costa 
Rica, with active moderate to deep convection along the front 
from 14N to the S coast of Jamaica. Northerly winds continue to 
gradually diminish to the W of the front, and are assumed to 
have dropped to 20-25 kt to the S of 20N and between the front 
and 84W this morning, while 15-20 kt N winds are elsewhere W of 
front. Buoy 42057 between Jamaica and Honduras has fallen to 8 
ft. Atlantic high pressure nosing into the E Caribbean is 
responsible for nudging the front W and is producing gentle to 
moderate E to SE tradewinds to the E of 73W. A few clusters of 
shallow convection are noted on satellite imagery between 68W 
and 72W, associated with a weak easterly perturbation. The front 
is forecast to meander across this general area and gradually 
weaken through Thursday.

Fair weather conditions prevail across the island this morning 
while the stationary front remains to the W across far E Cuba. 
Dry and fairly stable atmospheric conditions are expected across 
the island today, with best low level moisture expected to 
converge across W portions of the island this afternoon due to 
proximity of the front and diurnal sea breezes.

Water vapor imagery indicates a weakening narrowing middle to 
upper level troughing over the western North Atlc waters to near 
30N70W and supports a lingering stationary front extending from 
near 31N60W to just NW of the Turks and Caicos to the E end of 
Cuba. Satellite imagery suggests very minor waves or undulations 
along the boundary E of 70W. Broken to overcast low and middle 
level clouds prevail within 120 nm NW of the front, where 
scattered light to moderate showers are occurring. A next broad 
deep layered trough is currently sweeping from the Great Lakes 
region into the N central Gulf states, and supporting a 
reinforcing cold front across the N Gulf. Weak and narrow 
surface ridging extends from the Gulf of Mexico NE across S 
Florida to near Bermuda ahead of this approaching front. A 
strong and broad prevail elsewhere across the central and E 
Atlc, centered on a 1035 mb high near 38N32W. Fresh to locally 
strong anticylonic flow is seen S and SW of the ridge, and 
generally E of 53W, where a surface trough is found drifting W. 
A weakening and narrow middle to upper layer trough is found 
along 50W and is acting to enhance an area of scattered moderate 
to strong convection from 16N to 30N between 45W and 50W. 
Farther E, a cold front is moving S and SSW across the NE Atlc 
and a back door fashion, extending from the SW coast of Western 
Sahara near 22N17W to 26N33.5W. 

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