Tropical Weather Discussion
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AXNT20 KNHC 132256

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
555 PM EST Wed Dec 13 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 1800 UTC surface analysis and satellite imagery through
2315 UTC.


A tight pressure gradient between a 1033 mb high pressure located
just south of the Azores and a low pressure system over western
Africa is resulting in gale force winds in the High Seas Forecast
area called Agadir, along the coast of Morocco. Very rough seas
are within the area of these winds. Winds and seas are forecast to
gradually diminish tonight into Thu. Please, refer to the Meteo-
France High Seas Forecast for more details.

The monsoon trough extends from the African coast near 07N12W to
06N18W. The Intertropical Convergence Zone axis continues from
06N18W to the coast of NE Brazil near 03N51W. Scattered moderate
convection is within about 60 nm N of the ITCZ axis between 23W-


A reinforcing and dry cold front is dissipating along 22N. A 1019
mb high pressure has developed over the NE Gulf while a 1023 mb
High pressure is near Tampico, Mexico. Under this weather pattern,
mainly light to gentle winds are noted across the Gulf region with
the exception of moderate northerly winds across the SE waters ,
including the Yucatan Channel. Broken cold air stratocumulus
clouds are still noted over the eastern Gulf in the wake of the
dissipating front. Water Vapor imagery shows a band of transverse
high clouds over northern Mexico and the NW Gulf in association
with a subtropical jet that is drawing upper level moisture from
the EPAC region into the Gulf region. Looking ahead, another cold
front is forecast to enter the northern Gulf Thu, then reach from
the Florida Big Bend area in the NE Gulf to near Tampico Mexico
by Fri afternoon, then stall from Tampa to the Bay of Campeche on
Sat before lifting back to the W and NW through Sun. Gale force
winds are possible along the coast of Mexico near Tampico Fri
night and Sat.

A weakening stationary front extends from northern Haiti to the
easternmost tip of Jamaica to the SW Caribbean near 11N80W. A wide
band of multi-layered clouds is associated with the frontal
boundary. A well defined swirl of low clouds is along the frontal
bondary near 13N79W moving southward. This front produced heavy
rains over eastern Cuba Sunday through Thuesday. The front will
continue to dissipate to a remnant trough tonight. Moisture
associated with this trough is forecast to move westward across
the western Caribbean Thu and Fri in an easterly wind flow. An
earlier scatterometer satellite pass showed moderate to locally
fresh northerly winds across the Windward Passage in the wake of
the front. Gentle to moderate trades are noted across the east and
central Caribbean, with moderate to fresh winds within about 90 nm
of the coast of Colombia. Winds are forecast to increase to 20-25
kt over the south-central Caribbean on Thu night, with gale
conditions possible Sat night and Sun night as high pressure
builds N of area. A reinforcing and dry cold front has reached
western Cuba. This will reinforce the cool and dry airmass over
western Cuba. Temperatures could drop below 10 degree Celsius
(50F)in some places across the Havana-Matanzas plains overnight

Cloudiness has increased over Hispaniola today due to the
proximity of a weakening stationary front that currently crosses
northern Haiti. Isolated to scattered light to moderate showers
are still possible tonight and early Thu. Then, moisture will
diminish later on Thu as the frontal boundary continues to weaken
and begins to drift westward.

Water vapor imagery indicates middle to upper level troughing
moving offshore of the eastern CONUS this morning supporting the
Special Features cold front extending from 32N72W SW to the
southern Florida peninsula near Key Biscayne. The reinforcing
cold front is expected to merge with a stationary front on
Thursday that is currently analyzed to the E-SE from 32N65W to
the Turks and Caicos islands to the Windward Passage region. The
reinforcing cold front remains relatively convection-free...while
isolated showers are occurring within 120 nm either side of the
stationary front. Farther east...a surface ridge influences much
of the central and eastern Atlc...anchored by a 1034 mb high
centered S of the Azores near 37N28W. However...within the
southeastern periphery of the ridge nearing the Cape Verde
Islands...a dissipating cold front extends from the coast of
Africa near 16N17W to 18N26W. The primary area of concern with
the front is the large area of strong to near gale force NE winds
generally N of 20N E of 33W. The pressure gradient associated
with this wind field is expected to relax by Friday.

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