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Atlantic Tropical Weather Discussion (Text)



000
AXNT20 KNHC 042319
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0005 UTC Fri Dec 4 2020

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
2300 UTC.

...MONSOON TROUGH/ITCZ...

The monsoon trough enters the Atlantic Ocean through Sierra Leone
and continues westward to near 07N15W. The ITCZ extends from 
07N15W to 06N34W to near the coast of French Guiana. A trough is
analyzed within the ITCZ and extends along 39W from 04N-12N. 
Scattered moderate convection is from 07N-10N between 20W-30W,
from 04N-12N between 30W-40W, and from 03N-06.5N between 40W-
45W.

GULF OF MEXICO...

A cold front extends from a 1015 mb low pressure over eastern
Alabama to near 23N92W where it becomes stationary. Abundant low-
level clouds with some shower activity are noted behind the 
front, and are banked up along the eastern slopes of the Sierra 
Madre Mountains in Mexico. An area of showers with embedded 
thunderstorms is observed ahead of the frontal boundary over the 
east-central Gulf reaching the Florida peninsula. Fresh northerly
winds are behind the front per recent scatterometer data, with 
seas of 8-11 ft. These winds will persist through this evening. 

The northern half of the cold front will move slowly across the 
Gulf. By Sat afternoon, the front will extend from the SW Florida
peninsula to the Bay of Campeche. South of 25N, the front will 
remain stationary. The cold front will weaken by Sat night. A 
new, stronger cold front will develop near the Mexican coast late
Sat. This new front will extend from Alabama to the Bay of 
Campeche by Sun afternoon, and exit the SE Gulf Mon afternoon. 
Near gale-force NW to N winds are expected west of the new cold 
front on Sun. Winds and seas will diminish across the Gulf by 
Tue.

CARIBBEAN SEA...

A large area of showers and scattered thunderstorms is noted over 
the western Caribbean and western Cuba, including the Isle of
Youth. A diffluent pattern aloft is helping to induce this convective
activity that roughly covers the area N of 15N W of 80W. Abundant
moisture will persist in this region, in a SE wind flow, tonight
and Sat.

The pressure gradient between a high pressure located W of Bermuda
and low pressure over N South America is causing strong trades 
across the central Caribbean. The most recent satellite-derived 
wind data confirmed the presence of these winds. As the Bermuda 
High retreats northeastward well north of these waters, a reduced
pressure gradient will weaken the trade winds across the Caribbean
through Mon, with peak winds of primarily fresh E trades just 
north of Colombia. 

A cold front should reach the Yucatan Channel on Mon afternoon, 
extend from Cuba to Honduras Tue afternoon, and perhaps move to 
the SW Caribbean on Wed afternoon. Increasing winds and seas are
expected in the wake of the front over the NW Caribbean, including
the Yucatan Channel and the Gulf of Honduras Mon night into Tue.

ATLANTIC OCEAN...

A cold front extends from a 1017 mb low pressure center near 
31N57W to 26N61W, then continues as a stationary front across the
SE Bahamas into to eastern Cuba. This front will dissipate by 
Sat. Patches of low level clouds are noted along the frontal 
boundary. Fresh NE winds are still seen behind the front over the
SE Bahamas. A 1028 mb surface high located W of Bermuda follows 
the front and dominates most of the SW N Atlantic, including 
Florida and the Bahamas. 

The high pressure will move northeastward ahead of another cold 
front moving off the NE coast of Florida. Strong S to SW winds 
will develop east of N Florida tonight ahead of the front. This 
system will extend from 31N74W to central Florida on Sat afternoon,
then weaken from 29N65W to the central Bahamas on Sun afternoon.
A developing low pressure system will sweep a new, strong cold 
front across the W Atlantic Mon and Tue. Strong to near gale SW 
winds are expected ahead of the new front with fresh to strong 
NW winds behind it. 

Farther E, and area of showers and thunderstorms persists over 
the Central Atlantic, extending from 18N-25N between 42W-48W. 
This convective activity is the result of an upper level low 
spinning near 24N46W. An upper-level trough extends from the low 
to near 04N48W. Upper diffluence ahead of this trough is helping 
to support convection near the ITCZ and the aforementioned trough
along 39W. At the surface, another trough, likely reflection of 
this low, is analyzed from 30N52W to 20N48W. Fresh to strong 
winds are on the E side of the trough axis due to the pressure 
gradient between the trough and strong high pressure located well
N of the area. A ridge dominates the eastern Atlantic.

$$
GR

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Page last modified: Friday, 04-Dec-2020 23:19:48 UTC