[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 171743
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST SAT DEC 17 2011

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 1700 UTC.

...THE ITCZ/THE MONSOON TROUGH...

THE ITCZ EXTENDS ACROSS FAR WRN AFRICA TO THE SRN COAST OF
LIBERIA NEAR 5N9W CONTINUING W ALONG 7N26W 6N39W 6N47W.
SCATTERED MODERATE/STRONG CONVECTION IS WITHIN 200 NM N...AND
100 NM S OF THE AXIS BETWEEN 29W-45W.

...DISCUSSION...

THE GULF OF MEXICO...
A COLD FRONT CONTINUES TO SLOWLY SHIFT SE ACROSS THE NRN GULF
EXTENDING FROM NRN FLORIDA NEAR 31N83W CONTINUING WSW ALONG
28N89W 27N95W BECOMING STATIONARY AND TURNING SWD ALONG 24N96W
AND MOVING INLAND INTO MEXICO NEAR 21N97W CONTINUING NWD INTO N
CENTRAL MEXICO. OVERCAST SKIES WITH POSSIBLE FOG AND ISOLATED
SHOWERS ARE WITHIN 150 NM NW OF THE FRONT ALONG WITH NELY WINDS
UP TO 20 KTS. THE FRONT LACKS ANY STRONG UPPER LEVEL SUPPORT AS
A STRONG UPPER LEVEL RIDGE COVERS MUCH OF THE BASIN WITH AXIS
EXTENDING FROM THE WRN CARIBBEAN INTO THE WRN ATLC. A WEAK
SHORTWAVE UPPER TROUGH TO THE N OF THE AREA IS THE ONLY SUPPORT
THE SYSTEM HAS. THE UPPER RIDGE IS SUPPORTING A WEAK SURFACE
RIDGE TO THE E OVER THE WRN ATLC WHICH IS INFLUENCING THE
REMAINDER OF THE GULF AND MAINTAINING MOSTLY FAIR CONDITIONS
WITH A FEW PATCHES OF CLOUDS AND POSSIBLE ISOLATED SHOWERS. DUE
TO THE LACK OF UPPER LEVEL SUPPORT...THE FRONT IS EXPECTED TO
STALL AND DISSIPATE OVER THE NEXT DAY OR SO AS HIGH PRESSURE
BUILDS OVER THE REGION.

THE CARIBBEAN SEA...
MUCH OF THE NRN CARIBBEAN IS EXPERIENCING MOSTLY FAIR WEATHER
DUE TO DRY AIR ALOFT AROUND AN UPPER LEVEL RIDGE EXTENDING FROM
NRN COLOMBIA ACROSS ERN CUBA INTO THE WRN ATLC. THIS PATTERN IS
ALSO PROVIDING DIFFLUENCE ALOFT OVER THE SW CARIBBEAN...WHICH
COMBINED WITH SURFACE CONVERGENCE NEAR THE MONSOON TROUGH
EXTENDING ACROSS PANAMA TO NRN COLOMBIA IS HELPING PRODUCE
SCATTERED SHOWERS/THUNDERSTORMS S OF 14N BETWEEN 79W-85W...AS
WELL AS S OF 12N BETWEEN 75W-79W. ACROSS THE ERN CARIBBEAN...A
SHEAR LINE EXTENDS ACROSS THE FAR SE PORTION ALONG 12N62W T0
12N71W DEPICTING THE DELINEATION BETWEEN STRONGER NE WINDS UP TO
20 KTS TO THE N...AND WEAKER ELY WINDS OF 10 KTS. ISOLATED
SHOWERS ARE WITHIN 75 NM N OF THE AXIS. EXPECT LITTLE CHANGE
OVER THE NEXT 24 HOURS WITH MOISTURE REMAINING OVER THE SW
CARIBBEAN AND STRONG NE WINDS OVER THE CENTRAL AND ERN
CARIBBEAN.

THE ATLANTIC OCEAN...
UPPER LEVEL RIDGING COVERS THE WRN ATLC SUPPORTING A 1023 MB
HIGH NEAR 29N68W PROVIDING MOSTLY FAIR WEATHER ACROSS THE WRN
ATLC BESIDES A FEW AREAS OF STRATOCUMULUS CLOUDS THAT MAY SOURCE
A FEW ISOLATED SHOWERS. AN UPPER LEVEL LOW IS TO THE E NEAR
28N50W SUPPORTING A 1009 MB LOW NEAR 26N50W. TWO FRONTAL
BOUNDARIES ACCOMPANY THE LOW. THE MAIN FRONT IS NOW BEGINNING TO
DISSIPATE WITH AN OCCLUDED PORTION ALONG 28N52W TO 29N48W THEN
TURNING TO COLD ALONG 26N45W 20N46W 15N52W. A SHEAR AXIS
CONTINUES FARTHER TO THE W ALONG 13N56W TO 12N62W AND INTO THE
SE CARIBBEAN. A SECONDARY COLD FRONT EXTENDS FROM THE LOW CENTER
ALONG 24N49W TO 18N54W. FINALLY...A PRE-FRONTAL TROUGH IS E OF
THE PRIMARY FRONT ALONG 18N46W TO 12N51W. THE STRONGEST
SHOWER/THUNDERSTORM ACTIVITY IS E OF THE MAIN FRONT N OF 19N
BETWEEN 41W-47W. ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO NEAR
THE LOW CENTER FROM 23N-30N BETWEEN 47W-53W. THE REMAINDER OF
THE ERN ATLC IS EXPERIENCING MOSTLY FAIR WEATHER DUE TO SURFACE
RIDGING AROUND A 1036 MB HIGH BETWEEN THE AZORES AND MADEIRA
ISLANDS NEAR 35N23W. THE RIDGE IS SUPPORTED BY AN UPPER LEVEL
RIDGE CENTERED NEAR 35N25W. TO THE S...AN UPPER LEVEL LOW IS
NEAR 23N27W CAUSING NO SIGNIFICANT WEATHER BESIDES A FEW UPPER
LEVEL CLOUDS. EXPECT THE LOW PRESSURE SYSTEM IN THE CENTRAL ATLC
TO REMAIN SOMEWHAT STATIONARY OVER THE NEXT DAY OR SO.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
WALTON





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