[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 310543
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST SAT DEC 31 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0500 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF
LIBERIA NEAR 6N11W CONTINUING TO 5N14W. THE ITCZ CONTINUES FROM
5N14W ALONG 3N25W 2N34W 2N43W EQ50W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS WITHIN 60 NM EITHER SIDE THE AXIS BETWEEN
11W-16W. SIMILAR ACTIVITY IS FROM 3N-5N BETWEEN 30W-39W. SOME OF
THIS ACTIVITY IS INFLUENCE BY AN UPPER LEVEL LOW TO THE N NEAR
19N37W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY CONTINUES TO SHOW MOSTLY DRY AIR ALOFT IN
WSW FLOW ACROSS THE GULF OF MEXICO TONIGHT AROUND A BROAD UPPER
RIDGE COVERING THE CARIBBEAN AND W ATLC...WHICH IS HELPING
MAINTAIN MOSTLY FAIR SURFACE CONDITIONS WITH LIGHT WINDS AND
CLEAR SKIES BASIN-WIDE. WEAK SURFACE RIDGING AROUND A 1020 MB
HIGH NEAR 26N87W IS HELPING CONTRIBUTE TO THE FAIR WEATHER.
SATELLITE IMAGERY INDICATES A SMALL AREA OF FOG ALONG THE TEXAS
COASTLINE. A WEAK SURFACE TROUGH EXTENDS DOWN THE YUCATAN
PENINSULA WHICH IS SUPPORTING A FEW ISOLATED SHOWERS JUST N OF
THE LANDMASS. A SHORTWAVE UPPER TROUGH IS BEGINNING TO MOVE
ACROSS THE NRN GULF...CURRENTLY OVER LOUISIANA...WHICH IS
SUPPORTING A COLD FRONT N OF THE AREA. COMPUTER GUIDANCE
INDICATES THAT THE FRONT WILL STAY N OF THE AREA...AND WEAK
SURFACE RIDGE WILL REMAIN ACROSS THE BASIN THROUGH LATE
SATURDAY/EARLY SUNDAY BEFORE THE NEXT COLD FRONT MOVES OFF THE
TEXAS COAST INTO THE NW GULF WITH STRONG NE WINDS BEHIND IT.

CARIBBEAN SEA...
A BROAD UPPER RIDGE IS ACROSS THE CARIBBEAN TONIGHT WITH AXIS
ALONG 66W. WATER VAPOR IMAGERY ALSO INDICATES DRY AIR
ACCOMPANYING THE RIDGE WHICH IS LIMITING CONVECTION. A FEW
ISOLATED SHOWERS ARE NOTED FROM 16N-20N BETWEEN 73W-76W...AND
FROM 17N-18N BETWEEN 62W-66W. THE REMAINDER OF THE BASIN HAS
MOSTLY CLEAR SKIES. NE-E TRADEWIND FLOW OF 20-25 KTS IS ACROSS
THE AREA REACHING 30 KTS IN THE FAR ERN CARIBBEAN AND THE SW
CARIBBEAN NEAR THE COAST OF COLOMBIA. THE STRONG PRESSURE
GRADIENT BETWEEN HIGH PRESSURE ACROSS THE GULF AND W ATLC AND
LOWER PRESSURES OVER S AMERICA IS HELPING MAINTAIN THE STRONG
WINDS. THIS WILL PERSIST THROUGH THE WEEKEND UNTIL A FRONT MOVES
THROUGH THE GULF OF MEXICO ON SUNDAY AND INTO THE W ATLC
ALLOWING THE PRESSURE GRADIENT TO RELAX.

ATLANTIC OCEAN...
BROAD UPPER LEVEL RIDGING DOMINATES THE MAJORITY OF THE ATLC
WHICH IS HELPING SUPPORT A BROAD SURFACE RIDGE EXTENDING FROM A
1041 MB HIGH JUST E OF THE AZORES ISLANDS WITH AXIS EXTENDING
WSW ALONG 32N50W 29N66W TO SE FLORIDA. HOWEVER...A WEAKNESS IN
THE UPPER RIDGE ALONG 66W IS SUPPORTING A SURFACE TROUGH ALONG
25N70W TO 20N72W WITH SCATTERED SHOWERS/POSSIBLE THUNDERSTORMS
TO THE E FROM 23N-28N BETWEEN 65W-68W. THE REMNANTS OF A
STATIONARY FRONT ALSO STILL REMAIN ALONG 32N65W 28N72W 24N75W
WITH NO ASSOCIATED SHOWER ACTIVITY. THIS BOUNDARY IS EXPECTED TO
CONTINUE TO DISSIPATE DUE TO THE LACK OF UPPER LEVEL SUPPORT.
THE REMAINDER OF THE BASIN IS DOMINATED BY THE AFOREMENTIONED
SURFACE HIGH NEAR THE AZORES ISLANDS MAINTAINING MOSTLY FAIR
WEATHER. HOWEVER...AN UPPER LEVEL LOW IS S OF THE SURFACE HIGH
CENTERED NEAR 18N38W PROVIDING DIFFLUENCE ALOFT ACROSS THE SE
ATLC WHICH IS HELPING SUPPORT UPPER LEVEL CLOUDS AND SOME
CONVECTION NEAR THE ITCZ. THE SURFACE RIDGE WILL REMAIN THE
DOMINANT FEATURE THROUGHOUT THE NEXT 12 HOURS BEFORE A COLD
FRONT ENTERS THE W ATLC WATERS LATER THIS AFTERNOON/EVENING.

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

$$
WALTON





This weather bulletin was brought to you by:
www.nashvilleweather.net