[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 191754
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST WED DEC 19 2012

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 1715 UTC.

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

THE MONSOON TROUGH EXTENDS 100 NM OFF THE NORTHWESTERN COAST OF
LIBERIA. THE ITCZ CONTINUES FROM 5N12W SOUTHWESTWARD TOWARDS THE
EQUATOR AND 22W THEN TO 1N35W TO THE COAST OF NORTHERN BRAZIL
CLOSE TO THE EQUATOR AND 49W. SCATTERED PRECIPITATION IS
OBSERVED FROM THE EQUATOR TO 6N BETWEEN 12W AND 22W. SIMILAR
TYPE OF CONVECTION IS OBSERVED WITHIN 250 NM N OF THE ITCZ
BETWEEN 25W AND 32W.

...DISCUSSION...

THE GULF OF MEXICO...

AT THE MIDDLE TO UPPER LEVELS...THE SOUTHERN PORTION OF A RIDGE
POSITIONED OVER THE CENTRAL AND EASTERN U.S.A IS PROVIDING
WESTERLY AND NORTHWESTERLY WIND FLOW. AT THE SURFACE
SOUTHEASTERLY WINDS OR RETURN FLOW OF 10 KT TO 20 KT ASSOCIATED
TO A 1021 MB HIGH PRESSURE OVER NORTHEASTERN FLORIDA DOMINATE
THE REGION. AN EXTENSION OF A DYING COLD FRONT IS ACROSS THE
FLORIDA KEYS AND EXTENDS TO THE EASTERN GULF NEAR 25N82W.
ACCORDING TO THE WATER VAPOR IMAGERY THERE IS MODERATE TO STRONG
SUBSIDENCE OVER THE GULF SUPPORTING NO CONVECTIVE ACTIVITY AT
THIS TIME.

WITHIN THE NEXT 24 HOURS...THE RETURN FLOW IS
EXPECTED TO CONTINUE OVER THE REGION WHILE A NEW COLD FRONT
STARTS ENTERING THE NORTHWESTERN GULF.

THE CARIBBEAN SEA...

AT THE MIDDLE TO UPPER LEVELS...THE NORTHWESTERN CARIBBEAN HAS
WESTERLY TO SOUTHWESTERLY WINDS UP TO 45 KT ASSOCIATED TO THE
UPPER RIDGE AXIS THAT EXTENDS OVER THE GULF REGION. THE CENTRAL
AND EASTERN CARIBBEAN IS DOMINATED BY UPPER LEVEL SOUTHEASTERLY
WIND ASSOCIATED TO RETURN FLOW FROM AN ANTICYCLONE LOCATED IN
THE TROPICAL CENTRAL ATLC. AT THE SURFACE...WEAK PRESSURE
GRADIENT DOMINATES THE REGION. TRADE WINDS OF 10 KT TO 20 KT ARE
E OF 75W IN THE CENTRAL AND EASTERN CARIBBEAN. IN THE WESTERN
CARIBBEAN RETURN FLOW OF THE SAME MAGNITUDE COVERS THE REGION.
WATER VAPOR IMAGERY SHOWS MODERATE TO STRONG SUBSIDENCE OVER THE
ENTIRE CARIBBEAN WHICH IS ALLOWING FAIR WEATHER CONDITIONS.

WITHIN 24 HOURS...MOSTLY RETURN FLOW WILL COVER THE REGION AS
THE HIGH PRESSURE LOCATED OVER NORTHER FLORIDA DISPLACES TO THE
SOUTHWEST IN THE WESTERN ATLC. AN INCREASE OF WIND MAGNITUDE UP
TO 25 KT IS POSSIBLE IN THE CENTRAL AND SOUTHERN CARIBBEAN.

THE ATLANTIC OCEAN...

IN THE MIDDLE TO UPPER LEVELS...A TROUGH ASSOCIATED TO AN UPPER
LOW CENTERED NEAR 41N67W COVERS THE WESTERN ATLC FOLLOWED BY AN
UPPER RIDGE IN THE CENTRAL ATLANTIC WITH AXIS EXTENDING TO THE
GREATER AND LESSER ANTILLES. THE UPPER LEVEL TROUGH IS
SUPPORTING A COLD FRONT THAT ENTERS THE REGION NEAR 30N63W AND
EXTENDS SOUTHWEST TO 27N71W THEN TO THE S OF THE FLORIDA
PENINSULA NEAR 25N80W. NO CONVECTIVE ACTIVITY IS OBSERVED
ASSOCIATED TO THIS SURFACE FEATURE. IN THE CENTRAL ATLC...A
NARROW UPPER LEVEL TROUGH SUPPORTS A SURFACE TROUGH THAT EXTENDS
FROM 28N38W SOUTHWESTWARD TO 24N44W 19N49W. THIS UPPER LEVEL
NARROW TROUGH ALSO SUPPORTS A STATIONARY FRONT NE OF THE SURFACE
TROUGH THAT ENTERS THE REGION NEAR 29N27W AND CONTINUES
SOUTHWESTWARD TO 26N34W. IN THE EASTERN ATLC...E OF THE
STATIONARY FRONT A 1021 MB HIGH NEAR 29N20W STEADILY DISPLACES
NORTHEAST OUT OF THE REGION IN 24 HOURS. SOME SHOWER ACTIVITY
CAN BE FOUND AHEAD OF THE STATIONARY FRONT WHERE THE BOUNDARY
BETWEEN THE MIDDLE TO UPPER LEVEL NARROW TROUGH AND A RIDGE THAT
STARTS TO BUILD E OF 35W IS FOUND. THIS AREA OF PRECIPITATION
LIES N 16N BETWEEN 20W AND 36W.

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

$$
NR/CW






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