[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181742 CCA
TWDAT

TROPICAL WEATHER DISCUSSION...CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST TUE DEC 18 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 ACROSS AFRICA AND IT REACHES THE WEST
AFRICAN COAST NEAR THE SIERRA LEONE AND LIBERIA BORDER. THE ITCZ
CONTINUES FROM 7N12W 5N26W 5N40W TO 3N47W.
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS WITHIN 200
NM S OF THE ITCZ BETWEEN 10W AND 40W. ISOLATED MODERATE
CONVECTION IS WITHIN 300 NM N OF THE ITCZ BETWEEN 40W AND 50W.

...DISCUSSION...

THE GULF OF MEXICO...

IN THE MIDDLE TO UPPER LEVELS A DEEP LAYER TROUGH IS DIGGING
THROUGH THE SOUTHEASTERN U.S.A....PASSING THROUGH THE
NORTHEASTERN CORNER OF THE GULF OF MEXICO...INTO THE CENTRAL
GULF WATERS...TO THE MEXICO GULF COAST NEAR 22N98W. MOSTLY
WESTERLY TO SOUTHWESTERLY WINDS GREATER THAN 50 KT ARE
SUPPORTING A FAST MOVING COLD FRONT IN THE SURFACE. THE COLD
FRONT EXTENDS FROM NORTHWESTERN FLORIDA NEAR 30N83W THEN EXTENDS
ACROSS THE CENTRAL GULF NEAR 24N90W TO 22N93W. A STATIONARY
FRONT CONTINUES TO THE BAY OF CAMPECHE NEAR 19N94W. A
PRE-FRONTAL TROUGH EXTENDS ACROSS CENTRAL FLORIDA FROM 30N78W
27N82W TO 25N86W. NO PRECIPITATION IS CURRENTLY ASSOCIATED WITH
THE FRONT OR PRE-FRONTAL TROUGH. ANOTHER SURFACE TROUGH IS
NORTHWEST OF THE YUCATAN PENINSULA FROM 23N87W 21N89W TO 19N91W.
BEHIND THE COLD FRONT...A SURFACE 1017 MB HIGH IS CENTERED IN
THE NORTHERN GULF COAST.

WITHIN 24 HOURS...THE SURFACE HIGH IS EXPECTED TO MOVE
NORTHEASTWARD TOWARD N FLORIDA. THIS WILL DISPLACE THE COLD
FRONT ACROSS FLORIDA AND INTO THE WEST ATLANTIC.

THE CARIBBEAN SEA...

IN THE MIDDLE TO UPPER LEVELS...ANTICYCLONIC WIND FLOW COVERS
THE ENTIRE CARIBBEAN. WIND MAGNITUDE UP TO 30 KT IN THE MIDDLE
LEVELS AND DRY AIR SUBSIDENCE AS SHOWN BY THE WATER VAPOR
SATELLITE IMAGERY DOMINATE THE REGION PROVIDING FAIR CONDITIONS.
AT THE SURFACE...TRADE WINDS OF 15 KT TO 20 KT WITH A WEAK
PRESSURE GRADIENT IS ACROSS THE AREA. WITHIN 24 HOURS...SIMILAR
CONDITIONS AT THE SURFACE ARE EXPECTED.

THE ATLANTIC OCEAN...

IN THE WESTERN ATLC...THE MIDDLE TO UPPER LEVEL TROUGH MENTIONED
IN THE GULF OF MEXICO SECTION ABOVE SUPPORTS THE SURFACE
PREFRONTAL TROUGH PORTION THAT LIES 105 NM EAST OF THE
NORTHEASTERN FLORIDA COASTLINE. SURFACE RIDGING DOMINATES THE
REMAINDER OF THE WEST ATLC. ALOFT IN THE CENTRAL ATLC...A RIDGE
TROUGH PATTERN WITH UPPER LEVEL WINDS GREATER THAN 50 KT
CHARACTERIZES THE REGION. THE TROUGH PORTION OF THIS PATTERN
SUPPORTS A SURFACE COLD FRONT THAT ENTERS THE REGION FROM 29N32W
SOUTHWESTWARD TO 27N36W 24N40W. A SURFACE TROUGH CONTINUES TO
22N45W. THERE ARE SCATTERED SHOWERS WITHIN 100 NM AHEAD OF THE
COLD FRONT. WEAK SURFACE RIDGING COVERS THE REST OF THE CENTRAL
ATLC. IN THE EASTERN ATLC...DRY AIR SUBSIDENCE FROM ALOFT AND
WEAK SURFACE RIDGING ARE PROVIDING FAIR WEATHER CONDITIONS N OF
8N E OF 25W.

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

$$
NAR/CW








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