[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 151134
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST TUE DEC 15 2009

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...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1030 UTC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 5N7W 5N22W 6N38W 1N53W. ISOLATED
MODERATE CONVECTION IS WITHIN 100 NM N OF THE AXIS BETWEEN
26W-32W...AND WITHIN 30 NM EITHER SIDE OF THE AXIS BETWEEN
38W-41W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 0900 UTC...A SURFACE TROUGH HUGS THE NW GULF OF MEXICO
COASTLINE FROM NEAR BATON ROUGE LOUISIANA CONTINUING PARALLEL TO
THE TEXAS COASTLINE TO OFF THE NE MEXICO COAST NEAR 24N97W. A
LINE OF STRONG SHOWERS/THUNDERSTORMS IS WITHIN 30 NM OF THE
TROUGH AXIS...WITH SCATTERED SHOWERS EXTENDING TO THE NE ACROSS
THE SE UNITED STATES. FLASH FLOOD WATCHES AND FLOOD WARNINGS
REMAIN IN EFFECT FOR PORTIONS OF THE GULF COAST STATES. THE
TROUGH IS SUPPORTED BY AN UPPER LEVEL TROUGH EXTENDING OVER THE
GREAT PLAINS. DIFFLUENT FLOW ALOFT BETWEEN THIS UPPER TROUGH AND
AN UPPER LEVEL RIDGE EXTENDING FROM THE CARIBBEAN INTO THE W
ATLC IS ENHANCING THE SHOWER ACTIVITY ACROSS THE GULF COAST. THE
UPPER LEVEL TROUGH ALSO SUPPORTS A STRONG COLD FRONT CURRENTLY
ACROSS TEXAS WHICH IS FORECAST TO REACH THE GULF WATERS LATER
TODAY. BESIDES THE MOISTURE ACROSS THE NRN GULF...THE REMAINDER
OF THE BASIN IS COVERED BY DRY AIR ALOFT SUPPORTING GENERALLY
FAIR WEATHER ACROSS THE BASIN. ISOLATED SHOWERS ARE NOTED ACROSS
S FLORIDA AND THE FAR SE GULF S OF 25N E OF 86W DUE TO
CONVERGENCE NEAR A SURFACE TROUGH EXTENDING FROM S OF WEST PALM
BEACH TO N OF KEY WEST. EXPECT CONTINUED SHOWER ACTIVITY ACROSS
THE N GULF AS THE COLD FRONT CURRENTLY OVER TEXAS MOVES OFF THE
COAST LATER TODAY.

CARIBBEAN SEA...
STRONG ELY TRADEWINDS CONTINUE ACROSS THE CARIBBEAN AS A RESULT
OF A STRONG PRESSURE GRADIENT BETWEEN HIGH PRESSURE OVER THE W
ATLC AND LOW PRESSURE OVER NRN COLOMBIA. GALE FORCE WINDS TO 35
KT REMAIN NEAR THE COAST OF COLOMBIA AND ARE FORECAST TO PERSIST
THROUGH THE AFTERNOON. STRONG SUBSIDENCE IS ACROSS THE BASIN
AROUND AN UPPER LEVEL RIDGE CENTERED IN THE N CENTRAL CARIBBEAN
NEAR 18N75W PROVIDING GENERALLY FAIR WEATHER ACROSS THE AREA.
HOWEVER...ISOLATED LOW-LEVEL SHOWERS EMBEDDED IN THE ELY TRADES
ARE MOVING QUICKLY ACROSS PORTIONS OF THE CARIBBEAN CONCENTRATED
MOST E OF THE LESSER ANTILLES AND S OF HISPANIOLA. EXPECT THE
STRONG PRESSURE GRADIENT ACROSS THE BASIN TO WEAKEN AS A COLD
FRONT MOVES ACROSS THE GULF OF MEXICO ALLOWING THE GALE FORCE
WINDS TO DIMINISH.

ATLANTIC OCEAN...
A SHORTWAVE UPPER LEVEL TROUGH OVER THE N CENTRAL ATLC N OF THE
DISCUSSION AREA SUPPORTS A COLD FRONT THAT CLIPS THE AREA ALONG
32N55W 31N61W LIFTING N AS A WARM FRONT FROM 31N68W  TO THE
SOUTH CAROLINA COASTLINE NEAR 33N79W. POSSIBLE ISOLATED SHOWERS
ARE S OF THE FRONT FROM 27N-30N BETWEEN 62W-68W. RADAR IMAGERY
ALSO INDICATES ISOLATED SHOWERS ARE ALSO OFF THE S FLORIDA COAST
BETWEEN THE COASTLINE AND THE BAHAMAS DUE TO SURFACE CONVERGENCE
NEAR A SURFACE TROUGH EXTENDING FROM NW OF FREEPORT BAHAMAS TO S
OF WEST PALM BEACH FLORIDA TO N OF KEY WEST. ELSEWHERE ACROSS
THE W ATLC...A BROAD SURFACE RIDGE DOMINATES ANCHORED BY A 1021
MB HIGH NEAR 27N64W. THE SURFACE RIDGE IS SUPPORTED BY AN UPPER
LEVEL RIDGE EXTENDING FROM THE CARIBBEAN. FARTHER E...A DEEP
LAYER UPPER LEVEL TROUGH IS SUPPORTING A COLD FRONT EXTENDING
FROM E OF THE AZORES ISLANDS ENTERING THE DISCUSSION AREA NEAR
32N21W ALONG 25N25W 21N34W. A SHEAR LINE CONTINUES FROM THE
FRONT ALONG 20N44W 18N54W. ISOLATED SHOWERS ARE POSSIBLE WITHIN
60 NM OF THE FRONT AND SHEAR AXIS. WEAK HIGH PRESSURE IS SE OF
THE FRONT ANCHORED BY A 1015 MB HIGH NE OF THE CAPE VERDE
ISLANDS NEAR 19N20W.

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

$$
WALTON







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