[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 041800
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST FRI DEC 04 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1700 UTC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 7N11W 5N20W 3N34W 2N54W. ISOLATED
MODERATE CONVECTION IS FROM 3N-6N BETWEEN 25W-27W. SCATTERED
MODERATE CONVECTION IS FROM 7N-11N BETWEEN 34W-39W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 1500 UTC...A STATIONARY EXTENDS FROM THE SRN TIP OF THE
FLORIDA PENINSULA NEAR 25N81W ALONG 25N85W TO THE YUCATAN PENINSULA
NEAR 21N89W. RADAR IMAGERY INDICATES ISOLATED SHOWERS/THUNDERSTORMS
WITHIN 75 NM OF THE FRONT AXIS...WITH SCATTERED
SHOWERS/THUNDERSTORMS FARTHER N AFFECTING CENTRAL FLORIDA FROM
26N-28N E OF 84W. THE FRONTAL SYSTEM IS SUPPORTED BY AN UPPER LEVEL
TROUGH DIGGING ACROSS THE CENTRAL CONUS INTO TEXAS AND NRN MEXICO.
DIFFLUENT FLOW ALOFT BETWEEN THIS UPPER TROUGH AND AN UPPER LEVEL
RIDGE EXTENDING FROM THE CARIBBEAN INTO THE W ATLC IS SUPPORTING THE
SHOWER ACTIVITY NEAR THE FRONT...AS WELL AS SCATTERED
SHOWERS/THUNDERSTORMS ACROSS N FLORIDA AND THE NE GULF WATERS FROM N
OF 28N W OF 26W. A SURFACE TROUGH IS ANALYZED IN THE NW GULF...THE
BEGINNINGS OF A LOW PRESSURE AREA EXPECTED TO FORM LATER THIS
AFTERNOON. THE AXIS EXTENDS FROM 29N94W ALONG 26N95W TO 23N94W. GALE
FORCE WINDS ARE EXPECTED TO DEVELOP ACROSS THE NW GULF AS A STRONG
PRESSURE GRADIENT CONTINUES BUILDING BETWEEN THE LOW PRESSURE
FORMING OVER WATER AND STRONG HIGH PRESSURE TO THE NW OVER NRN
TEXAS. WINDS UP TO 30 KT ARE ALREADY BEING REPORTED OFF THE S TEXAS
COAST. RADAR IMAGERY INDICATES CONTINUED SHOWER ACTIVITY OVER THE NW
GULF N OF 24N W OF 92W...TURNING TO SNOW NEAR THE TEXAS/LOUISIANA
COASTLINE. EXPECT CONTINUED SHOWER ACTIVITY ACROSS THE MAJORITY OF
THE GULF OVER THE NEXT 24 HRS AS THE STATIONARY FRONT REMAINS IN
PLACE OVER THE SE GULF...AND LOW PRESSURE FORMS OVER THE W GULF AND
QUICKLY PUSHES E THEN NE. ALSO EXPECT GALE FORCE WINDS TO DEVELOP
OVER THE NEXT FEW HRS IN THE NW GULF.

CARIBBEAN SEA...
THE MAJORITY OF THE CARIBBEAN IS EXPERIENCING GENERALLY FAIR WEATHER
TODAY UNDER THE INFLUENCE OF DRY AIR AND STRONG SUBSIDENCE ACROSS
THE BASIN NOTED IN WATER VAPOR IMAGERY. UPPER LEVEL ANTI-CYCLONIC
FLOW DOMINATES THE AREA AROUND AN UPPER LEVEL RIDGE EXTENDING FROM
COSTA RICA ACROSS THE WINDWARD PASSAGE INTO THE W ATLC. A NARROW
UPPER LEVEL TROUGH ACCOMPANIED BY STRONG SUBSIDENCE EXTENDS FROM THE
CENTRAL ATLC ACROSS THE LESSER ANTILLES TO NRN COLOMBIA. FRESH TO
STRONG TRADEWINDS ARE ACROSS MUCH OF THE BASIN WITH THE STRONGEST
WINDS NEAR THE COAST OF COLOMBIA. EXPECT LITTLE CHANGE ACROSS THE
MAJORITY OF THE AREA WITH POSSIBLE SHOWERS FORMING ACROSS THE NW
GULF AS A STATIONARY FRONT CURRENTLY OVER THE SE GULF GETS A SWD
PUSH INTO THE NW CARIBBEAN WATERS.

ATLANTIC OCEAN...
A STATIONARY FRONT EXTENDS ACROSS THE SW ATLC ENTERING THE
DISCUSSION AREA NEAR 31N74W CONTINUING ALONG 28N78W CLIPPING THE NW
BAHAMAS TO THE SRN TIP OF THE FLORIDA PENINSULA NEAR 25N81W.
SCATTERED SHOWERS/THUNDERSTORMS ARE WITHIN 50 NM NE OF THE FRONT
BETWEEN 75W-80W. ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS ARE
ELSEWHERE BETWEEN THE FRONT AND THE UNITED STATES COASTLINE...AND
WITHIN 50 NM AHEAD OF THE FRONT. A LONGWAVE UPPER LEVEL TROUGH
COVERING THE CENTRAL AND ERN CONUS SUPPORTS THE FRONT. DIFFLUENT
FLOW ALOFT BETWEEN THIS UPPER TROUGH AND AN UPPER LEVEL RIDGE
EXTENDING FROM THE CARIBBEAN ACROSS THE WINDWARD PASSAGE INTO THE W
ATLC IS SUPPORTING THE SHOWER ACTIVITY ALONG AND BEHIND THE FRONT.
THE UPPER LEVEL RIDGE ALSO SUPPORTS A SURFACE RIDGE COVERING THE
REMAINDER OF THE W ATLC ANCHORED BY A 1028 MB HIGH NEAR 34N45W. A
PAIR OF SURFACE TROUGHS PROTRUDE INTO THE SURFACE RIDGE IN THE
CENTRAL ATLC. THE FIRST...EXTENDING FROM 28N41W TO 22N45W...IS A
SURFACE REFLECTION OF AN UPPER LEVEL LOW NEAR 22N43W. ISOLATED
SHOWERS ARE E OF THE TROUGH AXIS FROM 22N-26N BETWEEN 39W-44W. THE
SECOND IS THE TAIL END OF A STATIONARY FRONT EXTENDING FROM 31N42W
TO 27N48W. NO SHOWERS ACCOMPANY THIS TROUGH. THE REMAINDER OF THE E
ATLC IS DOMINATED BY A BROAD SURFACE RIDGE ANCHORED BY A 1028 MB
HIGH BETWEEN THE AZORES ISLANDS AND THE CANARY ISLANDS NEAR 35N18W.
A STRONG UPPER LEVEL WLY JET ACROSS THE TROPICAL ATLC IS SHEARING
MOISTURE AND HIGH CLOUDS FROM THE CENTRAL ITCZ TO THE ENE.

$$
WALTON





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