[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 271757
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST THU NOV 27 2008

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
1715 UTC.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 7N12W 6N30W 8N40W 5N57W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 5N-10N
BETWEEN 32W-50W. SIMILAR CONVECTION IS NEAR 5N16W...AND NEAR
4N21W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 1500 UTC...A 1024 MB SFC HIGH CENTERED OVER THE NE CORNER
OF THE GULF NEAR 28N83W IS PRODUCING MOSTLY FAIR WEATHER OVER
THE ENTIRE REGION...INCLUDING ALSO THE SE CONUS AND THE FLORIDA
PENINSULA. WINDS ARE GENERALLY LIGHT IN THE 5-10 KT RANGE.
ALOFT...A RIDGE DOMINATES THE AREA WITH A JET STREAM BRANCH OF
90-110 KT CROSSING THE SE CONUS AND NORTHERN FLORIDA.
CONSIDERABLE UPPER LEVEL MOISTURE IS OVER THE N GULF WATERS N OF
27N WHILE STRONG SUBSIDENCE COVERS THE REMAINDER OF THE GULF AS
WELL AS SOUTH-CENTRAL MEXICO AND THE YUCATAN PENINSULA. THE
SURFACE HIGH WILL SLOWLY MOVE EWD TO N-CENTRAL FLORIDA NEAR
28N81W IN ABOUT 24 HOURS. A COLD FRONT IS FORECAST TO MOVE OUT
OF THE TEXAS COAST SAT MORNING...AND WILL EXTEND FROM THE
FLORIDA BIG BEND TO THE BAY OF CAMPECHE SUNDAY AFTERNOON. SLY
RETURN FLOW WILL DEVELOP AHEAD OF THE FRONT OVER THE WESTERN
GULF PRODUCING SOME SHOWER ACTIVITY ALONG THE TEXAS AND
LOUISIANA COASTS. NLY WINDS OF 20 TO 30 KT ARE EXPECTED IN THE
WAKE OF THE FRONT. TRANQUIL WEATHER CONDITIONS ARE IN PLACE OVER
SOUTH FLORIDA WHERE A VERY STABLE ATMOSPHERE PREVAILS.

CARIBBEAN SEA...
THE CARIBBEAN SEA IS PRETTY QUIET EARLY THIS AFTERNOON WITH A
RIDGE DOMINATING THE GREATER ANTILLES. PATCHES OF LOW LEVEL
MOISTURE WITH EMBEDDED LIGHT SHOWERS ARE OVER PARTS OF
HONDURAS...BELIZE AND GUATEMALA. THE PANAMANIAN/COLOMBIAN LOW IS
NEAR 10N78W GENERATING SCATTERED SHOWERS OVER PANAMA AND COASTAL
WATERS. SOME SHOWER ACTIVITY IS ALSO NOTED NEAR THE GUAJIRA
PENINSULA ENHANCED BY UPPER DIFFLUENCE. THE TAIL END OF A
DYING FRONTAL BOUNDARY ACROSS THE ATLC IS PRODUCING SCATTERED
SHOWERS OVER TRINIDAD AND TOBAGO ISLANDS AND THE FAR NE OF
VENEZUELA. FRESH TRADEWINDS ARE NOTED OVER THE ENTIRE BASIN.
IN THE UPPER LEVELS...A MAINLY ZONAL FLOW DOMINATES THE REGION.
THE RIDGE N OF THE AREA WILL SHIFT E AND SLOWLY WEAKEN...
ALLOWING TRADEWINDS TO DECREASE ACROSS MUCH OF THE BASIN GOING
INTO THE WEEKEND. LONG PERIOD N SWELLS WILL CONTINUE TO AFFECT
THE TROPICAL N ATLC AND E CARIBBEAN PASSAGES THROUGH SAT. AS A
RESULT...A HIGH SURF ADVISORY IS IN EFFECT FOR THE NORTH FACING
COASTLINES IN PUERTO RICO AND THE US VIRGIN ISLANDS THROUGH AT
LEAST FRI NIGHT. THE NEXT COLD FRONT IS FORECAST TO REACH
WESTERN CUBA AND THE NW CARIBBEAN ON MON...KEEPING TEMPERATURES
ON THE COOL SIDE.

ATLANTIC OCEAN...
SURFACE HIGH PRES CENTERED OVER THE NW CORNER OF THE GULF OF
MEXICO EXTENDS A RIDGE OVER THE W ATLC AND THE BAHAMAS PRODUCING
MOSTLY FAIR WEATHER. A WEAKENING COLD FRONT ENTERS THE REGION
NEAR 31N61W THEN CONTINUES SW TO NEAR 23N69W. ISOLATED SHOWERS
ARE WITHIN 30 NM OF THE FRONT. A 1003 MB LOW CONTINUES TO SPIN
OVER THE CENTRAL ATLANTIC NEAR 28N44W. A RECENT ASCAT PASS SHOWS
THE STRONGEST WINDS OF 20-25 KT WITHIN 140 NM SOUTH SEMICIRCLE
OF THIS LOW. SIMILAR WIND SPEEDS ARE ALSO NOTED WITHIN 500 NM W
OF THE LOW DUE TO THE PRESSURE GRADIENT BETWEEN THIS LOW AND THE
RIDGE OVER THE W ATLC. VIS SAT IMAGERY REVEALS A WELL DEFINED
SWIRL OF LOW CLOUDS ASSOCIATED WITH THIS FEATURE THAT IS
FORECAST TO MOVE N-NE AND OUT OF AREA IN ABOUT 24 HOURS. THE
ATTENDANT COLD FRONT IS WEAKENING AND CURRENTLY EXTENDS ALONG
31N35W 26N36W 19N42W. AT THIS POINT...A SURFACE TROUGH CONTINUES
SW TO NEAR TRINIDAD AND TOBAGO ISLANDS. SCATTERED MODERATE TO
ISOLATED STRONG CONVECTION IS AHEAD OF THE FRONT N OF 25N AND
BETWEEN 33W AND 33W. A DIFFLUENT PATTERN ALOFT IS SUPPORTING
THIS CONVECTIVE ACTIVITY. THE E ATLC IS UNDER THE INFLUENCE OF A
SURFACE RIDGE CENTERED WELL N OF THE DISCUSSION AREA. PRES
GRADIENT BETWEEN THIS RIDGE AND LOWER PRES OVER AFRICA IS
RESULTING IN NLY WINDS OF 20-25 KT ACROSS THE MADEIRA/CANARY
ISLANDS. IN THE UPPER LEVELS...A MOSTLY ZONAL FLOW DOMINATES
MUCH OF THE REGION WITH A CUT-OFF LOW NEAR 31N44W.

$$
GR








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