[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 281125
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST FRI NOV 28 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1045 UTC.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 8N12W 4N22W 4N33W 7N45W 6N58W. A
SURFACE TROUGH...EXTENDING FROM 11N48W TO 10N49W TO 8N50W...IS
EMBEDDED WITHIN THE ITCZ. A RECENT ASCAT PASS DEPICTS CYCLONIC
CURVATURE IN THE LOW LEVEL WIND FIELD IN THE VICINITY OF THIS
TROUGH. SCATTERED MODERATE CONVECTION IS OCCURRING WITHIN 60 NM
EITHER SIDE OF THIS SURFACE TROUGH N OF 10N. ELSEWHERE...
SCATTERED MODERATE CONVECTION IS WITHIN 90 NM S OF THE ITCZ AXIS
BETWEEN 12W-25W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION
IS FROM 3N-10N BETWEEN 29W-38W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL RIDGE COVERS THE GULF REGION...WITH STRONG UPPER
LEVEL WINDS ACROSS THE NORTHERN PERIPHERY OF THE RIDGE OVER THE
SE CONUS AND N GULF. UPPER LEVEL MOISTURE CONTINUES STREAMING
ACROSS THE N GULF...WHILE DEEP LAYER DRY AIR IS PRESENT OVER THE
S GULF. DEEP LAYER SUBSIDENCE AND STABLE ATMOSPHERIC CONDITIONS
ARE RESULTING IN FAIR WEATHER ACROSS MUCH OF THE GULF REGION.
THIS DEEP LAYER SUBSIDENCE IS BEING ENHANCED ACROSS E PORTIONS
OF THE GULF REGION...WHERE UPPER LEVEL CONVERGENCE IN THE SE
QUADRANT OF A 100-110 KT UPPER LEVEL JET MAXIMUM OVER THE
ALABAMA AND FLORIDA PANHANDLE COASTS IS SUPPORTING A 1021 MB
SURFACE HIGH OVER THE CENTRAL FLORIDA PENINSULA NEAR 28N82W.
FARTHER NW...A DEEP TROUGH OVER THE W CONUS IS SUPPORTING A
SURFACE FRONT THAT EXTENDS FROM THE GREAT LAKES REGION TO THE
SOUTHERN PLAINS AND EXTENDS ACROSS THE CENTRAL ROCKIES OF THE
CONUS. AS THE DEEP TROUGH MOVES EASTWARD...THE SURFACE FRONT
WILL MOVE SOUTHWARD ACROSS THE GULF LATE THIS WEEKEND AS A COLD
FRONT...WITH SOUTHERLY FLOW INCREASING AHEAD OF THE FRONT. THE
FRONT IS ALSO FORECAST TO BE ACCOMPANIED BY SCATTERED SHOWERS
AND THUNDERSTORMS. STRONG WINDS ARE ALSO EXPECTED WITH THE
FRONT...WITH GALE CONDITIONS EXPECTED ON SUNDAY FOR THE MIDDLE
GULF N OF 25N BETWEEN 85W-90W AND FOR THE E GULF N OF 25N
BETWEEN 81W-85W. IN THE WAKE OF THE COLD FRONT...RELATIVELY
COOLER AND DRIER CONDITIONS ARE EXPECTED...ALONG N TO NW SURFACE
WINDS.

CARIBBEAN SEA...
IN THE SW CARIBBEAN...A 1011 MB SURFACE LOW IS CENTERED N OF
PANAMA NEAR 10N78W. LOW LEVEL CONVERGENCE NEAR THIS SURFACE LOW
IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS S OF
10N W OF 77W...INCLUDING PANAMA AND S COSTA RICA. THIS ACTIVITY
IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE IN THE VICINITY OF
AN UPPER RIDGE PRESENT OVER THE W CARIBBEAN...WITH THE AXIS OF
THIS UPPER RIDGE EXTENDING FROM N COLOMBIA NEAR 10N75W TO 13N83W
TO SE MEXICO NEAR 18N91W TO THE W GULF. OVER THE N CARIBBEAN...
DEEP LAYER SUBSIDENCE IS IN PLACE RESULTING IN FAIR
WEATHER...WHERE STRONG WESTERLY CONFLUENT FLOW ALOFT IS PRESENT.
RELATIVELY DRY CONDITIONS PREVAIL ACROSS PORTIONS OF THE N
CARIBBEAN...WITH DEWPOINTS IN THE UPPER 50S AND LOWER 60S ACROSS
CUBA. THIS DRIER AIR IS A RESULT OF NE SURFACE WINDS ADVECTING
A STRONGLY MODIFIED CONTINENTAL POLAR AIRMASS ACROSS THE N
CARIBBEAN REGION. THIS AIRMASS ORIGINATES FROM THE 1021 MB
SURFACE HIGH OVER THE CENTRAL FLORIDA PENINSULA NEAR 28N82W AND
IS IN THE WAKE OF A COLD FRONT THAT IS E OF THE BAHAMAS.
OUTSIDE OF SHOWER AND THUNDERSTORM ACTIVITY...FRESH TRADEWINDS
GENERALLY PREVAIL ACROSS THE CARIBBEAN.

ATLANTIC OCEAN...
STRONG WESTERLY FLOW ALOFT COVERS MUCH OF THE W AND CENTRAL
ATLC. A SURFACE RIDGE EXTENDS INTO THE W ATLC FROM A 1021 MB
SURFACE HIGH OVER THE CENTRAL FLORIDA PENINSULA NEAR 28N82W...
WITH SUBSIDENCE AND FAIR WEATHER IN THE VICINITY OF THIS RIDGE.
TO THE E OF THE BAHAMAS...A SURFACE COLD FRONT EXTENDS FROM
23N68W TO 27N59W TO 32N54W TO N OF THE DISCUSSION AREA. LOW
LEVEL CONVERGENCE IS RESULTING IN SCATTERED SHOWERS WITHIN 90 NM
EITHER SIDE OF THIS COLD FRONT. FARTHER TO THE E...UPPER LEVEL
DIVERGENCE IN THE NE QUADRANT OF A 90-100 KT UPPER LEVEL JET
MAXIMUM IS SUPPORTING A 1000 MB SURFACE LOW IN THE CENTRAL ATLC
NEAR 31N40W...WITH THREE ASSOCIATED SURFACE TROUGHS. ONE SURFACE
TROUGH EXTENDS FROM 32N40W TO 32N31W...WITH ANOTHER SURFACE
TROUGH EXTENDING FROM 32N32W TO 23N31W...AND ANOTHER SURFACE
TROUGH EXTENDS FROM 31N50W TO 30N45W. LOW LEVEL CONVERGENCE NEAR
THE SURFACE LOW AND THREE SURFACE TROUGHS IS SUPPORTING
SCATTERED SHOWERS AND THUNDERSTORMS N OF 28N BETWEEN 25W-35W. AN
ASSOCIATED UPPER TROUGH AXIS IS TILTED FROM 28N28W TO 32N42W TO
NW OF THE DISCUSSION AREA...WITH UPPER DIFFLUENCE E OF THE UPPER
TROUGH AXIS ENHANCING THE SHOWER AND THUNDERSTORM ACTIVITY N OF
26N BETWEEN 26W-35W. ACROSS THE E ATLC...A SURFACE RIDGE IS N OF
18N E OF 26W...WHERE SUBSIDENCE IS RESULTING IN GENERALLY FAIR
WEATHER. FARTHER TO THE S...AN UPPER RIDGE IS PRESENT S OF 12N W
OF 19W...WITH ASSOCIATED UPPER LEVEL DIFFLUENCE ENHANCING THE
CONVECTION IN THE VICINITY OF THE ITCZ. ADDITIONALLY...A SURFACE
TROUGH OVER THE TROPICAL N ATLC EXTENDS FROM 15N45W TO 11N51W TO
9N59W. A RECENT ASCAT PASS INDICATES LOW LEVEL CONFLUENCE IN THE
VICINITY OF THIS TROUGH...WITH SCATTERED SHOWERS AND
THUNDERSTORMS WITHIN 90 NM EITHER SIDE OF THIS FEATURE. ALSO...A
SURFACE TROUGH...EXTENDING FROM 11N48W TO 9N48W TO 7N49W...IS
EMBEDDED WITHIN THE ITCZ...WITH SCATTERED SHOWERS AND
THUNDERSTORMS OCCURRING WITHIN 180 NM EITHER SIDE OF THIS
SURFACE TROUGH N OF 10N. BY LATE THIS WEEKEND...A COLD FRONT
WILL BEGIN TO MOVE ACROSS PORTIONS OF THE W ATLC...WITH
SCATTERED SHOWERS AND THUNDERSTORMS ACCOMPANYING THE FRONT.
ADDITIONALLY...STRONG WINDS ARE EXPECTED WITH THE FRONT...WITH
GALE CONDITIONS EXPECTED LATE SUNDAY AND MONDAY FOR THE SW N
ATLC FROM 27N-31N BETWEEN 65W-70W. IN THE WAKE OF THE COLD
FRONT...RELATIVELY COOLER AND DRIER CONDITIONS ARE EXPECTED...
ALONG W TO NW SURFACE WINDS.

$$
COHEN


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