[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 132317
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST THU NOV 13 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2245 UTC.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 11N13W 7N22W 8N36W 9N49W 7N60W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 3N-7N
BETWEEN 13W-18W. SCATTERED MODERATE CONVECTION IS WITHIN 90 NM
EITHER SIDE OF THE ITCZ AXIS BETWEEN 29W-34W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS FROM 7N-12N BETWEEN
36W-53W.

...DISCUSSION...

GULF OF MEXICO...
MOIST SOUTHWESTERLY FLOW ALOFT IS OVER THE NW GULF IN ADVANCE OF
A DEEP LAYER TROUGH THAT EXTENDS FROM THE PLAINS OF THE CONUS TO
CENTRAL MEXICO. ALSO...STRONG UPPER LEVEL DIVERGENCE IS
AFFECTING PORTIONS OF THE NW GULF TO THE S OF A MID/UPPER-LEVEL
WIND SPEED MAXIMUM PRESENT OVER SE TEXAS. AS A RESULT...NUMEROUS
SHOWERS AND THUNDERSTORMS ARE AFFECTING THE NW GULF TO THE W OF
A LINE FROM 23N98W TO 29N93W...INCLUDING COASTAL AREAS OF SE
TEXAS. THIS ACTIVITY IS BEING ENHANCED BY LOW LEVEL CONVERGENCE
IN THE VICINITY OF A SURFACE STATIONARY FRONT THAT EXTENDS FROM
22N98W TO A 1009 MB SURFACE LOW E OF BROWNSVILLE TEXAS NEAR
27N96W TO 28N89W. TO THE E OF THE SURFACE STATIONARY FRONT...A
SURFACE COLD FRONT EXTENDS FROM 28N89W TO 29N87W TO A 1013 MB
SURFACE LOW IN SOUTH CENTRAL ALABAMA NEAR 31N87W...WITH A
SURFACE STATIONARY FRONT EXTENDING TO THE NE OF THIS LOW FROM
31N87W TO 32N84W TO NE OF THE DISCUSSION AREA. THESE FEATURES
ARE SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS OVER THE NE
GULF N OF 28N E OF 86W...AFFECTING PORTIONS OF THE FLORIDA
PANHANDLE. FARTHER TO THE S...VISIBLE SATELLITE IMAGERY
INDICATES LOW-LEVEL CYCLONIC CIRCULATION AROUND A SURFACE TROUGH
EXTENDING FROM 28N85W TO 26N85W TO 23N85W. ISOLATED SHOWERS ARE
OCCURRING WITHIN 120 NM EITHER SIDE OF THIS SURFACE TROUGH.
HOWEVER...DEEP LAYER DRY AIR IS LIMITING DEEP CONVECTION ACROSS
MUCH OF THE S AND E GULF.

CARIBBEAN SEA...
AN UPPER RIDGE IS AFFECTING THE W CARIBBEAN...WITH THE UPPER
RIDGE AXIS EXTENDING FROM W CUBA NEAR 22N79W TO E COSTA RICA
NEAR 10N83W. SUBSIDENCE AND DEEP LAYER DRY AIR IN THE VICINITY
OF THIS UPPER RIDGE ARE BRINGING FAIR WEATHER CONDITIONS TO MUCH
OF THE W CARIBBEAN. OVER THE E CARIBBEAN...AN UPPER LEVEL TROUGH
IS PRESENT...WHICH IS ANCHORED BY AN UPPER LOW N OF THE LEEWARD
ISLANDS NEAR 19N63W. WEAK INSTABILITY...COMBINED WITH GREATER
DEEP MOISTURE OVER THE E CARIBBEAN...IS SUPPORTING SCATTERED
SHOWERS E OF 67W...INCLUDING PORTIONS OF THE LESSER ANTILLES.
THIS ACTIVITY IS FURTHER BEING ENHANCED BY A SURFACE TROUGH THAT
EXTENDS FROM SE OF PUERTO RICO NEAR 17N66W TO 19N65W
NORTHEASTWARD TO THE SW ATLC. ALSO...SCATTERED SHOWERS AND
THUNDERSTORMS ARE OCCURRING OVER PORTIONS OF N PANAMA...
N COLOMBIA...AND N VENEZUELA...AS WELL AS THE ADJACENT CARIBBEAN
SEA. THIS CONVECTION IS BEING ENHANCED BY GREATER INSTABILITY
OVER HIGHER TERRAIN.

ATLANTIC OCEAN...
AN UPPER RIDGE AXIS IS OVER THE W ATLC EXTENDING FROM W CUBA
NEAR 22N79W TO 29N75W TO 31N74W TO NE OF THE DISCUSSION AREA.
DEEP LAYER DRY AIR IS INHIBITING DEEP CONVECTION ACROSS MUCH OF
THE W ATLC. FARTHER TO THE E...THE AXIS OF A DEEP LAYER TROUGH
EXTENDS FROM AN UPPER LOW N OF THE LEEWARD ISLANDS NEAR 19N63W
TO 26N62W TO 29N59W. THIS DEEP LAYER TROUGH IS ACCOMPANIED BY A
SURFACE TROUGH THAT EXTENDS FROM 26N62W TO 22N64W TO 17N66W. LOW
LEVEL CONVERGENCE NEAR THIS SURFACE TROUGH...COMBINED WITH UPPER
LEVEL DIFFLUENCE...IS SUPPORTING SCATTERED SHOWERS AND
THUNDERSTORMS FROM 11N-24N BETWEEN 56W-64W...INCLUDING PORTIONS
OF THE LESSER ANTILLES. ALTHOUGH UPPER-LEVEL WINDS ARE ONLY
MARGINALLY FAVORABLE...SOME ADDITIONAL DEVELOPMENT OF THIS
SYSTEM IS POSSIBLE OVER THE NEXT COUPLE OF DAYS AS IT MOVES
WESTWARD AT 10 TO 15 KT. ALSO...A COLD FRONT EXTENDS FROM 31N55W
TO NE OF THE DISCUSSION AREA...WITH DEEP LAYER DRY AIR
INHIBITING DEEP CONVECTION NEAR THE COLD FRONT S OF 32N. FARTHER
TO THE E...AN UPPER TROUGH IS N OF 19N BETWEEN 18W-39W. THIS
UPPER TROUGH IS SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM
31N36W TO 28N36W TO 24N35W. ISOLATED SHOWERS WITHIN 60 NM EITHER
SIDE OF THE SURFACE TROUGH N OF 27N. OVER THE TROPICAL ATLC...AN
UPPER HIGH IS CENTERED NEAR 2N47W...AND AN UPPER RIDGE IS S OF
8N BETWEEN 11W-20W. UPPER LEVEL DIVERGENCE OVER THE N PERIPHERY
OF EACH OF THESE FEATURES IS ENHANCING THE CONVECTION NEAR THE
ITCZ.

$$
COHEN



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