[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 121733 CCA
TWDAT

TROPICAL WEATHER DISCUSSION...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST FRI DEC 12 2008

...CORRECTED PHRASING OF THE THIRD SENTENCE IN ATLANTIC OCEAN
SECTION...

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
1645 UTC.

...THE ITCZ...
THE ITCZ IS CENTERED ALONG 6N9W 3N23W 3N34W 4N43W 7N54W. A
SURFACE TROUGH IS EMBEDDED WITHIN THE ITCZ. THIS SURFACE TROUGH
EXTENDS FROM 13N55W TO 9N55W TO N SURINAME NEAR 6N56W. LOW LEVEL
CONVERGENCE IS SUPPORTING SCATTERED MODERATE CONVECTION WITHIN
270 NM E AND 90 NM W OF THIS SURFACE TROUGH TO THE S OF 9N.
ELSEWHERE...SCATTERED MODERATE CONVECTION IS FROM 3N-6N BETWEEN
10W-14W. SCATTERED MODERATE CONVECTION IS ALSO FROM 4N-6N
BETWEEN 26W-29W. SIMILAR CONVECTION IS S OF 7N BETWEEN 41W-44W.

...DISCUSSION...

GULF OF MEXICO...
A RELATIVELY COOLER AND DRIER AIRMASS IS PRESENT ACROSS THE GULF
REGION IN THE WAKE OF A SURFACE COLD FRONT THAT EXTENDS FROM THE
W ATLC INTO THE W CARIBBEAN. THIS AIRMASS IS BEING REINFORCED BY
A SECONDARY SURFACE COLD FRONT THAT EXTENDS FROM THE SOUTH
CENTRAL FLORIDA PENINSULA NEAR 27N81W TO 25N84W TO 23N89W. THE
INCREASED SURFACE PRESSURE GRADIENT IN THE VICINITY OF THIS
SECONDARY COLD FRONT IS SUPPORTING NORTHERLY AND NORTHWESTERLY
SURFACE WINDS OF 20 TO 25 KT ACROSS PORTIONS OF THE MIDDLE AND
E GULF. AS THE RELATIVELY COOL AIR IS ADVECTED OVER THE WARMER
GULF WATERS...LOW LEVEL INSTABILITY IS SUPPORTING SCATTERED
STRATOCUMULUS CLOUDS SE OF A LINE FROM THE COAST OF THE W
FLORIDA PANHANDLE NEAR 30N85W TO 27N90W TO THE SE TEXAS COAST
NEAR 26N97W. HOWEVER...DEEP LAYER SUBSIDENCE IN STRONG WESTERLY
AND NORTHWESTERLY FLOW ALOFT IS INHIBITING DEEP CONVECTION
ACROSS THE GULF REGION. THIS SUBSIDENCE IS BEING ENHANCED OVER
THE W GULF...WHERE A SURFACE RIDGE IS PRESENT. THIS SURFACE
RIDGE IS BEING ANCHORED BY A 1026 MB SURFACE HIGH IN SE TEXAS
NEAR 30N98W.

CARIBBEAN SEA...
THE SURFACE COLD FRONT OVER THE W ATLC EXTENDS INTO THE
W CARIBBEAN. THIS COLD FRONT EXTENDS FROM CENTRAL CUBA NEAR
21N78W TO 16N81W TO CENTRAL COSTA RICA NEAR 10N84W. LOW LEVEL
CONVERGENCE IN THE VICINITY OF THIS FRONT IS SUPPORTING
SCATTERED SHOWERS ALONG AND WITHIN 60 NM EITHER SIDE OF THIS
FRONT. TO THE W OF THIS COLD FRONT...A RELATIVELY COOLER AND
DRIER AIRMASS IS PRESENT. ALSO...AN UPPER RIDGE AXIS EXTENDS
FROM N COLOMBIA NEAR 9N76W TO 12N82W TO N GUATEMALA NEAR 17N91W.
UPPER LEVEL DIVERGENCE ASSOCIATED WITH THIS UPPER RIDGE IS
SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ACROSS
THE SW CARIBBEAN S OF 11N BETWEEN 76W-80W...WHICH ARE BEING
SUPPORTED BY LOW LEVEL CONVERGENCE IN THE VICINITY OF A 1009 MB
SURFACE LOW IN N COLOMBIA NEAR 8N74W. ACROSS MUCH OF THE CENTRAL
AND E CARIBBEAN REGION...MODERATE TO FRESH TRADE WINDS ARE
PRESENT...WHERE DEEP LAYER DRY AIR AND SUBSIDENCE ARE RESULTING
IN FAIR WEATHER CONDITIONS.

ATLANTIC OCEAN...
MOIST SOUTHWESTERLY FLOW ALOFT IS PRESENT OVER PORTIONS OF THE
W ATLC...AS A DEEP TROUGH OVER THE E CONUS CONTINUES PROGRESSING
EASTWARD. AT THE SAME TIME...AN ASSOCIATED SURFACE COLD
FRONT...WHICH ENTERS THE W CARIBBEAN FROM THE W ATLC...EXTENDS
FROM CENTRAL CUBA NEAR 21N78W TO 28N76W TO 32N74W TO N OF THE
DISCUSSION AREA. INSTABILITY TO THE E OF THE COLD FRONT...AND
LOW LEVEL CONVERGENCE IN THE VICINITY OF THE COLD FRONT...ARE
SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ALONG
AND WITHIN 90 NM E OF THE COLD FRONT. THIS ACTIVITY IS BEING
ENHANCED BY LOW LEVEL CONVERGENCE ASSOCIATED WITH A SURFACE
TROUGH...LOCATED TO THE E OF THE COLD FRONT...THAT EXTENDS FROM
24N76W TO 29N74W TO 32N73W TO N OF THE DISCUSSION AREA. TO THE W
OF THE SURFACE COLD FRONT...A SECONDARY SURFACE COLD FRONT
EXTENDS FROM 31N78W TO 28N80W TO THE SOUTH CENTRAL FLORIDA
PENINSULA NEAR 27N81W. RELATIVELY COOLER AND DRIER CONDITIONS
ARE PRESENT TO THE W OF THESE COLD FRONTS. FARTHER TO THE
E...SUBSIDENCE AROUND A 1040 MB SURFACE HIGH NEAR 38N35W IS
SUPPORTING FAIR WEATHER CONDITIONS ACROSS MUCH OF THE CENTRAL
ATLC. HOWEVER...AN UPPER LOW IS CENTERED NEAR 28N53W... WITH
ATMOSPHERIC INSTABILITY ASSOCIATED WITH THIS UPPER LOW
SUPPORTING SCATTERED SHOWERS FROM 22N-30N BETWEEN 45W-54W.
ALSO...UPPER LEVEL DIVERGENCE ASSOCIATED WITH AN UPPER LEVEL JET
MAXIMUM OVER THE E ATLC IS SUPPORTING SCATTERED SHOWERS AND
THUNDERSTORMS FROM 9N-15N BETWEEN 36W-43W. ACROSS THE TROPICAL
ATLC...GENERALLY WESTERLY FLOW ALOFT IS PRESENT. ALSO...A
SURFACE TROUGH...EXTENDING FROM 13N55W TO 9N55W TO N SURINAME
NEAR 6N56W...IS EMBEDDED WITHIN THE ITCZ. LOW LEVEL CONVERGENCE
IS SUPPORTING SCATTERED MODERATE CONVECTION WITHIN 270 NM E AND
90 NM W OF THIS SURFACE TROUGH TO THE S OF 9N.

$$
COHEN




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