[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 041748
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST THU DEC 04 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 ANALYZED ALONG 8N12W 6N21W 3N32W 5N43W 6N57W.
SCATTERED MODERATE CONVECTION IS FROM 2N-5N BETWEEN 8W-14W.
SCATTERED MODERATE CONVECTION IS ALSO S OF 6N BETWEEN 22W-34W.

...DISCUSSION...

GULF OF MEXICO...
STRONG SOUTHWESTERLY FLOW ALOFT COVERS THE GULF REGION...AS A DEEP
LAYER TROUGH MOVES EASTWARD OVER THE E CONUS. AN ASSOCIATED SURFACE
COLD FRONT IS MOVING SOUTHEASTWARD ACROSS THE NW GULF...EXTENDING
FROM A 1018 MB SURFACE LOW IN S MISSISSIPPI NEAR 31N91W TO 27N94W TO
NE MEXICO NEAR 24N100W AND EXTENDS FARTHER NORTHWESTWARD ACROSS N
MEXICO. LOW LEVEL CONVERGENCE IN THE VICINITY OF THIS COLD FRONT...
COMBINED WITH ATMOSPHERIC LIFT IN MOIST SOUTHWESTERLY FLOW ALOFT...
IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ALONG AND
WITHIN 60 NM AHEAD OF THE COLD FRONT. INCREASED N TO NE SURFACE
WINDS ARE USHERING IN A RELATIVELY COOLER AND DRIER AIRMASS ACROSS
THE S CONUS AND NW GULF IN THE WAKE OF THE COLD FRONT. THIS AIRMASS
IS BEING SUPPORTED BY A STRONG SURFACE HIGH PRESSURE RIDGE EXTENDING
FROM THE PLAINS OF THE CONUS NORTHWESTWARD ACROSS THE NORTHERN ROCKY
MOUNTAINS. OVER THE W GULF...A SURFACE TROUGH INTERSECTS THE COLD
FRONT NEAR 25N97W AND EXTENDS FARTHER SOUTHWARD FROM 25N97W TO
21N96W TO 19N94W. LOW LEVEL CONFLUENCE NEAR THIS SURFACE TROUGH IS
ENHANCING THE SHOWER AND THUNDERSTORM ACTIVITY ASSOCIATED WITH THE
COLD FRONT N OF 24N. DEEP LAYER DRY AIR IS INHIBITING DEEP
CONVECTION OVER THE SE GULF...WHERE GENERALLY FAIR WEATHER PREVAILS.
OVER THE NEXT DAY...THE COLD FRONT IS FORECAST TO CONTINUE MOVING
SOUTHEASTWARD OVER THE GULF...BUT IS EXPECTED TO SLOW ITS PROGRESS
AS THE STRONGEST UPPER LEVEL ENERGY LIFTS NORTHEAST OF THE GULF
REGION. ADDITIONALLY...STRONG N SURFACE WINDS ARE FORECAST TO BLOW
THROUGH THE ISTHMUS OF TEHUANTEPEC RESULTING IN GALE FORCE WINDS IN
THE EAST PACIFIC REGION BEGINNING AT 05/0600 UTC.

CARIBBEAN SEA...
AN UPPER HIGH IS CENTERED S OF THE DOMINICAN REPUBLIC NEAR
16N70W...WITH AN UPPER RIDGE AXIS EXTENDING FROM THE UPPER HIGH TO
THE NE CARIBBEAN NEAR 18N63W INTO THE W ATLC. UPPER LEVEL DIFFLUENCE
SW OF THE UPPER HIGH IS COMBINING WITH DEEP MOISTURE OVER THE SW
CARIBBEAN TO RESULT IN NUMEROUS SHOWERS AND SCATTERED THUNDERSTORMS
S OF 14N W OF 78W. THIS ACTIVITY IS BEING ENHANCED BY LOW LEVEL
CONVERGENCE IN THE VICINITY OF A SURFACE TROUGH EXTENDING FROM
13N79W TO 11N80W TO N OF PANAMA NEAR 9N80W. FARTHER TO THE E...A
SECOND SURFACE TROUGH EXTENDS FROM 16N76W TO 13N76W TO N OF COLOMBIA
NEAR 10N76W...WITH SCATTERED SHOWERS WITHIN 60 NM EITHER SIDE OF
THIS SURFACE TROUGH. ALSO...A SURFACE STATIONARY FRONT OVER THE NW
CARIBBEAN EXTENDS FROM E OF THE YUCATAN PENINSULA NEAR 20N86W TO
CENTRAL CUBA NEAR 22N79W TO THE W ATLC...WITH SCATTERED SHOWERS
WITHIN 60 NM EITHER SIDE OF THIS STATIONARY FRONT. NEAR AND E OF THE
AFOREMENTIONED UPPER HIGH NEAR 16N70W...FAIR WEATHER CONDITIONS
PERSIST OVER THE E CARIBBEAN WHERE DEEP LAYER SUBSIDENCE IS
ENHANCING STABLE ATMOSPHERIC CONDITIONS IN THE PRESENCE OF DEEP
LAYER DRY AIR.

ATLANTIC OCEAN...
SOUTHWESTERLY FLOW ALOFT CONTINUES TO INCREASE OVER THE W ATLC AS
THE DEEP TROUGH OVER THE E CONUS PROGRESSES EASTWARD. A SURFACE
TROUGH E OF THE FLORIDA PENINSULA EXTENDS FROM 31N81W TO 28N80W TO
26N79W. HOWEVER...THE PRESENCE OF DEEP LAYER DRY AIR ACROSS THE W
ATLC IS INHIBITING DEEP CONVECTION NEAR THE SURFACE TROUGH. FARTHER
TO THE E...A SURFACE STATIONARY FRONT EXTENDS FROM CENTRAL CUBA NEAR
22N79W TO THE BAHAMAS NEAR 23N74W TO 25N68W...WITH A SURFACE COLD
FRONT EXTENDING FROM 25N68W TO 29N62W TO 32N57W TO NE OF THE
DISCUSSION AREA. LOW LEVEL CONVERGENCE IS SUPPORTING ISOLATED
SHOWERS WITHIN 60 NM EITHER SIDE OF THE SURFACE STATIONARY FRONT AND
COLD FRONT. E OF THESE FRONTS...THE FLOW ALOFT IS MORE AMPLIFIED...
WITH AN UPPER RIDGE AXIS EXTENDING FROM THE NE CARIBBEAN NEAR 18N63W
TO 25N56W TO 32N49W TO NE OF THE DISCUSSION AREA AND A SHARP UPPER
LEVEL TROUGH N OF 14N BETWEEN 37W-46W. THIS UPPER TROUGH IS
ASSOCIATED WITH AN UPPER LOW NEAR 32N40W...AS WELL AS A SURFACE
TROUGH EXTENDING FROM A 1011 MB SURFACE LOW NEAR 29N48W TO 29N45W TO
A 1012 MB SURFACE LOW NEAR 25N44W TO 20N48W. LOW LEVEL CONVERGENCE
NEAR THESE SURFACE LOWS AND TROUGHS IS SUPPORTING SCATTERED SHOWERS
N OF 21N BETWEEN 41W-48W. E OF THE UPPER TROUGH AXIS...NUMEROUS
SHOWERS AND ISOLATED THUNDERSTORMS N OF 22N BETWEEN 32W-38W ARE
BEING SUPPORTED BY STRONG ATMOSPHERIC LIFT ASSOCIATED WITH A 90-100
KT JET MAXIMUM...ALONG WITH THE PRESENCE OF INCREASED DEEP MOISTURE.
OVER THE E ATLC... SUBSIDENCE AND FAIR WEATHER PREVAIL IN THE
VICINITY OF A SURFACE RIDGE EXTENDING FROM A 1029 MB SURFACE HIGH
NEAR 34N21W TO 26N22W TO 19N25W. FARTHER TO THE S...AN UPPER RIDGE
IS S OF 19N BETWEEN THE AFRICAN COAST AND 35W...WITH AN UPPER HIGH
NEAR 9N29W. UPPER LEVEL DIVERGENCE ASSOCIATED WITH THE UPPER HIGH
AND UPPER RIDGE IS SUPPORTING SCATTERED SHOWERS FROM 13N-16N BETWEEN
23W-31W...AS WELL AS THE CONVECTION ASSOCIATED WITH THE ITCZ.

$$
COHEN


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