[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 241131
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST MON NOV 24 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
1115 UTC.

...SPECIAL FEATURE...
IN THE SW CARIBBEAN...A 1007 MB SURFACE LOW IS CENTERED N OF
PANAMA NEAR 10N80W. LOW LEVEL CONVERGENCE IN THE VICINITY OF
THIS SURFACE LOW IS INTERACTING WITH DEEP LAYER MOISTURE OVER
THE W CARIBBEAN TO RESULT IN NUMEROUS SHOWERS AND THUNDERSTORMS
OVER THE CARIBBEAN S OF 15N W OF 77W...INCLUDING PORTIONS OF
COSTA RICA...PANAMA...AND E NICARAGUA. THIS SHOWER AND
THUNDERSTORM ACTIVITY CONTINUES TO BECOME BETTER ORGANIZED...
AND A TROPICAL DEPRESSION MAY FORM IN THE NEXT DAY OR TWO IF THE
SYSTEM REMAINS OVER WATER AS IT DRIFTS SLOWLY WESTWARD. HEAVY
RAINFALL AND LOCALIZED FLOODING WILL BE POSSIBLE OVER PORTIONS
OF PANAMA...COSTA RICA...AND NICARAGUA DURING THE NEXT COUPLE OF
DAYS EVEN IF NO TROPICAL CYCLONE FORMS.

...TROPICAL WAVES...
TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN ALONG 75W S OF 17N
MOVING W 10-15 KT. SATELLITE IMAGERY DEPICTS A DISTINCT AREA OF
CYCLONIC CIRCULATION COINCIDING WITH THIS WAVE...WHERE A MAXIMUM
IN DEEP LAYER MOISTURE IS PRESENT BASED ON TOTAL PRECIPITABLE
WATER PRODUCT FROM CIMSS. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS OCCURRING WITHIN 90 NM EITHER SIDE OF THE WAVE
AXIS S OF 15N. THIS WAVE IS BECOMING ABSORBED BY THE BROAD
LOW LEVEL CYCLONIC CIRCULATION ASSOCIATED WITH THE 1007 MB
SURFACE LOW NEAR 10N80W. THIS IS THE SAME 1007 MB LOW PRESSURE
CENTER WHICH MAY DEVELOP INTO A TROPICAL CYCLONE.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 9N12W 5N22W 6N33W 8N45W 6N58W.
SCATTERED MODERATE IS FROM 5N-8N BETWEEN 19W-26W. SIMILAR
CONVECTION IS WITHIN 120 NM EITHER SIDE OF THE ITCZ AXIS BETWEEN
40W-49W.

...DISCUSSION...

GULF OF MEXICO...
STRONG SOUTHWESTERLY AND WESTERLY UPPER LEVEL WINDS COVER THE
GULF REGION...WITH UPPER LEVEL MOISTURE STREAMING ACROSS THE
N GULF REGION FROM THE E PACIFIC REGION. AT THE SURFACE...
A RELATIVELY COOL AND DRY AIRMASS IS IN PLACE ACROSS THE GULF
REGION...WITH TEMPERATURES GENERALLY BELOW SEASONAL AVERAGES.
THIS AIRMASS IS BEING SUPPORTED BY A 1030 MB SURFACE HIGH OVER
SOUTH CAROLINA NEAR 33N82W...WITH AN ASSOCIATED SURFACE RIDGE
EXTENDING ACROSS THE NE GULF. SUBSIDENCE AND STABLE ATMOSPHERIC
CONDITIONS ARE INHIBITING DEEP CONVECTION ACROSS THE GULF
REGION. FARTHER NORTH...A VIGOROUS UPPER TROUGH IS OVER THE
PLAINS OF THE CONUS...WITH AN ASSOCIATED SURFACE FRONT EXTENDING
FROM THE SOUTHERN PLAINS OF THE CONUS TO THE ROCKY MOUNTAINS.
AS THIS UPPER TROUGH TRANSLATES SOUTHEASTWARD OVER THE NEXT
DAY... THE FRONT WILL BEGIN TO MOVE ACROSS THE GULF REGION.
IN THE WAKE OF THIS FRONT...A REINFORCING COOLER AND DRIER
AIRMASS... CHARACTERIZED AS A MODIFIED CONTINENTAL POLAR
AIRMASS...WILL AFFECT THE GULF REGION.

CARIBBEAN SEA...
IN THE SW CARIBBEAN...A 1007 MB SURFACE LOW NEAR 10N80W IS
SUPPORTING SHOWER AND THUNDERSTORM ACTIVITY. THIS AREA OF LOW
PRESSURE MAY BECOME A TROPICAL CYCLONE DURING THE NEXT DAY OR
TWO. THE INCREASED SURFACE PRESSURE GRADIENT ASSOCIATED WITH
THIS SURFACE LOW IS SUPPORTING N TO NE SURFACE WINDS OF 20 TO
30 KT FOR MUCH OF THE CARIBBEAN...WITH THE STRONGEST WINDS OVER
THE SW CARIBBEAN AND AROUND THE WINDWARD PASSAGE. THE SHOWER AND
THUNDERSTORM ACTIVITY ASSOCIATED WITH THE SURFACE LOW IS BEING
ENHANCED BY STRONG 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 12N72W TO 15N79W TO
THE NW CARIBBEAN NEAR 20N84W. OVER THE E AND CENTRAL
CARIBBEAN...UPPER LEVEL DIFFLUENCE IS SUPPORTING SCATTERED
SHOWERS AND THUNDERSTORMS S OF 15N BETWEEN 68W-76W. THIS
ACTIVITY IS BEING ENHANCED BY LOW LEVEL CONVERGENCE ASSOCIATED
WITH THE TROPICAL WAVE ALONG 75W.

ATLANTIC OCEAN...
OVER THE W ATLC...A RELATIVELY COOL AND DRY AIRMASS IS IN
PLACE...WITH TEMPERATURES BELOW SEASONAL AVERAGES ACROSS
FLORIDA. THIS AIRMASS IS BEING SUPPORTED BY A 1030 MB SURFACE
HIGH OVER SOUTH CAROLINA NEAR 33N82W. FARTHER E...AN UPPER
TROUGH TILTED FROM NW TO SE OVER THE CENTRAL ATLC CONTINUES TO
DIG SOUTHWARD AS A 120 KT CYCLONICALLY-CURVED UPPER LEVEL JET
BEGINS TO ROUND THE BASE OF THIS TROUGH. DEEP AND STRONG ASCENT
ORIGINATING FROM STRONG UPPER LEVEL DIVERGENCE IN THE NE
QUADRANT OF THIS JET IS APPROACHING A SURFACE STATIONARY FRONT.
THIS FRONT CURRENTLY EXTENDS FROM 21N71W TO 27N57W TO 32N53W TO
N OF THE DISCUSSION AREA...AND IS WEAKENING W OF 63W. AS THE
DEEP ASCENT CONTINUES TO APPROACH THE STATIONARY FRONT...
A 1003 MB SURFACE LOW IS FORECAST TO FORM IN THE VICINITY OF THE
FRONT NEAR 31N50W BY 25/0600 UTC. THE CORRESPONDING TIGHTENING
OF THE SURFACE PRESSURE GRADIENT WILL RESULT IN GALE FORCE
SURFACE WINDS WITHIN 240 NM OF THE SW QUADRANT OF THE DEVELOPING
SURFACE LOW. ALSO...AS THIS LOW DEVELOPS ALONG THE STATIONARY
FRONT... RELATIVELY COOLER AIR TO THE W WILL BEGIN TO WRAP
CYCLONICALLY AROUND THE LOW...FORCING THE STATIONARY FRONT
TO MOVE EASTWARD AS A COLD FRONT S OF THE LOW. AT PRESENT...
INCREASING LOW LEVEL CONVERGENCE IN THE VICINITY OF THIS
DEVELOPING SURFACE LOW IS STRENGTHENING THE FRONT...WITH THE
RESULTING ASCENT SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS
N OF 27N BETWEEN 51W-56W. FARTHER TO THE S...A SURFACE TROUGH
EXTENDS FROM 14N59W TO A 1011 MB SURFACE LOW NEAR 14N55W TO
13N51W. ISOLATED SHOWERS ARE OCCURRING WITHIN 60 NM OF THIS
SURFACE LOW AND SURFACE TROUGH. OVER THE E ATLC...AN UPPER
TROUGH IS N OF 23N BETWEEN 29W-42W WITH AN UPPER LOW NEAR
31N35W. AN ASSOCIATED SURFACE TROUGH EXTENDS FROM 28N29W TO
A 1012 MB SURFACE LOW NEAR 25N32W TO A 1013 MB SURFACE LOW
NEAR 22N35W TO 21N36W. THE 1012 MB LOW IS NEW ON THE
24/0600 UTC SURFACE ANALYSIS...WHILE THE 1013 MB LOW CONTINUES
TO WEAKEN...AS THE STRONGEST UPPER LEVEL DIFFLUENCE ASSOCIATED
WITH THE UPPER TROUGH TRANSLATES NORTHEASTWARD. THE COMBINATION
OF LOW LEVEL CONVERGENCE WITH THE SURFACE LOWS AND SURFACE
TROUGH AND UPPER LEVEL DIFFLUENCE IS SUPPORTING SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS FROM 24N-29N BETWEEN
24W-27W. ALSO...UPPER LEVEL DIVERGENCE IN THE VICINITY OF
A MID/UPPER-LEVEL WIND SPEED MAXIMUM OVER THE E ATLC IS
SUPPORTING SCATTERED SHOWERS FROM 14N-19N BETWEEN 16W-27W.

$$
COHEN/MT


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