[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 301149
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST SUN NOV 30 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.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 10N13W 6N22W 4N33W 4N41W 2N51W.
SCATTERED MODERATE CONVECTION IS FROM 5N-9N BETWEEN 11W-16W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 2N-6N
BETWEEN 17W-29W. SCATTERED MODERATE CONVECTION IS WITHIN 180 NM
EITHER SIDE OF THE ITCZ AXIS BETWEEN 32W-41W.

...DISCUSSION...

GULF OF MEXICO...
A VIGOROUS DEEP TROUGH OVER THE CENTRAL CONUS EXTENDS INTO N
MEXICO...WITH AN ASSOCIATED SURFACE COLD FRONT EXTENDING FROM A
1000 MB SURFACE LOW OVER W ALABAMA NEAR 34N88W TO THE ALABAMA
COAST NEAR 30N89W ACROSS THE NW GULF TO 26N93W TO NE MEXICO NEAR
24N99W. ADDITIONALLY...A SURFACE TROUGH IS LOCATED TO THE E OF
THIS COLD FRONT. THIS SURFACE TROUGH EXTENDS FROM THE FLORIDA
PANHANDLE NEAR 31N85W TO 27N90W TO A 1005 MB SURFACE LOW IN THE
SW GULF NEAR 20N96W TO S MEXICO NEAR 18N95W. STRONG UPPER LEVEL
DIVERGENCE IN THE SE QUADRANT OF AN ANTICYCLONICALLY-CURVED
140-150 KT UPPER LEVEL JET MAXIMUM ORIENTED FROM SOUTH-SOUTHWEST
TO NORTH-NORTHEAST OVER THE SE CONUS IS SUPPORTING NUMEROUS
STRONG THUNDERSTORMS ALONG AND WITHIN 120 NM E OF THE COLD FRONT
N OF 23N. THIS ACTIVITY IS RESULTING IN THE DEVELOPMENT OF A
WEAK 1004 MB SURFACE HIGH OVER SE ALABAMA NEAR 31N86W. AT THE
SAME TIME...SOUTHERLY SURFACE WINDS CONTINUE TO ADVECT LOW LEVEL
MOISTURE AHEAD OF THE COLD FRONT...WITH INSTABILITY FORECAST TO
CONTINUE INCREASING AHEAD OF THE FRONT. THIS FRONT IS FORECAST
TO CONTINUE MOVING SOUTHEASTWARD ACROSS THE GULF THROUGH
TONIGHT...WITH INCREASING CHANCES FOR STRONG TO SEVERE
THUNDERSTORMS ALONG AND AHEAD OF THE FRONT AS IT ENCOUNTERS THE
INCREASINGLY MOIST AND UNSTABLE AIRMASS. THE INCREASING DEEP
LAYER SHEAR ASSOCIATED WITH PARTICULARLY STRONG SOUTHWESTERLY
FLOW ALOFT WILL ENHANCE THE STRONG TO SEVERE THUNDERSTORM
THREAT. AT PRESENT...A TORNADO WATCH IS IN EFFECT FOR PORTIONS
OF N FLORIDA AND THE ADJACENT COASTAL WATERS UNTIL NOON EST
TODAY. ALSO...GALE CONDITIONS ARE FORECAST TO OCCUR FOR PORTIONS
OF THE MIDDLE AND EAST GULF DURING THE NEXT DAY. IN THE WAKE OF
THE COLD FRONT...RELATIVELY COOLER AND DRIER CONDITIONS ARE
PRESENT.

CARIBBEAN SEA...
IN THE SW CARIBBEAN...A 1010 MB SURFACE LOW IS CENTERED N OF
PANAMA NEAR 10N81W. LOW LEVEL CONVERGENCE NEAR THIS SURFACE LOW
IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS S OF
12N W OF 78W...INCLUDING PORTIONS OF PANAMA AND 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 17N81W TO 20N84W. OVER THE N AND E CARIBBEAN...DEEP
LAYER SUBSIDENCE AND DEEP LAYER DRY AIR ARE IN PLACE RESULTING
IN FAIR WEATHER...WHERE NORTHWESTERLY FLOW ALOFT IS PRESENT. THE
SURFACE COLD FRONT OVER THE GULF OF MEXICO IS EXPECTED TO
APPROACH THE NW CARIBBEAN OVER THE NEXT DAY...ENTERING THE NW
CARIBBEAN ON MONDAY.

ATLANTIC OCEAN...
A VIGOROUS DEEP LAYER TROUGH OVER THE CENTRAL CONUS CONTINUES
APPROACHING THE W ATLC. OVER THE NEXT DAY...THE ASSOCIATED COLD
FRONT WILL MOVE SOUTHEASTWARD ACROSS PORTIONS OF THE W ATLC...
WITH NUMEROUS SHOWERS AND THUNDERSTORMS ACCOMPANYING THE FRONT.
THE THREAT FOR STRONG TO SEVERE THUNDERSTORMS WILL EXIST ACROSS
THE W ATLC ALONG AND AHEAD OF THE FRONT...ESPECIALLY GIVEN THE
PRESENCE OF STRONG DEEP LAYER WIND SHEAR. AT PRESENT...A TORNADO
WATCH IN EFFECT FOR PORTIONS OF N FLORIDA AND THE ADJACENT
COASTAL WATERS UNTIL NOON EST TODAY. ALSO...IN THE WAKE OF THE
COLD FRONT...RELATIVELY COOLER AND DRIER CONDITIONS ARE PRESENT.
FARTHER TO THE E...A SURFACE RIDGE IS PRESENT ACROSS PORTIONS OF
THE W ATLC...WHICH IS ASSOCIATED WITH A 1021 MB SURFACE HIGH
NEAR 29N59W...WITH SUBSIDENCE AND FAIR WEATHER IN THE VICINITY
OF THE SURFACE HIGH AND RIDGE. TO THE E...A SURFACE TROUGH
EXTENDS FROM 31N42W TO 29N39W TO 28N38W...WITH LOW LEVEL
CONVERGENCE RESULTING IN SCATTERED SHOWERS WITHIN 60 NM EITHER
SIDE OF THIS FEATURE. THIS ACTIVITY IS BEING ENHANCED BY
ATMOSPHERIC INSTABILITY IN THE VICINITY OF AN UPPER TROUGH WITH
AN AXIS EXTENDING FROM 19N53W TO 26N48W TO 32N44W TO NW OF THE
DISCUSSION AREA. FARTHER TO THE S...A SURFACE TROUGH EXTENDS
FROM 22N35W TO 17N42W TO 13N52W TO 9N60W...WITH LOW LEVEL
CONFLUENCE SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS WITHIN
90 NM EITHER SIDE OF THIS FEATURE. THIS ACTIVITY N OF 15N IS
BEING ENHANCED BY UPPER LEVEL DIVERGENCE IN THE SW QUADRANT OF A
110-120 KT ANTICYCLONICALLY-CURVED UPPER LEVEL JET MAXIMUM OVER
THE E ATLC. ADDITIONALLY...AN UPPER RIDGE IS S OF 16N BETWEEN
THE AFRICAN COAST AND 42W...WITH AN UPPER HIGH NEAR 8N24W. UPPER
LEVEL DIFFLUENCE ASSOCIATED WITH THIS UPPER RIDGE AND UPPER HIGH
IS ENHANCING THE CONVECTION IN THE VICINITY OF THE ITCZ BETWEEN
14W-28W. ADDITIONALLY...GALE CONDITIONS ARE FORECAST DURING THE
NEXT DAY FOR PORTIONS OF THE W ATLC.

OF NOTE...NOVEMBER 30 MARKS THE CONCLUSION OF THE 2008 ATLANTIC
HURRICANE SEASON. DURING THIS SEASON...SIXTEEN NAMED TROPICAL
CYCLONES OCCURRED. OF THESE SIXTEEN...EIGHT WERE HURRICANES...OF
WHICH FIVE WERE MAJOR HURRICANES OF SAFFIR-SIMPSON CATEGORY
THREE STRENGTH OF STRONGER. THIS SEASON WAS THE FIRST EVER WHEN
SIX CONSECUTIVE TROPICAL CYCLONES MADE LANDFALL ON THE CONUS
MAINLAND. OVERALL...THE 2008 HURRICANE SEASON IS TIED AS THE
FOURTH MOST ACTIVE IN TERMS OF NUMBER OF NAMED STORMS AND MAJOR
HURRICANES...AND IS ALSO TIED AS FIFTH MOST ACTIVE IN TERMS OF
NUMBER OF HURRICANES SINCE 1944...THE BEGINNING OF THE AERIAL
RECONNAISSANCE ERA. FINALLY...THIS IS THE TENTH SEASON TO
PRODUCE ABOVE-NORMAL TROPICAL CYCLONE ACTIVITY SINCE 1995 WHEN
THE CURRENT ACTIVE HURRICANE ERA BEGAN. ADDITIONALLY...A TOTAL
OF 64 TROPICAL WAVES MOVED OFF THE COAST OF AFRICA THIS SEASON
WHICH IS NEAR THE SEASONAL AVERAGE.

$$

COHEN/GR


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