[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 011129
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST MON DEC 01 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
1045 UTC.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 9N13W 5N22W 5N31W 5N40W 1N51W.
SCATTERED MODERATE CONVECTION IS FROM 5N-9N BETWEEN 12W-17W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 3N-8N
BETWEEN 20W-29W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM
EITHER SIDE OF THE ITCZ AXIS BETWEEN 33W-37W. SCATTERED MODERATE
CONVECTION IS ALSO FROM 5N-8N BETWEEN 42W-47W.

...DISCUSSION...

GULF OF MEXICO...
A VIGOROUS DEEP LAYER TROUGH OVER THE E CONUS...WITH AN
ASSOCIATED 140-150 KT OVER THE SE CONUS...EXTENDS ACROSS THE
GULF REGION...WITH AN ASSOCIATED SURFACE COLD FRONT EXTENDING
FROM THE FLORIDA BIG BEND NEAR 30N83W ACROSS THE GULF TO 24N91W
TO 25N96W...AND A SURFACE STATIONARY FRONT THAT EXTENDS FROM
25N96W TO 26N98W AND EXTENDS WESTWARD ACROSS NORTHERN MEXICO.
AS COOLER AIR IS ADVECTED OVER THE RELATIVELY WARMER GULF
WATERS...LOW LEVEL INSTABILITY IS SUPPORTING SCATTERED
STRATOCUMULUS CLOUDS OVER THE GULF IN THE WAKE OF THE FRONT
N OF 25N. THE PRESENCE OF DEEP LAYER DRY AIR AND STABLE
ATMOSPHERIC CONDITIONS HIGHER IN THE ATMOSPHERE ARE PREVENTING
THE DEVELOPMENT OF DEEP CONVECTION ACROSS THE GULF REGION.
SUBSIDENCE IS OCCURRING OVER THE NW GULF IN THE VICINITY OF
A SURFACE RIDGE EXTENDING SOUTHEASTWARD FROM A 1021 MB SURFACE
HIGH NEAR THE TEXAS-MEXICO BORDER NEAR 29N101W. GALE CONDITIONS
ARE FORECAST TO OCCUR FOR PORTIONS OF THE MIDDLE AND EAST GULF
DURING THE NEXT DAY. STRONG N TO NE SURFACE WINDS ARE FORECAST
TO BLOW THROUGH THE ISTHMUS OF TEHUANTEPEC RESULTING IN GALE
FORCE WINDS IN THE EAST PACIFIC REGION BEGINNING AT 02/0600 UTC.

CARIBBEAN SEA...
A SECOND COLD FRONT THAT IS ALSO ASSOCIATED WITH THE VIGOROUS
E CONUS AND GULF REGION DEEP LAYER TROUGH IS ENTERING THE
NW CARIBBEAN...AND EXTENDS FROM W CUBA NEAR 23N83W TO THE
NW CARIBBEAN NEAR 21N85W TO THE YUCATAN PENINSULA NEAR 19N90W.
LOW LEVEL CONVERGENCE WITH THIS FRONT...INSTABILITY ALONG AND
AHEAD OF THE FRONT...AND STRONG DEEP LAYER WIND SHEAR OVER THE
NW CARIBBEAN ARE SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS
N OF 18N BETWEEN 76W-83W...INCLUDING PORTIONS OF CENTRAL CUBA.
THIS ACTIVITY IS BEING ENHANCED BY UPPER LEVEL DIVERGENCE IN THE
SE QUADRANT OF THE VIGOROUS 140-150 KT UPPER LEVEL JET MAXIMUM
FROM THE SE CONUS. IN THE SW CARIBBEAN...A 1009 MB SURFACE LOW
IS CENTERED E OF NICARAGUA NEAR 13N83W. LOW LEVEL CONVERGENCE
NEAR THIS SURFACE LOW IS SUPPORTING SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS S OF 16N W OF 79W. THIS ACTIVITY IS BEING
ENHANCED BY UPPER LEVEL DIVERGENCE IN MOIST SOUTHWESTERLY FLOW
ALOFT. OVER THE CENTRAL AND E CARIBBEAN...AN UPPER RIDGE IS
PRESENT...WHERE SUBSIDENCE AND DEEP LAYER DRY AIR ARE RESULTING
IN GENERALLY FAIR WEATHER. HOWEVER...SUFFICIENT LOW LEVEL
CONVERGENCE IS GENERATING SCATTERED SHOWERS WITHIN 60 NM EITHER
SIDE OF A SURFACE TROUGH OVER THE E CARIBBEAN THAT EXTENDS FROM
16N64W TO 13N65W TO N VENEZUELA NEAR 10N66W.

ATLANTIC OCEAN...
A VIGOROUS DEEP LAYER TROUGH IS OVER THE E CONUS AND GULF.
STRONG UPPER LEVEL DIVERGENCE ASSOCIATED WITH AN UPPER LEVEL JET
MAXIMUM OVER THE SE CONUS...COMBINED WITH INSTABILITY AND STRONG
DEEP LAYER WIND SHEAR...IS GENERATING SCATTERED SHOWERS AND
THUNDERSTORMS N OF 21N BETWEEN 71W-78W...INCLUDING PORTIONS OF
CENTRAL CUBA AND THE BAHAMAS. THIS ACTIVITY IS BEING ENHANCED BY
LOW LEVEL CONVERGENCE IN THE VICINITY OF A SURFACE COLD FRONT
THAT EXTENDS FROM W CUBA NEAR 23N83W TO 28N77W TO 32N76W AND
BEYOND THE DISCUSSION AREA. IN THE WAKE OF THE COLD FRONT...
RELATIVELY COOLER AND DRIER CONDITIONS ARE PRESENT. GALE
CONDITIONS ARE FORECAST DURING THE NEXT DAY OVER PORTIONS OF
THE W ATLC. TO THE E...A 1025 MB SURFACE HIGH IS PRESENT NEAR
29N56W...WITH SUBSIDENCE AND FAIR WEATHER IN THE VICINITY OF THE
SURFACE HIGH. FARTHER TO THE E...A SURFACE TROUGH EXTENDS FROM
27N37W TO 30N36W TO A 1012 MB SURFACE LOW NEAR 34N37W...WITH LOW
LEVEL CONVERGENCE NEAR THESE FEATURES RESULTING IN SCATTERED
SHOWERS N OF 28N BETWEEN 36W-39W. THIS ACTIVITY IS BEING
ENHANCED BY ATMOSPHERIC INSTABILITY IN THE VICINITY OF AN UPPER
TROUGH WITH AN AXIS EXTENDING FROM 15N56W TO 24N41W TO AN UPPER
LOW NEAR 36N37W. ALSO...A SURFACE TROUGH EXTENDS FROM 9N55W TO
18N39W TO 30N32W...WITH LOW LEVEL CONFLUENCE RESULTING IN
SCATTERED SHOWERS WITHIN 90 NM EITHER SIDE OF THIS FEATURE.
THE ACTIVITY N OF 15N IS BEING ENHANCED BY UPPER LEVEL
DIVERGENCE IN THE VICINITY OF A 90-100 KT UPPER LEVEL JET
MAXIMUM OVER THE E ATLC. ALSO ACROSS THE E ATLC...A WEAKENING
SURFACE WARM FRONT EXTENDS FROM 25N25W TO 32N28W TO NW OF THE
DISCUSSION AREA...WITH SCATTERED SHOWERS WITHIN 120 NM EITHER
SIDE OF THIS FRONT. ALSO...A WEAKENING SURFACE COLD FRONT
E OF THE CANARY ISLANDS EXTENDS FROM 27N14W TO 27N13W EASTWARD
ACROSS N AFRICA...WHICH IS ASSOCIATED WITH AN UPPER TROUGH
OVER PORTIONS OF N AFRICA...AND A SURFACE TROUGH EXTENDS FROM
A 1010 MB SURFACE LOW OVER SENEGAL NEAR 13N14W TO 15N15W TO
17N15W...WITH DEEP LAYER DRY AIR INHIBITING DEEP CONVECTION
IN THE VICINITY OF THE SURFACE COLD FRONT...LOW...AND TROUGH.
ADDITIONALLY...AN UPPER RIDGE IS S OF 18N BETWEEN THE AFRICAN
COAST AND 37W...WITH AN UPPER HIGH NEAR 8N14W. UPPER LEVEL
DIFFLUENCE ASSOCIATED WITH THIS UPPER RIDGE AND UPPER HIGH IS
ENHANCING CONVECTION IN THE VICINITY OF THE ITCZ E OF 37W.

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/MT/GR


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