[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181142
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST TUE NOV 18 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.

...TROPICAL WAVES...
A TROPICAL WAVE IS OVER THE E CARIBBEAN ALONG 69W/70W S OF 17N
MOVING W 10-15 KT. WELL-DEFINED CYCLONIC CURVATURE IS PRESENT IN
SURFACE WIND OBSERVATIONS IN THE VICINITY OF THE WAVE AXIS.
ADDITIONALLY...A MAXIMUM IN DEEP LAYER MOISTURE COINCIDES WITH
THE WAVE AXIS BASED ON CIMSS TOTAL PRECIPITABLE WATER PRODUCT.
SCATTERED SHOWERS ARE FROM 11N-15N BETWEEN 65W-71W...WHICH ARE
LIKELY BEING ENHANCED BY THIS TROPICAL WAVE.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 8N12W 6N22W 7N36W 8N51W 8N60W.
SCATTERED MODERATE CONVECTION IS WITHIN 90 NM EITHER SIDE OF THE
ITCZ AXIS BETWEEN 18W-25W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 7N-12N BETWEEN 33W-42W. SCATTERED MODERATE
CONVECTION IS FROM 8N-11N BETWEEN 44W-48W. SCATTERED MODERATE
CONVECTION IS ALSO FROM 10N-13N BETWEEN 52W-60W...AFFECTING
PORTIONS OF THE WINDWARD ISLANDS.

...DISCUSSION...

GULF OF MEXICO...
A BROAD UPPER LEVEL TROUGH OVER THE E CONUS EXTENDS INTO THE
GULF...WITH WESTERLY FLOW ALOFT AND DEEP LAYER DRY AIR COVERING
MUCH OF THE GULF REGION. ALSO...A MODIFIED CONTINENTAL POLAR
AIRMASS PERSISTS ACROSS THE GULF REGION. AS A RESULT...
TEMPERATURES ACROSS THE GULF REGION ARE BELOW SEASONAL AVERAGES.
THIS RELATIVELY COOLER AND DRIER AIRMASS IS BEING SUPPORTED BY A
1029 MB SURFACE HIGH CENTERED OVER SE TEXAS NEAR 29N98W...WITH
AN ASSOCIATED SURFACE RIDGE EXTENDING INTO THE W GULF. AS THE
COOLER AIR IS BEING ADVECTED OVER THE RELATIVELY WARMER GULF
WATERS...WEAK LOW LEVEL INSTABILITY IS SUPPORTING SCATTERED
STRATOCUMULUS CLOUDS MAINLY S OF 25N ACROSS THE GULF.
HOWEVER...SUBSIDENCE AND STABLE ATMOSPHERIC CONDITIONS HIGHER IN
THE ATMOSPHERE ARE INHIBITING DEEP CONVECTION ACROSS THE GULF
REGION. THE AFOREMENTIONED BROAD UPPER TROUGH IS ALSO SUPPORTING
A SURFACE FRONT FURTHER NORTH. THIS FRONT IS CURRENTLY DRAPED
FROM THE SE CONUS INTO THE PLAINS OF THE CONUS. AS THE
ASSOCIATED UPPER LEVEL ENERGY TRANSLATES SOUTHWARD...THE SURFACE
FRONT WILL MOVE SOUTHWARD AS A COLD FRONT ACROSS THE CENTRAL AND
E GULF REGION OVER THE NEXT DAY. AN EVEN COOLER AND DRIER
AIRMASS IS IN THE WAKE OF THIS FRONT...WITH FREEZE WARNINGS AND
WIND CHILL ADVISORIES IN EFFECT FOR INLAND PORTIONS OF FLORIDA
ADJACENT TO THE GULF COAST FOR TONIGHT. ADDITIONALLY...STRONG N
TO NE SURFACE WINDS ARE BLOWING THROUGH THE ISTHMUS OF
TEHUANTEPEC RESULTING IN GALE FORCE WINDS IN THE E PACIFIC
REGION...WHICH ARE FORECAST TO BECOME STORM FORCE AT 19/0000 UTC.

CARIBBEAN SEA...
ACROSS THE NW CARIBBEAN...A SURFACE STATIONARY FRONT EXTENDS
FROM E CUBA NEAR 21N76W TO 17N80W TO S NICARAGUA NEAR 11N84W.
LOW LEVEL CONVERGENCE NEAR THIS FRONT IS INTERACTING WITH DEEP
MOISTURE OVER THE W CARIBBEAN TO GENERATE SCATTERED SHOWERS AND
THUNDERSTORMS S OF 18N W OF 77W. THIS ACTIVITY IS BEING ENHANCED
BY UPPER LEVEL DIVERGENCE IN THE VICINITY OF AN UPPER RIDGE
PRESENT OVER THE W CARIBBEAN...WITH THE AXIS OF THE UPPER RIDGE
EXTENDING FROM N COLOMBIA NEAR 12N72W TO 15N74W TO 20N75W. OVER
THE E CARIBBEAN...AN UPPER LEVEL TROUGH IS PRESENT...WITH UPPER
LEVEL DIVERGENCE IN MOIST SOUTHWESTERLY FLOW ALOFT SUPPORTING
SCATTERED SHOWERS OVER THE E CARIBBEAN S OF 15N E OF 71W. THIS
ACTIVITY IS BEING ENHANCED BY THE TROPICAL WAVE ALONG 68W/69W.

ATLANTIC OCEAN...
A BROAD UPPER TROUGH IS OVER THE E CONUS AND THE W ATLC...WHICH
IS SUPPORTING A SURFACE STATIONARY FRONT THAT EXTENDS FROM E
CUBA NEAR 21N76W TO 28N67W TO 32N62W TO NE OF THE DISCUSSION
AREA. ISOLATED SHOWERS ARE WITHIN 60 NM EITHER SIDE OF THIS
STATIONARY FRONT...WITH THE COVERAGE OF THIS ACTIVITY BEING
LIMITED AS THE STRONGEST UPPER LEVEL ENERGY REMAINS N OF THE
DISCUSSION AREA. TO THE W OF THIS STATIONARY FRONT...A MODIFIED
CONTINENTAL POLAR AIRMASS IS IN PLACE...WITH TEMPERATURES BELOW
SEASONAL AVERAGES ACROSS THE FLORIDA PENINSULA. FARTHER TO THE
E...A 1017 MB SURFACE HIGH IS CENTERED NEAR 29N55W...WHICH IS
BEING SUPPORTED BY AN UPPER LEVEL RIDGE WITH AN AXIS EXTENDING
FROM 27N56W TO 30N56W TO 32N54W TO N OF THE DISCUSSION AREA. TO
THE E...AN UPPER LOW IS CENTERED NEAR 32N39W THAT IS ACCOMPANIED
BY AN UPPER TROUGH N OF 17N BETWEEN 28W-43W. THE UPPER LOW AND
UPPER TROUGH ARE ACCOMPANIED BY A SURFACE LOW AND TWO SURFACE
TROUGHS. ONE SURFACE TROUGH EXTENDS FROM A 1005 MB SURFACE LOW
NEAR 32N41W TO 29N40W TO 25N41W...WITH SCATTERED SHOWERS N OF
27N BETWEEN 34W-43W. THE SECOND SURFACE TROUGH EXTENDS FROM
31N30W TO 26N32W TO 22N36W...WITH NUMEROUS SHOWERS AND
THUNDERSTORMS N OF 25N BETWEEN 27W-32W. THE ACTIVITY ASSOCIATED
WITH THE SECOND SURFACE TROUGH IS BEING ENHANCED BY STRONG UPPER
LEVEL DIFFLUENCE IN SOUTHWESTERLY FLOW ALOFT BETWEEN THE
ACCOMPANYING UPPER TROUGH...AND AN UPPER RIDGE THAT IS N OF 24N
BETWEEN THE AFRICAN COAST AND 27W. OVER THE TROPICAL ATLC...AN
UPPER RIDGE IS S OF 10N BETWEEN THE AFRICAN COAST AND 25W...WITH
ANOTHER UPPER RIDGE PRESENT S OF 7N BETWEEN 29W-39W. UPPER LEVEL
DIVERGENCE IN THE VICINITY OF THESE UPPER RIDGES IS ENHANCING
THE CONVECTION ASSOCIATED WITH THE ITCZ.

$$
COHEN



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