[Tropical] Tropical Weather Discussion

Tue Nov 18 23:19:43 CST 2008

AXNT20 KNHC 190520
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST WED NOV 19 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0445 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 42W S OF 17N MOVING W AT 10-15 KT. THIS
TROPICAL WAVE COINCIDES WITH A NORTH-TO-SOUTH ELONGATED DEEP
LAYER MOISTURE MAXIMUM BASED ON TOTAL PRECIPITABLE WATER PRODUCT
FROM CIMSS. ALSO...CIMSS WAVETRAK PRODUCT INDICATES A MAXIMUM IN
LOW LEVEL CYCLONIC CIRCULATION ALONG THE WAVE AXIS. SCATTERED
MODERATE CONVECTION IS WITHIN 180 NM EITHER SIDE OF WAVE S OF
13N.

A TROPICAL WAVE IS ALONG 72W/73W S OF 16N MOVING W 10-15 KT. A
MAXIMUM IN DEEP LAYER MOISTURE AND A MAXIMUM IN LOW LEVEL
CYCLONIC CIRCULATION COINCIDE WITH THIS WAVE. SATELLITE IMAGERY
INDICATES AN INVERTED-V PATTERN TO THE CLOUD COVERAGE IN THE
VICINITY OF THE WAVE. SCATTERED MODERATE CONVECTION IS WITHIN
120 NM EITHER SIDE OF WAVE S OF 12N...INCLUDING PORTIONS OF N
COLOMBIA AND NW VENEZUELA WHERE THE CONVECTION IS BEING ENHANCED
BY RELATIVELY GREATER INSTABILITY OVER HIGHER TERRAIN.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 8N12W 5N22W 6N36W 9N51W 7N60W.
SCATTERED MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF
THE ITCZ AXIS BETWEEN 24W-38W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS FROM 8N-13N BETWEEN 44W-59W.

...DISCUSSION...

GULF OF MEXICO...
A BROAD UPPER LEVEL TROUGH OVER THE E CONUS EXTENDS INTO THE E
GULF...WITH WEST-NORTHWESTERLY 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 REINFORCED BY
SURFACE COLD FRONT THAT EXTENDS FROM THE NORTH CENTRAL GULF NEAR
28N90W TO 27N84W TO THE SOUTH FLORIDA PENINSULA NEAR 26N81W.
FREEZE WARNINGS AND WIND CHILL ADVISORIES ARE IN EFFECT FOR
TONIGHT...WITH FREEZE WATCHES IN EFFECT FOR WEDNESDAY
NIGHT...FOR INLAND PORTIONS OF FLORIDA ADJACENT TO THE GULF
COAST. ALSO...A 1030 MB SURFACE HIGH IS CENTERED OVER NE TEXAS
NEAR 25N100W...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 26N ACROSS
THE GULF. HOWEVER...SUBSIDENCE AND STABLE ATMOSPHERIC CONDITIONS
HIGHER IN THE ATMOSPHERE ARE INHIBITING DEEP CONVECTION ACROSS
THE GULF REGION. ADDITIONALLY...STRONG N TO NE SURFACE WINDS ARE
BLOWING THROUGH THE ISTHMUS OF TEHUANTEPEC RESULTING IN STORM
FORCE WINDS IN THE E PACIFIC REGION.

CARIBBEAN SEA...
ACROSS THE NW CARIBBEAN...A SURFACE STATIONARY FRONT EXTENDS
FROM E CUBA NEAR 20N75W TO 16N80W TO N COSTA RICA NEAR 11N84W.
LOW LEVEL CONVERGENCE NEAR THIS FRONT IS INTERACTING WITH DEEP
MOISTURE OVER THE W CARIBBEAN TO GENERATE SCATTERED SHOWERS AND
THUNDERSTORMS WITHIN 60 NM EITHER SIDE OF THE STATIONARY FRONT.
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
11N73W TO 14N75W TO 17N78W. OVER THE E CARIBBEAN...AN UPPER
LEVEL RIDGE EXTENDS FROM AN UPPER HIGH NEAR 16N64W TO 18N63W TO
THE SW ATLC...WITH UPPER LEVEL DIVERGENCE S AND SW OF THE UPPER
HIGH SUPPORTING SCATTERED SHOWERS OVER THE E CARIBBEAN S OF 13N
E OF 79W. THIS ACTIVITY IS BEING ENHANCED BY THE TROPICAL WAVE
ALONG 72W/73W.

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 20N75W TO 26N67W TO 32N61W 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 FLORIDA . THIS RELATIVELY COOLER AND
DRIER AIRMASS IS BEING REINFORCED BY A SURFACE COLD FRONT THAT
EXTENDS FROM THE SOUTH CENTRAL FLORIDA PENINSULA NEAR 26N81W TO
28N74W TO 32N67W TO NE OF THE DISCUSSION AREA WITH SCATTERED
STRATOCUMULUS CLOUDS BETWEEN THIS FRONT AND THE COAST OF THE SE
CONUS...WITH ANOTHER SURFACE COLD FRONT THAT EXTENDS FROM 31N73W
TO 32N72W TO NE OF THE DISCUSSION AREA. FARTHER TO THE E...A
1016 MB SURFACE HIGH IS CENTERED NEAR 27N54W...WHICH IS BEING
SUPPORTED BY AN UPPER LEVEL RIDGE WITH AN AXIS EXTENDING FROM
18N63W TO 25N58W TO 32N54W TO N OF THE DISCUSSION AREA. TO THE
E...AN UPPER LOW IS CENTERED NEAR 33N40W THAT IS ACCOMPANIED BY
AN UPPER TROUGH N OF 17N BETWEEN 28W-43W. THE UPPER LOW AND
UPPER TROUGH ARE ACCOMPANIED A 1009 MB SURFACE LOW NEAR
30N43W...A 1010 MB SURFACE LOW NEAR 30N47W...AND A SURFACE
TROUGH EXTENDING FROM 19N38W TO 28N31W TO 32N34W TO NW OF THE
DISCUSSION AREA. LOW LEVEL CONVERGENCE NEAR THESE TWO SURFACE
LOWS AND SURFACE TROUGH IS SUPPORTING SCATTERED SHOWERS N OF 26N
BETWEEN 25W-38W...WITH ISOLATED SHOWERS N OF 27N BETWEEN
38W-47W. THIS ACTIVITY IS BEING ENHANCED BY UPPER LEVEL
DIFFLUENCE IN SOUTHWESTERLY FLOW ALOFT BETWEEN THE ACCOMPANYING
UPPER TROUGH...AND AN UPPER RIDGE THAT IS N OF 26N BETWEEN THE
AFRICAN COAST AND 25W. OVER THE TROPICAL ATLC...AN UPPER RIDGE
IS S OF 7N BETWEEN 25W-41W. UPPER LEVEL DIVERGENCE IN THE
VICINITY OF THIS UPPER RIDGE IS ENHANCING THE CONVECTION
ASSOCIATED WITH THE ITCZ...AS WELL AS THE TROPICAL WAVE
ALONG 42W.

$$
COHEN

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