[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 301748
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED SEP 30 2009

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 28W S OF 12N MOVING W NEAR 15 KT. THE
WAVE COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE AS NOTED IN
TOTAL PRECIPITABLE WATER IMAGERY...AS WELL AS EXHIBITING LOW- TO
MIDDLE-LEVEL CYCLONIC FLOW EVIDENT IN SATELLITE IMAGERY AND
SATELLITE DERIVED WINDS. CIMSS WAVETRAK MODEL GUIDANCE ALSO
INDICATES A BROAD AREA OF 850 MB RELATIVE VORTICITY ERN ATLC
FROM 5N-15N BETWEEN 20W-35W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS MOSTLY W OF THE WAVE AXIS FROM 6N-11N BETWEEN
27W-34W.

TROPICAL WAVE IS ALONG 47W S OF 18N MOVING W NEAR 15 KT. THE
WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN
TOTAL PRECIPITABLE WATER IMAGERY. ALSO...CIMSS WAVETRAK MODEL
GUIDANCE INDICATES A CONCENTRATED AREA OF 850 MB RELATIVE
VORTICITY CENTERED ALONG THE WAVE AXIS FROM 10N-17N. THIS
LOW-LEVEL VORTICITY COUPLED WITH AN UPPER LEVEL DIFFLUENT
PATTERN ALOFT IS GENERATING SCATTERED MODERATE CONVECTION FROM
8N-15N BETWEEN 43W-49W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 8N13W 8N27W 7N29W 11N44W 11N49W
9N61W. ISOLATED STRONG CONVECTION IS ALONG THE W AFRICA COAST
FROM 12N-14N BETWEEN 15W-20W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 1500 UTC...A COLD FRONT EXTENDS ACROSS THE SRN FLORIDA
PENINSULA FROM WEST PALM BEACH TO NEAR NAPLES AND INTO THE SERN
GULF NEAR 26N84W. THE FRONT CONTINUES WWD AS A STATIONARY FRONT
ALONG 26N84W 25N90W BECOMING MORE DIFFUSE TO THE TEXAS GULF
COAST NEAR CORPUS CHRISTI. THE FRONT IS SUPPORTED BY AN UPPER
LEVEL TROUGH WHICH COVERS MUCH OF THE NE CONUS AND EXTENDS
TROUGHING S ACROSS THE SERN COASTAL STATES AND W ATLC WATERS.
SCATTERED SHOWERS AND TSTMS COVER THE SE GULF AND STRAITS OF
FLORIDA FROM 23N-26N BETWEEN THE SE BAHAMAS AND 91W. WATER VAPOR
IMAGERY INDICATES AN EMBEDDED MID-LEVEL SHORTWAVE TROUGH OVER
THE NE GULF WHICH WILL MOVE THE COLD FRONT INTO THE W ATLC AS
THE REMAINING BOUNDARY ACROSS THE SE GULF WILL STALL AND BECOME
DIFFUSE OVER THE NEXT 24-36 HOURS. THE REMAINDER OF THE GULF W
OF 90W IS UNDER THE ERN PERIPHERY OF AN UPPER LEVEL RIDGE
CENTERED OVER MEXICO THAT IS PROVIDING NWLY UPPER LEVEL FLOW AND
VERY DRY AND STABLE CONDITIONS. GENERALLY FAIR SKIES ARE
OBSERVED ACROSS THE WRN GULF AND BAY OF CAMPECHE THIS AFTERNOON
DUE TO THE STRONG SUBSIDENCE IN PLACE.

CARIBBEAN SEA...
THE UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED OVER MEXICO
EXTENDS UPPER LEVEL RIDGING ACROSS CENTRAL AMERICA AND THE WRN
CARIBBEAN TO 73W. NWLY FLOW DOMINATES ALOFT OVER THIS AREA WITH
MODERATE TO STRONG SUBSIDENCE IN PLACE. SPEED CONVERGENCE OF THE
LOW-LEVEL TRADE WINDS ALONG WITH THE UPPER LEVEL DIFFLUENT
ENVIRONMENT ASSOCIATED WITH THE UPPER LEVEL RIDGE IS GENERATING
SCATTERED SHOWERS AND ISOLATED TSTMS ACROSS THE SW CARIBBEAN
FROM 10N-15N BETWEEN 81W-85W. A RELATIVELY WEAK UPPER LEVEL
TROUGH IS ACROSS THE ERN CARIBBEAN E OF 73W PROVIDING THE ERN
CARIBBEAN WITH MOIST SWLY FLOW ALOFT. A FEW PASSING ISOLATED
SHOWERS ARE BEING USHERED IN ON MODERATE TO FRESH TRADE WINDS N
OF 14N E OF 70W.

ATLANTIC OCEAN...
AS OF 1500 UTC...A COLD FRONT ENTERS THE DISCUSSION AREA NEAR
32N69W AND EXTENDS SW TO THE FLORIDA COAST NEAR WEST PALM BEACH.
ISOLATED SHOWERS AND TSTMS ARE WITHIN 60 NM E OF THE FRONT. A
PAIR OF PRE-FRONTAL SURFACE TROUGHS ARE AHEAD OF THE FRONT WITH
ONE EXTENDING FROM 28N76W ACROSS THE BAHAMAS TO 24N79W AND THE
OTHER EXTENDING FROM 27N72W TO 25N75W. SCATTERED SHOWERS AND
TSTMS COVER AN AREA OF THE W ATLC FROM 23N-27N BETWEEN 69W-81W.
THE FRONTAL BOUNDARY AND ASSOCIATED CONVECTION IS ENHANCED BY
DIFFLUENT FLOW ALOFT BETWEEN AN UPPER LEVEL TROUGH ACROSS THE
ERN CONUS AND W ATLC AND AN UPPER LEVEL RIDGE WITH AXIS FROM
20N65W NNE TO BEYOND 32N59W. FURTHER TO THE E ACROSS THE CENTRAL
ATLC...A SURFACE TROUGH EXTENDS FROM 17N55W TO 23N54W. LOW-LEVEL
CONVERGENCE NEAR THE TROUGH IS SUPPORTING SCATTERED SHOWERS FROM
18N-25N BETWEEN 49W-57W. UPPER LEVEL DIFFLUENT FLOW BETWEEN AN
UPPER LEVEL TROUGH WITH AXIS ALONG 57W AND AN UPPER LEVEL RIDGE
WITH AXIS ALONG 48W IS ENHANCING THIS AREA OF CONVECTION. A COLD
FRONT DIPS INTO THE DISCUSSION AREA NEAR 32N20W AND CONTINUES WSW
ALONG 28N30W 28N40W THEN STATIONARY TO 29N50W. ISOLATED SHOWERS
AND TSTMS ARE WITHIN 90 NM SE EITHER SIDE OF THE FRONT. THE
REMAINDER OF THE THE ATLC IS DOMINATED BY A PAIR OF 1020 MB
SURFACE HIGHS CENTERED NEAR 21N36W AND 25N20W.

$$
HUFFMAN





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