[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 302352
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN AUG 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

AN ACTIVE TROPICAL WAVE EXTENDS FROM 18N45W TO 8N49W WITH AN
ASSOCIATED 1007 MB SURFACE LOW CENTER NEAR 11N48W. THE WAVE IS
MOVING W NEAR 15 KT. SATELLITE IMAGERY INDICATES ELONGATED
CYCLONIC FLOW IN THE VICINITY OF THE WAVE AXIS CONCENTRATED
AROUND THE LOW CENTER. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS MAINLY TO THE NW OF THE WAVE AXIS FROM 14N-18N
BETWEEN 47W-49W..AND TO THE W OF LOW CENTER FROM 8N-14N BETWEEN
48W-54W. THIS SYSTEM HAS A HIGH CHANCE...GREATER THAN 50
PERCENT...OF BECOMING A TROPICAL CYCLONE IN THE NEXT 48 HRS.

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 24W S OF 16N SLOWLY DRIFTING W.
LOW/MID-LEVEL CYCLONIC FLOW IS NOTED IN CURRENT SATELLITE
IMAGERY AND SATELLITE DERIVED WINDS. THE CYCLONIC FLOW HAS
REMAINED NEARLY STATIONARY FOR THE PAST 24 HRS CENTERED OVER THE
CAPE VERDE ISLANDS. THE WAVE COINCIDES WITH A DEEP LAYER
MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY.
HOWEVER...DRY AIR AND SUBSIDENCE TO THE W OF THE WAVE AXIS IS
INHIBITING DEEP CONVECTION.

A TROPICAL WAVE IS ALONG 72W/73W S OF 17N MOVING W NEAR 15 KT.
THE WAVE TRAILS AN AREA OF RELATIVELY INCREASED MOISTURE
OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. HOWEVER...THE WAVE
IS CURRENTLY EMBEDDED WITHIN AN AREA OF DRY STABLE AIR
INHIBITING ANY DEEP CONVECTION.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 11N15W 9N27W 16N40W 8N51W 8N61W.
A LARGE CLUSTER OF NUMEROUS STRONG CONVECTION IS ALONG THE
AFRICA COAST FROM 10N-14N BETWEEN 12W-17W.

...DISCUSSION...

GULF OF MEXICO...
A COLD FRONT CLIPS THE NW GULF EXTENDING FROM A 1013 MB LOW OVER
SRN MISSISSIPPI NEAR 31N89W CONTINUING ALONG 30N93W 28N98W. A
PRE-FRONTAL SURFACE TROUGH EXTENDS AHEAD OF THE FRONT ALONG
28N92W 25N95W CONTINUING S INTO THE BAY OF CAMPECHE TO NEAR
19N95W. SURFACE CONVERGENCE NEAR THE FRONT AND PRE-FRONTAL
TROUGH IS SUPPORTING SCATTERED SHOWERS THUNDERSTORMS ACROSS THE
WRN GULF WITHIN 300 NM NW OF A LINE ALONG 20N94W 26N89W 31N84.
THIS SHOWER ACTIVITY IS ENHANCED BY UPPER LEVEL DIFFLUENCE
BETWEEN AN UPPER LEVEL TROUGH ACROSS THE CENTRAL AND ERN CONUS
AND AN UPPER LEVEL RIDGE ACROSS THE WRN GULF CENTERED OVER
MEXICO NEAR 19N100W. THE REMAINDER OF THE GULF IS EXPERIENCING
GENERALLY FAIR WEATHER BESIDES A FEW ISOLATED
SHOWERS/THUNDERSTORMS DUE TO MOIST SWLY FLOW ALOFT AROUND THE
UPPER LEVEL TROUGH ACROSS THE ERN CONUS. EXPECT THE COLD FRONT
IN THE FAR NW GULF TO MOVE FARTHER INTO THE AREA AND CONTINUE TO
THE FLORIDA PANHANDLE ON MONDAY...WEAKENING TO A TROUGH BY WED.

CARIBBEAN SEA...
AN UPPER LEVEL TROUGH IS OVER THE W CARIBBEAN WITH AXIS ALONG
85W. UPPER LEVEL DIFFLUENCE BETWEEN THIS UPPER TROUGH AND AN
UPPER LEVEL RIDGE OVER THE CENTRAL CARIBBEAN CENTERED S OF HAITI
NEAR 17N75W...ALONG WITH MOIST SLY FLOW ALOFT ARE SUPPORTING
ISOLATED SHOWERS/THUNDERSTORMS ACROSS THE SW CARIBBEAN S OF 16N
BETWEEN 75W-84W. SCATTERED SHOWERS/THUNDERSTORMS ARE ALSO ACROSS
JAMAICA...CUBA AND THE ADJACENT COASTAL WATERS. THE ERN
CARIBBEAN REMAINS FAIRLY CALM DESPITE THE PRESENCE OF A TROPICAL
WAVE ALONG 72W/73W DUE TO DRY AIR AND SUBSIDENCE ALOFT. A FEW
SHOWERS/THUNDERSTORMS ARE ACROSS HISPANIOLA AND PUERTO RICO DUE
TO UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL HIGH S OF
HAITI AND AN UPPER LEVEL LOW N OF PUERTO RICO NEAR 21N65W. FRESH
TO STRONG TRADE WINDS ARE ACROSS MUCH OF THE BASIN. EXPECT THE
TROPICAL WAVE IN THE CENTRAL CARIBBEAN TO CONTINUE WWD.
INTERESTS IN THE LESSER ANTILLES SHOULD MONITOR THE ACTIVE
TROPICAL WAVE EXTENDING FROM 18N45W TO 8N49W WHICH MAY AFFECT
THE ISLANDS IN THE NEXT COUPLE DAYS...SEE SPECIAL FEATURES
ABOVE.

ATLANTIC OCEAN...
ISOLATED SHOWERS/THUNDERSTORMS ARE ACROSS THE WRN ATLC WITHIN
200 NM NW OF A LINE ALONG 23N79W 27N74W 32N69W INCLUDING
PORTIONS OF CUBA...THE BAHAMAS...AND S FLORIDA. THIS ACTIVITY IS
ENHANCED BY MOIST SWLY FLOW ALOFT AND UPPER LEVEL DIFFLUENCE E
OF THE UPPER LEVEL TROUGH OVER THE ERN CONUS. ISOLATED SHOWERS
ARE N OF PUERTO RICO FROM 19N-26N BETWEEN 59W-69W IN ASSOCIATED
WITH AN UPPER LEVEL TROUGH EXTENDING THROUGH A PAIR OF UPPER
LEVEL LOWS NEAR 21N65W AND 28N51W. ELSEWHERE ACROSS THE ATLC...A
BROAD SURFACE RIDGE DOMINATES ANCHORED BY A 1030 MB HIGH WELL N
OF THE DISCUSSION AREA NEAR 42N45W. IN THE UPPER LEVELS...A
BROAD UPPER LEVEL RIDGE IS E OF THE PAIR OF UPPER LOWS CENTERED
NEAR 17N35W. AN UPPER LEVEL TROUGH DOMINATES THE FAR E ATLC WITH
AXIS ALONG 24N. THIS UPPER TROUGH MAY BE INFLUENCING THE LACK OF
FASTER WWD MOVEMENT OF THE TROPICAL WAVE ALONG 24N.

$$
WALTON





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