[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 251751
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT JUL 25 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 EXTENDS FROM 22N44W TO 11N38W MOVING W 15-20 KT.
THIS WAVE IS ALONG THE LEADING EDGE OF A WEAK DEEP LAYER
MOISTURE MAXIMUM AS OBSERVED IN TOTAL PRECIPITABLE WATER
IMAGERY. VISIBLE SATELLITE IMAGERY INDICATES LOW LEVEL CYCLONIC
CURVATURE MAINLY N OF 17N. THE PRESENCE OF DRY SAHARAN AIR IS
LIMITING DEEP CONVECTION NEAR THE WAVE.

TROPICAL WAVE IS ALONG 80W/81W S OF 21N MOVING NEAR W 20 KT.
THIS WAVE IS EMBEDDED WITHIN A BROAD AREA OF DEEP LAYER MOISTURE
MAXIMUM AS OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY.
SUBSIDENCE AND DRY AIR OVER THE CENTRAL CARIBBEAN IS LIMITING
DEEP CONVECTION.

TROPICAL WAVE IS FROM 21N95W THROUGH THE GULF OF TEHUANTEPEC
INTO THE E PACIFIC REGION MOVING WNW 20-25 KT. VISIBLE SATELLITE
IMAGERY INDICATES THAT THIS WAVE HAS SPLIT WITH THE NORTHERN
PORTION OVER THE GULF OF MEXICO WHILE THE REMAINDER OF THE WAVE
IS OVER THE COAST OF CENTRAL AMERICA IN THE E PACIFIC REGION.
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE S OF 22N TO OVER
THE BAY OF CAMPECHE BETWEEN 92W-97W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 14N16W 9N35W 11N54W 10N64W. AN
AREA OF UPPER DIFFLUENCE IS OVER THE W TROPICAL ATLC GENERATING
CLUSTERS OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION
FROM 8N-14N BETWEEN 48W-55W. SMALL CLUSTERS OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION ARE FROM 9N-13N BETWEEN
26W-30W. ISOLATED CLUSTERS OF SCATTERED MODERATE CONVECTION ARE
WITHIN 120 NM ALONG THE COAST OF GUINEA AND WITHIN 120 NM S OF
THE ITCZ FROM 23W-39W.

...DISCUSSION...

GULF OF MEXICO...
A BROAD UPPER LEVEL TROUGH EXTENDS DOWN FROM THE GREAT LAKES
REGION THROUGH LOUISIANA AND INTO NE MEXICO COVERING THE GULF NW
OF A LINE FROM TAMPICO MEXICO TO NAPLES FLORIDA. THIS UPPER
LEVEL TROUGH CONTINUES TO SUPPORT A WEAKENING STATIONARY FRONT
EXTENDING ALONG THE N GULF COAST STATES FROM S GEORGIA ALONG THE
COASTLINE FROM PENSACOLA FLORIDA TO THE MISSISSIPPI/LOUISIANA
BORDER. LOW LEVEL CONVERGENCE AND UPPER DIFFLUENCE SE OF THE
FRONT IS SUPPORTING NUMEROUS/SCATTERED SHOWERS/THUNDERSTORMS
WITHIN 120 NM OF LINE FROM 26N92W TO OVER THE FLORIDA PANHANDLE
NEAR PANAMA CITY. AN ISOLATED CLUSTER OF SHOWERS/THUNDERSTORMS
ARE N OF THE YUCATAN PENINSULA WITHIN A 60 NM RADIUS OF
23.5N87.5W. UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL
TROUGH OVER THE GULF AND AN UPPER LEVEL RIDGE OVER THE W ATLC IS
SUPPORTING NUMEROUS/SCATTERED SHOWERS/THUNDERSTORMS ACROSS S
FLORIDA AND THE STRAITS OF FLORIDA FROM 24N TO LAKE OKEECHOBEE E
OF 82W INTO THE W ATLC. THE REMAINDER OF THE GULF REMAINS
TRANQUIL THIS AFTERNOON DOMINATED BY DRY AIR AND A 1017 MB
SURFACE HIGH JUST OFF THE COAST OF TAMPA FLORIDA.

CARIBBEAN SEA...
BROAD UPPER LOW IN THE CENTRAL ATLC EXTENDS ACROSS THE NE
CARIBBEAN FROM THE LEEWARD ISLANDS TO HISPANIOLA AND INTO THE
CENTRAL CARIBBEAN NEAR 13N75W SETTING UP THE WEAK UPPER RIDGE
OVER THE W ATLC TO THE E OF THE UPPER TROUGH OVER THE GULF OF
MEXICO. UPPER LEVEL DIFFLUENCE BETWEEN THESE FEATURES IS
SUPPORTING ISOLATED SHOWERS ACROSS THE NW CARIBBEAN N OF 20N W
OF 80W. LOW LEVEL CONVERGENCE AND THE CLOSE PROXIMITY OF THE
ITCZ IN THE E PACIFIC ARE GENERATING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS ACROSS THE SW CARIBBEAN SW OF A LINE FROM CENTRAL
NICARAGUA NEAR 13N84W TO PANAMA NEAR 9N80W. THE REMAINDER OF THE
CARIBBEAN IS DOMINATED BY DRY AIR GIVING THE CENTRAL AND E
CARIBBEAN TRANQUIL WEATHER THIS AFTERNOON. FRESH TO STRONG TRADE
WINDS ARE ACROSS MOST OF THE CARIBBEAN WITH THE STRONGEST WINDS
OF UP TO 30 KT OCCURRING NEAR THE COAST OF COLUMBIA.

ATLANTIC OCEAN...
A SURFACE TROUGH EXTENDS FROM 30N80W TO INLAND OVER CENTRAL
FLORIDA NEAR LAKE OKEECHOBEE. THE BROAD UPPER LEVEL TROUGH OVER
THE GULF OF MEXICO AND A BROAD UPPER TROUGH OVER THE CENTRAL
ATLC IS INDUCING AN UPPER RIDGE OVER THE W ATLC PROVIDING UPPER
LEVEL DIFFLUENCE TO GENERATE NUMEROUS/SCATTERED SHOWERS/
THUNDERSTORMS WITHIN 200/240 NM SW OF THE TROUGH S OF 29N AND
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 27N-30N BETWEEN
70W-76W. A SECOND SURFACE TROUGH EXTENDS FROM 27N67W TO 23N70W.
THE BROAD UPPER TROUGH COVERING THE CENTRAL ATLC IS BETWEEN
56W-70W AND EXTENDS INTO THE E CARIBBEAN WITH AN UPPER LOW NEAR
28N60W. UPPER LEVEL DIFFLUENCE TO THE E OF THE UPPER TROUGH IS
GENERATING SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS
WITHIN 75 NM OF LINE FROM 27N59W TO 32N56W. THE REMAINDER OF THE
ATLC IS DOMINATED BY A BROAD UPPER RIDGE WHICH IS PROVIDING
UPPER LEVEL DIFFLUENCE TO GENERATE THE ACTIVITY ASSOCIATED WITH
THE ITCZ. A SURFACE RIDGE COVERS THE ENTIRE ATLC BASIN INTO THE
GULF OF MEXICO ANCHORED BY A 1029 MB HIGH JUST N OF THE
DISCUSSION AREA NEAR 33N36W. THIS IS GIVING THE E ATLC AND THE
REMAINDER OF THE CENTRAL ATLC FAIR WEATHER THIS AFTERNOON.

$$
WALLACE





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