[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 081757
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED JUL 08 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...

A TROPICAL WAVE IS ALONG 45W MOVING W NEAR 15 KT. A WEAK LOW-
LEVEL INVERTED-V CLOUD SIGNATURE IS OBSERVED ON VISIBLE
SATELLITE IMAGERY ALONG WITH A LARGE AREA OF SAHARAN DUST
SURROUNDING THE WAVE THAT COVERS THE TROPICAL ATLC E OF 55W TO W
AFRICA. WITH THE DRY SAHARAN AIR LAYER SURROUNDING THE WAVE...NO
DEEP CONVECTION IS IN THE VICINITY OF THE WAVE.

A TROPICAL WAVE EXTENDS FROM THE NRN YUCATAN PENINSULA NEAR
21N87W ALONG 14N89W AND INTO THE E PACIFIC MOVING W NEAR 18 KT.
THIS WAVE COINCIDES WITH A SIGNIFICANT AREA OF INCREASED
PRECIPITABLE WATER ACROSS THE WRN CARIBBEAN AND CENTRAL AMERICA.
INTERACTING WITH A DIFFLUENT ATMOSPHERE ALOFT...SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS FOUND ACROSS THE WRN
CARIBBEAN AND PORTIONS CENTRAL AMERICA FROM 14N-19N BETWEEN
82W-90W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 12N16W 7N25W 6N43W 7N48W 9N61W.
SCATTERED MODERATE CONVECTION IS FROM 4N-10N BETWEEN 11W-27W.

...DISCUSSION...

GULF OF MEXICO...
MOSTLY S TO SW SURFACE WINDS ARE OBSERVED ACROSS THE GULF OF
MEXICO AS A RIDGE OF HIGH PRESSURE EXTENDS FROM THE W ATLC
THROUGH THE STRAITS OF FLORIDA AND WRN CUBA TO THE ERN COAST OF
MEXICO. A 1130 UTC SCATTEROMETER PASS DEPICTED WINDS UP TO 15 KT
ACROSS THE ERN AND NW GULF...ALONG WITH S-SE WINDS UP TO 20 KT
ACROSS THE SW GULF AND BAY OF CAMPECHE. AS THE WIND FIELD ROUNDS
THE RIDGE AXIS POSITIONED ACROSS THE CENTRAL GULF...LOW-LEVEL
CONVERGENCE ALONG A SURFACE TROUGH EXTENDING FROM THE WRN
FLORIDA PANHANDLE TO 30N95W S OF NEW ORLEANS IS GENERATING
SCATTERED SHOWERS AND TSTMS N OF 26N E OF 93W OVER THE NRN GULF
COAST AND NRN FLORIDA. AN UPPER LEVEL SHORTWAVE TROUGH IS
PROGRESSING E-SE ACROSS THE SE CONUS AND IS ALSO ENHANCING THIS
ACTIVITY. ELSEWHERE ACROSS THE REMAINDER OF THE GULF S OF
27N...MOSTLY CLEAR SKIES ARE NOTED ON VISIBLE SATELLITE IMAGERY
AS SURFACE RIDGING AND MODERATE SUBSIDENCE ALOFT PREVAIL.

CARIBBEAN SEA...
A TROPICAL WAVE IS TRACKING WWD ACROSS THE ERN YUCATAN PENINSULA
AND CENTRAL AMERICA CONTINUING TO IMPACT THE NW CARIBBEAN WATERS
AND PORTIONS OF CENTRAL AMERICA. THE WAVE CONTINUES TO MOVE
BENEATH AN UPPER LEVEL ANTICYCLONE CENTERED OVER WRN GUATEMALA
NEAR 15N92W AND THE INTERACTION BETWEEN THESE TWO FEATURES IS
GENERATING SCATTERED SHOWERS AND TSTMS FROM 14N-19N BETWEEN
82W-90W...INCLUDING PORTIONS OF HONDURAS...BELIZE AND GUATEMALA.
ALSO SCATTERED SHOWERS AND TSTMS ARE ACROSS THE SW CARIBBEAN AND
FAR ERN COASTAL AREAS OF WRN PANAMA...COSTA RICA AND SE
NICARAGUA FROM 8N-13N W OF 80W. SURFACE CONVERGENCE DUE TO THE
PROXIMITY OF THE E PACIFIC ITCZ ALONG 8N IS ENHANCING THIS
ACTIVITY. THE REMAINDER OF THE CARIBBEAN...WITH THE EXCEPTION OF
THE FAR NERN WATERS...IS UNDER THE INFLUENCE OF A SAHARAN AIR
LAYER OF DUST SUSPENDED IN THE MIDDLE LEVELS OF THE ATMOSPHERE.
THE SUSPENDED DUST IS OBSERVED ON VISIBLE SATELLITE IMAGERY AND
NUMEROUS OF THE UPPER AIR TIME SECTION ANALYSES ACROSS THE ERN
AND CENTRAL CARIBBEAN. WITH THIS DRIER AIR IN PLACE...ONLY A FEW
ISOLATED LOW-LEVEL SHOWERS ARE NOTED N OF 16N E OF 67W IN
ASSOCIATION WITH A SURFACE TROUGH THAT EXTENDS FROM THE CENTRAL
ATLC TO NEAR MONTSERRAT. FRESH TO STRONG ELY TRADE WIND FLOW
CONTINUES ACROSS THE BASIN AND IS FORECAST TO PERSIST THROUGH
FRIDAY AND INTO THE WEEKEND.

ATLANTIC OCEAN...
SCATTERED SHOWERS AND TSTMS ARE ACROSS THE SW NORTH ATLC N OF
29N W OF 68W. THIS ACTIVITY IS DRIVEN BY LOW-LEVEL CONVERGENCE
ALONG AND S OF A STATIONARY FRONT THAT PARALLELS 32N BETWEEN 73W
AND THE SOUTH CAROLINA COAST. THIS ACTIVITY IS FURTHER ENHANCED
BY UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL RIDGE OVER THE
W ATLC CENTERED NEAR 29N67W AND AN UPPER LEVEL SHORTWAVE TROUGH
OVER THE SE CONUS. A 1023 MB SURFACE HIGH IS OVER THE CENTRAL
ATLC NEAR 29N42W AND EXTENDS A RIDGE ACROSS THE REMAINDER OF THE
SW NORTH ATLC...INCLUDING THE BAHAMAS...PROVIDING GENERALLY FAIR
WEATHER. HOWEVER...A WEAKNESS IN THE SURFACE RIDGE IS ANALYZED
AS A SURFACE TROUGH THAT EXTENDS FROM 25N47W TO THE LEEWARD
ISLANDS NEAR 16N62W. SCATTERED SHOWERS ARE WITHIN 150 NM W OF
THE SURFACE TROUGH IN MODERATE ELY TRADES. ANOTHER WEAKNESS IN
THE SURFACE RIDGE LOCATED ACROSS THE NE ATLC IS A SURFACE TROUGH
THAT ENTERS THE DISCUSSION AREA NEAR 32N22W AND EXTENDS S-SW TO
24N28W. POSSIBLE ISOLATED SHOWERS ARE WITHIN 60 NM EITHER SIDE
OF THE TROUGH.

$$
HUFFMAN






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