000
AXNT20 KNHC 072335
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE JUL 07 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 2230 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE EXTENDS FROM 17N39W TO 5N41W MOVING W AT 15-20 
KT. A LOW-LEVEL INVERTED-V CLOUD BAND IS PRESENT IN VISIBLE 
SATELLITE IMAGERY AS WELL AS SAHARAN DUST E OF THE AXIS TO THE W 
AFRICA COAST. THIS WAVE ALSO COINCIDES WITH A DEEP LAYER 
MOISTURE MAXIMUM OBSERVED ON TOTAL PRECIPITABLE WATER IMAGERY. 
DUE TO THE PRESENCE OF THE SAHARAN AIR LAYER...NO DEEP 
CONVECTION IS CURRENTLY ASSOCIATED WITH THE WAVE.

A TROPICAL WAVE IS ALONG 83W/84W S OF 21N MOVING W AT 20-25 KT. 
VISIBLE SATELLITE IMAGERY INDICATES LOW-LEVEL CYCLONIC FLOW 
AROUND THE VICINITY OF THE WAVE AXIS. THIS WAVE ALSO COINCIDES 
WITH A SIGNIFICANT AREA OF INCREASED DEEP LAYER MOISTURE 
OBSERVED ON TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED 
MODERATE/ISOLATED STRONG CONVECTION IS AFFECTING MUCH OF THE NW 
CARIBBEAN FROM 12N-23N BETWEEN 78W-85W INCLUDING PORTIONS OF 
NICARAGUA..HONDURAS...AND CUBA.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 12N13W 7N23W 9N38W 10N47W AND 
INTO S AMERICA NEAR 8N60W. SCATTERED MODERATE/ISOLATED STRONG 
CONVECTION IS FROM 5N-9N BETWEEN 17W-21W. ISOLATED MODERATE 
CONVECTION IS FROM 3N-6N BETWEEN 21W-26W AND FROM 6N-8N BETWEEN 
31W-33W. 

...DISCUSSION...

THE GULF OF MEXICO...
ACROSS THE NRN GULF OF MEXICO...SURFACE CONFLUENCE DUE TO A 
STATIONARY/COLD FRONT OVER THE SE UNITED STATES ANCHORED BY A 
SURFACE LOW OFF THE COAST OF NORTH CAROLINA IS SUPPORTING 
SCATTERED SHOWERS/THUNDERSTORMS N OF 27N CONTINUING INTO THE W 
ATLC. THE REMAINDER OF THE GULF IS UNDER A WEAK SURFACE RIDGE 
EXTENDING FROM THE SW N ATLC ACROSS S FLORIDA TO THE SW GULF. 
MOSTLY CLEAR SKIES ARE PRESENT WITH SE TO S WIND UP TO 15 KT W 
OF 90W SHIFTING SW TO W E OF 90W. AN UPPER LEVEL RIDGE COVERS 
THE MAJORITY OF THE GULF BRINGING MODERATE SUBSIDENCE TO THE SRN 
GULF SUPPORTING THE FAIR WEATHER. 

THE CARIBBEAN SEA...
A TROPICAL WAVE IS ALONG 83W/84W SUPPORTING SCATTERED 
SHOWERS/THUNDERSTORMS ACROSS THE WRN CARIBBEAN FROM 12N-23N 
BETWEEN 78W-85W INCLUDING PORTIONS OF NICARAGUA..HONDURAS...AND 
CUBA. AN UPPER LEVEL HIGH IS NEAR 14N90W ENHANCING THE 
SHOWERS/THUNDERSTORMS ASSOCIATED WITH THE WAVE. THE ERN GULF IS 
UNDER THE INFLUENCE OF A SAHARAN AIR LAYER OF DUST IN THE MID 
LEVELS OF THE ATMOSPHERE. THIS DRIER AIR IS PREVENTING MOST 
SHOWER ACTIVITY BUT A FEW ISOLATED SHOWERS ARE NOTED OVER PUERTO 
RICO AND HISPANIOLA. FRESH TO STRONG ELY TRADE WINDS CONTINUE 
ACROSS THE BASIN AND ARE FORECAST TO PERSIST THROUGH THE END OF 
THE WEEK. 

THE ATLANTIC OCEAN...
SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS THE SW N ATLC N OF 
27N W OF 68 AHEAD OF A FRONTAL SYSTEM N OF THE DISCUSSION AREA. 
THIS ACTIVITY IS SUPPORTED BY UPPER LEVEL DIFFLUENCE BETWEEN A 
BROAD UPPER LEVEL RIDGE THAT EXTENDS OVER THE GULF OF MEXICO AND 
INTO THE WRN ATLC AND AN UPPER LEVEL TROUGH OVER THE NE UNITED 
STATES. A PAIR OF SURFACE HIGHS DOMINATE THE CENTRAL ATLC...A 
1023 MB SURFACE HIGH NEAR 29N54W...AND A 1022 MB SURFACE HIGH 
NEAR 29N43W...BRINGING GENERALLY FAIR WEATHER TO THE AREA. A 
SURFACE TROUGH EXTENDS FROM 19N54W TO 24N43W. NO SHOWERS ARE 
CURRENTLY ASSOCIATED WITH THIS SYSTEM. FARTHER E...ANOTHER 
SURFACE TROUGH EXTENDS FROM 24N35W TO 32N23W CONTINUING N OF THE 
DISCUSSION AREA. IN THE UPPER LEVELS...AN UPPER LEVEL RIDGE IS N 
OF 20N BETWEEN 40W-60W...WHILE AN UPPER LEVEL TROUGH COVERS THE 
E ATLC N OF 23N. A BROAD UPPER LEVEL RIDGE IS OVER THE TROPICAL 
ATLC S OF 20N SUPPORTING CONVECTION ALONG THE ITCZ. 

$$
WALTON