Atlantic Tropical Weather Discussion

000
AXNT20 KNHC 042356
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT JUL 04 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.

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 21W S OF 17N MOVING W NEAR 18 KT. THIS 
WAVE EXHIBITS AN INVERTED-V SATELLITE SIGNATURE IN THE LOW-LEVEL 
CLOUDS THAT REMAIN LARGELY EMBEDDED WITHIN THE ITCZ AXIS. ALSO 
OF NOTE THIS WAVE IS ENCOMPASSED BY A SAHARAN AIR LAYER OF DUST 
THAT IS LIMITING ANY DEEP CONVECTION N OF 13N. SCATTERED 
MODERATE CONVECTION IS FROM 7N-12N BETWEEN 18W-23W. 

A TROPICAL WAVE EXTENDS FROM 20N54W TO 6N56W MOVING W 20-25 KT. 
THIS LARGE AND HIGH AMPLITUDE WAVE COINCIDES WITH A MAXIMUM IN 
DEEP LAYER MOISTURE AS OBSERVED ON THE TPW PRODUCT FROM CIMSS. A 
VORTICITY/MOISTURE MAXIMUM IS ALSO EVIDENT W OF THE ANALYZED 
AXIS NEAR 14N59W APPROACHING THE LESSER ANTILLES. SCATTERED 
MODERATE CONVECTION IS FROM 7N-13N BETWEEN 52W-57W AND FROM 
13N-17N BETWEEN 58W-63W...LIKELY SUPPRESSED BY SAHARAN DUST. 

TROPICAL WAVE IS ALONG 72W S OF 19N MOVING W 20-25 KT. THIS WAVE 
COINCIDES WITH A WELL DEFINED MOISTURE MAXIMUM IN TOTAL 
PRECIPITABLE WATER. THE INTERACTION WITH AN UPPER LOW OVER 
HISPANIOLA AND THE N/CENTRAL CARIBBEAN IS GENERATING SCATTERED 
SHOWERS AND TSTMS ACROSS THE CENTRAL CARIBBEAN FROM 12N-17N 
BETWEEN 65W-74W.

A TROPICAL WAVE IS OVER INLAND BELIZE AND GUATEMALA ALONG 89W S 
OF 18N MOVING W NEAR 20 KT. THE WAVE POSITION IS MAINLY BASED ON 
CONTINUITY AS LITTLE SIGNATURE OR CONVECTION IS NOTED IN THE 
VICINITY OF THE WAVE AXIS ACROSS CENTRAL AMERICA.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 12N16W 11N20W 10N23W 7N40W 
9N54W. SCATTERED MODERATE TO STRONG CONVECTION IS ACROSS W 
AFRICA APPROACHING THE ERN ATLC OCEAN COAST FROM 7N-14N E OF 
15W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM OF THE AXIS 
BETWEEN 22W-29W.

...DISCUSSION...

GULF OF MEXICO...
A 1020 MB SURFACE HIGH IS CENTERED OVER THE SE GULF NEAR 25N86W. 
WINDS REMAIN LIGHT IN THE VICINITY OF THE HIGH EXCEPT FOR OVER 
THE ERN BAY OF CAMPECHE WHERE NE 15-20 KT WINDS ARE OBSERVED AND 
ALSO SE WINDS UP TO 15 KT OVER THE WRN GULF W OF 96W. THIS 
ENHANCED FLOW IS DUE TO THE TIGHTENED GRADIENT BETWEEN THE HIGH 
AND LOWER PRESSURE OVER TEXAS AND MEXICO. ALOFT...THE REGION 
LIES BETWEEN AN AMPLIFIED RIDGE OVER THE CENTRAL U.S. AND A 
TROUGH OVER THE W ATLC. SCATTERED SHOWERS AND ISOLATED TSTMS ARE 
ONGOING IN THE DIFFLUENT AREA OVER THE N/CENTRAL WATERS N OF 27N 
BETWEEN 88W-91W. SIMILAR ACTIVITY IS OCCURRING OVER THE FLORIDA 
PENINSULA S OF 29N REMAINING E OF 83W.

CARIBBEAN SEA...
ACROSS THE SW CARIBBEAN...AN UPPER LEVEL HIGH IS CENTERED N OF 
PANAMA NEAR 12N79W. UPPER DIFFLUENCE BETWEEN THIS HIGH AN AN 
INVERTED UPPER TROUGH OVER THE E PACIFIC IS SUPPORTING SCATTERED 
SHOWERS AND TSTMS S OF 12N...INCLUDING PORTIONS OF COSTA 
RICA...PANAMA AND NRN COLOMBIA. ACROSS THE CENTRAL CARIBBEAN... 
ATMOSPHERIC INSTABILITY IN THE VICINITY OF AN UPPER LOW OVER ERN 
HISPANIOLA AND A TROPICAL WAVE ALONG 72W ARE SUPPORTING 
SCATTERED SHOWERS AND TSTMS FROM 12N-17N BETWEEN 65W-74W. ACROSS 
THE E CARIBBEAN...DEEP LAYER DRY AIR AND ATMOSPHERIC STABILITY 
AROUND AN UPPER LEVEL RIDGE ARE SUPPORTING GENERALLY FAIR 
WEATHER. HOWEVER...A MIDDLE LEVEL VORTICITY/MOISTURE MAXIMUM 
PRECEDING THE TROPICAL WAVE ALONG APPROXIMATELY 55W IS 
GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS FROM 13N-17N 
BETWEEN 58W-63W ACROSS THE LESSER ANTILLES AND ADJACENT COASTAL 
WATERS.

ATLANTIC OCEAN...
A SHARP UPPER LEVEL TROUGH IS POSITIONED ACROSS THE W ATLC 
EXTENDING SOUTH TO OVER THE NW BAHAMAS. THIS TROUGH SUPPORTS A 
COLD FRONT THAT ENTERS THE DISCUSSION AREA NEAR 32N72W EXTENDING 
TO 31N77W AND CONTINUING AS A STATIONARY BOUNDARY TO NEAR 
JACKSONVILLE FLORIDA AND OVER THE FLORIDA PANHANDLE. UPPER 
DIFFLUENCE AND MOIST SW FLOW E OF THE UPPER TROUGH AXIS IS 
SUPPORTING ISOLATED SHOWERS OVER THE NW BAHAMAS AND WITHIN 50 NM 
OF A LINE FROM 26N77W TO 30N72W. FARTHER TO THE E...DEEP LAYER 
HIGH PRESSURE IS ESTABLISHED OVER THE SUBTROPICAL CENTRAL ATLC 
NEAR 28N60W AS A 1023 MB SURFACE HIGH. THE TIGHT PRESSURE 
GRADIENT BETWEEN THIS HIGH AND THE TROPICAL WAVES ARE PRODUCING 
STRONG TRADES ACROSS THE TROPICAL ATLC W OF 50W. THE MAIN LOW 
PRESSURE FEATURE IN THE DISCUSSION ZONE IS A 1011 MB LOW NEAR 
32N37W. THIS LOW IS STRONGLY SHEARED WITH SCATTERED MODERATE 
CONVECTION LOCATED OVER THE ERN SEMICIRCLE N OF 30N BETWEEN 
31W-37W. SATELLITE IMAGERY INDICATES A TROUGH EXTENDING SW FROM 
THE LOW ALONG 29N40W INTO A WEAK 1016 MB LOW NEAR 28N46W. AN 
UPPER TROUGH ACROSS THE ERN ATLC SUPPORTS THESE SURFACE FEATURES 
WITH ENHANCED CLOUDINESS AND POSSIBLE SCATTERED SHOWERS S OF THE 
SURFACE TROUGH FROM 23N-27N BETWEEN 32W-50W.

$$
HUFFMAN