Atlantic Tropical Weather Discussion

000
AXNT20 KNHC 041728
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1715 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE EXTENDS FROM 19N52W TO 06N54W MOVING W 20-25 KT. 
THIS LARGE AND HIGH AMPLITUDE WAVE HAS TAKEN MORE OF AN INVERTED 
V APPEARANCE IN SATELLITE IMAGERY TODAY. A VORTICITY/MOISTURE  
MAXIMUM REMAINS EVIDENT JUST W OF THE ANALYZED AXIS NEAR 14N55W. 
CONVECTION IS LIMITED AND CONFINED TO THE INTERSECTION OF THE 
ITCZ FROM 7N-11N BETWEEN 50W-56W...LIKELY SUPPRESSED BY SAHARAN 
DUST. 

TROPICAL WAVE IS ALONG 69W/70W 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 IS GENERATING SCATTERED SHOWERS AND TSTMS WITHIN 180 
NM OF THE AXIS. SFC OBSERVATIONS FROM THE A-B-C ISLANDS SHOW THE 
PRESENCE OF THIS WAVE WITH A SLIGHT WIND SHIFT ABOUT THE AXIS 
AND A 2 MB PRESSURE FALL OVER THE PAST 24 HOURS.   

A TROPICAL WAVE IS OVER THE GULF OF HONDURAS ALONG 87W S OF 17N 
MOVING W 15-20 KT. THIS WAVE POSITION IS MAINLY BASED ON 
CONTINUITY AS LITTLE SIGNATURE/CONVECTION IS NOTED NEAR THE WAVE.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 12N17W 8N26W 6N41W 6N53W. 
SCATTERED MODERATE TO STRONG CONVECTION IS FROM 8N-12N BETWEEN 
18W-27W AND NEAR THE LARGE TROPICAL WAVE AS DISCUSSED ABOVE. 

...DISCUSSION...

GULF OF MEXICO...
A 1018 MB SFC HIGH IS CENTERED OVER THE CENTRAL GULF NEAR 
25N87W. CONSEQUENTLY...WINDS ARE LIGHT EXCEPT FOR OVER THE BAY 
OF CAMPECHE WHERE LATEST SCATTEROMETER DATA SHOWS AN AREA OF SE 
15-20 KT WINDS. THIS ENHANCED FLOW IS DUE TO THE TIGHTENED 
GRADIENT BETWEEN THE HIGH AND LOWER PRESSURE OVER MEXICO. 
ALOFT...THE REGION LIES BETWEEN AN AMPLIFIED RIDGE OVER THE 
CENTRAL U.S. AND A TROUGH OVER THE WRN ATLC. A FEW TSTMS HAVE 
DEVELOPED IN THE DIFFLUENT AREA OVER THE N CENTRAL WATERS AND 
ARE MOVING SW WITH THE UPPER FLOW. SIMILAR ACTIVITY IS OCCURRING 
OVER THE SW BAY OF CAMPECHE WITHIN AN MOIST ENVIRONMENT.   

CARIBBEAN SEA...
ACROSS THE SW CARIBBEAN...AN UPPER LEVEL HIGH IS CENTERED N OF 
PANAMA NEAR 12N80W. UPPER DIFFLUENCE BETWEEN THIS HIGH AN AN 
INVERTED UPPER TROUGH OVER THE E PACIFIC IS SUPPORTING NUMEROUS 
SHOWERS AND THUNDERSTORMS S OF 12N W OF 78W INCLUDING PORTIONS 
OF COSTA RICA AND PANAMA. ACROSS THE CENTRAL CARIBBEAN... 
ATMOSPHERIC INSTABILITY IN THE VICINITY OF AN UPPER LOW OVER E 
HISPANIOLA IS SUPPORTING SCATTERED SHOWERS AND ISOLATED 
THUNDERSTORMS N OF 14N BETWEEN 72W-77W...WITH ADDITIONAL 
CONVECTIVE ACTIVITY NEAR THE TROPICAL WAVE ALONG 69W/70W. ACROSS 
THE E CARIBBEAN...DEEP LAYER DRY AIR AND ATMOSPHERIC STABILITY 
AROUND AN UPPER LEVEL RIDGE ARE SUPPORTING GENERALLY FAIR 
WEATHER. THE PRESSURE GRADIENT S OF A SURFACE RIDGE OVER THE 
CENTRAL AND E ATLC IS SUPPORTING NE TO E WINDS OF 20 TO 30 KT 
ACROSS A LARGE PART OF THE CARIBBEAN...HIGHEST NEAR THE COAST OF 
COLOMBIA.

ATLANTIC OCEAN...
DEEP LAYER HIGH PRESSURE IS WELL ESTABLISHED OVER THE 
SUBTROPICAL CENTRAL ATLC NEAR 30N55W. THE TIGHT PRESSURE 
GRADIENT BETWEEN THE 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 1009 MB LOW NEAR 
32N39W. THIS LOW IS STRONGLY SHEARED WITH ITS CONVECTIVE AREA 
LOCATED WELL TO THE E OF THE EXPOSED CENTER N OF 31N BETWEEN 
32W-37W. SCATTEROMETER AND VISIBLE SATELLITE IMAGERY INDICATE A 
TROUGH EXTENDING SW FROM THE LOW TO 28N43W TO 28N47W TO 31N51W. 
A VORTICITY MAXIMUM IS EVIDENT ALONG THE TROUGH NEAR 28N46W WITH 
SCATTERED SHOWERS AND TSTMS TO ITS S AND E FROM 25N-27N BETWEEN 
44W-46W AND FARTHER NE NEAR THE UPPER TROUGH AXIS FROM 28N-30N 
BETWEEN 36W-38W. ELSEWHERE...UPPER DIFFLUENCE AND MOIST SW FLOW 
TO THE E OF A SHARP UPPER TROUGH IS SUPPORTING SCATTERED SHOWERS 
AND TSTMS OVER THE W BAHAMAS AND NEARBY WATERS. THE REMAINDER OF 
THE REGION IS EXPERIENCING MAINLY FAIR WEATHER. 

$$
CANGIALOSI/COHEN