000
AXNT20 KNHC 291040
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT WED APR 29 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 05N09W TO THE EQUATOR AT 16W TO 
01S28W TO 05S35W. SCATTERED MODERATE CONVECTION IS OBSERVED 
WITHIN 90 NM S OF AXIS BETWEEN 09W AND 12W. SCATTERED MODERATE 
CONVECTION ALSO OBSERVED WITHIN 120 NM N OF AXIS BETWEEN 24W AND 
31W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER TROUGH EXTENDING FROM THE FLORIDA BIG BEND AREA SW TO 
THE SOUTH CENTRAL BAY OF CAMPECHE IS SPONSORING A WEAK INVERTED 
TROUGH AT THE SURFACE THAT EXTENDS ACROSS THE SOUTH CENTRAL GULF 
AND THE YUCATAN PENINSULA. THE UPPER TROUGH IS DAMPENING 
OUT...WHICH IN TURN IS WEAKENING THE CORRESPONDING SURFACE 
FEATURE. BUOYS ARE SHOWING E TO SE WINDS DIMINISHING FROM 15 TO 
20 KT TO MOSTLY 10 TO 15 KT CURRENTLY. THE EXCEPTION REMAINS 
OVER THE STRAITS OF FLORIDA WHERE CMAN SITES ARE SHOWING STEADY 
20 KT FLOW AT THIS TIME. AS THE INVERTED TROUGH WEAKENS...A 
SURFACE RIDGE EXTENDING FROM THE WESTERN ATLC THROUGH N FLORIDA 
AND INTO THE SW GULF IS BECOMING THE DOMINANT FEATURE ALLOWING 
WINDS TO VEER SLIGHTLY MORE TO THE SE THROUGH THU.

CARIBBEAN SEA...
HIGH PRESSURE LOCATED N OF AREA MAINTAINS FRESH TO STRONG 
SURFACE WIND ACROSS MUCH OF THE BASIN WITH THE STRONGEST WINDS 
IN THE TYPICAL AREA NEAR THE COAST OF COLOMBIA. THIS WEATHER 
PATTERN IS FORECAST TO PERSIST DURING THE NEXT 24 HOURS. THE 
HIGH IS FORECAST TO GRADUALLY WEAKEN TUE THROUGH FRI AND AS A 
RESULT... THE TRADE WINDS ARE EXPECTED TO DIMINISH DURING THIS 
TIME FRAME AS WELL. DIFFLUENCE ALOFT ON THE SE SIDE OF UPPER 
TROUGH FROM THE BAHAMAS TO THE WESTERN GULF OF MEXICO IS 
ENHANCING SHOWER ACTIVITY IN THE TRADE WIND FLOW...MAINLY OVER 
THE NE CARIBBEAN. SOME EMBEDDED THUNDERSTORMS ARE POSSIBLE WITH 
THIS ACTIVITY AS THE UPPER TROUGH OVER THE WESTERN GULF SHIFTS 
SE THROUGH THU. 

ATLANTIC OCEAN...
W OF 60W...AN UPPER LEVEL LOW REMAINS CENTERED NEAR 29N72W OVER 
A 1029 MB SURFACE HIGH CENTERED OFF THE CAROLINA COAST NEAR 
34N68W. 15 TO 20 KT TRADES ARE EVIDENT ON THE SOUTHERN FRINGE OF 
THE HIGH PRES S OF 25N. DIFFLUENCE ALOFT ON THE SE SIDE OF THE 
UPPER LOW IS ENHANCING SCATTERED SHOWERS IN THE TRADE WIND FLOW 
NORTH OF PUERTO RICO AND HISPANIOLA. THESE SHOWERS WILL PERSIST 
INTO THU AS A TRAILING UPPER TROUGH FOLLOWS THE UPPER LOW AS IT 
SHIFTS EAST. DRY SUBSIDENT AIR DOMINATES MAINLY N OF 25N. 
E OF 60W...A HIGH PRES RIDGE EXTENDS FROM A 1027 MB HIGH PRES 
CELL IN PLACE NEAR THE AZORES...TO ANOTHER 1027 MB HIGH PRES 
CENTER NEAR 20N45W. SCATTEROMETER DATA SHOW 20 TO 25 KT NE FLOW 
BETWEEN OFF THE NW AFRICAN COAST BETWEEN THE HIGH PRES AND LOW 
PRES OVER WEST AFRICA...BRINGING THE DRY AND DUSTY SAHARAN AIR 
LAYER AS FAR WEST AS 40W. 15 TO 20 KT TRADES ARE NOTED MAINLY S 
OF 20N W OF 30W. ALOFT...A BLOCKING UPPER RIDGE N OF 32N ALONG 
55W STARTS TO BREAK DOWN TONIGHT AHEAD OF DEEP LAYER TROUGH 
DIGGING INTO THE N CENTRAL ATLC. AN ASSOCIATED SURFACE FRONT 
APPROACHES THE AREA S OF 32N E OF 55W BY THU NIGHT...BUT STALLS 
AND DISSIPATES THROUGH FRI AS UPPER ENERGY LIFTS OUT TO THE 
NE...LEAVING HIGH PRES IN PLACE.

$$
CHRISTENSEN