000
AXNT20 KNHC 270557
TWDAT 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT MON APR 27 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0530 UTC.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 04N8W TO 00N22W TO 03S31W. SCATTERED 
MODERATE CONVECTION IS NOTED WITHIN 120 NM N OF AXIS BETWEEN 33W 
AND 37W.

...DISCUSSION...

GULF OF MEXICO...
SHIP AND BUOY REPORTS IN ADDITION TO A QUIKSCAT PASS FROM 00Z 
INDICATED MAINLY 15 TO 20 KT E TO SE WINDS ACROSS THE GULF OF 
MEXICO THIS EVENING. BUOYS OVER THE WESTERN GULF ARE REPORTING 
GUSTS TO 25 KT...WITH SITES ON THE TEXAS COAST SHOWING PEAK 
WINDS TO AS HIGH AS 35 KT. THE STRONGER WINDS ARE THE RESULT OF 
A TIGHT GRADIENT BETWEEN A 1032 MB HIGH PRES CELL OVER THE 
WESTERN ATLC...AND DEEP LAYER TROUGHING EXTENDING FROM THE 
SOUTHERN U.S. PLAINS TO THE MEXICAN PLATEAU. STRONG TSTMS ARE 
NOTED OVER TEXAS AHEAD OF FRONT AND DRY LINE COMPLEX...BUT THIS 
ACTIVITY SHOULD REMAIN N OF THE GULF WATERS TODAY. MODEST 
CONVECTION IS NOTED OVER THE SOMEWHAT UNSTABLE AIR ABOVE THE 
WARM LOOP CURRENT IN THE CENTRAL GULF...AHEAD OF AN APPROACHING 
UPPER TROUGH. GENERALLY SCATTERED CLOUDS PERSIST OVER THE 
GULF...EXCEPT FOR BROKEN TO OVERCAST LOW CLOUDS NEAR THE TEXAS 
COAST.

CARIBBEAN SEA...
THE MAIN DRIVER FOR WEATHER ACROSS THE CARIBBEAN CONTINUES TO BE 
THE 1032 MB HIGH PRES CENTERED NEAR 32N69W. 12Z SOUNDINGS FROM 
AROUND THE CARIBBEAN SHOWED GENERALLY 15 TO 20 KT FLOW FROM THE 
SFC TO 10 KFT. THE EVENING SOUNDING FROM SAN JUAN ALONG WITH THE 
05Z VWP PRODUCT SHOW 20 TO 25 KT FROM THE SFC TO 10 
KFT...INDICATING THAT THE PRESSURE GRADIENT HAS TIGHTENED A BIT 
AS THE SURFACE HIGH PRES BUILDS TO THE NORTH. THERE IS ENOUGH 
MOISTURE AVAILABLE IN THE LOWER TO MID LEVELS OF THE ATMOSPHERE 
TO SUPPORT BANDS OF SHOWERS ACROSS THE CARIBBEAN INDUCED BY THE 
TRADE WIND CONVERGENCE. SCATTEROMETER ALONG WITH BUOY AND SHIP 
OBSERVATIONS INDICATED GENERALLY 2O TO 25 KT TRADE WIND FLOW 
OVER THE CENTRAL CARIBBEAN...AND 15 TO 20 KT FLOW IN THE FAR 
EASTERN AND WESTERN SECTIONS OF THE BASIN. THE HIGH PRES WILL 
REMAIN IN PLACE AT LEAST THROUGH MID WEEK WITH CURRENT 
CONDITIONS PERSISTING.

ATLANTIC FROM THE EQUATOR TO 32N...
SCATTEROMETER AND BUOY OBSERVATIONS SHOW A BROAD SWATH OF 20 KT 
TRADE WIND FLOW ACROSS THE TROPICAL ATLC WATERS...SOUTH OF A 
PAIR OF HIGH PRES CELLS...SPLIT BY A WEAK STATIONARY FRONT NEAR 
50W. SATELLITE IMAGERY HINTS OF SCATTERED SHOWERS EMBEDDED IN 
THIS TRADE WIND FLOW ACROSS THE BASIN. ALOFT...AN AMPLIFIED 
UPPER PATTERN IS NOTED N OF 25N OVER MAINLY THE CENTRAL AND 
EASTERN ATLANTIC...WITH MAINLY ZONAL FLOW ELSEWHERE. A STRONG 
SHORT WAVE TROUGH IS DIGGING EAST THROUGH 50W N OF 30N...CUTTING 
OFF A MID/UPPER LOW BETWEEN N FLORIDA AND BERMUDA TO THE SOUTH 
OF AN UPPER RIDGE BUILDING OFF THE VIRGINIA COAST. THIS SETS UP 
A BLOCKING PATTERN FOR THE NEXT COUPLE OF DAYS OVER THE WESTERN 
ATLC...LEAVING MOST OF THE UPPER ENERGY TO MOVE INTO THE CENTRAL 
AND EASTERN ATLC THROUGH MID WEEK. THIS WILL REINFORCE A COLD 
FRONT CURRENTLY OFF NEW ENGLAND AS IT SHIFTS 
SOUTHEASTWARD...WEAKENING A 1035 MB SURFACE HIGH PRES AREA 
CURRENTLY CENTERED NEAR THE AZORES. THE MAIN IMPACT AT THE 
SURFACE WILL BE SLIGHTLY WEAKENED TRADE WIND FLOW OVER THE 
CENTRAL TROPICAL ATLC WATERS SOUTH OF THIS SURFACE HIGH PRES 
THROUGH WED. THE MAIN UPPER ENERGY REMAINS WELL NORTH OF 32N 
THROUGH THE PERIOD. 

$$
CHRISTENSEN