000
AXPZ20 KNHC 091511
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT MAY 09 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1245 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE LIES ALONG A LINE FROM 
08N83W TO 07N91W TO 10N107W TO 06N126W TO 07N140W. SCATTERED 
MODERATE WITH ISOLATED STRONG CONVECTION CAN BE FOUND WITHIN 210 
NM S OF AXIS BETWEEN 92W AND 95W AND WITHIN 120 NM N OF AXIS W 
OF 136W. 

...DISCUSSION...
UPPER LEVEL SOUTHERLY FLOW TO 50 KT ALONG 110W IS DIRECTING 
TROPICAL MOISTURE AND HIGH CLOUDS NORTH-NORTHEASTWARD INTO 
CENTRAL MEXICO. THIS UPPER JET IS WEDGED BETWEEN A STRONG UPPER 
LOW NEAR 21N118W AND AN ANTICYCLONE NEAR 13N101W. THE REGION 
BETWEEN 210 NM AND 600 NM IN THE W SEMICIRCLE OF THE UPPER LOW 
IS MARKED BY STRONG SUBSIDENCE. A SURFACE TROUGH EMBEDDED IN THE 
ITCZ FROM 12N108W TO 04N111W COINCIDES WITH THE REAR RIGHT 
QUADRANT OF THE AFOREMENTIONED UPPER JET. THIS TROUGH IS EVIDENT 
IN THE 0430 ASCAT IMAGERY. SCATTERED MODERATE CONVECTION CAN BE 
FOUND WITHIN 120 NM E OF THE TROUGH FROM 11N AND 12N AND WITHIN 
210 NM W OF THE TROUGH FROM 05N TO 06N. THE JET IS EXPECTED TO 
SLOWLY SHIFT WEST AND DIMINISH AS THE UPPER LOW TO ITS WEST 
WEAKENS AND JOINS WITH THE WEAK UPPER TROUGH CURRENTLY OVER NW 
WATERS...LEAVING A BROAD NEGATIVELY TILTED UPPER TROUGH OVER 
FORECAST WATERS W OF 110W ON SUN. THE SURFACE TROUGH SHOULD 
SHIFT W WITH THE UPPER JET...CARRYING CONVECTION W WITH IT ALONG 
THE ITCZ. IN ADDITION...THE DISRUPTION OF THE DEEP LAYER 
EASTERLY FLOW OVER W CENTRAL WATERS HAS CAUSED THE TRADE WINDS 
TO DIMINISH.

TO THE S OF THE UPPER LEVEL ANTICYCLONE NEAR 21N118W LIES AN 
UPPER LOW NEAR 01N94W. CONFLUENT FLOW BETWEEN THESE TWO FEATURES 
IS INHIBITING CONVECTION ALONG THE ITCZ W OF THE SURFACE TROUGH 
GENERALLY BETWEEN 95W AND 105W. FARTHER E...DIFFLUENCE BETWEEN 
THIS ANTICYCLONE AND THE ANTICYCLONE OVER NORTHERN SOUTH AMERICA 
HAS ALLOWED FOR SCATTERED MODERATE WITH ISOLATED STRONG 
CONVECTION TO DEVELOP ALONG THE ITCZ BETWEEN 92W AND 95W.

OVER NE WATERS...DENSE LOW LEVEL CLOUDINESS CAN BE FOUND ALONG 
THE COAST OF BAJA CALIFORNIA IN THE VICINITY OF THE CALIFORNIA 
CURRENT. OFFSHORE...N WINDS TO 25 KT ARE EVIDENT ON THE ASCAT 
PASSES FROM 0616 AND 0436 UTC N OF 24N BETWEEN 120W AND 128W. 
THE STRONG PRESSURE GRADIENT CURRENTLY IN PLACE BETWEEN 
TROUGHING OVER THE SW U.S. AND NW MEXICO AND THE 1027 MB HIGH 
PRESSURE SYSTEM NEAR 35N136W WILL WEAKEN OVER FORECAST 
WATERS...ALONG WITH THE WINDS...AS THE TROUGHING TO THE E 
WEAKENS. HOWEVER...STRONG WINDS FARTHER N ALONG THE CA COAST 
WILL CONTINUE TO BRING NORTHERLY SWELL TO NE WATERS.

GAP WINDS...THE RETURN OF STRONG TRADE WINDS IN THE SW CARIBBEAN 
WILL ALLOW FOR EASTERLY FLOW TO BLEED THROUGH NORTHERN COSTA 
RICA AND SOUTHERN NICARAGUA THROUGH THE GULF OF PAPAGAYO...WITH 
20 KT WINDS EXPECTED BY SUN MORNING. 

$$
SCHAUER CLARK