000
AXPZ20 KNHC 251604
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN APR 25 2010

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 
1515 UTC.

...ITCZ...
AXIS ANALYZED ALONG 09N79W TO 07N86W TO 08N102W TO 06N123W TO 
06N140W. SCATTERED TO LOCALLY NUMEROUS MODERATE TO STRONG 
CONVECTION WAS FROM 02N TO 10N E OF 94W. SCATTERED MODERATE 
ISOLATED STRONG CONVECTION WAS WITHIN 120 NM S AND 300 NM S OF 
AXIS E OF 100W.

...DISCUSSION...
SHARP MID/UPPER LEVEL TROUGH HAS ENTERED NW CORNER OF E PAC 
OVERNIGHT EXTENDING SW TO 17N146W. A MID/UPPER LOW WAS EMBEDDED 
WITHIN THE N PORTION OF THIS TROUGH NEAR 29N138W WHILE A SECOND 
ELONGATED LOW WAS WITHIN THE SW END. UPPER CONVERGENCE AND 
SUBSIDENCE DOMINATED ALL BUT THE ERN SEMICIRCLE OF THE NRN MOST 
LOW. THIS TROUGH IS FORECAST CONTINUE EWD OVER THE NEXT FEW DAYS 
AND REACH BAJA CALIFORNIA TUE EVENING AS A PROGRESSIVE PATTERN 
CONTINUES N OF 25N. THE SW PORTION OF THE TROUGH CONTINUED WWD 
AND TO THE S OF THE HAWAIIAN ISLANDS AS A TUTT AXIS. TO THE S OF 
THIS TUTT A TROPICAL JET EXTENDED FROM THE CENTRAL PAC E-NE TO 
11N150W THEN NE TO 25N123W AND OVER THE CREST OF A LARGE UPPER 
RIDGE CENTERED NEAR 12N117W. ANTICYCLONIC FLOW WAS BRINGING 
AMPLE MID TO UPPER LEVEL MOISTURE...MAINLY TROPICAL CONVECTIVE 
DEBRIS FROM THE ITCZ...FROM THE WRN SEMICIRCLE OF THE RIDGE OVER 
THE RIDGE AND THEN DIMINISHING AS IT ENTERED BAJA CALIFORNIA. 
FURTHER DOWNSTREAM A SECOND UPPER RIDGE WAS CENTERED OVER THE SW 
CARIBBEAN EXTENDING NE ACROSS THE BAHAMAS. SEPARATING THESE TWO 
UPPER RIDGES WAS A BROAD MID/UPPER TROUGH EXTENDING FROM CENTRAL 
TEXAS S INTO N MEXICO AND THEN S-SE ACROSS MEXICO TO NEAR 
20N99W.  UPPER CONVERGENCE ACROSS THE NE QUADRANT OF THE EPAC 
RIDGE EXTENDING SE INTO THE BACK SIDE OF THIS TROUGH ACROSS 
MEXICO TO OFFSHORE OF ACAPULCO. THE EPAC UPPER RIDGE EXTENDS 
DOWNWARD AND INTO THE LOWER LEVELS OF THE ATMOSPHERE TO NEAR 850 
HPA ALONG 13N PER RECENT GFS ANALYSIS. THIS POSITIONING IS 
ACTING TO INCREASE LLVL MOISTURE CONVERGENCE ACROSS THE TROPICAL 
EPAC E OF 100W...WHERE VERY ACTIVE CONVECTION CONTINUES THIS 
MORNING. AIDING IN THIS CONVECTION HAS BEEN TO EVOLUTION OF THE 
NW S AMERICAN MONSOON GYRE OVER THE PAST FEW WEEKS...WITH LLVL S 
TO SW FLOW NOW EXTENDING AS FAR W AS 100W AND NORTHWARD TO 
08-09N. GOOD CYCLONIC TURNING ASSOCIATED WITH THIS GYRE WILL 
CONTINUE ACROSS THE TROPICS E OF 90W OVER THE NEXT FEW DAYS TO 
MAINTAIN ACTIVE CONVECTION BETWEEN COLOMBIA...NICARAGUA...AND 
THE ITCZ. THIS ACTIVE CONVECTIVE ZONE AND ANOTHER ALONG THE ITCZ 
BETWEEN 105W AND 125W WILL HELP TO MAINTAIN UPPER RIDGING AND 
DIFFLUENCE ACROSS THESE RESPECTIVE AREAS OVER THE NEXT FEW 
DAYS.  

ELSEWHERE AT THE SURFACE...
A 1028 MB HIGH CENTER BEAR 35N132W IS FORECAST TO QUICKLY WEAKEN 
AND DRIFT S NEXT FEW DAYS AND RELAXING THE PRES GRADIENT N OF 
THE ITCZ...AND EFFECTIVELY SHUT DOWN THE PRESENT FRESH NE TRADES 
OCCURRING S OF 15N AND W OF 120W WITHIN 48 HRS. LARGE LONG 
PERIOD NW SWELLS WILL CONTINUE TO PROPAGATE THROUGH BASIN 
THROUGHOUT FORECAST PERIOD AND MERGE WITH SRN HEMI SW SWELL 
ACROSS THE TROPICS.    

$$
STRIPLING