000
AXPZ20 KNHC 252141
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SUN APR 25 2010

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1945 UTC.

...ITCZ...
INTERTROPICAL CONVERGENCE ZONE AXIS WAS ANALYZED ALONG 08N78W TO 
07N92W TO 08N102W TO 09N122W TO 06N140W. SCATTERED MODERATE WITH 
ISOLATED STRONG CONVECTION WAS WITHIN 210 NM S AND 150 NM N OF 
THE ITCZ AXIS E OF 89W. ISOLATED MODERATE CONVECTION WAS WITHIN 
210 NM S AND 120 NM N OF THE ITCZ AXIS BETWEEN 105W AND 135W.

...DISCUSSION...
A RIDGE AXIS EXTENDS SW TO NEAR 15N110W FROM A 1029 MB HIGH 
CENTERED AT 32N134W. THIS HIGH PRES SYSTEM WILL WEAKEN AS AN 
UPPER LEVEL TROUGH PASSES THROUGH N WATERS OVER IT AND A STRONG 
COLD FRONT IMPINGES UPON IT FROM THE W. THIS WILL SEND THE 
DISSIPATING HIGH CENTER S INTO FORECAST WATERS OVERNIGHT 
TONIGHT. WHAT REMAINS OF THE HIGH WILL MERGE WITH STRONGER HIGH 
PRES TO THE W ON MON. THE LATEST ASCAT PASS AT 1740 UTC SHOWS 
THE AREA OF FRESH TRADES HAS SHRUNK SOUTHWARD AND SHIP NWS0009 
NEAR 11N122W REPORTED 18-19 KT WINDS FROM 1700-2000 UTC ON THE 
FAR E EDGE OF THE TRADE AREA. THE TRADES WILL CONTRACT TO THE W 
MON AS THE HIGHEST PRES SHIFTS W. MEANWHILE...A 100-120 KT 
SOUTHWESTERLY UPPER JET ON THE LEADING EDGE OF THE TROUGH OVER N 
WATERS IS TRANSPORTING UPPER LEVEL MOISTURE MANIFESTED AS CIRRUS 
NORTHEASTWARD FROM THE ITCZ JUST W OF THE AREA INTO N CENTRAL 
WATERS. LOOK FOR THE CIRRUS SHIELD TO SHIFT E WITH THE UPPER 
TROUGH AND ITS ASSOCIATED JET. BY TUE...THE COLD FRONT IMPINGING 
UPON THE SURFACE HIGH CURRENTLY N OF THE AREA WILL MAKE ITS WAY 
INTO NW WATERS AS A WEAK LOW LEVEL BOUNDARY. THE PRIMARY IMPACT 
FROM THE SYSTEM WILL BE A SURGE IN NW SWELL WITH SIGNIFICANT 
WAVE HEIGHTS RISING TO 9 FT IN NW WATERS TUE AFTERNOON.

A SURFACE TROUGH IS EMBEDDED IN THE ITCZ FROM 12N122W TO 
02N125W. DESPITE THE FACT THAT THIS TROUGH LIES UNDER AN UPPER 
RIDGE AXIS...ONLY HIGHLY SCATTERED CONVECTION IS NOTED ALONG THE 
ITCZ NEAR THE TROUGH WHICH LIES IN A RELATIVE MINIMUM OF 
AVAILABLE LOW LEVEL MOISTURE. THE UPPER RIDGE AXIS EXTENDS NE 
INTO AN ANTICYCLONE NEAR 13N110W THAT IS EXPECTED TO SLOWLY MOVE 
EASTWARD AWAY FROM THE TROUGH AS THE AFOREMENTIONED UPPER TROUGH 
TO ITS NW MOVES THROUGH N WATERS. THE DIFFLUENCE ASSOCIATED WITH 
THE REAR RIGHT QUADRANT OF THE JET ON THE LEADING EDGE OF THIS 
UPPER TROUGH MAY HELP INCREASE THE CHANCE OF CONVECTION NEAR THE 
SURFACE TROUGH AS SLOWLY MOVES MON AND TUE. 

A BROAD LOW LEVEL CYCLONIC GYRE LIES OVER SE WATERS. THE 1422 
UTC ASCAT PASS SHOWED 20 TO 25 KT SW WINDS FEEDING INTO THE 
EASTERN EDGE OF THE GYRE AND SHIP A8NQ5 REPORTED 24 KT S WINDS 
NEAR 03N84W AT 1500 UTC. SATELLITE PRECIPITABLE WATER VALUES ARE 
AT OR ABOVE 2.5 INCHES IN MUCH OF THE AREA E OF 93W...ALLOWING 
FOR PLENTY OF LOW LEVEL MOSITURE TO CONVERGE ALONG THE ITCZ. 
STRONG CONVECTION WILL LIKELY REMAIN OVER THE AREA E OF 90W FOR 
THE NEXT FEW DAYS AS CONDITIONS ALOFT ARE EXPECTED TO REMAIN 
DIFFLUENT BETWEEN THE SE EDGE OF A WEAKENING AND EASTWARD MOVING 
UPPER LEVEL ANTICYCLONE THAT CURRENTLY RESIDES OVER THE WESTERN 
CARIBBEAN AND ANOTHER ANTICYCLONE S OF THE EQUATOR NEAR 13S90W 
THAT IS ALSO EXPECTED TO MOVE EASTWARD. 

FINALLY...LARGE LONG PERIOD NW SWELLS WILL CONTINUE TO PROPAGATE 
THROUGH THE BASIN AND MERGE WITH CROSS-EQUATORIAL SW SWELL 
ACROSS THE TROPICS THROUGH TUE. 

$$
SCHAUER