000
AXPZ20 KNHC 210939
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE APR 21 2009

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE AXIS LIES ALONG 02N78W TO 
06N88W TO 04N105W TO 06N130W TO 06N140W. SCATTERED MODERATE 
CONVECTION IS EVIDENT WITHIN 120 NM S OF AXIS BETWEEN 90W AND 
95W. 

...DISCUSSION...
W OF 100W...
UPPER LEVEL BLOCKING PATTERN OFF THE U.S. WEST COAST 
IS BREAKING DOWN AS A LONG WAVE TROUGH DIGS THROUGH THE PACIFIC 
NORTHWEST AREA INTO THE NORTHERN ROCKIES...AND IS STARTING TO 
ERODE A MID/UPPER LEVEL RIDGE IN PLACE OVER THE WESTERN U.S. A 
COMPACT CUTOFF CYCLONE NEAR 30N130W IS STARTING TO OPEN UP AND 
APPEARS LESS DEFINED AS IT SHIFTS EASTWARD TOWARD SOUTHERN 
CALIFORNIA. THIS ALLOWS A WEAK 1020 MB SURFACE HIGH TO REMAIN IN 
PLACE NEAR 26N130W THROUGH THURSDAY. MEANWHILE A BROAD UPPER 
CYCLONE REMAINS CUT OFF FROM THE LONG WAVE TROUGH N OF HAWAII 
NEAR 35N152W. AN ASSOCIATED SURFACE LOW IS EVIDENT UNDER THE 
UPPER LOW ACCOMPANIED BY A COLD FRONT EXTENDING TO THE NORTH OF 
HAWAII. THE FRONT WILL MAKE SLOW PROGRESS EAST GIVEN THE LIMITED 
UPPER SUPPORT...AND IS EXPECTED TO STALL JUST WEST OF THE 
SURFACE NEAR 30N140W THROUGH THURSDAY...BEFORE DISSIPATING. 
SCATTEROMETER DATA SHOW A SMALL AREA OF TRADES WINDS...MAINLY 
FROM 09N TO 18N W OF 130W...THAT WILL PERSIST S OF THE SURFACE 
HIGH THROUGH MID WEEK.

A CLUSTER OF CONVECTION IS ACTIVE NEAR 13N122W. A QUIKSCAT PASS 
SHOWED SOME HINT OF CYCLONIC TURNING NEAR CONVECTION INDICATING 
A WEAK SURFACE TROUGH. DIFFLUENT FLOW ALOFT ASSOCIATED WITH AN 
UPPER TROUGH ALONG 132W S OF 20N IS AIDING THE CONVECTION AS 
WELL. THE SURFACE TROUGH MAY DAMPEN OUT TODAY...BUT THE UPPER 
TROUGH MIGRATES EAST TO 120W THROUGH THURSDAY...AN WILL LIKELY 
SUPPORT MODEST CONVECTION N OF THE ITCZ. 

MEANWHILE LONG PERIOD SW SWELL CONTINUES TO PUSH INTO THE AREA 
FROM SOUTH PACIFIC...STAYING MAINLY S OF 15N.

E OF 100W...
GULF OF TEHUANTEPEC...MAIN ISSUE CONTINUES TO BE GALE FORCE 
WINDS THROUGH THE GULF OF TEHUANTEPEC. A 01Z QUIKSCAT PASS AND A 
04Z ASCAT PASS BOTH SHOWED WINDS TO 35 KT IN THE GULF OF 
TEHUANTEPEC. CONSENSUS AMONG MODEL GUIDANCE CONTINUES TO HINT 
THIS WILL BE A RELATIVELY SHORT LIVED GALE EVENT...ENDING BY 
LATE TUE NIGHT INTO EARLY WED MORNING...ALTHOUGH 30 KT FLOW WILL 
PERSIST LATER INTO WED. IN ADDITION...THE STRONG N TO NE GAP 
FLOW WILL CONTRAST WITH LONG PERIOD SW SWELL MOVING INTO THE 
AREA...ALLOWING FOR CONFUSED SEAS THROUGH LATE WED.

GULFS OF PAPAGAYO AND PANAMA...SHIP REPORTS SHOWED NORTHERLY 
WINDS IN EXCESS OF 20 KT IN BOTH AREAS...ALTHOUGH TWO EARLIER 
SCATTEROMETER PASSES HINTED OF WINDS BELOW 20 KT IN THE GULF OF 
PANAMA. GLOBAL MODELS INDICATE THAT THE PAPAGAYO EVENT WILL 
CONTINUE WITH ENHANCED EAST TRADES IN THE CARIBBEAN...BUT WINDS 
IN PANAMA WILL DIMINISH.

MEANWHILE...THE AFOREMENTIONED LONG PERIOD SW SWELL WILL REACH 
THE CENTRAL AMERICAN AND MEXICAN COASTS BY LATE TODAY...CREATING 
CONFUSED SEAS NEAR PAPAGAYO...AND THE POTENTIAL FOR HIGH SURF 
CONDITIONS ELSEWHERE.


$$
CHRISTENSEN