000
AXPZ20 KNHC 230952
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC FRI APR 23 2010

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...
AXIS ALONG 05N77W TO 04N85W TO 05N92W TO 04N103W TO 09N110W TO 
07N123W TO 09N131W TO 06N140W.  ISOLATED MODERATE CONVECTION 
WITHIN 150 NM N AND 75 NM S OF AXIS E OF 106W.  SCATTERED 
MODERATE TO STRONG CONVECTION WITHIN 120 NM OF EMBEDDED TROUGH 
AXIS EXTENDING FROM 06N111W TO 13N104W.
 
...DISCUSSION...
SHARP UPPER LEVEL RIDGE CREST ALONG 132W N OF 23N...JUST N OF 
STEADY ZONAL W WIND...BRING CONVERGING FLOW OF SUBSIDING DRY AIR 
INTO E PAC W OF 120W N OF ITCZ.  UPPER LEVEL CYCLONIC VORTEX AT 
35N112W HAS TROUGH AXIS TO 25N120W.  MID/UPPER LEVEL MOISTURE 
ROUNDS BASE OF VORTEX WITH AVAILABLE MOISTURE N OF 29N E OF 119W 
RIDING ON 120 KT JET CORE JUST SE OF CYCLONE.  WEAK SURFACE 
TROUGH NEAR SW ARIZONA MAY USE AVAILABLE WATER AS IT INTENSIFIES 
ON ITS WAY E ON FRI.  OTHERWISE E PAC REMAINS DRY N OF 20N.

MID/UPPER LEVEL ANTICYCLONE AT 06N104W PROVIDES AMPLE DIFFLUENT 
FLOW ALOFT OVER SURFACE TROUGH ALONG 108W ENHANCING DEEP 
CONVECTION AND TRANSPORTING ITS ABUNDANT DEBRIS NE ACROSS 
CENTRAL MEXICO INTO GULF OF MEXICO...BUT WITH NO LOW LEVEL 
TRIGGER TO PROMPT PRECIPITATION. 

DOWNSTREAM SHARP UPPER LEVEL TROUGH RUNS S OF HONDURAS ALONG 90W 
TO THE EQUATOR SEPARATES ABOVE MENTIONED ANTICYCLONE FROM SECOND 
ONE OVER SOUTH AMERICA.  TROUGH EXPECTED TO WEAKEN AS LATTER 
GYRE BUILDS W AND MERGE WITH FIRST ANTICYCLONE.  

ELSEWHERE AT THE SURFACE...
SURFACE TROUGH EMBEDDED ALONG ITCZ FROM 13N104W TO 06N111W 
REMAINS UNDER FAVORABLE DIFFLUENT UMBRELLA PROVIDED BY MENTIONED 
UPPER LEVEL ANTICYCLONE.  ITS SCATTERED MODERATE TO STRONG 
CONVECTION EXPECTED TO DIMINISH AS TROUGH MOVES W INTO LESS 
FAVORABLE UPPER LEVEL ENVIRONMENT FRI AND SAT.  

BROAD SURFACE HIGH PRES 1031 MB AT 32N138W EXPECTED TO WEAKEN AS 
COLD FRONT PUSHES IT E FRI AND SAT.  THIS WOULD WEAKEN IT AND 
DIMINISH STRONG NE TRADES PRESENTLY IN PLACE FROM 10N TO 26N W 
OF 120W.  ADDITIONALLY...NW WINDS ALONG BAJA CALIFORNIA COAST 
ALSO PROMPTED BY TIGHT GRADIENT BETWEEN HIGH PRES AND SURFACE 
TROUGH OVER ARIZONA SHOULD ALSO WEAKEN BY END OF FORECAST 
PERIOD.

CLOSER TO THE EQUATOR...
SE TRADES S OF EQUATOR FORCE CROSS EQUATORIAL SWELLS UP TO 9 FT 
W OF 95W REACHING 05N.  BY SAT...STRONGER WINDS EXPAND EASTWARD 
AND BRING WARM MOIST AIR MASS NEAR PANAMA LOW PRES WITH 
POSSIBILITY OF STRONG DEEP CONVECTION AND INCREASED LOW LEVEL 
VORTICITY.  SEVERAL MODEL SOLUTIONS INDICATE DEVELOPMENT OF LOW 
PRES NEAR COAST OF COSTA RICA LATE IN FORECAST PERIOD WITH GFS 
MOST AGGRESSIVE WHILE NAM AND EUROPEAN TAMER AND SLOWER.  
EXPANSION OF SOUTH AMERICAN UPPER LEVEL RIDGE OVER REGION WOULD 
FAVOR DEVELOPMENT.

$$
WALLY BARNES