000
AXPZ20 KNHC 202155
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC WED MAY 20 2009

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 
2100 UTC.

...ITCZ...
AXIS ALONG 07N77W TO 11N107W TO 13N117W TO 05N135W TO 05N140W.  
SCATTERED MODERATE CONVECTION WITHIN 120 NM OF AXIS E OF 82W.  
SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 120 NM N OF 
AXIS FROM 93W TO 102W.  SCATTERED MODERATE TO STRONG CONVECTION 
WITHIN 210 NM OF 11N109W AND 13N120W.  SCATTERED MODERATE TO 
STRONG CONVECTION WITHIN 120 NM OF AXIS W OF 127W.

.DISCUSSION...
UPPER LEVEL CYCLONIC VORTEX NEAR 34N120W DRIFT E OVER CALIFORNIA 
HAS TROUGH EXTENDING ACROSS MAINLAND MEXICO.  QUASI-ZONAL FLOW 
ALOFT S OF 25N FROM 100W-130W COMBINES TO PROVIDE GOOD DIFFLUENT 
PATTERN AND ENHANCE CONVECTION PRODUCED BY SURFACE LOW PRES AT 
31N112W OVER N HALF OF MEXICO.   

ELSEWHERE AT THE SURFACE...
STATIONARY SURFACE TROUGH 07N121W TO 16N119W HAS WEAK EMBEDDED 
SURFACE LOW PRES 1008 MB AT 13N120W.  UPPER ENVIRONMENT NOT 
UNFAVORABLE BUT DRY AND STABLE AIR MASS AWAITS TROUGH AND LOW 
PRES IF THEY START MOVING W...DOOMING CHANCES OF DEVELOPING ANY 
ORGANIZED CONVECTION.  SECOND STATIONARY LOW PRES 1008 MB AT 
11N109W IS ASSOCIATED WITH DEEP CONVECTION AND HAS FAVORABLE 
UPPER LEVEL ENVIRONMENT WHICH COULD ENHANCE BETTER ORGANIZATION.
THIS SYSTEM SHOULD BE MONITORED FOR DEVELOPMENT. 

SURFACE RIDGE 1031 MB WELL N OF AREA HAS RIDGE EXTEND TO 20N109W 
SQUEEZE GRADIENT COMBINED WITH LOW PRES AT 20N112W WITH N GALE 
FORCE WINDS AGAINST COAST OF CALIFORNIA.  N WINDS 20 KT SPILL 
INTO E PAC N OF 25N E OF 125W BUT SHOULD BE SHORT-LIVED AND LAST 
THROUGH THU ONLY.  

GULF OF TEHUANTEPEC REGION GALE CONDITIONS ALLOWED TO EXPIRE AT 
18 UTC BUT LINGERING 20-25 KT WINDS AND 8-10 FT SEAS REMAIN 
THROUGH THU.

$$
WALLY BARNES