000
AXPZ20 KNHC 210316
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC THU MAY 21 2009

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0300 UTC.

...ITCZ...
AXIS ALONG 08N78W TO 08N87W TO 06N96W TO 10N108W TO 13N117W TO 
05N135W TO 05N140W. SCATTERED MODERATE TO STRONG WITHIN 240 NM 
OF AXIS FROM 108W TO 121W. ISOLATED MODERATE TO STRONG WITHIN 90 
NM OF AXIS W OF 123W.

.DISCUSSION...
UPPER LEVEL CYCLONIC VORTEX NEAR 33N120W DRIFT E OVER CALIFORNIA 
HAS TROUGH EXTENDING ACROSS MAINLAND MEXICO. QUASI-ZONAL 90 KT 
FLOW ALOFT FROM 18N-28N BETWEEN 100W-130W COMBINES TO PROVIDE 
GOOD DIFFLUENT PATTERN AND ENHANCE CONVECTION PRODUCED BY 
SURFACE LOW PRES 1009 MB 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 1030 MB WELL N OF AREA WITH RIDGE EXTENDING TO 
17N110W SQUEEZE GRADIENT COMBINED WITH LOW PRES 1005 MB AT 
31N112W WITH N GALE FORCE WINDS AGAINST COAST OF CALIFORNIA.
N WINDS 20 KT SPILL INTO E PAC N OF 25N E OF 125W ALONG WITH 8 
FT SWELLS...BUT SHOULD LAST TILL EARLY THU.  

GULF OF TEHUANTEPEC REGION GALE CONDITIONS ALLOWED TO EXPIRE AT 
18 UTC BUT LINGERING 20 KT WINDS AND 9 FT SEAS REMAIN THROUGH 
LATE THU.

$$
WALLY BARNES