000
AXPZ20 KNHC 290305
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC FRI JUL 29 2011

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

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

...ITCZ/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM 10N86W TO 10N98W TO 13N109W TO 
11N120W HENCE ITCZ TO 13N125W TO 10N140W.  SCATTERED MODERATE 
CONVECTION WITHIN 45 NM OF 13N116W.

...DISCUSSION...
UPPER LEVEL CYCLONIC VORTEX TOOK OVER NW PART OF BASIN BY 
FORCING ANTICYCLONE OUT W OF REGION.  NOW CENTERED AT 26N132W 
VORTEX MAINTAINS DRY AIR MASS N OF 18N W OF 120W.  SECOND 
CYCLONE AT 21N112W EXTEND DRY AIR ALOFT EASTWARD N OF 15N TO 
MEXICAN COAST.  SMALL BUT WELL DEFINED ANTICYCLONE AT 16N118W 
TRAPPED BETWEEN CYCLONES EDGED S AND KEEPS 20 KT EASTERLY SHEAR 
WINDS OVER WEAK SURFACE LOW PRES AT 12N116W.  SECOND SURFACE LOW 
PRES CENTER AT 10N90W COMING UNDER AREA OF CONVERGING UPPER 
LEVEL WINDS WITH A DOWNTURN IN CONVECTION AS NE WIND SHEAR 
INCREASES.  

WEAK UPPER LEVEL ANTICYCLONE DEVELOPING NEAR 07N79W PROVIDES 
DIVERGENT FLOW OVER EXTREME E PORTION OF MONSOON TROUGH 
ENHANCING CONVECTION AND RAINFALL OVER PANAMA AND COSTA RICA. 

ELSEWHERE AT THE LOW LEVELS...
BROAD HIGH PRES CENTER 1034 MB WELL NW OF BASIN HAS PROMPTED 
GALE FORCE WINDS ALONG N CALIFORNIA COAST.  MODERATE TO FRESH N 
BREEZE SPILL S CLOSE TO 30N AND ATTENDANT SWELLS ENCROACH INTO E 
PAC N OF 24N W OF 130W BY SAT. 

LOW PRES 1009 MB AT 10N91W ABLE TO STRENGTHEN WITH FAVORABLE 
ENVIRONMENT ALOFT AND INCREASE SW WINDS WITHIN 180 NM IN ITS SE 
QUADRANT TO ADD TO ALREADY PRESENT CROSS EQUATORIAL SW SWELL 
BUILDING SEAS UP TO 9-10 FT.  
   
$$
WALLY BARNES