000
AXPZ20 KNHC 282201
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU JUL 28 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...ITCZ/MONSOON TROUGH...

MONSOON TROUGH EXTENDS FROM 09N79W TO 10N91W TO 11N105W TO 
08N122W HENCE ITCZ AXIS TO 08N131W TO BEYOND 07N140W.  SCATTERED 
MODERATE CONVECTION WITHIN 45 NM OF AXIS FROM 93W TO 96W. 

...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 EXTEND DRY AIR ALOFT EASTWARD N OF 15N TO MEXICAN COAST. 
SMALL BUT WELL DEFINED ANTICYCLONE AT 18N118W TRAPPED BETWEEN 
CYCLONES EDGED W AND KEEPS 20 KT EASTERLY SHEAR WINDS OVER WEAK 
SURFACE LOW PRES AT 11N114W.  THAT MOVE WEAKENS NE SHEAR OVER 
SECOND SURFACE LOW PRES CENTER AT 10N91W ALLOWING CONVECTION TO 
INCREASE AND LOW PRES TO STRENGTHEN.  

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 DRIFT N AWAY
BUT HAS PROMPTED GALE FORCE WINDS ALONG N CALIFORNIA COAST.  
FRESH N WINDS 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 ITS SE QUADRANT 
TO ADD TO ALREADY PRESENT CROSS EQUATORIAL SW 8-9 FT SWELL.  
SEAS ABLE TO BUILD TO 11 FT BY LATE IN FORECAST PERIOD.  
   
$$
WALLY BARNES