000
AXPZ20 KNHC 200954
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE AUG 20 2013

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.
                                    
...SPECIAL FEATURE...                                            
LOW PRES CENTER AT 13N109W MOVING IN PHASE WITH UPPER LEVEL 
ANTICYCLONE AT 20N110W.  THIS IMPROVES UPPER LEVEL SCENARIO MUCH
MORE FAVORABLE FOR DEVELOPMENT AS REGION OF MODERATE DIVERGENCE
AND LIGHTER WINDS ALOFT ENHANCE CONVECTION.  ONLY ADVERSITY IS
DRY STABLE AIR MASS NOTED N OF 18N...BUT THAT MAY SOON CHANGE AS
RIDGE ITSELF IS ADVECTING CONVECTIVE DEBRIS FROM MONSOON TROUGH 
NORTHWARD JUST W OF 112W.  MODEL SOLUTIONS AGREE WITH TROPICAL
CYCLONE FORMATION BY THU TRACKING N-NW TOWARDS SOUTHERN BAJA 
CALIFORNIA.  MARINE INTERESTS SHOULD CLOSELY MONITOR EVOLUTION
OF TROPICAL CYCLONE DURING NEXT SEVERAL DAYS.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...          
MONSOON TROUGH FROM 09N83W TO 08N91W TO 13N100W TO LOW PRES AT 
13N109W 1009 MB TO LOW PRES AT 15N121W 1009 MB TO 11N130W TO 
BEYOND 12N140W. SCATTERED MODERATE ISOLATED STRONG WITHIN 180 NM 
S AND 120 NM N OF AXIS FROM 92W TO 132W. 

...DISCUSSION...
BROAD UPPER LEVEL ANTICYCLONE AT 21N137W DRIFT W.  VERY DRY AND
STABLE SUBSIDING AIR MASS N OF 15N W OF 124W AND N OF 19N E OF 
124W.  

WELL DEFINED CYCLONE ALOFT AT 33N125W HAS LARGE AMPLITUDE TROUGH
EXTEND S TO 15N125W. CYCLONE CONTRIBUTES TO NORTHBOUND ADVECTION
OF CONVECTIVE DEBRIS FROM MONSOON TROUGH.  TROUGH ALSO BRINGING
STRONG SW SHEAR OVER SECOND SURFACE LOW PRES CENTER AT 15N121W
PREVENTING ITS FULL DEVELOPMENT.

...ELSEWHERE AT THE LOWER LEVELS...
HIGH PRES CENTER 1027 MB WELL N OF BASIN FORCED FURTHER N BY 
APPROACHING WEAK COLD FRONT NOW W OF AREA.  THIS IN TURN WEAKENS
NE TRADES W OF 120W.  

SECOND LOW PRES CENTER MENTIONED ABOVE DRIFT NW BUT APPROACHES
COOLER WATERS AND DRIER AIR MASS WITHIN IN A DAYS TRAVEL. SOME 
MODEL SOLUTIONS STRENGTHEN SYSTEM BUT IT IS SHORT-LIVED IF ANY
AT ALL. MOST OTHER MODELS ARE LESS AGGRESSIVE...BUT AGREE WITH A
SECOND LOW W OF TROPICAL CYCLONE MENTIONED IN SPECIAL FEATURES. 
 
$$
WALLY BARNES