000
AXPZ20 KNHC 030959
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC MON SEP 03 2012

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 
0915 UTC.

...SPECIAL FEATURE...
TROPICAL STORM JOHN AT 19.4N 111.7W 1001 MB AT 0900 UTC MOVING 
W-NW OR 305 DEG AT 12 KT ALONG SOUTHERN PERIPHERY OF MID TO 
UPPER LEVEL RIDGE.  CURRENTLY NUMEROUS MODERATE AND SCATTERED  
STRONG CONVECTION IS WITHIN 120 NM SE AND 90 NM NW SEMICIRCLES.  
MAXIMUM SUSTAINED WINDS 35 WITH GUSTS TO 45 KT WITHIN 180 NM NE 
SEMICIRCLE.  JOHN IS UNDER MODERATE NE WIND SHEAR ALOFT AND IS 
QUICKLY APPROACHING COOLER SEA TEMPERATURES WHICH ARE EXPECTED 
TO CURTAIL ITS DEVELOPMENT.  FORECAST CALLS FOR JOHN TO WEAKEN 
BACK TO A TROPICAL DEPRESSION LATE TUE AS ADVERSE CONDITIONS 
TAKE THEIR TOLL ON SYSTEM.  SEE THE LATEST NHC FORECAST/ADVISORY 
UNDER AWIPS/WMO HEADERS MIATCMEP5/WTPZ25 KNHC FOR MORE DETAILS. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

MONSOON TROUGH FROM 09N84W TO 09N92W TO 13N101W THEN RESUMES 
FROM 14N112W TO 09N134W TO BEYOND 10N140W.  SCATTERED MODERATE 
CONVECTION BETWEEN MONSOON TROUGH AND 04N FROM 88W TO 100W.  

...DISCUSSION...
UPPER LEVEL SHORTWAVE TROUGH EXTENDS SW INTO BASIN FROM 32N124W 
TO 27N128W BRINGING VERY DRY AIR MASS INTO E PAC W OF 126W.  
REMNANTS OF ILEANA CURRENTLY AT 22N125W HAVE COMPLETELY DRIED 
OUT UNDER SHORTWAVE.  UPPER LEVEL ANTICYCLONE CENTERED OVER NW 
MEXICO ADVECTS LARGE AMOUNT OF TROPICAL MOISTURE INTO E PAC E OF 
120W...IT ALSO ENHANCED OUTFLOW OVER SURFACE LOW PRES...HELPING 
IT INTENSIFY TO TROPICAL STORM JOHN. 

E OF 120W E PAC IS RIPE FOR TROPICAL ACTIVITY AS NECESSARY 
INGREDIENTS ARE AVAILABLE JUST WAITING FOR UPLIFTING MECHANISMS 
TO START.  ON THE OTHER HAND...STEADY MODERATE TO STRONG NE 
WINDS SE OF ABOVE MENTIONED ANTICYCLONE MAY BE CURTAILING ANY 
DEEP CONVECTION THAT MAY DEVELOP. 

ELSEWHERE IN THE LOW LEVELS...
SURFACE HIGH PRES CENTER 1032 MB N OF AREA AT 37N147W PROMPTS 
LIGHT TO MODERATE NE TRADES W OF REMNANTS OF ILEANA N OF MONSOON 
TROUGH. 

$$
WALLY BARNES