000
AXPZ20 KNHC 040952
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE SEP 04 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 DEPRESSION JOHN AT 22.5N 115.6W 1004 MB AT 0900 UTC 
MOVING NW OR 305 DEG AT 11 KT ALONG SW PERIPHERY OF MID TO UPPER 
LEVEL RIDGE.  DEEP CONVECTION HAS DIMINISHED SIGNIFICANTLY IN 
COVERAGE AND STRENGTH AND IS PULLING AWAY FROM CIRCULATION 
CENTER.  MAXIMUM SUSTAINED WINDS 30 GUSTS TO 40 KT OVER N 
SEMICIRCLE.  JOHN REMAINS UNDER MODERATE NE WIND SHEAR ALOFT AND 
MOVING OVER MUCH COOLER SURFACE WATERS.  IT IS EXPECTED TO 
FURTHER WEAKEN OVER NEXT FEW DAYS INTO A REMNANT LOW PRES.
SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP5/WTPZ25 KNHC FOR MORE DETAILS.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM 08N78W TO 09N00W TO 12N118W TO 
09N126W THEN ITCZ TO 06N135W TO BEYOND 07N140W.  SCATTERED 
MODERATE ISOLATED STRONG BETWEEN AXIS AND 04N E OF 92W.  
ISOLATED MODERATE 300 NM S OF AXIS FROM 113W TO 119W.

...DISCUSSION...
COMPLEX DUAL BARREL UPPER LEVEL CYCLONES N OF AREA HAVE ROUGH 
EXTEND S TO 32N133W TO 26N134W TO 23N140W.  VERY DRY AIR MASS 
DUE TO MODERATE TO STRONG SUBSIDENCE COVER BASIN W OF 125W... 
EFFECTIVELY ABSORBING ALL CONVECTION FROM REMNANTS OF ILEANA NOW 
NEAR 20N128W.  WELL DEFINED ANTICYCLONE ALOFT AT 29N112W ADVECTS 
ABUNDANT TROPICAL MOISTURE INTO E PAC E OF 125W AND ENHANCES 
OUTFLOW OF TROPICAL DEPRESSION JOHN...BUT THE T.D HAS ITS DAYS 
COUNTED AS IT DRIFTS INTO COOL SEA SURFACE TEMPERATURES AND 
STRUGGLES AGAINST STRONG WIND SHEAR ALOFT.  INVERTED UPPER LEVEL 
TROUGH EXTENDS FROM GULF OF TEHUANTEPEC TO 05N102W ALSO BRINGING 
PLENTY OF TROPICAL MOISTURE INTO E PAC ALONG MONSOON TROUGH 
LATITUDES BUT STILL LACK A SOURCE OF UPLIFT TO TRIGGER DEEP 
CONVECTION.

ELSEWHERE AT THE LOW LEVELS...SURFACE 1032 MB HIGH PRES CENTER  
NW OF AREA RIDGES SE TO 28N120W.

$$
WALLY BARNES