000
AXPZ20 KNHC 042111
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1915 UTC.

...SPECIAL FEATURE...
POST-TROPICAL REMNANT LOW JOHN AT 24.3N 117.7W 1006 MB AT 2100 
UTC MOVING NW OR 315 DEG AT 12 KT. DEEP CONVECTION REMAINS 
DIMINISHED WITH NO SIGNIFICANT CONVECTIVE ACTIVITY WITH THE 
SYSTEM. MAXIMUM SUSTAINED WINDS 30 KT GUSTS TO 40 KT OVER N 
SEMICIRCLE. JOHN REMAINS UNDER MODERATE NE WIND SHEAR ALOFT AND 
HAS MOVED OVER SURFACE WATERS THAT ARE COOLER THAN 24 DEGREES 
CELSIUS. IT IS EXPECTED TO WEAKEN FURTHER OVER THE NEXT FEW 
DAYS. SEE LAST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP5/WTPZ25 KNHC FOR MORE DETAILS.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH AXIS FROM 09N84W TO 11N94W TO 08N106W TO 11N114W 
TO 12N124W TO 11N128W. ITCZ AXIS FROM 11N128W TO 09N140W. 
SCATTERED MODERATE CONVECTION WITHIN 45 NM N AND 120 NM S OF THE 
AXIS BETWEEN 85W AND 91W AND WITHIN 120 NM N OF THE AXIS BETWEEN 
97W AND 101W.

...DISCUSSION...
THE UPPER LEVEL PATTERN E OF 125W CONSISTS OF A TROUGH FROM 
12N108W INTO CENTRAL MEXICO BOOKENDED BY ANTICYCLONES OVER 
CENTRAL BAJA CALIFORNIA AND HONDURAS. SIGNIFICANT DEEP 
CONVECTION ALONG THE MONSOON TROUGH/ITCZ AXIS IS LIMITED TO THE 
REGION BETWEEN 85W AND 101W WHERE THE UPPER RIDGE AXIS THAT 
EXTENDS FROM THE ANTICYCLONE OVER HONDURAS TO 04N105W IS 
ENHANCING THE VERTICAL LIFT OF THE LOW LEVEL MOISTURE POOLED 
ALONG THE MONSOON TROUGH. 

W OF 125W...THE UPPER PATTERN CONSISTS OF A VERY DRY AIR MASS 
WITH MODERATE TO STRONG SUBSIDENCE... EFFECTIVELY ABSORBING ALL 
CONVECTION FROM REMNANTS OF ILEANA NOW NEAR 20N130W. THE 1824 
UTC ASCAT PASS SHOWS THE FRESH TO STRONG WINDS IN THE NW 
QUADRANT OF REMNANT LOW ILEANA HAVE SHRUNK TO WITHIN 240 NM. THE 
CIRCULATION CENTER IS EXPECTED TO WEAKEN AND OPEN UP OVER THE 
NEXT DAY OR SO...WITH WINDS AND SEAS DIMINISHING BELOW ADVISORY 
CRITERIA.

ELSEWHERE AT THE LOW LEVELS...THE SUBTROPICAL RIDGE EXTENDS FROM 
1034 MB HIGH PRES NEAR 43N143W TO THE NW SIDE OF REMNANT LOW 
JOHN NEAR 26N121W. THE SUBTROPICAL HIGH IS EXPECTED TO MIGRATE 
ABOUT 5 DEGREES W OVER THE NEXT FEW DAYS...FURTHER WEAKENING THE 
SUBTROPICAL RIDGE OVER THE FORECAST AREA AND DIMINISHING THE 
PRES GRADIENT ON THE W SIDE OF THE REMNANTS OF JOHN.

$$
SCHAUER