000
AXPZ20 KNHC 050337
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC WED SEP 05 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0045 UTC.

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

THE MONSOON TROUGH AXIS WAS ANALYZED FROM 08N78W TO 11N94W TO 
08N106W TO 11N115W TO 10N117W. THE ITCZ AXIS WAS ANALYZED FROM 
10N117W TO 08N140W. SCATTERED MODERATE WITH ISOLATED STRONG 
CONVECTION WAS WITHIN 120 NM N AND 210 NM S OF THE AXIS BETWEEN 
91W AND 96W. SCATTERED MODERATE CONVECTION WAS ALSO FOUND NEAR 
THE MONSOON TROUGH WITHIN 120 NM OF THE COAST BETWEEN 81W AND 
89W.

...DISCUSSION...

THE UPPER LEVEL PATTERN E OF 125W CONSISTS OF A TROUGH FROM 
14N110W INTO CENTRAL MEXICO BOOKENDED BY ANTICYCLONES OFF 
CENTRAL BAJA CALIFORNIA NEAR 28N118W AND OVER GUATEMALA NEAR 
15N91W. STRONG CONVECTION ALONG THE MONSOON TROUGH/ITCZ AXIS IS 
LIMITED TO THE REGION BETWEEN 91W AND 96W WHERE THE UPPER RIDGE 
AXIS THAT EXTENDS FROM THE ANTICYCLONE OVER GUATEMALA TO 04N103W 
IS ENHANCING THE VERTICAL LIFT OF THE LOW LEVEL MOISTURE POOLED 
ALONG THE MONSOON TROUGH. DIFFLUENCE ASSOCIATED WITH THIS 
ANTICYCLONE IS ALSO ENHANCING THE CONVECTION ALONG THE COAST 
FROM PANAMA TO EL SALVADOR NEAR THE MONSOON TROUGH AS NOTED IN 
THE SECTION ABOVE. FARTHER N...THE RIDGE AXIS THAT EXTENDS NE 
FROM THE ANTICYCLONE OFF BAJA CALIFORNIA IS ENHANCING THE 
SCATTERED MODERATE CONVECTION FOUND IN THE GULF OF CALIFORNIA 
FROM 26N TO 30N.

POST-TROPICAL REMNANT LOW JOHN WAS ANALYZED NEAR 25N118W 1007 
MB. THE LOW WAS MOVING NW AROUND 15 KT. THERE HAS BEEN NO DEEP 
CONVECTION NEAR THIS LOW FOR OVER 20 HOURS. HOWEVER...MAXIMUM 
WINDS REMAIN 30 KT IN THE NE QUADRANT ACCORDING TO THE 2032 UTC 
OSCAT PASS. THE SUBTROPICAL RIDGE EXTENDS FROM 1035 MB HIGH PRES 
NEAR 44N143W TO THE N SIDE OF REMNANT LOW JOHN NEAR 28N117W. THE 
PRES GRADIENT BETWEEN THIS RIDGE AND THE REMNANT LOW CENTER IS 
KEEPING THE WINDS FRESH TO STRONG...BUT 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 THE RESULTING PRES GRADIENT ON THE W SIDE OF THE 
REMNANTS OF JOHN. THE REMNANTS OF JOHN ARE EXPECTED TO DIMINISH 
ON THU UNDER MODERATE NE WIND SHEAR ALOFT AND COLD SEA SURFACE 
TEMPERATURES. SIGNIFICANT WAVE HEIGHTS TO 12 FT WERE ANALYZED AT 
0000 UTC BUT WILL RAPIDLY SUBSIDE AS THE WINDS DIMINISH.

W OF 125W...THE UPPER PATTERN CONSISTS OF A VERY DRY AIR MASS 
WITH MODERATE TO STRONG SUBSIDENCE...EFFECTIVELY ABSORBING ALL 
CONVECTION FROM THE REMNANTS OF ILEANA NEAR 19N130W. THE 2034 
UTC ASCAT PASS SHOWS THE FRESH TO STRONG WINDS IN THE NW 
QUADRANT OF REMNANT LOW ILEANA HAVE SHRUNK TO WITHIN 210 NM OF 
CENTER. THE CIRCULATION CENTER IS EXPECTED TO WEAKEN AND OPEN UP 
OVER THE NEXT DAY OR SO...WITH WINDS AND SEAS DIMINISHING BELOW 
ADVISORY CRITERIA BY SUNRISE THU.


$$
SCHAUER