000
AXPZ20 KNHC 111552
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC THU OCT 11 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1545 UTC.

...SPECIAL FEATURE...

A LOW 1009 MB IS EMBEDDED ALONG THE MONSOON TROUGH AT 12N93W. A 
SECOND LOW 1009 MB IS EMBEDDED ALONG THE MONSOON TROUGH NEAR 
11N103W. BOTH LOW PRES SYSTEMS HAVE BEEN SPORADICALLY SHOWING OF 
DEVELOPMENT OVER THE PAST 24 HOURS...AND ATMOSPHERIC CONDITIONS 
ARE CONDUCIVE FOR SOME GRADUAL DEVELOPMENT OF ONE OR BOTH OF 
THESE LOW PRES AREAS OVER THE NEXT 48 HRS AS THEY MOVE WNW WITH 
A MEDIUM CHANCE OF INTENSIFYING INTO A TROPICAL STORM.

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

THE MONSOON TROUGH EXTENDS FROM 10N86W TO LOW PRES 1009 MB NEAR 
12N92W...TO LOW PRES 1009 MB NEAR 11N103W...TO 09N130W. THE ITCZ 
EXTENDS FROM 09N13W TO 08N140W. SCATTERED MODERATE ISOLATED 
STRONG N OF MONSOON TROF FROM 12N TO 14N BETWEEN 95W AND 98W. 
SCATTERED MODERATE ISOLATED STRONG FROM 13N TO 15N BETWEEN 102W 
AND 107W. SCATTERED MODERATE WITHIN 60 NM S OF ITCZ AXIS BETWEEN 
125W AND 135W...AND WITHIN 180 NM N OF AXIS BETWEEN 135W AND 
138W.

...DISCUSSION...

W OF 110W...A CUTOFF UPPER LEVEL LOW IS MIGRATING SE ALONG THE 
COAST OF SOUTHERN CALIFORNIA...AND WILL PUSH ACROSS SOUTHERN 
CALIFORNIA AND NORTHERN BAJA THROUGH FRI. THIS FEATURE HAD BEEN 
SUPPORTING A WEAK COLD FRONT MOVING SE N OF 25N...BUT HAS SINCE 
BEEN DOWNGRADED TO A TROUGH EXTENDING FROM SOUTHERN CALIFORNIA 
TO 30N118W TO 27N123W. THE TRANSIT OF THE TROUGH THROUGH 
NORTHERN BAJA ALONG WITH THE SUPPORTING UPPER FEATURE...AND 
FOLLOWED BY A SURFACE RIDGE NOSING EASTWARD ALONG 25N...WILL AID 
DEVELOPMENT OF LARGELY 15 TO 20 KT NW TO N WINDS ALONG THE 
NORTHERN COAST OF BAJA AND THE NORTHERN GULF OF CALIFORNIA 
THROUGH FRI. 

AN UPPER SHORT WAVE TROUGH IS DIGGING W FROM THE N 
CENTRAL PACIFIC N OF 30N...SUPPORTING A COLD FRONT MOVING TOWARD 
THE WEST COAST N OF 30N. THE SOUTHERN EXTENT OF THIS FRONT 
APPEARS TO BE STALLING HOWEVER...AND WILL LIKELY NOT REACH THE 
DISCUSSION AREA S OF 30N THROUGH FRI. 

THIS WILL LEAVE THE SURFACE RIDGE LARGELY IN TACT ALONG ROUGHLY 
25N THROUGH THE NEXT 48 HOURS...WHICH WILL IN TURN MAINTAIN 15 
TO 20 KT TRADE WIND FLOW FURTHER SOUTH...MAINLY FROM 12N TO 18N 
W OF 125W. THE MODERATE TO FRESH TRADE WIND FLOW IS ENHANCING 
CLUSTERS OF CONVECTION ALONG THE ITCZ W OF 125W. NW SWELL 
CONTINUES TO PROPAGATE FROM THE N CENTRAL PACIFIC INTO THE 
AREA...MAINLY N OF 20N W OF 135W CURRENTLY...BUT COVERING MUCH 
OF THE AREA N OF 10N W OF 130W WITH SEAS TO 9 FT AND PERIODS TO 
16 SECONDS. 

E OF 110W...THE DOMINANT FEATURES ARE THE TWO LOW PRES AREAS 
ALONG THE MONSOON TROUGH LISTED IN THE SPECIAL FEATURES. THESE 
FEATURES HAVE PREVIOUSLY BENEFITED IN PART BY PASSING TROPICAL 
WAVE ACTIVITY IN THE LOWER TO MIDDLE PORTIONS OF THE 
ATMOSPHERE...AND TO SOME EXTENT BY PULSES OF FRESH TO STRONG GAP 
WIND FLOW THROUGH THE GULF OF TEHUANTEPEC AND PERHAPS THE GULF 
OF FONSECA. THE GFS DEVELOPS BOTH OF THESE SYSTEMS MORE OR LESS 
INDEPENDENTLY OVER THE NEXT SEVERAL DAYS...ALTHOUGH KEEPS THE 
INTENSITY FAIRLY LIMITED INTO EARLY NEXT WEEK. THE ECMWF IS ALSO 
SHOWING GRADUAL DEVELOPMENT...BUT PRIMARILY FOR THE WESTERNMOST 
LOW PRES AREA. AT THIS STAGE...CLUSTERS OF CONVECTION ARE 
PULSING N OF THE MONSOON TROUGH...IN MODEST EASTERLY SHEAR ALOFT 
ON THE SOUTHERN EDGE OF AN UPPER ANTICYCLONE CENTERED OVER W 
CENTRAL MEXICO. ASCAT AND ALTIMETER DATA SHOW THE SW FLOW INTO 
THE MONSOON TROUGH REMAINS FAIRLY LIGHT...AND SO FAR HAS NOT 
BEEN VERY CONDUCIVE TO DEVELOPMENT. ADDED VORTICITY FROM THE 
GULF OF TEHUANTEPEC THROUGH THE NEXT 48 HOURS ALONG PERSISTENT 
CONVECTION WILL OFFER SOME POTENTIAL FOR FURTHER DEVELOPMENT OF 
ONE OR BOTH SYSTEMS.
 
$$
CHRISTENSEN