000
AXPZ20 KNHC 121519
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT OCT 12 2013

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 
1500 UTC.

...SPECIAL FEATURES...

A 1007 MB LOW PRES SYSTEM IS EMBEDDED IN THE MONSOON TROUGH NEAR 
15N108W...OR SEVERAL HUNDRED MILES SW OF MANZANILLO MEXICO. AN 
AREA OF MODERATE TO STRONG CONVECTION FLARED NEAR THE CENTER OF 
THE LOW OVERNIGHT BUT WAS SHEARED TO THE WEST AND IS STARTING 
DIMINISH. AN ASCAT PASS FROM AROUND 05 UTC JUST MISSED THE AREAS 
AROUND THE LOW PRES...BUT DID INDICATE SW FLOW INTO THE THE LOW 
S OF THE MONSOON TROUGH WAS NOT AS STRONG AS PREVIOUSLY 
EXPECTED. SIMILARLY...DESPITE THE NOCTURNAL FLARE 
UP...CONVECTION HAS BEEN FAIRLY LIMITED. OVERALL ENVIRONMENTAL 
CONDITIONS REMAIN FAVORABLE FOR SOME FURTHER DEVELOPMENT AND THE 
LOW STILL HAS A MEDIUM CHANCE OF BECOMING A TROPICAL CYCLONE 
DURING THE NEXT 48 HOURS.

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

THE MONSOON TROUGH EXTENDS FROM 07N77W TO 16N102W TO LOW PRES 
NEAR 14N108W 1007 MB TO LOW PRES NEAR 13N117W 1007 MB TO 
08N130W...THEN RESUMES FROM LOW PRES NEAR 14N133W 1011 MB TO 
09N140W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS 
WITHIN 120 NM OF THE MONSOON TROUGH BETWEEN 85W AND 95W...AND 
WITHIN 210 NM OF THE MONSOON TROUGH BETWEEN 105W AND 120W.

...DISCUSSION...

AN UPPER LEVEL TROUGH REMAINS IN PLACE FROM SOUTHERN CALIFORNIA 
TO 12N125W...MAKING LITTLE PROGRESS EASTWARD AGAINST AN UPPER 
RIDGE ANCHORED OVER CENTRAL MEXICO. MODERATE TO FRESH SW LOW 
LEVEL FLOW INTO THE MONSOON TROUGH IS SUSTAINING AREAS OF 
CONVECTION WITHIN 210 NM OF THE TROUGH BETWEEN 105W AND 
120W...WITH UPPER EXHAUST PROVIDED BY S TO SW FLOW BETWEEN THE 
UPPER TROUGH AND THE RIDGE. THE UPPER TROUGH IS MAINTAINING 
FAIRLY DRY AIR OVER THE REGION W OF 1205W...WHICH IS ADVECTING 
NE ACROSS BAJA CALIFORNIA NORTE. ANOTHER LOW PRES SYSTEM IS 
CENTERED NEAR 13N117W. THE RESEARCH VESSEL WECB IS JUST NE OF 
THIS LOW...AND INDICATED FAIRLY LIGHT WINDS EARLIER REACHING 25 
KT IN THE PAST HOUR NEAR THUNDERSTORM ACTIVITY. 

MODERATE TO FRESH NW WINDS ARE NOTED IN SHIP OBSERVATIONS AND 
SCATTEROMETER DATA ALONG THE COAST OF BAJA CALIFORNIA...BETWEEN 
HIGH PRES W OF THE AREA AND TROUGHING OVER N CENTRAL MEXICO.

FARTHER WEST...A 1011 MB LOW PRES AREA IS CENTERED NEAR 14N133W. 
SCATTEROMETER DATA AND AN ALTIMETER PASS OVER THE PREVIOUS 
SEVERAL HOURS INDICATED WINDS ARE 20 KT ON THE NORTH SIDE OF THE 
LOW. AN AREA OF NORTHERLY SWELL IS MIXING WITH THE SHORTER 
PERIOD SEAS AROUND THE LOW PRES. THE ALTIMETER PASS SHOWED 
COMBINED SEAS REACHING 8 TO 10 FT WITHIN 120 NM IN THE NW 
QUADRANT OF THE LOW PRES. NO CONVECTION IS NOTED WITH THIS 
FEATURE...AND IT IS EXPECTED TO CONTINUE TO DRIFT SW AND OPEN 
INTO A TROUGH BY 48 HOURS.

GULF OF TEHUANTEPEC...A TROPICAL WAVE COUPLED WITH AN UPPER 
TROUGH IS EXPECTED TO MOVE THROUGH CENTRAL AMERICA SUN AND MON. 
THIS WILL ENHANCE GAP WIND FLOW DUE TO OVERNIGHT DRAINAGE 
THROUGH THE GULF OF TEHUANTEPEC LATE SUN INTO MON...WITH WINDS 
REACHING AS HIGH AS 25 KT AND SEAS TO 8 FT. A RESIDUAL TIGHT 
GRADIENT IN THE WAKE OF THE TROPICAL WAVE WILL ENHANCE DRAINAGE 
FLOW AGAIN MON NIGHT INTO TUE MORNING WITH WINDS PEAKING AT 20 
KT. 
 
$$
CHRISTENSEN