000
AXPZ20 KNHC 181514
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI NOV 18 2011

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 
1515 UTC.

...SPECIAL FEATURE...

A 1007 MB AREA OF LOW PRES IS EMBEDDED IN THE MONSOON TROUGH NEAR 
9N96W MOVING W AROUND 15 KT. CONVECTION HAS DECREASED ALONG THE MAIN 
BAND DURING THE PAST SEVERAL HOURS PARTIALLY DUE TO SOME COOLER 
SURFACE WATER TEMPERATURES S OF THE GULF OF TEHUANTEPEC. 
ENVIRONMENTAL CONDITIONS ARE OTHERWISE GENERALLY CONDUCIVE FOR 
GRADUAL DEVELOPMENT OF THIS SYSTEM...AND THE LOW HAS A MEDIUM CHANCE 
OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 24-48 HOURS.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
 
THE MONSOON TROUGH EXTENDS FROM 10N85W TO 10N90W TO LOW PRES NEAR 
09N96W TO 07N110W TO 09N116W. THE INTERTROPICAL CONVERGENCE ZONE 
CONTINUES FROM 09N116W TO 12N125W TO 08N140W. SCATTERED STRONG 
WITHIN 90 NM NW SEMICIRCLE OF 09N96W LOW. SCATTERED STRONG WITHIN 45 
NM OF TROUGH ALONG 125W FROM 08N TO 11N. ELSEWHERE ISOLATED MODERATE 
FROM 07N TO 13N BETWEEN 120W AND 129W. SCATTERED MODERATE TO STRONG 
FROM 06N TO 09W W OF 135W. 

...DISCUSSION...

AN UPPER LEVEL TROUGH HAS MOVED INTO THE FAR NW PORTION OF THE 
DISCUSSION AREA N OF 20N W OF 120W. EXTENSIVE MID/UPPER LEVEL 
MOISTURE IS IN THE AREA MOVING E. MAINLY ZONAL UPPER LEVEL FLOW IS 
AHEAD OF THE TROUGH. WATER VAPOR SATELLITE IMAGERY INDICATES STRONG 
SUBSIDENCE WITH DRY AND STABLE AIR S OF 26N E OF 120W. AN UPPER 
LEVEL ANTICYCLONIC CIRCULATION IS S OF EL SALVADOR NEAR 10N89W WITH 
A RIDGE AXIS EXTENDING FROM IT TO NEAR 13N115W. UPPER LEVEL 
DIFFLUENCE OVER THIS REGION IS ENHANCING CONVECTION ASSOCIATED WITH 
THE LOW DESCRIBED UNDER SPECIAL FEATURES.

AT THE SURFACE...A RIDGE EXTENDS FROM NEAR 32N137W SE TO 21N115W. 
HIGH PRES COVERS THE AREA N OF 16N AND W OF 115W. NW SWELLS ARE
RESULTING IN COMBINED SEAS TO 9 FT N OF 27N BETWEEN 119W-129W.
THIS SWELL WILL SUBSIDE TO LESS THAN 8 FT WITHIN THE NEXT 24 HOURS. 
A NEW SET OF LARGE LONG PERIOD NW SWELL WITH PEAK WAVE PERIODS OF 
16-18 SECONDS WILL PUSH S OF 30N EARLY SAT MORNING WITH SEAS 
BUILDING TO 13 FT NEAR 30N BY SAT EVENING.

A SURFACE TROUGH IS ANALYZED EXTENDING FROM 14N125W TO 06N126W.  
SCATTERED STRONG CONVECTION IS WITHIN 45 NM OF THE TROUGH FROM 8N TO 
11N. THE TROUGH WILL GRADUALLY WEAKEN AND DISSIPATE DURING THE NEXT 
24 HOURS.

GAP WINDS...STRONG HIGH PRES IS BUILDING IN BEHIND A COLD FRONT 
MOVING THROUGH THE SW GULF OF MEXICO RESULTING IN A TIGHT PRES 
GRADIENT ACROSS SOUTHERN MEXICO. THIS IS RESULTING IN N-NE WINDS TO 
GALE FORCE (30-40 KT) IN THE GULF OF TEHUANTEPEC AND A GALE WARNING 
IS NOW IN EFFECT THROUGH EARLY THIS AFTERNOON. 

$$
FORMOSA