000 AXPZ20 KNHC 182325 RRA TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2100 UTC. ...SPECIAL FEATURE... AN 1007 MB AREA OF LOW PRES IS EMBEDDED IN THE MONSOON TROUGH NEAR 09N96.5W MOVING W AROUND 5 KT. ASSOCIATED CONVECTION HAS DECREASED DURING THE PAST SEVERAL HOURS MAINLY DUE TO DRIER AND MORE STABLE AIR SURGING DOWN TOWARD THE LOW FROM THE GULF OF TEHUANTEPEC. SCATTERED MODERATE CONVECTION IS WITHIN 180-210 NM IN THE NE QUADRANT OF THE LOW CENTER...AND ALSO NEARBY WITHIN 90 NM EITHER SIDE OF A LINE FROM 07N99W TO 13N104W. MORNING SCATTEROMETER PASSES INDICATED 20-25 KT S-SW WINDS FROM 02N TO 09N BETWEEN 93W AND 99W. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BECOME A LITTLE MORE CONDUCIVE FOR DEVELOPMENT...AND THE LOW HAS A A MEDIUM CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 24-48 HOURS. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH IS ALONG 10N85W TO LOW PRES NEAR 09N96.5W TO 07N107W TO 09N117W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 09N117W TO 11N124W THEN RESUMES FROM 11N128W TO 08N140W. SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 60-90 NM EITHER SIDE OF THE ITCZ W OF 129W. ...DISCUSSION... AN UPPER LEVEL TROUGH REACHES FROM NEAR POINT CONCEPTION CALIFORNIA INTO THE AREA NEAR 32N126W TO 24N136W. PLENTIFUL MID TO UPPER LEVEL MOISTURE IS BEING ADVECTED TO THE NE WITHIN 300-390 NM AHEAD OF THE TROUGH AXIS. ADDITIONAL MID TO UPPER LEVEL MOISTURE IS PRESENT FROM 16N TO 24N W OF 130W. MAINLY SW-W ZONAL FLOW EXISTS N OF 16N E OF 120W WITH WATER VAPOR SATELLITE IMAGERY INDICATING DRY AND STABLE AIR UNDER MODERATE TO STRONG SUBSIDENCE ACROSS THIS AREA. AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS S OF GUATEMALA NEAR 10N93W WITH A RIDGE AXIS EXTENDING FROM IT TO NEAR 13N115W. UPPER LEVEL DIFFLUENCE OVER THIS REGION IS ENHANCING CONVECTION ASSOCIATED WITH THE SURFACE LOW DESCRIBED IN THE SPECIAL FEATURE SECTION ABOVE. AN ELONGATED UPPER LEVEL ANTICYCLONIC CIRCULATION IS NEAR 10N138W WITH A RIDGE AXIS ALONG 10N/11N W OF 122W. UPPER LEVEL DIFFLUENCE OVER THIS REGION IS ALSO ENHANCING CONVECTION ALONG THE ITCZ AS IS DESCRIBED IN THE SECTION ABOVE. ELSEWHERE AT THE SURFACE...A RIDGE EXTENDS FROM NEAR 31N140W SE TO 20N110W. A SMALL AREA OF LINGERING 8 FT NW SWELL RESIDES FROM N OF 28N BETWEEN 119W AND 123W. THIS SWELL WILL DECAY TO LESS THAN 8 FT DURING THE NEXT 24 HOURS WHILE A NEW SET OF LARGER NW SWELL WITH PEAK WAVE PERIODS OF 16-18 SECONDS PROPAGATES INTO THE NW PORTION OF THE DISCUSSION WATERS. A DEVELOPING COLD FRONT WILL PRECEDE THIS SWELL ALTHOUGH ASSOCIATED WINDS ARE FORECAST TO REMAIN LESS THAN 20 KT WITH THIS FRONT. A REINFORCING AND STRONGER COLD FRONT WILL ARRIVE SUN MORNING REACHING FROM 30N127W TO 28N134W TO 29N140W BY 12 UTC SUN...THEN WILL WEAKEN AS IT EXTENDS FROM 30N124W TO 27N130W TO 27N140W BY 18 UTC SUN. THE NW SWELL WILL BUILD TO 13/14 FT ALONG 30N BETWEEN 24-48 HOURS. ALSO...AN AREA OF 20-25 KT WESTERLY WINDS WILL ACCOMPANY THIS REINFORCING FRONT OVER THE FAR N CENTRAL WATERS. A SURFACE TROUGH IS ANALYZED ALONG THE ITCZ EXTENDING FROM 15N123W TO 07N127W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS WITHIN 75 NM W OF THE TROUGH FROM 08N TO 10N. A RECENT 1846 UTC ASCAT SCATTEROMETER PASS CAPTURED 20 KT NE-E WINDS FROM 11N TO 15N BETWEEN 123W AND 132W...WHILE A 1800 UTC ENVISAT ALTIMETER PASS SAMPLED 8 FT SEAS IN THIS SAME GENERAL AREA. THE TROUGH IS FORECAST TO DISSIPATE DURING THE NEXT 24 HOURS WHILE THE AREA OF 20 KT WINDS AND 8 FT SEAS TRANSLATES WESTWARD TOWARD 140W. GAP WINDS...STRONG HIGH PRES CONTINUES TO BUILD IN BEHIND A COLD FRONT WHICH MOVED THROUGH THE BAY OF CAMPECHE EARLIER TODAY. THE PRES GRADIENT HAS BEGUN TO WEAKEN OVER THE GULF OF TEHUANTEPEC REGION AND THE GALE WARNING WAS ALLOWED TO EXPIRE AT 1800 UTC BASED ON THE LATEST IN-SITU AND REMOTE SENSING DATA. WINDS AND SEAS WILL GRADUALLY DIMINISH TO LESS THAN ADVISORY CRITERIA DURING THE NEXT 24 HOURS AS THE GRADIENT CONTINUES TO RELAX AND WEAKEN. $$ LEWITSKY