000 AXPZ20 KNHC 011624 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC SAT SEP 01 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 1500 UTC. ...SPECIAL FEATURES... TROPICAL STORM ILEANA NEAR 23.0N 118.6W 999 MB AT 1500 UTC SEP 01 MOVING W OR 280 DEG AT 8 KT. MAXIMUM SUSTAINED WINDS 45 KT GUSTS 55 KT. CONVECTION CONTINUES TO DIMINISH...WITH SCATTERED MODERATE CONVECTION WITHIN 60 NM OF CENTER. ILEANA IS PROGRESSING OVER INCREASINGLY COOLER SEA SURFACE TEMPERATURES... WITH DRIER AND VERY STABLE AIR 90 TO 120 NM TO THE W...AND WILL WEAKEN STEADILY OVER THE NEXT 24 HOURS. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS. LONG PERIOD SOUTHERN HEMISPHERIC SW SWELL HAS MOVED INTO THE REGIONAL WATERS IN THE PAST 36 HOURS AND IS HELPING TO PRODUCE AN AREA OF 12 FT SEAS TYPICALLY LARGER THAN ONE WOULD EXPECT FOR THIS DECAYING SYSTEM. AN ELONGATED CYCLONIC CIRCULATION OCCURRING ALONG AND N OF THE MONSOON TROUGH IS LOCATED FROM THE MEXICAN COAST S TO 08N BETWEEN 97W AND 112W. ABUNDANT TROPICAL MOISTURE IS CONVERGING WITHIN THIS AREA...AND PRODUCING SCATTERED TO NUMEROUS CONVECTION MENTIONED BELOW. SEVERAL LOW LEVEL CLOUD SWIRLS ARE NOTED IN SATELLITE IMAGERY THIS MORNING......WHILE PARTIAL SCATTEROMETER PASSES OVERNIGHT SUGGESTED A SURFACE LOW FORMING NEAR 12N101W. CONVECTION REMAINS UNORGANIZED AT THIS TIME. HOWEVER...GLOBAL MODELS SUGGEST A BROAD LOW PRES CENTER MAY GRADUALLY CONSOLIDATE AND MOVE NW WITH TIME. THE PRESSURE GRADIENT BETWEEN THIS ELONGATED LOW PRESSURE SYSTEM AND HIGH PRESSURE BUILDING INTO THE GULF OF MEXICO IS PRODUCING E TO SE WINDS TO 20 TO 25 KT ACROSS THE MEXICAN COASTAL WATERS S TROUGH W OF THE GULF OF TEHUANTEPEC...AND ARE EXPECTED TO INCREASE TO 20-30 KT IN THE NEXT 24 HOURS. THIS SYSTEM HAS A MEDIUM CHANCE OF ORGANIZING INTO A TROPICAL CYCLONE IN THE NEXT 48 HOURS AS IT SHIFTS NW. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... MONSOON TROUGH EXTENDS FROM LOW PRES OVER COLOMBIA NEAR 10N74W 1010 MB TO 08N80W TO 14N95W TO LOW PRES AT 12N102W 1009 MB...THEN RESUMES FROM 15N112W TO 10N121W TO 10N130W...THEN TRANSITIONS TO ITCZ...CONTINUING TO BEYOND 10N140W. SCATTERED TO LOCALLY NUMEROUS MODERATE TO STRONG CONVECTION WITHIN 180 NM OF AXIS FROM 97W TO 101W AND ELSEWHERE FROM 08N TO 16N BETWEEN 101W AND 113W. ...DISCUSSION... UPPER LEVEL LONG WAVE TROUGH ACROSS THE FAR NE PACIFIC IS SHIFTING E INTO NW PORTIONS OF N AMERICA...WITH TROUGH EXTENDING S TO 27N BETWEEN 120W AND 136W. A PAIR OF UPPER ANTICYCLONES LIE TO THE S OF THIS FEATURE...BETWEEN ILEANA AND 144W...YIELDING BROADSCALE CONVERGENCE ALOFT AND A VERY STABLE AND SUBSIDENT REGION AHEAD OF ILEANA. AN UPPER LEVEL RIDGE EXTENDING FROM GULF OF MEXICO W INTO THE E PAC N OF 20N IS AIDING TO FORCE ILEANA W...AND CONTRIBUTING TO NE TO ELY FLOW ALOFT ACROSS THE REMAINDER OF THE AREA. VERTICAL WIND SHEAR IS GENERALLY LIGHT ACROSS THE REGION S OF 20N E OF 115W...AND CONDUCIVE FOR DEEP CONVECTION. ELSEWHERE AT THE LOW LEVELS...1027 MB HIGH PRESSURE IS CENTERED NEAR 35N148W...PRODUCING LIGHT TO MODERATE NE FLOW ACROSS THE AREA W OF ILEANA...WITH FRESH TRADES IN A VERY NARROW ZONE N OF THE ITCZ W OF 136W. MONSOONAL SW TO W FLOW IS WELL ESTABLISHED ACROSS THE REGION...WITH A 180 NM WIDE ZONE OF WINDS AROUND 20 KT LOCATED S OF THE MONSOON TROUGH BETWEEN 118W AND 102W. THIS IS HELPING TO MAINTAIN SEAS 8 TO 10 FT ACROSS THIS AREA. LONG PERIOD S CROSS EQUATORIAL SOUTHERLY SWELLS CONTINUE TO SPREAD N AND NE ACROSS THE ENTIRE BASIN TODAY AND ARE PRODUCING COMBINED SEAS 8 FT AND GREATER ACROSS ALL BUT NW PORTIONS OF THE AREA. THESE SWELLS HAVE PEAKED IN THE PAST 12-18 HOURS...AND AREA STILL PRODUCING LARGE SURF AND VERY STRONG AND DANGEROUS RIP CURRENTS ALONG MOST OF THE PACIFIC COASTLINES AND REEFS. $$ STRIPLING