000 AXPZ20 KNHC 120249 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC WED OCT 12 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0230 UTC. ...SPECIAL FEATURES... THE CENTER OF CATEGORY TWO HURRICANE JOVA IS ABOUT TO MAKE LANDFALL ON THE COAST OF MEXICO. AT 12/0300 UTC...HURRICANE JOVA IS CENTERED NEAR 19.0N 105.2W MOVING N-NE OR 020 DEG AT 7 KT. ON THE FORECAST TRACK...THE CENTER OF THE HURRICANE WILL CROSS THE COAST WITHIN THE HURRICANE WARNING AREA IN A FEW HOURS...AND MOVE OVER WESTERN MEXICO WEDNESDAY AND WEDNESDAY NIGHT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 973 MB. MAXIMUM SUSTAINED WIND SPEED IS 85 KT WITH GUSTS TO 105 KT. LITTLE CHANGE IN STRENGTH IS LIKELY PRIOR TO LANDFALL...AND STEADY WEAKENING IS EXPECTED AFTER THE CENTER CROSSES THE COAST. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP5/WTPZ25 KNHC FOR MORE DETAILS. VERY HAZARDOUS CONDITIONS IN THE FORM OF VERY HEAVY RAINFALL IN AMOUNTS OF 6-12 INCHES OVER THE STATES OF MICHOACAN...COLIMA...JALISCO...AND NAYARIT...WITH POSSIBLE ISOLATED MAXIMUM AMOUNTS OF 20 INCHES WILL RESULT IN FLASH FLOODING AND LIFE-THREATENING MUDSLIDES. LARGE AND DANGEROUS SWELLS WILL CONTINUE TO PROPAGATE TO THE W CENTRAL MEXICO COASTLINE RESULTING IN LIFE-THREATENING RIP CURRENTS. ALSO...DANGEROUS STORM SURGE IS EXPECTED TO PRODUCE SIGNIFICANT COASTAL FLOODING NEAR AND TO THE E OF WHERE THE CENTER MAKES LANDFALL. NUMEROUS MODERATE TO STRONG CONVECTION IS WITHIN 45 NM N AND 120 NM S SEMICIRCLES OF JOVA. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS ELSEWHERE FROM 16N TO 20N BETWEEN 102W AND 108W. PART OF THIS CONVECTION IS ALREADY AFFECTING SW MEXICO. AT 12/0300 UTC...TROPICAL STORM IRWIN IS CENTERED NEAR 14.7N 113.2W MOVING E OR 065 DEG AT 10 KT. A TURN TOWARD THE EAST-NORTHEAST WITH SOME INCREASE IN FORWARD SPEED IS EXPECTED ON WEDNESDAY...FOLLOWED BY A TURN BACK TOWARD THE EAST ON THURSDAY. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. LITTLE CHANGE IN STRENGTH IS FORECAST DURING THE NEXT 48 HOURS. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP1/WTPZ21 KNHC FOR MORE DETAILS. AN AREA OF NUMEROUS MODERATE TO STRONG CONVECTION IS NOTED BETWEEN 50 AND 150 NM N OF IRWIN. A BAND OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS WITHIN 90 NM EITHER SIDE OF LINE 17N112W TO 15N115W TO 11N115W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH AXIS IS OVER NORTHERN CENTRAL AMERICA ENTERING THE PACIFIC WATERS NEAR 15N92W TO LOW PRES NEAR 13N94W...THEN RESUMES W OF IRWIN FROM 12N117W TO 08N130W TO 10N140W. ALL SIGNIFICANT AREAS OF DEEP CONVECTION ARE ASSOCIATED WITH THE TROPICAL CYCLONES AND LOW PRES AT 13N94W. ...DISCUSSION... THE EASTERN PACIFIC IS VERY ACTIVE TONIGHT WITH TWO TROPICAL CYCLONES...T.S. IRWIN AND HURRICANE JOVA...AND A LOW PRES SYSTEM NEAR THE GULF OF TEHUANTEPEC. SOUTH OF THESE SYSTEMS...A LARGE AREA OF FRESH SW FLOW CAN BE FOUND. ...E OF 125W... A DEEP LAYER TROUGH PROGRESSING SOUTHEASTWARD EXTENDS FROM THE SOUTHWESTERN U.S. SW CROSSING BAJA CALIFORNIA SUR TO NEAR 20N120W. A BROAD UPPER RIDGE IS BUILDING SOUTHEASTWARD TOWARDS THE WESTERN U.S. IN THE WAKE OF THE TROUGH. AN ANTICYCLONIC CIRCULATION IS CENTERED OVER SE MEXICO NEAR 18N91W. HURRICANE JOVA IS MOVING AROUND THE WESTERN PERIPHERY OF THIS SYSTEM. THE COMBINATION OF THIS ANTICYCLONE AND THE PRESENCE OF THE DEEP LAYER TROUGH OVER BAJA CALIFORNIA SHOULD CAUSE THE HURRICANE TO TURN NORTHWARD DURING THE NEXT 12-24 HOURS...WITH THE CENTER CROSSING THE COAST OF MEXICO LATE TONIGHT. AN ELONGATED AREA OF LOW PRESSURE LOCATED NEAR 13N97W IS PRODUCING DISORGANIZED SHOWERS AND THUNDERSTORMS. SIGNIFICANT DEVELOPMENT OF THIS DISTURBANCE IS NOT LIKELY DUE TO STRONG UPPER-LEVEL WINDS...AND THIS SYSTEM HAS A LOW CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. THIS LOW IS DRIFTING NORTHWARD AND THE ASSOCIATED HEAVY RAINS ARE EXPECTED TO SPREAD OVER PORTIONS OF SOUTHEASTERN MEXICO AND GUATEMALA DURING THE NEXT DAY OR TWO...WHICH MAY CAUSE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES. IN FACT...NUMEROUS MODERATE TO ISOLATED STRONG CONVECTION IS NOTED OVER PARTS OF NORTHERN CENTRAL AMERICA DUE TO THE NWD MOVEMENT OF THE MONSOON TROUGH. NUMEROUS MODERATE TO STRONG CONVECTION IS WITHIN 90 NM NE AND 60 NM SW SEMICIRCLES OF LOW PRES. THE PRES GRADIENT BETWEEN A RIDGE THAT DOMINATES THE N WATERS AND LOWER PRES OVER NW MEXICO IS GENERATING A SMALL AREA OF FRESH N WINDS OVER N CENTRAL FORECAST WATERS N OF 23N BETWEEN 118W-128W WHERE N-NE 20 KT AND SEAS OF 8-10 FT IN MIXED NW-N SWELL ARE EVIDENT. AS THE GRADIENT SLACKENS OVER THE NEXT 48 HRS...THIS AREA OF NLY WINDS WILL DIMINISH TO N OF 28N BETWEEN 123W-130W IN 48 HRS...HOWEVER SEAS WILL REMAIN ON THE HIGH SIDE...UP TO 12 FT...IN A MIXED NW-N SWELL. AS HURRICANE JOVA APPROACHES THE COAST TONIGHT INTO EARLY WED...EXPECT THE PRES GRADIENT TO ALSO TIGHTEN OVER THE GULF OF CALIFORNIA WHERE JUST RECENTLY NW 20 KT HAVE BEGUN. THESE WINDS ARE FORECAST TO INCREASE TO 20-25 KT BY WED EVENING...BEFORE DROPPING OFF TO LESS THAN 20 KT BY THU MORNING. FRESH SOUTHWESTERLY MONSOON FLOW DOMINATES THE AREA S OF THE TROPICAL CYCLONES AND LOW PRES NOTED ABOVE. THE PRES GRADIENT IS STRONGEST BETWEEN HIGH PRES OVER THE EASTERN SOUTH PACIFIC AND THE AFOREMENTIONED LOW PRES SYSTEM NEAR 13N94W. SEVERAL PASSES OF SCATTEROMETER DATA CONFIRMED THE PRESENCE OF THESE FRESH WINDS. THESE SW WINDS ARE FORECAST TO MERGE WITH THE LOW PRES SYSTEM AS PRESSURES FALL ALONG THE MONSOON TROUGH AND AROUND THIS LOW. THE 8-12 FT SEAS WILL THAN BUILD UP TO 14 FT IN 24 HRS...AND CONTINUE INTO 48 HRS AS A NEW BATCH OF SW SWELL MOVES INTO SOUTHERN PORTION S OF THE MONSOON TROUGH. SEAS CONTINUE TO REMAIN CHAOTIC OVER CENTRAL WATERS WHERE NW SWELL FROM THE FRONTAL SYSTEMS TO THE N...CROSS-EQUATORIAL SW SWELL...AND NE SWELL LINGERING FROM THE DIMINISHED TRADE WINDS ARE MERGING IN THE VICINITY OF HURRICANE JOVA AND TROPICAL STORM IRWIN. A NEW PULSE OF NW SWELL IS CURRENTLY PROPAGATING THROUGH THE AREA N OF 20N AND WILL HELP KEEP SEAS TO 9 FT OVER N CENTRAL WATERS WHERE THE AFOREMENTIONED FRESH N WINDS ARE IN PLACE. ...W OF 125W... MID/UPPER RIDGING MOSTLY PERSISTS OVER THIS PART OF THE AREA. AN UPPER LEVEL TROUGH W OF AREA IS PRODUCING STRONG S TO SW FLOW OVER THE FAR NW PORTION OF THE AREA...PARTICULARLY N OF 15N W OF 136W. SATELLITE WATER VAPOR IMAGERY SHOWS MODERATE SUBSIDENCE HERE...EXCEPT W OF 136W WHERE UPPER LEVEL MOISTURE IN THE FORM OF BROKEN CIRRUS CLOUDS STREAMING NORTHEASTWARD IS NOTED. AT THE SURFACE...A 1022 MB HIGH IS CENTERED NEAR 30N140W WITH A RIDGE E TO 120W. THE PRES GRADIENT BETWEEN THE RIDGE AND LOWER PRES TO THE S IS RESULTING IN NE-E WINDS OF 15-20 KT FROM ABOUT 19N-24N. THE GRADIENT IS EXPECTED TO DIMINISH IN ABOUT 12-18 HRS AS THE HIGH SHIFTS W AND WEAKENS. $$ GR/JA