000 AXPZ20 KNHC 290302 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC SAT SEP 29 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0200 UTC. ...SPECIAL FEATURE... TROPICAL DEPRESSION NORMAN NEAR 25.2N 109.0W 1003 MB AT 0300 UTC SEP 29 MOVING NNW OR 345 DEG AT 9 KT. MAXIMUM SUSTAINED WINDS HAVE WEAKENED TO 30 KT GUSTS 40 KT WITH MINIMUM PRESSURE 1003 MB. THE SAME MIDDLE TO UPPER LEVEL TROUGH RESPONSIBLE FOR THE DEMISE OF MIRIAM A FEW DAYS AGO HAS CONTINUED TO MOVE E...AND WAS ENTERING NW MEXICO THIS EVENING...AND PRODUCING 2O KT OF WLY WIND SHEAR ACROSS NORMAN PER THE MOST RECENT UW-CIMSS ANALYSIS. SCATTERED MODERATE CONVECTION WAS OCCURRING WITHIN 60 NM ACROSS THE SW SEMICIRCLE OF NORMAN...WHILE THE SHEAR HAS DISPLACED SCATTERED MODERATE TO STRONG CONVECTION WITHIN 120 NM ACROSS THE E SEMICIRCLE. NORMAN IS EXPECTED TO CONTINUE TO MOVE NORTHWARD TONIGHT AND ASHORE ALONG THE W COAST OF MEXICO ALONG N PORTIONS OF THE STATE OF SINALOA AFTER MIDNIGHT. 20 TO 30 KT WINDS AND SEAS 8 TO 12 FT WILL CONTINUE ACROSS THE ENTRANCE INTO THE GULF OF CALIFORNIA S OF NORMAN AND E OF 109W UNTIL LANDFALL...THEN QUICKLY FADE THROUGH SAT MORNING. OTHERWISE... THE MAIN THREAT FROM NORMAN IS CONTINUED HEAVY RAINFALL WELL E AND SE OF NORMAN...ALONG THE W SLOPES AND COASTAL PLAINS OF THE SIERRA MADRE OCCIDENTALES. HEAVY RAINS FROM JALISCO TO SINALOA COULD LEAD TO FLASH FLOODING AND MUDSLIDES. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... MONSOON TROUGH FROM 09N76W TO 10N96W TO 13N102W WHERE IT REMAINS FRACTURED...THEN RESUMES FROM NEAR 18N108W TO 10N130W TO 09N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED WITHIN 120 NM N AND 180 NM S OF TROUGH E OF 102W. SCATTERED MODERATE CONVECTION ASSOCIATED WITH MOIST FLOW SE OF NORMAN NOTED FROM 15N TO 26N BETWEEN 103W AND 107W. CLUSTERS OF SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 90 NM S OF TROUGH BETWEEN 121W AND 131W. ...DISCUSSION... POST-TROPICAL REMNANT LOW MIRIAM CONTINUES TO LINGER NEAR 21N 115.5W AND IS WINDING DOWN SLOWLY OVER COOL WATERS. HOWEVER... THE REMNANTS OF MIRIAM RETAIN CONSIDERABLE SIZE...SOME 400 NM WIDE...WHICH IS HELPING TO STEER MOIST SW MONSOON WINDS FROM THE DEEP TROPICS...NE AND N TOWARD NORMAN AND INTO WESTERN MEXICO...WHERE HEAVY RAIN POTENTIAL WILL CONTINUE OVERNIGHT. FRESH WINDS TO 25 KT ON THE S SIDE OF THIS LOW ARE MIXING WITH SW SWELL TO MAINTAIN SEAS 8 TO 10 FT WITHIN 180 NM OF THE CENTER. THE LOW WILL DRIFT SLOWLY SOUTHWARD THROUGH SUN AND EVENTUALLY DEGENERATE INTO AN OPEN TROUGH BY TUE. A WEAKENING COLD FRONT EXTENDING FROM 40N134W TO 33N150W BISECTS THE SUBTROPICAL HIGH NW OF THE AREA INTO TWO HIGH PRES CELLS... CENTERED NEAR 38N150W AND 31N150W. NW SWELL ASSOCIATED WITH THE WEAK FRONT WILL SWEEP INTO THE NW PORTION OF THE DISCUSSION AREA LATE TONIGHT...BUILDING SEAS TO 10 FT NW OF A LINE FROM 30N127W TO 22N140W BY SAT EVENING. THE SUBTROPICAL HIGH WILL STRENGTHEN SAT AND SHIFT WELL N OF THE AREA...TO W OF OREGON NEAR 43N133W ON SUN. THIS WEAK RIDGE PATTERN WILL SUPPORT MODERATE N-NE TRADE WINDS OVER MOST OF THE REGION N OF 16N W OF 120W THROUGH THE WEEKEND. WITH NORMAN LIFTING QUICKLY N INTO THE GULF OF CALIFORNIA... FRESH SWLY WINDS OCCURRING ALONG AND S OF THE MONSOON TROUGH HAVE BEGUN...AND WERE CONFINED TO BETWEEN 112W AND 121W EARLY THIS EVENING. GFS MODEL GUIDANCE SHOWS THE SW WINDS ASSOCIATED WITH THE MONSOON TROUGH GRADUALLY DIMINISHING BELOW 20 KT TONIGHT THROUGH SAT NIGHT. EXPECT THE TROUGH TO REMAIN CONVECTIVELY ACTIVE FOR THE NEXT COUPLE OF DAYS PARTICULARLY BETWEEN 115W AND 135W WITH MULTIPLE WEAK VORTICES EMBEDDED WITHIN THE CONVERGENCE ZONE. HIGH SEAS 8-10 FT GENERATED BY FRESH SW WINDS BETWEEN 105W-125W WILL SUBSIDE BELOW 8 FT BY SAT AFTERNOON. $$ STRIPLING