000 WTPZ44 KNHC 241447 TCDEP4 TROPICAL STORM IVO DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092013 800 AM PDT SAT AUG 24 2013 EVEN WITH THE HELP OF MICROWAVE DATA...THE CENTER OF IVO HAS BEEN DIFFICULT TO LOCATE THIS MORNING. OSCAT SCATTEROMETER DATA DURING THE NIGHT INDICATED THAT THE CENTER WAS ELONGATED FROM NORTH TO SOUTH...AND A RECENT SSM/I OVERPASS SUGGESTED THAT MULTIPLE LOW-LEVEL VORTICITY CENTERS WERE PRESENT. FIRST LIGHT VISIBLE IMAGERY SUPPORTS A CENTER WEST OF THE PREVIOUS ADVISORY...NEAR THE NORTHERNMOST OF THE TWO MAIN CONVECTIVE MASSES. THERE IS NO CHANGE TO ANY OF THE INTENSITY ESTIMATES...SO THE INITIAL INTENSITY REMAINS 40 KT. THE INITIAL MOTION IS AN UNCERTAIN 340/10. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY DESPITE THE UNCERTAINTIES IN THE CENTER POSITION AND INITIAL MOTION. IVO SHOULD CONTINUE TO MOVE GENERALLY NORTH-NORTHWESTWARD ON THE WEST SIDE OF A SUBTROPICAL RIDGE LOCATED OVER MEXICO FOR THE NEXT DAY OR SO. AFTER THAT...THE DYNAMICAL MODELS ARE NOW IN MUCH BETTER AGREEMENT THAT THE CYCLONE WILL SHEAR APART IN 24-48 HR...WITH THE MID/UPPER-LEVEL PORTION CONTINUING NORTHWARD AND THE LOW-LEVEL CENTER STALLING WEST OF THE BAJA CALIFORNIA PENINSULA. THE NEW FORECAST TRACK FOLLOWS THIS SCENARIO...AND IT IS SHIFTED A LITTLE TO THE WEST OF THE PREVIOUS TRACK BASED ON THE INITIAL POSITION. IVO SHOULD START WEAKENING WITHIN 12-24 HOURS AS IT MOVES OVER THE COLDER WATER WEST OF THE BAJA CALIFORNIA PENINSULA. THE CYCLONE IS EXPECTED TO DEGENERATE INTO A REMNANT LOW BY 36 HR AND DISSIPATE COMPLETELY BY 96 HR. RAIN ASSOCIATED WITH IVO IS SPREADING OVER THE SOUTHERN AND CENTRAL BAJA CALIFORNIA PENINSULA. MOISTURE FROM THE CYCLONE IS EXPECTED TO SPREAD NORTHWARD ACROSS THE REMAINDER OF THE BAJA CALIFORNIA PENINSULA...NORTHWESTERN MEXICO...AND THE SOUTHWESTERN UNITED STATES...AND CAUSE LOCALLY HEAVY RAINS AND FLASH FLOODING DURING THE NEXT COUPLE OF DAYS. FORECAST POSITIONS AND MAX WINDS INIT 24/1500Z 22.5N 113.4W 40 KT 45 MPH 12H 25/0000Z 23.8N 114.1W 40 KT 45 MPH 24H 25/1200Z 25.4N 115.0W 35 KT 40 MPH 36H 26/0000Z 26.6N 115.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 26/1200Z 27.0N 116.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 27/1200Z 27.5N 116.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 28/1200Z...DISSIPATED $$ FORECASTER BEVEN