000 WTPZ44 KNHC 240231 TCDEP4 TROPICAL STORM IVO DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092013 800 PM PDT FRI AUG 23 2013 THE CLOUD PATTERN HAS NOT BECOME ANY BETTER ORGANIZED DURING THE PAST FEW HOURS...AND IVO STILL CONSISTS OF A LARGE CIRCULATION DEVOID OF AN INNER CORE. IN FACT...THE CENTER OF CIRCULATION OR THE AREA OF MINIMUM PRESSURE HAS BEEN PIVOTING WITHIN A LARGER CYCLONIC GYRE. IN ADDITION...THE AREA OF DEEP CONVECTION IS CURRENTLY DIMINISHING...AND THERE IS LITTLE THUNDERSTORM ACTIVITY NEAR THE ESTIMATED CENTER. ALTHOUGH THE SUBJECTIVE AND OBJECTIVE DVORAK ESTIMATES SUGGEST LOWER WINDS...EARLIER ASCAT DATA AS WELL AS SHIP REPORTS SUGGEST THAT THE MAXIMUM WINDS ARE STILL 40 KNOTS. THESE STRONG WINDS ARE WELL REMOVED FROM THE CENTER. IVO HAS A SMALL OPPORTUNITY TO STRENGTHEN SLIGHTLY BEFORE THE CYCLONE MOVES OVER COOLER WATERS IN ABOUT 24 HOURS OR SOONER. SINCE THE CENTER HAS BEEN REFORMING WITHIN THE LARGE GYRE...THE INITIAL MOTION IS HIGHLY UNCERTAIN. IT APPEARS...HOWEVER...THAT THE CYCLONE IS MOVING NORTHWARD OR 350 DEGREES AT 10 KNOTS...A LITTLE FASTER THAN EARLIER TODAY. IVO CONTINUES TO BE LOCATED ON THE WESTERN EDGE OF A MID-LEVEL RIDGE AND IS HEADING TOWARD A WEAKNESS INDUCED BY AN AMPLIFYING TROUGH TO THE NORTHWEST. THIS PATTERN SHOULD CONTINUE TO STEER IVO NORTH-NORTHWESTWARD UNTIL THE CYCLONE WEAKENS...BECOMES SHALLOW...AND THEN BEGINS TO MEANDER WITHIN THE LOW-LEVEL FLOW IN ABOUT 3 TO 4 DAYS. MOST OF THE TRACK GUIDANCE IS CONSISTENT WITH THE NORTH-NORTHWEST TRACK FOR THE NEXT 24 TO 36 HOURS. AFTER THAT TIME...THE SPREAD IN THE GUIDANCE IS QUITE LARGE WITH SOME MODELS SHOWING A NORTHWARD TRACK AND OTHERS A TURN TO THE SOUTHWEST. THE LATTER SCENARIO...WHICH INCLUDE THE ECMWF...IS PROBABLY THE RESULT OF THE MODELS ASSUMING IVO TO BE A MUCH WEAKER AND SHALLOW CYCLONE. FORECAST POSITIONS AND MAX WINDS INIT 24/0300Z 20.7N 112.0W 40 KT 45 MPH 12H 24/1200Z 22.1N 112.4W 45 KT 50 MPH 24H 25/0000Z 23.8N 113.0W 45 KT 50 MPH 36H 25/1200Z 25.5N 114.0W 40 KT 45 MPH 48H 26/0000Z 26.5N 114.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 27/0000Z 28.0N 116.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 28/0000Z 28.0N 116.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 29/0000Z...DISSIPATED $$ FORECASTER AVILA