000 WTPZ44 KNHC 231437 TCDEP4 TROPICAL STORM IVO DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092013 800 AM PDT FRI AUG 23 2013 CONVECTION HAS INCREASED NEAR THE CENTER OF THE CYCLONE DURING THE PAST SEVERAL HOURS...WITH FIRST-LIGHT VISIBLE IMAGERY SHOWING THE CENTER NOW EMBEDDED IN THE CONVECTIVE OVERCAST. ASCAT DATA LAST NIGHT SHOWED SOME 35 KT VECTORS WELL TO THE EAST OF THE CENTER. BASED ON THESE DATA AND THE INCREASED ORGANIZATION...THE INITIAL INTENSITY IS INCREASED TO 35 KT. THE SCATTEROMETER DATA SHOWED THAT IVO HAS SOME CHARACTERISTICS OF MONSOON CYCLONES OF THE EASTERN HEMISPHERE...INCLUDING A VERY LARGE AREA OF 20-30 KT WINDS TO THE SOUTH AND EAST OF THE CENTER. IT SHOULD ALSO BE NOTED THAT THE CIRCULATION IS ELONGATED...WITH A TROUGH EXTENDING NORTHEASTWARD FROM THE CENTER TO JUST NORTH OF SOCORRO ISLAND. MICROWAVE IMAGERY SUGGESTS THE CENTER IS A LITTLE TO THE EAST OF THE PREVIOUS ADVISORY POSITION...AND THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 360/4. IVO IS ON THE WESTERN SIDE OF A LOW/MID-LEVEL RIDGE OVER MEXICO...AND IT IS EXPECTED TO MOVE TOWARD AN AREA OF SOUTHERLY STEERING FLOW BETWEEN A DEEP-LAYER RIDGE OVER THE CENTRAL UNITED STATES AND A DEEP-LAYER TROUGH WEST OF CALIFORNIA. THIS COMBINATION SHOULD CAUSE THE CYCLONE TO MOVE GENERALLY NORTH- NORTHWESTWARD FOR THE NEXT 48 HOURS. AFTER THAT... THERE IS SIGNIFICANT DIVERGENCE IN THE GUIDANCE. THE GFS...HWRF...NAVGEM... AND CANADIAN MODELS FORECAST IVO TO MOVE NORTHWARD ACROSS NORTHERN BAJA CALIFORNIA INTO THE SOUTHWESTERN UNITED STATES. ON THE OTHER HAND...THE UKMET AND ECMWF MODELS FORECAST THE SYSTEM TO SHEAR APART...WITH THE LOW-LEVEL CENTER STALLING OVER THE PACIFIC WEST OF BAJA CALIFORNIA. THE TRACK FORECAST FOLLOWS THE LATTER SCENARIO AND CALLS FOR A SLOW NORTH-NORTHWESTWARD MOTION AFTER 48 HR. THE NEW FORECAST TRACK IS SHIFTED TO THE EAST OF THE PREVIOUS TRACK BASED ON THE CURRENT POSITION AND MOTION. GRADUAL STRENGTHENING APPEARS LIKELY UNTIL IVO REACHES COLDER SEA SURFACE TEMPERATURES IN ABOUT 36 HOURS. AFTER THAT...THE CYCLONE IS EXPECTED TO DEGENERATE TO A REMNANT LOW OVER THE COLD WATERS WEST OF BAJA CALIFORNIA. THE NEW INTENSITY FORECAST IS UNCHANGED FROM THE PREVIOUS FORECAST. MOISTURE ASSOCIATED WITH IVO IS EXPECTED TO SURGE NORTHWARD OVER THE BAJA CALIFORNIA PENINSULA...NORTHWESTERN MEXICO AND THE SOUTHWESTERN UNITED STATES DURING THE NEXT FEW DAYS...INCREASING THE POSSIBILITY OF HEAVY RAINS AND FLASH FLOODING. FORECAST POSITIONS AND MAX WINDS INIT 23/1500Z 18.7N 112.4W 35 KT 40 MPH 12H 24/0000Z 19.8N 112.6W 35 KT 40 MPH 24H 24/1200Z 21.5N 113.0W 40 KT 45 MPH 36H 25/0000Z 23.3N 113.6W 40 KT 45 MPH 48H 25/1200Z 25.1N 114.4W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 26/1200Z 27.0N 115.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 27/1200Z 28.0N 116.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 28/1200Z...DISSIPATED $$ FORECASTER BEVEN