ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM IVO DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL EP092013 200 PM PDT FRI AUG 23 2013 SATELLITE IMAGERY AND ASCAT DATA INDICATE THAT THE CENTER OF IVO HAS REFORMED TO THE NORTHEAST DURING THE PAST SEVERAL HOURS. THE ASCAT DATA ALSO SHOW THAT THE MAXIMUM WINDS HAVE INCREASED TO 40 KT...AND THESE WINDS ARE MAINLY IN AN AREA ABOUT 150 N MI FROM THE CENTER OVER THE EASTERN AND SOUTHERN SEMICIRCLES. THE REFORMATION MAKES THE INITIAL MOTION VERY UNCERTAIN...WITH THE BEST ESTIMATE OF 360/5. IVO REMAINS 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 STILL SIGNIFICANT DIVERGENCE IN THE GUIDANCE. THE GFS...HWRF...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 THE BAJA CALIFORNIA PENINSULA. THE NAVGEM SPLITS THE DIFFERENCE BETWEEN THESE EXTREMES...SHOWING A CONTINUED SLOW NORTH-NORTHWESTWARD MOTION. THE TRACK FORECAST STILL FOLLOWS THE ECMWF/UKMET SCENARIO AND CALLS FOR THE LOW-LEVEL REMNANTS OF IVO TO STALL WEST OF BAJA AFTER 48 HR. THE NEW FORECAST TRACK IS SHIFTED TO THE EAST OF THE PREVIOUS TRACK BASED ON THE POSITION OF THE REFORMED CENTER. GRADUAL STRENGTHENING APPEARS LIKELY UNTIL IVO REACHES COLDER SEA SURFACE TEMPERATURES IN 24 HOURS OR SO. AFTER THAT...THE CYCLONE IS EXPECTED TO DEGENERATE TO A REMNANT LOW OVER THE COLD WATERS WEST OF THE BAJA CALIFORNIA PENINSULA. THE NEW INTENSITY FORECAST SHOWS A SLIGHTLY HIGHER PEAK INTENSITY THAN THE PREVIOUS FORECAST...BUT IS OTHERWISE SIMILAR TO IT. THE NEW FORECAST TRACK AND THE LARGE SIZE OF THE WIND FIELD REQUIRE A TROPICAL STORM WARNING AND WATCH FOR PORTIONS OF THE COAST OF THE BAJA CALIFORNIA PENINSULA. 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 23/2100Z 19.5N 111.8W 40 KT 45 MPH 12H 24/0600Z 20.6N 112.0W 40 KT 45 MPH 24H 24/1800Z 22.6N 112.6W 45 KT 50 MPH 36H 25/0600Z 24.4N 113.4W 40 KT 45 MPH 48H 25/1800Z 26.1N 114.1W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 26/1800Z 28.0N 115.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 27/1800Z 28.0N 116.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 28/1800Z...DISSIPATED $$ FORECASTER BEVEN NNNN