WTPA44 PHFO 121442 TCDCP4 TROPICAL STORM NORA DISCUSSION NUMBER 13 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP182015 500 AM HST MON OCT 12 2015 THE LATEST INFRARED SATELLITE IMAGERY CLEARLY SHOWS THE LOW LEVEL CIRCULATION CENTER (LLCC) OF NORA THIS MORNING. ALTHOUGH SOME NEW CONVECTIVE DEVELOPMENT HAS BEEN NOTED OVER THE PAST HOUR OR TWO...THE LLCC REMAINS LARGELY DEVOID OF DEEP CONVECTION. NORA REMAINS UNDER THE INFLUENCE OF STRENGTHENING WIND SHEAR...WITH THE LATEST UW-CIMSS VERTICAL WIND SHEAR ANALYSIS SHOWING 32 KNOTS OF SHEAR FROM 205 DEGREES...AND SHIPS INDICATING 21 KNOTS OF SHEAR FROM 225 DEGREES. THE LATEST FIXES FROM PHFO AND JTWC CAME IN AT 3.5/55 KNOTS...SAB CAME IN AT 3.0/45 KNOTS. THE ADT VALUE WAS 4.0/65 KNOTS...BUT LIKELY CONTINUES TO SUFFER FROM THE ERROR IN CENTER POSITION LAST EVENING...AND AS A RESULT IS OVER ESTIMATING CURRENT INTENSITY. THE INTENSITY FOR THE 15Z ADVISORY PACKAGE WILL BE LOWERED TO 55 KNOTS...BASED ON THE LATEST FIXES PROVIDED BY THE VARIOUS AGENCIES AND ACCOUNTING FOR THE INFLUENCE OF THE INCREASING SOUTH-SOUTHWESTERLY SHEAR. THE INITIAL MOTION BASED ON FIXES FROM THE VARIOUS AGENCIES...MICROWAVE IMAGERY AND SATELLITE INTERPOLATION WILL BE SET AT 285 DEGREES AT 8 KNOTS. NORA IS CURRENTLY BEING STEERED TO THE WEST-NORTHWEST ON THE SOUTHWESTERN PERIPHERY OF A LARGE UPPER LEVEL RIDGE LOCATED NORTHEAST OF THE SYSTEM. THIS MOTION IS EXPECTED TO CONTINUE THROUGH TONIGHT WITH A SHIFT TOWARD A MORE NORTHWARD TRACK TUESDAY THROUGH WEDNESDAY AS AN UPPER LEVEL TROUGH APPROACHES FROM THE WEST AND BEGINS TO INFLUENCE THE SYSTEM. WITH THE APPROACH OF THE UPPER LEVEL TROUGH...SHEAR WILL INCREASE SIGNIFICANTLY OVER NORA...WITH SHIPS GUIDANCE SHOWING 30 TO 35 KNOTS OF WEST-SOUTHWESTERLY VERTICAL WIND SHEAR OVER THE SYSTEM BY TUESDAY NIGHT. THE INCREASING SHEAR WILL LIKELY RESULT IN A LOSS OF ALL DEEP CONVECTION NEAR THE LLCC BY WEDNESDAY NIGHT...ALLOWING THE SYSTEM TO BE STEERED BY THE LOW LEVEL TRADE WIND FLOW AND OFF TO THE WEST. THE LATEST OFFICIAL FORECAST TRACK FROM CPHC HAS BEEN SHIFTED SLIGHTLY SOUTH AND WEST OF THE PREVIOUS OFFICIAL FORECAST...AND IS VERY CLOSE TO THE GFEX AND TVCN GUIDANCE TRACKS. SLOW WEAKENING OF NORA IS EXPECTED DURING THE NEXT SEVERAL DAYS AS VERTICAL WIND SHEAR INCREASES. THE OFFICIAL INTENSITY FORECAST SHOWS GRADUAL WEAKENING THROUGH WEDNESDAY...AS FAVORABLE SEA SURFACE TEMPERATURES (SSTS) AROUND 28 TO 29C ALONG WITH INCREASING UPPER FORCING FROM THE APPROACHING UPPER LEVEL TROUGH MAY ALLOW ENOUGH OF AN INCREASE IN DEEP CONVECTION NEAR THE CENTER TO HOLD THE INTENSITY OF THE SYSTEM UP...SIMILAR TO WHAT HAS OCCURRED WITH OTHER SYSTEMS THIS SEASON IN THE NORTH-CENTRAL PACIFIC. SHEAR SHOULD EVENTUALLY OVER POWER ANY CONTRIBUTION FROM THE FAVORABLE SSTS AND UPPER LEVEL DYNAMIC SUPPORT WEDNESDAY NIGHT...WITH STEADY WEAKENING EXPECTED THROUGH 120 HOURS. BASED ON THE LATEST INTENSITY FORECAST...NORA IS EXPECTED TO DROP BELOW TROPICAL STORM STRENGTH WEDNESDAY NIGHT OR THURSDAY AND BECOME A POST TROPICAL REMNANT LOW BY THURSDAY NIGHT. FORECAST POSITIONS AND MAX WINDS INIT 12/1500Z 12.7N 145.6W 55 KT 65 MPH 12H 13/0000Z 13.0N 146.8W 50 KT 60 MPH 24H 13/1200Z 13.5N 148.1W 45 KT 50 MPH 36H 14/0000Z 14.5N 149.0W 40 KT 45 MPH 48H 14/1200Z 15.5N 149.3W 40 KT 45 MPH 72H 15/1200Z 17.4N 149.3W 35 KT 40 MPH 96H 16/1200Z 18.0N 150.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 17/1200Z 17.5N 151.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ FORECASTER JELSEMA/HOUSTON