WDPN31 PGTW 032100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 27W (NYATOH) WARNING NR 018// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 26.1N 145.1E INITIAL INTENSITY: 75 KTS GEOGRAPHIC REFERENCE: 220 NM EAST-NORTHEAST OF IWO TO MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 34 KTS SIGNIFICANT WAVE HEIGHT: 32 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A RAPIDLY DECAYING SYSTEM WITH THE ASSOCIATED DEEP CONVECTION DISSIPATING OVER THE PAST SIX HOURS. ANALYSIS OF BOTH 37GHZ AND 89GHZ OF THE 031607Z AMSR2 PASS REVEALS THAT THE SYSTEM HAS BEEN DECOUPLED. ENVIRONMENTAL ANALYSIS INDICATES TY 27W IS IN SOMEWHAT HOSTILE CONDITIONS WITH FAVORABLE POLEWARD UPPER LEVEL OUTFLOW, OFFSET BY UNFAVORABLE (35-40 KTS) VWS AND BOARDER LINE SEA SURFACE TEMPERATURES (26-27 C). THE INITIAL POSITION AND INTENSITY ARE SET WITH MEDIUM CONFIDENCE BASED ON EXTRAPOLATION OF THE AFOREMENTIONED AMSR2 PASS AND MULTIPLE AGENCY POSITION AND DVORAK FIXES. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: DEEP-LAYARD SUBTROPICAL RIDGE POSITIONED TO THE EAST-SOUTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T5.0 - 90 KTS RJTD: T5.5 - 102 KTS CIMSS SATCON: 73 KTS AT 031639Z CIMSS ADT: 115 KTS AT 031430Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE VWS: 30+ KTS SST: 26-27 CELSIUS OUTFLOW: STRONG POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TY 27W WILL CONTINUE TO TRACK NORTHEASTWARD WHILE DISSIPATING AT AN ACCELERATED RATE. IN ADDITION TO THE UNFAVORABLE VERTICAL WIND SHEAR, TY NYATOH WILL CROSS INTO RELATIVELY COOLER WATERS (25 C) BY TAU 12. IN ADDITION AT TAU 12, DRY AIR LOCATED TO THE WEST WILL BEGIN TO BE INTRODUCED INTO THE LLCC, FURTHER CONTRIBUTING TO ITS DECAY. BETWEEN TAUS 24 AND 36, TY 27W IS FORECAST TO BECOME ABSORBED INTO THE FRONTAL BOUNDARY TO THE NORTHEAST. FULL DISSIPATION WILL OCCUR ON OR BEFORE TAU 48. MODEL DISCUSSION: THE JTWC TRACK IS PLACED WITH LOW CONFIDENCE DUE TO ALONG TRACK SPREAD AMONG THE MODEL CONSENSUS (CONW) MEMBERS. UK AND AFUM MEMBERS INDICATE THE STORM WILL SPEED UP SIGNIFICANTLY IN THE LATER TAUS, WHILE THE OTHER MEMBERS SHOW A MORE GRADUAL MOVEMENT. THIS IS MORE THAN LIKELY DUE TO DIFFICULT PLACEMENT OF THE VORTEX DURING RAPID DISSIPATION. THE JTWC INTENSITY FORECAST IS SET WITH LOW CONFIDENCE, HEDGED SLIGHTLY LOWER AND MODEL CONSENSUS. FORECAST CONFIDENCE: TRACK 0 - 72 HR: LOW INTENSITY 0 - 72 HR: LOW// NNNN