WDPN31 PGTW 200900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (NOKAEN) WARNING NR 023// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 17.7N 130.3E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 567 NM EAST-NORTHEAST OF MANILA, PHILIPPINES MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 13 KTS SIGNIFICANT WAVE HEIGHT: 14 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL STORM 01W (NOKAEN) WITH AN ILL-DEFINED CENTER AND HIGHLY ASYMMETRIC WIND FIELD. THE STRONGER WINDS REMAIN CONFINED TO THE WESTERN SEMICIRCLE WHILE MUCH WEAKER WINDS MAKE UP THE EASTERN SEMICIRCLE. DEEP CONVECTION IS CONFINED TO A SMALL POCKET WITHIN THE NORTHEASTERN PERIPHERY COINCIDING WITH AN AREA OF CONVERGENCE ALONG THE STATIONARY BOUNDARY. A PROMINENT FIELD OF STRATOCUMULUS CLOUDS ARE WRAPPING INTO THE SYSTEM FROM THE WEST, INDICATIVE OF VERY DRY MID-LEVEL AIR. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE IRREGULAR LOW-LEVEL CIRCULATION CENTER (LLCC) IN ANIMATED MSI. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED PRIMARILY ON PERSISTENCE FROM THE PARTIAL 200109Z METOP-B ASCAT PASS, WHICH SHOWED A LARGE SWATH OF 35 KNOT WINDS WITHIN THE WESTERN SEMICIRCLE. THE AGENCY DVORAK AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW FURTHER SUPPORT THE INITIAL INTENSITY. AGENCY DVORAK FIXES ARE ANALYZED TO BE UNDERESTIMATING THE CURRENT INTENSITY DUE TO THE WEAK CONVECTIVE STRUCTURE OF THE SYSTEM. ENVIRONMENTAL ANALYSIS INDICATES THAT 01W IS IN AN UNFAVORABLE ENVIRONMENT CHARACTERIZED BY STRONG POLEWARD OUTFLOW GREATLY OFFSET BY MODERATE (15-20 KTS) VERTICAL WIND SHEAR AND SIGNIFICANT DRY AIR ENTRAINMENT. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: A COMBINATION OF A NARROW EXTENSION OF A SUBTROPICAL RIDGE (STR) TO THE WEST AND THE STATIONARY FRONTAL BOUNDARY AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS RJTD: T2.0 - 30 KTS RCTP: T1.5 - 25 KTS KNES: T1.0 - 25 KTS CIMSS SATCON: 37 KTS AT 200442Z CIMSS ADT: 35 KTS AT 200540Z CIMSS AIDT: 33 KTS AT 200540Z CIMSS D-MINT: 25 KTS AT 200442Z CIMSS D-PRINT: 28 KTS AT 200540Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE VWS: 15-20 KTS SST: 27-28 CELSIUS OUTFLOW: STRONG POLEWARD OTHER FACTORS: SIGNIFICANT AMOUNTS OF DRY AIR ENTRAINMENT FROM THE WEST ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: 01W IS FORECAST TO BEGIN A SOUTHEASTWARD TURN OVER THE NEXT 12 HOURS AS THE VORTEX GETS PUSHED EQUATORWARD BY THE FRONTAL BOUNDARY INTERACTING WITH THE STRENGTHENING COLD SURGE. AFTER TAU 12, AS THE COLD SURGE FURTHER STRENGTHENS, THE TRACK IS EXPECTED TO BECOME MORE SOUTHWARD. THE OVERALL ENVIRONMENT WILL REMAIN UNFAVORABLE DUE TO DRY AIR COMPLETELY SMOTHERING THE VORTEX AND SOUTHERLY SHEAR INCREASING. AS THE VORTEX FURTHER INTERACTS WITH THE COLD SURGE AND FRONTAL BOUNDARY, IT IS EXPECTED TO BECOME INCREASINGLY STRETCHED. BY TAU 24, 01W IS FORECAST TO BECOME UNRAVELED AS IT GETS ABSORBED BY THE STRONG NORTHEASTERLY SURFACE FLOW. WINDS OF AROUND 30 KTS, ASSOCIATED WITH THE NORTHEASTERLY SURGE, WILL LIKELY PERSIST AS 01W WASHES OUT, HENCE THE DISSIPATION WITH AN INTENSITY ABOVE WARNING CRITERIA. MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE GENERALLY AGREES ON THE SOUTHEASTWARD TURN, BUT CROSS-TRACK SPREAD IS STILL QUITE HIGH, AT AROUND 180 NM AT TAU 24. THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE AGREES ON AN INTENSITY OF AROUND 30-35 KTS THROUGH TAU 24. THE JTWC INTENSITY FORECAST IS PLACED NEAR THE CONSENSUS WITH MEDIUM CONFIDENCE DUE TO UNCERTAINTIES REGARDING THE INTERACTION WITH THE FRONTAL BOUNDARY. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM// NNNN