WDPN31 PGTW 191500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (SAUDEL) WARNING NR 005// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 9.4N 153.7E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 156 NM NORTHEAST OF CHUUK MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 15 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL STORM 17W (SAUDEL) WITH A MUCH MORE DISORGANIZED APPEARANCE COMPARED TO 6 HOURS AGO. THE DEEP CONVECTION THAT WAS PREVIOUSLY NEAR THE CENTER HAS DISSIPATED AND NOW CONVECTIVE ACTIVITY IS CONFINED TO THE FAR SOUTHWESTERN PERIPHERY. THE LOW-LEVEL CIRCULATION CENTER (LLCC) ALSO APPEARS TO BE HIGHLY ELONGATED NOW, WITH POTENTIALLY MULTIPLE AREAS OF ENHANCED VORTICITY WITHIN THE LARGER-SCALE CIRCULATION. A 190757Z RCM-2 SAR PASS REVEALED A RATHER COMPACT CORE WITH WINDS AS HIGH AS 50 KTS WITHIN A SMALL POCKET IN THE SOUTHERN SEMICIRCLE. HOWEVER, THAT COMPACT SURFACE CIRCULATION MUST HAVE QUICKLY WASHED OUT AFTERWARD, BECAUSE THE EXPOSED LOW-LEVEL CLOUDS IN ANIMATED EIR AT AROUND 191200 LOOK QUITE LOOSE WITH NO CLEARLY IDENTIFIABLE CENTER. THEREFORE THE INITIAL POSITION IS PLACED WITH VERY LOW CONFIDENCE. THE INITIAL INTENSITY OF 35 KTS IS ALSO ASSESSED WITH LOW CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND CIMSS INTENSITY ESTIMATES BELOW. DESPITE THE STALL IN DEVELOPMENT, THE CURRENT ENVIRONMENT IS ANALYZED TO BE FAVORABLE FOR FURTHER DEVELOPMENT DUE TO STRONG EQUATORWARD OUTFLOW ALOFT, LOW (10-15 KTS) VERTICAL WIND SHEAR, AND WARM (29-30 C) SEA SURFACE TEMPERATURES. INITIAL WIND RADII BASIS: PERSISTENCE FROM 190757Z RCM-2 SAR DATA CURRENT STEERING MECHANISM: WEAK STEERING PATTERN WITH A COMBINED INFLUENCE OF THE SOUTHWESTERN EXTENT OF A SUBTROPICAL RIDGE (STR) POSITIONED FAR TO THE NORTHEAST AND A NEAR EQUATORIAL RIDGE (NER) TO THE SOUTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.5 - 35 KTS RCTP: T2.0 - 30 KTS KNES: T2.5 - 35 KTS CIMSS ADT: 43 KTS AT 191140Z CIMSS AIDT: 37 KTS AT 191140Z CIMSS D-MINT: 34 KTS AT 190958Z CIMSS D-PRINT: 33 KTS AT 191140Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG EQUATORWARD OTHER FACTORS: SLIGHT DRY AIR ENTRAINMENT FROM THE NORTH ANALYSIS CONFIDENCE: INITIAL POSITION: LOW INITIAL INTENSITY: LOW INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS 17W (SAUDEL) IS FORECAST TO TRACK NORTH-NORTHWESTWARD AS THE SUBTROPICAL RIDGE (STR) POSITIONED SOUTH OF HONSHU WEAKENS AND RETREATS NORTHWARD, LETTING 17W CONTINUE GAINING LATITUDE. THE STR THAT IS CURRENTLY TO THE NORTHEAST OF 17W IS EXPECTED TO BUILD AND PROPAGATE WESTWARD, BECOMING THE PRIMARY STEERING MECHANISM THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD. THE CPA TO SAIPAN HAS SLIGHTLY INCREASED COMPARED TO THE PREVIOUS FORECAST AND THE TIME OF CPA IS ABOUT 6 HOURS SOONER (NOW 212200Z). HOWEVER, THE UNCERTAINTY IN THE INITIAL POSITION MAY CAUSE THERE TO BE A SHIFT IN THE TRAJECTORY RELATIVE TO THE NORTHERN MARIANA ISLANDS. THE TRACK IS FORECAST TO BECOME MORE WEST-NORTHWESTWARD AFTER TAU 72 AS RIDGING EXTENDS TO THE NORTH OF 17W. THE ENVIRONMENT IS FORECAST TO IMPROVE OVER THE NEXT 12 HOURS AS THE DRY AIR ENTRAINMENT FROM THE NORTH LESSENS, ALLOWING FOR THE CORE OF THE VORTEX TO MOISTEN. THE TIMING OF THE AXISYMMETRIZATION OF THE WIND FIELD IS CURRENTLY THE LARGEST LIMITING FACTOR FOR INTENSIFICATION IN THE NEAR TERM. ONCE THE SYMMETRIZATION COMPLETES, 17W IS FORECAST TO STEADILY INTENSIFY THROUGH TAU 36 TO AROUND 65 KTS. AFTER TAU 36, 17W IS FORECAST TO RAPIDLY INTENSIFY THROUGH TAU 72 AS THE SYSTEM TAKES ADVANTAGE OF STRONG DUAL CHANNEL OUTFLOW, VERY WARM (OVER 30 C) SEA SURFACE TEMPERATURES, AND HIGH OCEAN HEAT CONTENT (OHC) VALUES EAST OF THE MARIANAS. 17W IS THEN FORECAST TO FURTHER INTENSIFY TO A PEAK OF AROUND 125 KTS AT TAU 96 BEFORE SLIGHTLY WEAKENING THROUGH TAU 120 AS THE SYSTEM BEGINS TO ENTER AN AREA OF INCREASED NORTHERLY SHEAR AND LOWER OHC. MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72 WITH NO NOTABLE OUTLIERS PRESENT. THE CROSS-TRACK SPREAD AT TAU 72 IS MEASURED TO BE ABOUT 100 NM. AFTER TAU 72, MODELS BEGIN TO FAN OUT CONSIDERABLY. GFS AND NAVGEM MAKE UP THE NORTHERNMOST MEMBERS WHILE THE ECMWF AND THE ECMWF ENSEMBLE MEAN MAKE UP THE SOUTHERNMOST. AS A RESULT, CROSS-TRACK SPREAD AT TAU 120 INCREASES TO 330 NM. THE JTWC TRACK FORECAST IS PLACED NEAR THE MULTI-MODEL CONSENSUS THROUGH TAU 72 AND THEN CLOSER TO THE ECMWF AND EXPERIMENTAL GOOGLE DEEPMIND ENSEMBLE MEANS THROUGH TAU 120. INTENSITY GUIDANCE CONTINUES TO BE IN RATHER POOR AGREEMENT. COAMPS-TC AND ITS CORRESPONDING RAPID INTENSIFICATION (RI) AID (CTR-1) CONTINUE TO SHOW A MUCH MORE RAPID RATE OF INTENSIFICATION THROUGH THE FIRST 36-48 HOURS. ADDITIONALLY, GFS NOW SHOWS RAPID DEVELOPMENT THROUGH TAU 36, SUGGESTING AN INTENSITY OF OVER 85 KTS AT THAT TIME. CONSIDERING THE CURRENT DISORGANIZED NATURE OF THE SYSTEM, THE JTWC INTENSITY FORECAST FOLLOWS THE HAFS-A AND HWRF DEPICTION THROUGH TAU 72 WITH MEDIUM CONFIDENCE. AFTER TAU 72, THERE IS EXTREME DISAGREEMENT IN INTENSITIES BETWEEN MODELS. ON ONE HAND, HAFS-A AND HWRF WEAKEN THE SYSTEM EXTREMELY QUICKLY, ON THE OTHER HAND, COAMPS-TC AND THE GOOGLE DEEPMIND SHOW ONLY A GRADUAL DECLINE THROUGH TAU 120. THE JTWC INTENSITY FORECAST IS SITUATED CLOSER TO THE LATTER GROUPING THROUGH TAU 120 WITH LOW CONFIDENCE. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN WDPN31 PGTW 191500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (SAUDEL) WARNING NR 005// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 9.4N 153.7E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 156 NM NORTHEAST OF CHUUK MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 15 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL STORM 17W (SAUDEL) WITH A MUCH MORE DISORGANIZED APPEARANCE COMPARED TO 6 HOURS AGO. THE DEEP CONVECTION THAT WAS PREVIOUSLY NEAR THE CENTER HAS DISSIPATED, AND ONVECTIVE ACTIVITY IS CONFINED TO THE FAR SOUTHWESTERN PERIPHERY. THE LOW-LEVEL CIRCULATION CENTER (LLCC) ALSO APPEARS TO BE HIGHLY ELONGATED NOW, WITH POTENTIALLY MULTIPLE AREAS OF ENHANCED VORTICITY WITHIN THE LARGER-SCALE CIRCULATION. A 190757Z RCM- 2 SAR PASS REVEALED A RATHER COMPACT CORE WITH WINDS AS HIGH AS 50 KTS WITHIN A SMALL POCKET IN THE SOUTHERN SEMICIRCLE. HOWEVER, THAT COMPACT SURFACE CIRCULATION MUST HAVE QUICKLY WASHED OUT AFTERWARD BECAUSE THE EXPOSED LOW-LEVEL CLOUDS IN ANIMATED EIR AT AROUND 191200Z LOOK QUITE LOOSE WITH NO CLEARLY IDENTIFIABLE CENTER. THEREFORE THE INITIAL POSITION IS PLACED WITH VERY LOW CONFIDENCE. THE INITIAL INTENSITY OF 35 KTS IS ALSO ASSESSED WITH LOW CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND CIMSS INTENSITY ESTIMATES BELOW. DESPITE THE STALL IN DEVELOPMENT, THE CURRENT ENVIRONMENT IS ANALYZED TO BE FAVORABLE FOR FURTHER DEVELOPMENT DUE TO STRONG EQUATORWARD OUTFLOW ALOFT, LOW (10-15 KTS) VERTICAL WIND SHEAR, AND WARM (29-30 C) SEA SURFACE TEMPERATURES. INITIAL WIND RADII BASIS: PERSISTENCE FROM 190757Z RCM-2 SAR DATA CURRENT STEERING MECHANISM: WEAK STEERING PATTERN WITH A COMBINED INFLUENCE OF THE SOUTHWESTERN EXTENT OF A SUBTROPICAL RIDGE (STR) POSITIONED FAR TO THE NORTHEAST AND A NEAR EQUATORIAL RIDGE (NER) TO THE SOUTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.5 - 35 KTS RCTP: T2.0 - 30 KTS KNES: T2.5 - 35 KTS CIMSS ADT: 43 KTS AT 191140Z CIMSS AIDT: 37 KTS AT 191140Z CIMSS D-MINT: 34 KTS AT 190958Z CIMSS D-PRINT: 33 KTS AT 191140Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG EQUATORWARD OTHER FACTORS: SLIGHT DRY AIR ENTRAINMENT FROM THE NORTH ANALYSIS CONFIDENCE: INITIAL POSITION: LOW INITIAL INTENSITY: LOW INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS 17W (SAUDEL) IS FORECAST TO TRACK NORTH- NORTHWESTWARD AS THE SUBTROPICAL RIDGE (STR) POSITIONED SOUTH OF HONSHU WEAKENS AND RETREATS NORTHWARD, LETTING 17W CONTINUE GAINING LATITUDE. THE STR THAT IS CURRENTLY TO THE NORTHEAST OF 17W IS EXPECTED TO BUILD AND PROPAGATE WESTWARD, BECOMING THE PRIMARY STEERING MECHANISM THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD. THE CPA TO SAIPAN HAS SLIGHTLY INCREASED COMPARED TO THE PREVIOUS FORECAST AND THE TIME OF CPA IS ABOUT 6 HOURS SOONER (NOW 212200Z). HOWEVER, THE UNCERTAINTY IN THE INITIAL POSITION MAY CAUSE THERE TO BE A SHIFT IN THE TRAJECTORY RELATIVE TO THE NORTHERN MARIANA ISLANDS. THE TRACK IS FORECAST TO BECOME MORE WEST-NORTHWESTWARD AFTER TAU 72 AS RIDGING EXTENDS TO THE NORTH OF 17W. THE ENVIRONMENT IS FORECAST TO IMPROVE OVER THE NEXT 12 HOURS AS THE DRY AIR ENTRAINMENT FROM THE NORTH LESSENS, ALLOWING FOR THE CORE OF THE VORTEX TO MOISTEN. THE TIMING OF THE AXISYMMETRIZATION OF THE WIND FIELD IS CURRENTLY THE LARGEST LIMITING FACTOR FOR INTENSIFICATION IN THE NEAR TERM. ONCE THE SYMMETRIZATION COMPLETES, 17W IS FORECAST TO STEADILY INTENSIFY THROUGH TAU 36 TO AROUND 65 KTS. AFTER TAU 36, 17W IS FORECAST TO RAPIDLY INTENSIFY THROUGH TAU 72 AS THE SYSTEM TAKES ADVANTAGE OF STRONG DUAL CHANNEL OUTFLOW, VERY WARM (OVER 30 C) SEA SURFACE TEMPERATURES, AND HIGH OCEAN HEAT CONTENT (OHC) VALUES EAST OF THE MARIANAS. 17W IS THEN FORECAST TO FURTHER INTENSIFY TO A PEAK OF AROUND 125 KTS AT TAU 96 BEFORE SLIGHTLY WEAKENING THROUGH TAU 120 AS THE SYSTEM BEGINS TO ENTER AN AREA OF INCREASED NORTHERLY SHEAR AND LOWER OHC. MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72 WITH NO NOTABLE OUTLIERS PRESENT. THE CROSS-TRACK SPREAD AT TAU 72 IS MEASURED TO BE ABOUT 100 NM. AFTER TAU 72, MODELS BEGIN TO FAN OUT CONSIDERABLY. GFS AND NAVGEM MAKE UP THE NORTHERNMOST MEMBERS WHILE THE ECMWF AND THE ECMWF ENSEMBLE MEAN MAKE UP THE SOUTHERNMOST. AS A RESULT, CROSS-TRACK SPREAD AT TAU 120 INCREASES TO 330 NM. THE JTWC TRACK FORECAST IS PLACED NEAR THE MULTI-MODEL CONSENSUS THROUGH TAU 72 AND THEN CLOSER TO THE ECMWF AND EXPERIMENTAL GOOGLE DEEPMIND ENSEMBLE MEANS THROUGH TAU 120. INTENSITY GUIDANCE CONTINUES TO BE IN RATHER POOR AGREEMENT. COAMPS-TC AND ITS CORRESPONDING RAPID INTENSIFICATION (RI) AID (CTR-1) CONTINUE TO SHOW A MUCH MORE RAPID RATE OF INTENSIFICATION THROUGH THE FIRST 36-48 HOURS. ADDITIONALLY, GFS NOW SHOWS RAPID DEVELOPMENT THROUGH TAU 36, SUGGESTING AN INTENSITY OF OVER 85 KTS AT THAT TIME. CONSIDERING THE CURRENT DISORGANIZED NATURE OF THE SYSTEM, THE JTWC INTENSITY FORECAST FOLLOWS THE HAFS-A AND HWRF DEPICTION THROUGH TAU 72 WITH MEDIUM CONFIDENCE. AFTER TAU 72, THERE IS EXTREME DISAGREEMENT IN INTENSITIES BETWEEN MODELS. ON ONE HAND, HAFS-A AND HWRF WEAKEN THE SYSTEM EXTREMELY QUICKLY; ON THE OTHER HAND, COAMPS-TC AND THE GOOGLE DEEPMIND SHOW ONLY A GRADUAL DECLINE THROUGH TAU 120. THE JTWC INTENSITY FORECAST IS SITUATED CLOSER TO THE LATTER GROUPING THROUGH TAU 120 WITH LOW CONFIDENCE. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN