WDPN31 PGTW 160300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 24W (TWENTYFOUR) WARNING NR 003// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 15.0N 148.7E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 168 NM EAST OF SAIPAN MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 02 KTS SIGNIFICANT WAVE HEIGHT: 14 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL DEPRESSION 24W WITH A MUCH MORE DEFINED AND SYMMETRIC LOW-LEVEL CIRCULATION CENTER (LLCC) THAT IS NOW PARTIALLY EXPOSED. CONVECTIVE ACTIVITY REMAINS MOSTLY CONFINED TO THE SOUTHWESTERN PERIPHERY. A TIMELY 152319Z METOP-C ASCAT BULLSEYE PASS REVEALED A DEFINED CENTER WITH WINDS OF 25-30 KTS PRIMARILY LOCATED WITHIN THE SOUTHEASTERN QUADRANT OF THE SYSTEM. THE INITIAL POSITION AND INTENSITY ARE BOTH PLACED WITH HIGH CONFIDENCE BASED ON THE ASCAT DATA. ENVIRONMENTAL ANALYSIS INDICATES THAT 24W REMAINS PLACED WITHIN A MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE OUTFLOW ALOFT, LOW (5-10 KTS) NORTHERLY VERTICAL WIND SHEAR, DRY AIR ENTRAINMENT FROM THE NORTH, AND WARM (29-30 C) SEA SURFACE TEMPERATURES. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: THE NORTHWARD EXTENSION OF ELONGATED NEAR EQUATORIAL RIDGE (NER) POSITIONED TO THE SOUTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T1.5 - 25 KTS RJTD: T2.0 - 30 KTS CIMSS SATCON: 33 KTS AT 152027Z CIMSS ADT: 34 KTS AT 160000Z CIMSS AIDT: 32 KTS AT 160000Z CIMSS D-MINT: 28 KTS AT 152026Z CIMSS D-PRINT: 38 KTS AT 160000Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE POLEWARD AND EQUATORWARD OTHER FACTORS: DRY AIR ENTRAINMENT FROM THE NORTH ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: 24W HAS NOW STARTED ON ITS NORTHWARD TRACK, PRIMARILY DRIVEN BY THE ELONGATED NER POSITIONED TO THE SOUTHEAST. THE SUBTROPICAL RIDGE (STR) THAT IS CURRENTLY TO THE NORTHEAST OF THE SYSTEM IS EXPECTED TO REORIENT EASTWARD AND WEAKEN AS AN UPPER-LEVEL TROUGH MOVES IN FROM THE WEST. AS A RESULT, A GENERALLY NORTHWARD TRACK IS EXPECTED TO PERSIST THROUGH TAU 24. THE SYSTEM WILL THEN BEGIN TO INTERACT WITH THE SOUTHWESTERN PERIPHERY OF THE STR NEAR TAU 24, WHICH WILL DIRECT THE VORTEX NORTHWESTWARD THROUGH TAU 72. AFTER TAU 72, 24W IS FORECAST TO ROUND THE WESTERN EXTENT OF THE RIDGE WITH A NORTHWARD TURN THROUGH TAU 96. FOLLOWING TAU 96, THE SYSTEM WILL BEGIN TO ACCELERATE NORTHEASTWARD AS IT CONTINUES TO ROUND THE RIDGE AXIS, TRACKING CLOSE TO THE EASTERN COAST OF HONSHU. 24W IS CURRENTLY FORECAST TO STAY EAST OF HONSHU, HOWEVER, THERE IS STILL SOME UNCERTAINTY IN THE TIMING AND TRAJECTORY OF THE NORTHEASTWARD TURN AFTER TAU 96. IF 24W STAYS ON A NORTHWESTWARD TRACK FOR LONGER THAN ANTICIPATED, IT COULD GET CLOSER TO THE COAST AND IMPACT AREAS NEAR THE KANTO PLAIN REGION. IN TERMS OF INTENSITY, 24W IS FORECAST TO STEADILY INTENSIFY THROUGH TAU 60 AS THE VORTEX CONSOLIDATES AND POLEWARD OUTFLOW GREATLY IMPROVES. AFTER TAU 60, THE SYSTEM WILL BATTLE WITH DRY AIR ENTRAINMENT FROM THE WEST, CAUSING THE SYSTEM TO HALT THE INTENSIFICATION TREND. IF 24W IS ABLE TO CONSOLIDATE AND FORM A MORE COMPACT CORE, THEN FURTHER INTENSIFICATION COULD BE POSSIBLE. AFTER TAU 96, SOUTHERLY SHEAR IS EXPECTED TO INCREASE WHILE THE SYSTEM SIMULTANEOUSLY TAPS INTO A ROBUST POLEWARD OUTFLOW CHANNEL PROVIDED BY A STRONG JET STREAK OVER NORTHERN JAPAN. NOTABLY, THE HAFS-A MODEL SHOWS THE SYSTEM STRUGGLING TO CONSOLIDATE AND IS THEREFORE NEVER ABLE TO FULLY STAVE OFF THE DRY AIR. AS IT STANDS, 24W IS FORECAST TO MAINTAIN LOW TYPHOON-STRENGTH THROUGH THE REMAINDER OF THE FORECAST PERIOD AS IT PASSES BY JUST EAST OF HONSHU. MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN MODERATE AGREEMENT THROUGH TAU 72 WITH THE VARIOUS AI-BASED MODELS MAKING UP THE EASTERN SIDE OF THE ENVELOPE WHILE THE PHYSICS-BASED MODELS ARE FURTHER WEST. SPECIFICALLY, THE EXPERIMENTAL GOOGLE DEEPMIND AND EC-AIFS ARE THE FURTHEST EAST WHILE JGSM AND NAVGEM ARE THE FURTHEST WEST. AFTER TAU 72, THE PRIMARY DIFFERENCE BETWEEN MODELS IS THE TRACK SPEED AROUND THE RIDGE. THE GOOGLE DEEPMIND IS THE FASTEST, SHOWING THE VORTEX NORTHEAST OF TOKYO AT TAU 120 WHILE THE JGSM BECOMES A SIGNIFICANT OUTLIER, SHOWING THE VORTEX SOUTHEAST OF YAKUSHIMA AT THE SAME TIME. THE JTWC TRACK FORECAST IS PLACED NEAR THE CONSENSUS THROUGH TAU 72 AND THEN CLOSER TO THE VARIOUS AI-BASED MODELS THROUGH TAU 120 DUE TO THEIR STRONG PERFORMANCE IN THE RECURVING TRACK TYPE. INTENSITY GUIDANCE GENERALLY AGREES ON INTENSIFICATION THROUGH TAU 60 FOLLOWED BY A STEADY INTENSITY THROUGH TAU 120. HWRF IS NOW THE MOST AGGRESSIVE MODEL, SUGGESTING AN INTENSITY OF AROUND 85 KTS AT TAU 120, HOWEVER, IT ALSO DEPICTS A MUCH SLOWER TRACK AROUND THE RIDGE THAN THE BULK OF RELIABLE TRACK GUIDANCE SUGGESTS. OVERALL, THE JTWC INTENSITY FORECAST IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN