WDPN31 PGTW 061500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (AERE) WARNING NR 025// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 34.0N 142.9E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 160 NM SOUTHEAST OF NARITA AIRPORT MOVEMENT PAST 6 HOURS: EASTWARD AT 10 KTS SIGNIFICANT WAVE HEIGHT: 16 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED SATELLITE (EIR) DEPICTS A RAGGED FULLY EXPOSED SYSTEM WITH THE MAIN CONVECTIVE STRUCTURE SHEARED WELL TO THE EAST OF THE SURFACE LLC. TD 05W APPEARS TO BE TRANSITIONING INTO A SUBTROPICAL SYSTEM WITH AN OVERALL BAROCLINIC LEAF STRUCTURE WITH SOME FRONTAL CHARACTERISTICS ON THE EIR LOOP. THE INITIAL POSITION IS PLACED WITH LOW CONFIDENCE BASED ON A LOW-RESOLUTION 061136Z AMSU-B 89GHZ IMAGE. THE INITIAL INTENSITY OF 30 KNOTS IS ASSESSED WITH LOW CONFIDENCE BASED ON A PARTIAL 061140Z METOP-B ASCAT IMAGE AND ADT. PGTW IS ONCE AGAIN ASSESSING THE SYSTEM USING THE SUBTROPICAL METHOD, WHICH CONTINUES TO YIELD A HIGHER INTENSITY OF T2.5(35KTS). THE CURRENT ENVIRONMENT REMAINS UNFAVORABLE FOR TROPICAL CYCLONE DEVELOPMENT WITH SEA SURFACE TEMPERATURES HOLDING SLIGHTLY ABOVE 25C, HIGH VWS, BEING SLIGHTLY OFFSET BY STRONG UPPER-LEVEL DIFFLUENT OUTFLOW ALOFT, AND A STRONG POSITIVE VORTICITY LOBE ASSOCIATED WITH A 500MB TROUGH RESIDING JUST OVER OF THE MAIN LLC. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A DEEP LAYER SUBTROPICAL RIDGE (STR) TO THE SOUTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS CIMSS ADT: 29 KTS AT 061140Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE VWS: 25-30 KTS SST: 25-26 CELSIUS OUTFLOW: STRONG EASTWARD ANALYSIS CONFIDENCE: INITIAL POSITION: LOW INITIAL INTENSITY: LOW 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: TD 05W IS MOVING SLOWLY EAST WHILE IT UNDERGOES SUBTROPICAL TRANSITION. DURING THE TRANSITION, THE UPPER-LEVEL TROUGH WILL BEGIN SYNCING UP WITH THE SURFACE SYSTEM AND STEADILY INTENSIFY TO TROPICAL STORM STRENGTH, REACHING A PEAK INTENSITY OF 35 KNOTS WITHIN THE NEXT 12 HOURS. THE OVERALL EASTWARD PROGRESSION WILL CONTINUE SLOWING AS IT ENTERS A WEAK STEERING ENVIRONMENT, AND ITS OVERALL MOTION BECOMES QUASI-STATIONARY THROUGH TAUS 24-36. THE SYSTEM WILL TRANSITION TO SUBTROPICAL COMPLETELY BY TAU 36 IF NOT SOONER. FROM TAU 36 AND BEYOND, TROPICAL DEVELOPMENT WILL BE FURTHER SUPPRESSED BY INCREASING DRY AIR ENTRAINMENT AND OCEAN TEMPERATURES DECREASING TO THE NORTH. THEREAFTER, TD 05W WILL MOVE SLOWLY NORTH UNDER THE REX BLOCK PATTERN UNTIL THE BLOCKING MECHANISM BEGINS TO BREAK DOWN BETWEEN TAU 48 AND NEAR TAU 60. AS THE REX BLOCK BREAKS DOWN AND THE STR REORIENTS TO A NORTH-SOUTH AXIS, EAST OF THE SYSTEM, TD 05W WILL RAPIDLY MOVE TO THE NORTH. AS THE SYSTEM ACCELERATES TO THE NORTH, IT WILL RAPIDLY WEAKEN DUE TO HIGHER VWS, COOLER SSTS, AND DROP BELOW 30KTS BY TAU 48 BEFORE EVER REACHING MAINLAND HONSHU OR HOKKAIDO. MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE REMAINS IN FAIR AGREEMENT IN THE FIRST 12 HRS AS THE SYSTEM TRACKS SLIGHTLY TO THE EAST-SOUTHEASTERLY DIRECTION BETWEEN TAUS 24-36. BY TAU 48, ALL GUIDANCE SUGGESTS A QUASI-STATIONARY LOOPING MOTION DUE TO THE WEAK STEERING PATTERN AND REX BLOCK SITUATION. THE FORECAST TRACK APPEARS TO LOOP BACK IN A COUNTERCLOCKWISE MANNER BY TAU 48 AND MOVE OFF RAPIDLY TO THE NORTH-NORTHWEST. THE HIGH UNCERTAINTY IN THE EXACT TRACK BETWEEN TAUS 36-48 INDUCES LOW CONFIDENCE IN THE OVERALL JTWC FORECAST TRACK DUE TO THE ERRATIC MOTION. ALL GUIDANCE SUGGESTS A NORTHWARD TRACK BY TAU 48-72. CONFIDENCE IN THE OVERALL INTENSITY IS ALSO LOW, DUE TO THE UNCERTAINTIES IN THE INITIAL INTENSITY ALONG WITH ALL MODELS CONSTRAINED WITHIN A 5 KNOT ENVELOPE THROUGH THE DURATION OF THE FORECAST. FORECAST CONFIDENCE: TRACK 0 - 72 HR: LOW INTENSITY 0 - 72 HR: LOW// NNNN