WDPN31 PGTW 070900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 22W (TWENTYTWO) WARNING NR 001// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 17.1N 111.0E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 372 NM SOUTHEAST OF HANOI, VIETNAM MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS SIGNIFICANT WAVE HEIGHT: 10 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TROPICAL DEPRESSION (TD) HAS SLOWLY CONSOLIDATED OVER THE PAST TWELVE HOURS AND HAS TRANSITIONED FROM A MONSOON DEPRESSION INTO A WARM-CORE TROPICAL SYSTEM. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS EXPOSED LOW-LEVEL CLOUD LINES WRAPPING INTO A BROAD CENTER WITH PERSISTENT CORE CONVECTION. A 070541Z AMSR2 89GHZ IMAGE REVEALS FORMATIVE CURVED BANDING PRIMARILY OVER THE EASTERN SEMICIRCLE WITH A RAGGED CENTER. A 070236Z ASCAT-B IMAGE INDICATES THE WIND FIELD HAS STRENGTHENED AND CONTRACTED WITH 25-30 KNOT WINDS WRAPPING IN CLOSER TO CENTER WITH A 70NM RADIUS OF MAXIMUM WINDS, WHICH IS MORE TYPICAL OF A TROPICAL SYSTEM. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE ASCAT-B IMAGE. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE ASCAT DATA BUT IS HEDGED SLIGHTLY HIGHER THAN THE AGENCY DVORAK ESTIMATES. ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE WITH MODERATE POLEWARD AND EQUATORWARD OUTFLOW AND LOW (5-10KT) VERTICAL WIND SHEAR. SEA SURFACE TEMPERATURES OF 29-30C ARE CONDUCIVE. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: TD 22W IS LOCATED WITHIN A COMPETING STEERING ENVIRONMENT WITH A NEAR-EQUATORIAL RIDGE TO THE EAST AND A SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T1.0 - 25 KTS RJTD: T1.5 - 25 KTS KNES: T1.5 - 25 KTS FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE POLEWARD AND EQUATORWARD OTHER FACTORS: PROXIMITY TO LAND ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY. FORECAST DISCUSSION: TD 22W IS TRACKING SLOWLY WITHIN A COMPETING STEERING ENVIRONMENT AND IS EXPECTED TO TRACK SLOWLY NORTHWESTWARD TO NORTH-NORTHWESTWARD THROUGH TAU 36 THEN TURN WESTWARD THROUGH TAU 72 AS THE LOW- TO MID-LEVEL STR BECOMES THE PRIMARY STEERING INFLUENCE. CONDITIONS SHOULD REMAIN FAVORABLE THROUGH TAU 24 WITH A PEAK INTENSITY OF 40 KNOTS FORECAST AT TAU 24, POSSIBLY SLIGHTLY HIGHER NEAR THE LANDFALL TIME. AFTER TAU 24, INTERACTION WITH LAND IS EXPECTED TO HINDER DEVELOPMENT WITH GRADUAL WEAKENING ANTICIPATED AS THE SYSTEM TRACKS ACROSS HAINAN ISLAND. AS THE SYSTEM EMERGES OVER THE GULF OF TONKIN AFTER TAU 48, REINTENSIFICATION IS UNLIKELY DUE TO LAND INTERACTION AND INCREASING NORTHEASTERLY VERTICAL WIND SHEAR. AFTER TAU 72, TD 22W WILL TURN SOUTHWESTWARD UNDER A NORTHEAST-SOUTHWEST ORIENTED STR. THE SYSTEM IS EXPECTED TO DISSIPATE BY TAU 96 AS IT TRACKS INLAND OVER MOUNTAINOUS TERRAIN. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72 WITH A 70NM SPREAD IN SOLUTIONS AT TAU 72 BUT DIVERGE AFTER TAU 72 WITH A LARGE SPREAD AND INCREASED UNCERTAINTY LENDING LOW CONFIDENCE TO THE JTWC FORECAST TRACK. THE JTWC FORECAST TRACK IS POSITIONED NEAR THE MULTI-MODEL CONSENSUS (CONW). INTENSITY GUIDANCE INDICATES A PEAK RANGING FROM 35 TO 45 KNOTS AT TAU 24 WITH STEADY WEAKENING THROUGH THE REMAINDER OF THE FORECAST PERIOD. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN