WDPN31 PGTW 072100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 22W (TWENTYTWO) WARNING NR 003// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 17.2N 110.6E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 151 NM EAST-NORTHEAST OF DA NANG, VIETNAM MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 06 KTS SIGNIFICANT WAVE HEIGHT: 10 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A BROAD AND DISORGANIZED CIRCULATION WITH A WEAK CONVECTIVE CORE EMBEDDED WITHIN THE LARGER CIRCULATION. WEAK FLARING CONVECTION IS OBSCURING THE LOW LEVEL CIRCULATION CENTER (LLCC), HOWEVER A 071754Z AMSR2 36GHZ MICROWAVE IMAGE SHOWED SHALLOW BANDS WRAPPING INTO A DEFINED LOW EMISSIVITY REGION. ANIMATED RADAR DATA AT THE EDGE OF THE DETECTION RANGE IN WHICH THE INITIAL OUTER CYCLONIC BAND ON THE WESTERN EDGE OF THE SYSTEM CAN BE SEEN, CONSTRAINED THE INITIAL POSITION, WHICH IS SET WITH MEDIUM CONFIDENCE. THE INITIAL INTENSITY OF 30 KNOTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE HIGHER END OF THE AGENCY DVORAK CURRENT INTENSITY ESTIMATES, THOUGH SLIGHTLY LOWER THAN THE OBJECTIVE ESTIMATES. THE CORE OF TD 22W LIES WITHIN A LARGER MONSOON DEPRESSION TYPE SYSTEM, WITH THE RADIUS OF MAXIMUM WINDS WITHIN ABOUT 50-NM OF THE CENTER, WITH ANOTHER BAND OF GALE FORCE WINDS EXTENDING IN A BAND APPROXIMATELY 200-NM OUT FROM THE CENTER, ACCORDING TO SHIP OBSERVATIONS. THE SYSTEM LIES IN GENERALLY FAVORABLE ENVIRONMENT WITH HIGH SSTS, LOW (5-10 KTS) VWS AND MODERATE POLEWARD AND EQUATORWARD OUTFLOW ALOFT. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T1.5 - 25 KTS RJTD: T2.0 - 30 KTS KNES: T2.0 - 30 KTS CIMSS SATCON: 38 KTS AT 071343Z CIMSS ADT: 39 KTS AT 071730Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE POLEWARD AND EQUATORWARD OTHER FACTORS: PROXIMITY TO LAND AND BROAD NATURE OF THE CIRCULATION. ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM 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 22W IS TRACKING SLOWLY NORTH-NORTHWESTWARD ALONG A RELATIVELY WEAK GRADIENT ON THE SOUTHWEST PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. THE SYSTEM IS FORECAST TO CONTINUE TRACKING NORTH-NORTHWESTWARD, WITH AN EXPECTED LANDFALL ALONG THE SOUTHEAST COAST OF HAINAN ISLAND NEAR TAU 24. A MID-LEVEL STR CENTER IS FORECAST TO DEVELOP OVER SOUTH-CENTRAL CHINA BY TAU 36 AND THIS SHOULD PUSH TD 22W OVER TO A WESTWARD TRACK BY TAU 48. THEREAFTER THE RIDGE REORIENTS TO A SOUTHWEST-NORTHEAST AXIS, AND TD 22W RESPONDS BY TURNING SLOWLY TOWARDS THE SOUTHWEST, WITH A SECOND LANDFALL EXPECTED ALONG THE NORTH-CENTRAL COAST OF VIETNAM SHORTLY AFTER TAU 72. ENVIRONMENTAL CONDITIONS ARE FORECAST TO REMAIN FAVORABLE OVER THE NEXT 24 TO 36 HOURS, ALLOWING FOR INTENSIFICATION TO 40 KNOTS PRIOR TO LANDFALL ON HAINAN. THE SYSTEM WILL WEAKEN SLIGHTLY AS IT TRANSITS OVER HAINAN, THEN REEMERGE INTO THE TONKIN GULF AS A WEAK TROPICAL STORM. UPPER-LEVEL OUTFLOW CONDITIONS ARE EXPECTED TO BE LESS FAVORABLE AFTER TAU 36 AND THUS WHILE THE SYSTEM IS EXPECTED TO REGAIN SOME OF ITS STRENGTH, THE LACK OF A ROBUST OUTFLOW MECHANISM AND SOME INCREASED EASTERLY VWS, WILL SERVE TO LIMIT THE POTENTIAL INTENSITY. AFTER THE SECOND LANDFALL IN VIETNAM, THE SYSTEM WILL QUICKLY DISSIPATE WHILE MOVING INLAND OVER ROUGH TERRAIN. MODEL DISCUSSION: TRACK GUIDANCE IS IN RELATIVELY GOOD AGREEMENT THROUGH TAU 48, WITH A 90NM SPREAD IN SOLUTIONS AS THE SYSTEM CROSSES HAINAN. THEREAFTER THE GUIDANCE DIVERGES SIGNIFICANTLY, WITH GFS, HWRF AND THE GFS ENSEMBLE SHOWING A SHARP TURN SOUTHWARD WITH A LANDFALL NEAR HUE, VIETNAM. THE REMAINDER OF THE CONSENSUS MEMBERS GENERALLY AGREE ON A WEST-SOUTHWEST TRACK, WITH SPREAD INCREASING TO 170NM BY TAU 72. THE JTWC FORECAST LIES ON THE WESTERN, THEN SOUTHERN SIDE OF THE GUIDANCE ENVELOPE THROUGH THE DURATION OF THE FORECAST WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS IN GOOD AGREEMENT OVERALL, WITH THE JTWC FORECAST LAID IN GENERAL AGREEMENT WITH THE CONSENSUS MEAN WITH MEDIUM CONFIDENCE DUE TO THE UNCERTAINTIES SURROUNDING THE IMPACT OF THE PASSAGE OVER HAINAN. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN