WDPN31 PGTW 010300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (NALGAE) WARNING NR 021// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 19.1N 116.1E INITIAL INTENSITY: 70 KTS GEOGRAPHIC REFERENCE: 220 NM SOUTH-SOUTHEAST OF HONG KONG MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 05 KTS SIGNIFICANT WAVE HEIGHT: 33 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RELATIVELY SYMMETRICAL SYSTEM WITH FEEDER BANDS IN THE WESTERN AND EASTERN SEMI-CIRCLES WRAPPING INTO AN ASSESSED LOW LEVEL CIRCULATION CENTER (LLCC). A 312245Z 91GHZ SSMIS PASS SHOWS THE AFOREMENTIONED BANDING AS WELL AS THE DEEPEST CONVECTION PRESENT IN THE WESTERN SEMI-CIRCLE. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED OF THE VISIBLE SATELLITE LOOP, THE AVAILABLE SSMIS IMAGERY AND SEVERAL AGENCY FIXES. THE INITIAL INTENSITY OF 70 KNOTS IS SET BASED ON CONSISTENCY FROM THE PREVIOUS FORECAST AND THE OVERALL STRUCTURE. THE INITIAL INTENSITY SET SLIGHTLY HIGHER THAN THE PGTW DVORAK ESTIMATE OF 4.0, AIDT OF 67 KNOTS, AND SET SLIGHTLY LOWER THAN SATCON WHICH IS AT 76 KNOTS. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: WESTERN AXIS OF THE SUBTROPICAL RIDGE (STR) TO THE EAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T4.0 - 65 KTS RJTD: T4.0 - 65 KTS KNES: T4.5 - 77 KTS CIMSS SATCON: 76 KTS AT 311757Z CIMSS ADT: 67 KTS AT 312340Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 20-25 KTS SST: 26-27 CELSIUS OUTFLOW: MODERATE POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TY NALGAE CONTINUES ITS NORTH-NORTHWEST TRACK ALONG THE WESTERN PERIPHERY OF THE STR TO THE EAST, REMAINING AT ITS PEAK INTENSITY OF 70 KNOTS. TY 26W WILL BEGIN TO SHOW SIGNS OF WEAKENING THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD DUE TO THE INTRODUCTION OF DRY AIR FROM THE NORTH AND WEST. MOREOVER, THE FURTHER NORTHWARD THE SYSTEM MOVES, IT WILL ENCOUNTER COOLER SSTS OF 25-26 C. THESE COOLER WATERS ARE BEING INTRODUCED INTO THE REGION DUE TO THE INTENSE NORTHEASTERLY WIND FLOW THROUGH THE TAIWAN STRAIT. IN ADDITION, TY 26W WILL BE ENTERING AN AREA OF INCREASED VERTICAL WIND SHEAR (VWS) DURING THIS TIME. AFTER TAU 36, THOSE INTENSE WINDS FROM THE NORTHEAST WILL BE THE MAIN STEERING MECHANISM OF THE SYSTEM AS IT MAKES A DRAMATIC TURN WESTWARD AND BEGIN TO FURTHER DECREASE IN INTENSITY DUE TO LAND INTERACTION WITH SOUTHEAST CHINA. IN ADDITION TO LAND INTERACTION, THE AFOREMENTIONED DRY AIR WILL BE FULLY ENTRAINED INTO THE SYSTEM, HAMPERING ANY FURTHER DEVELOPMENT. BY TAU 96, TY NALGAE WILL FULLY DISSIPATE OVER THE ISLAND OF HAINAN. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN GOOD AGREEMENT WITH THE CONSENSUS ENVELOPE CONTINUING TO MARCH SLIGHTLY MORE POLEWARD THAN PREVIOUS RUNS. UEMI AND AFUI ARE THE OUTLIERS SHOWING A MORE NORTHERLY PROGRESSION OVER THE FIRST 48 HOURS, FOLLOWED BY A SHARP TURN TO THE SOUTH-SOUTHWEST JUST AS THEY DID IN THE PREVIOUS RUN. DUE TO THESE OUTLIERS, THE JTWC TRACK WAS PLACED WITH MEDIUM CONFIDENCE SLIGHTLY TO THE LEFT OF THE CONSENSUS TRACK AND SLIGHTLY MORE POLEWARD THAN THE PREVIOUS JTWC FORECAST TRACK. THE JTWC TRACK NOW SKIRTS ALONG THE COAST OF SOUTHEAST CHINA BEFORE MAKING LANDFALL AND DISSIPATION OVER THE ISLAND OF HAINAN. INTENSITY CONSENSUS IS IN REALLY GOOD AGREEMENT UP TO TAU 72, WITH SOME DISAGREEMENT BETWEEN TAUS 72 TO 96. THIS IS MORE THAN LIKELY DUE TO VARIOUS SOLUTIONS TAKING THE SYSTEM OVER LAND SOONER RATHER THAN LATER. THE JTWC INTENSITY FORECAST IS SET WITH HIGH CONFIDENCE THROUGH TAU 72 AND MEDIUM CONFIDENCE THROUGH TAU 96. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: HIGH INTENSITY 72-120 HR: MEDIUM// NNNN