Advisories

WDPN31 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (DOLPHIN) WARNING NR 053//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.8N 123.2E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 186 NM NORTH-NORTHEAST OF TAIPEI, TAIWAN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 31 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON 12W
(DOLPHIN) WITH A COMPACT CENTRAL CORE AND ONLY A DIMPLE OF A CLOUD-
FILLED EYE REMAINING AS IT BEGINS ITS TERMINAL WEAKENING JUST PRIOR TO 
LANDFALL. MUCH OF THE WESTERN FLANK OF THE MASSIVE SYSTEM HAS ALREADY 
MADE LANDFALL OVER CHINA, WHILE THE CONVECTIVE BANDING THAT REMAINS 
OVER WATER HAS MAINTAINED ITS STRUCTURE WITH A RADIUS OF OVER 250 NM 
FROM THE CENTER, ONLY DISRUPTED BY A PARTIAL MOAT OF DRY AIR JUST 
OUTSIDE THE CORE EYEWALL. WITH THE EXCEPTION OF THE DRY AIR 
ENTRAINMENT, ENVIRONMENTAL ANALYSIS REVEALS OTHERWISE FAVORABLE 
CONDITIONS OF WARM (29-30 C) SEA SURFACE TEMPERATURES, LOW (5-10 KTS) 
VERTICAL WIND SHEAR (VWS), AND GOOD OUTFLOW ALOFT. THE INITIAL 
POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON MSI IMAGERY AND 
EXTRAPOLATION FROM THE MICROWAVE EYE VISIBLE IN A 082218Z MWI 89 GHZ 
MICROWAVE IMAGE. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM 
CONFIDENCE BASED ON THE SPREAD OF AGENCY DVORAK FIXES AND CIMSS 
OBJECTIVE ESTIMATES LISTED BELOW, OPTING TO DECREASE THE INTENSITY AS 
THE APPEARANCE ON SATELLITE IMAGERY HAS DETERIORATED.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED OVER
SOUTHERN HONSHU

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T4.0 - 65 KTS
   KNES: T5.0 - 90 KTS
   CIMSS ADT: 59 KTS AT 082300Z
   CIMSS AIDT: 66 KTS AT 082300Z
   CIMSS D-MINT: 91 KTS AT 082027Z
   CIMSS D-PRINT: 75 KTS AT 082300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: WEAK DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 12W IS FORECAST TO CONTINUE ITS WESTWARD
TRACK, WITH LANDFALL OVER MAINLAND CHINA EXPECTED TO OCCUR AT TAU
12. AFTER TAU 24, A POLEWARD TURN IS EXPECTED AS TY 12W WILL REMAIN
UNDER THE STEERING INFLUENCE OF THE SUBTROPICAL RIDGE (STR) CENTERED 
OVER SOUTHERN HONSHU, WHICH IS FORECAST TO BUILD AND EXTEND SOUTHWARD, 
PULLING TY 12W NORTHWESTWARD. IN REGARDS TO INTENSITY, A PARTIAL MOAT 
OF DRY AIR HAS PERSISTED JUST OUTSIDE THE COMPACT CORE, CONTRIBUTING 
TO THE FORECAST WEAKENING TREND OF TY 12W PRIOR TO LANDFALL. AFTER 
LANDFALL, THE INTENSITY WILL RAPIDLY DECREASE AS TY 12W INTERACTS WITH 
THE TERRAIN, ULTIMATELY DISSIPATING OVER EASTERN CHINA BY TAU 60.

MODEL DISCUSSION: TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT FOR THE
REMAINDER OF THE FORECAST PERIOD WITH THE EXCEPTION OF GFS, WHICH
REMAINS AN OUTLIER DISPLACED TO THE SOUTH. THE OFFICIAL JTWC TRACK IS 
PLACED WITH HIGH CONFIDENCE FOR THE REMAINDER OF THE FORECAST PERIOD, 
HEDGING CLOSER TO THE JTWC AI CONSENSUS TO ACCOUNT FOR THE EFFECT OF 
GFS WITHIN THE MULTI-MODEL CONSENSUS. INTENSITY GUIDANCE IS ALSO IN 
GOOD AGREEMENT FOR THE REMAINDER OF THE FORECAST PERIOD WITH HWRF 
COMING INTO BETTER AGREEMENT AND ALL MODELS DEPICTING THE SHARP 
DECREASE AS SOON AS LANDFALL OCCURS. THE OFFICIAL JTWC FORECAST IS 
ASSESSED WITH HIGH CONFIDENCE FOR THE REMAINDER OF THE FORECAST 
PERIOD.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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