Advisories

WDPN31 PGTW 081500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (DOLPHIN) WARNING NR 051//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.0N 124.8E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 164 NM WEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 34 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) DEPICTS TYPHOON
(TY) 12W WITH A VERY COMPACT INNER CORE UNDERGOING REORGANIZATION,
COCOONED WITHIN AN EXTENSIVE OUTER CIRCULATION DEFINED BY MULTIPLE 
RAINBANDS WRAPPING INTO A BROAD OUTER RING. ANIMATED RADAR IMAGERY 
SHOWS THAT THE EYEWALL WIDTH HAS DECREASED, WHILE SIMULTANEOUSLY THE 
EYE HAS EXPANDED AND CLEARED IN EIR IMAGERY, CONTINUING A CYCLE (ERC) 
OBSERVED REPEATEDLY WITH THIS SYSTEM. A 081020Z SSMIS 91GHZ IMAGE 
REVEALED A FRAGMENTED EYEWALL ON THE WESTERN FLANK, WHICH HAS SINCE 
RECONSOLIDATED. THE SYSTEM IS SITUATED OVER A TONGUE OF VERY WARM 
(30-31C) SSTS WITH RELATIVELY HIGH OHC, SUPPORTING THE RE-
INTENSIFICATION OF THE INNER CORE. THE INITIAL POSITION IS ASSESSED 
WITH HIGH CONFIDENCE BASED ON THE RADAR EYE. THE INITIAL INTENSITY IS 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON A BLEND OF SUBJECTIVE DVORAK 
CURRENT INTENSITY (CI) AND OBJECTIVE FIX ESTIMATES NOTED ABOVE. OF 
NOTE, WHILE THE ADT CI IS RELATIVELY LOW, THE INSTANTANEOUS RAW T-
NUMBER IS T4.7 (APPROXIMATELY 84 KNOTS). ENVIRONMENTAL CONDITIONS 
REMAIN FAVORABLE, WITH OPTIMAL OCEAN CONDITIONS, STRONG RADIAL 
OUTFLOW ALOFT, AND LOW VERTICAL WIND SHEAR. THE PRIMARY LIMITING 
FACTOR IS THE EXPANSIVE NATURE OF THE OUTER CIRCULATION AND THE 
COMPLEX/HYBRID STRUCTURE OF THE SYSTEM AS A WHOLE.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK STEERING PATTERN DOMINATED BY A
BUILDING SUBTROPICAL RIDGE (STR) OVER SOUTHERN JAPAN. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T4.0 - 65 KTS
   KNES: T5.0 - 90 KTS
   CIMSS ADT: 63 KTS AT 081200Z
   CIMSS AIDT: 79 KTS AT 081230Z
   CIMSS D-PRINT: 72 KTS AT 081130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: THE LARGER CIRCULATION ASSOCIATED WITH TY 12W 
SITS IN A WEAK STEERING PATTERN, SOUTH OF A WEAKNESS IN THE STR OVER 
KOREA, BUT IS GENERALLY MOVING SLOWLY WESTWARD. TRAPPED WITHIN THIS 
EXPANSIVE OUTER CIRCULATION, THE INNER CORE OF TY 12W CONTINUES TO 
EXHIBIT A TROCHOIDAL TRAJECTORY WHILE MEANDERING SLOWLY WESTWARD. OVER 
THE NEXT 12 HOURS, THE WEAKNESS TO THE NORTH IS FORECAST TO BE 
REPLACED BY A BUILDING RIDGE OVER SOUTHERN JAPAN, WHICH WILL DRIVE TY 
12W ONTO A WEST-NORTHWESTWARD TRAJECTORY TOWARDS THE EASTERN COAST OF 
CHINA. LANDFALL IN SOUTHEASTERN ZHEJIANG PROVINCE IS EXPECTED NEAR TAU 
24. AFTER LANDFALL, THE SYSTEM WILL CONTINUE TO TRACK INLAND AND BY 
THE END OF THE FORECAST PERIOD WILL BEGIN TO RECURVE NORTHWARD AROUND 
THE STR AXIS. IN TERMS OF INTENSITY, THE SYSTEM IS MOVING OVER A 
TONGUE OF HIGH OHC WATERS, SUPPORTING MAINTENANCE OF ITS CURRENT 
INTENSITY AT MINIMUM, WITH SLIGHT INTENSIFICATION POTENTIAL BY TAU 12. 
THE PRIMARY LIMITING FACTORS ARE THE EXPANSIVE NATURE OF THE OUTER 
CORE AND COMPLEX INTERPLAY WITH CYCLONIC OUTFLOW ALOFT, WHICH EXTENDS 
BEYOND THE INNER CORE RADIUS AND HAS PERSISTED FOR SEVERAL DAYS. THE 
FORECAST CALLS FOR THE SYSTEM TO MAINTAIN ITS CURRENT INTENSITY 
THROUGH LANDFALL, BEFORE UNDERGOING RAPID TERRAIN-INDUCED WEAKENING 
UNTIL COMPLETE DISSIPATION BY TAU 72.   

MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH THE
FORECAST PERIOD. THE SYSTEM WILL ACCELERATE SLIGHTLY THROUGH LANDFALL, 
THEN SLOW SLIGHTLY AS IT INTERACTS WITH TERRAIN OVER CHINA. THE JTWC 
FORECAST TRACK IS POSITIONED JUST NORTH OF THE MULTI-MODEL CONSENSUS 
MEAN WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS ALSO IN STRONG 
AGREEMENT THROUGH THE FORECAST PERIOD. HAFS-A IS THE ONLY OUTLIER 
INDICATING A SLIGHT (5 KNOTS) INTENSIFICATION THROUGH TAU 12, AND ALL 
MODELS DEPICT RAPID WEAKENING BEGINNING AFTER TAU 12. THE JTWC 
FORECAST IS PLACED ON THE UPPER-END OF THE GUIDANCE PACKAGE WITH HIGH 
CONFIDENCE. 

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