Advisories

WDPN31 PGTW 072100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (DOLPHIN) WARNING NR 048//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.6N 126.5E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 70 NM WEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 40 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
COMPACT INNER CORE WITH AN INTERMITTENTLY WELL-DEFINED SMALL
DIAMETER EYE. SURROUNDING DEEP CONVECTIVE BANDS ARE STILL SEPARATED
BY A MOAT OF DRIER AIR BUT VIGOROUS CONVECTION IS PRESENT IN ALL
QUADRANTS. THE EYE CONTINUES TO EXHIBIT CYCLIC PHASES OF WARMING
EYE TEMPERATURES SURROUNDED BY COOLING CONVECTIVE TOPS, AND VICE
VERSA. ANIMATED RADAR IMAGERY CONFIRMS THE PRESENCE OF THESE
FEATURES AND EXTENSIVE AREAS OF PRECIPITATION ASSOCIATED WITH THE
CORE CONVECTION AND CONVECTIVE BANDS. THE COMPACT CENTRAL CORE WITH
ITS PERSISTENT EYE HAS A NOTABLE WOBBLE WITHIN THE BROADER WIND
FIELD RESULTING IN ANOMALOUSLY ERRATIC 6 HOURLY POSITIONS OVER THE
PAST 24 HOURS, WHILE THE MEAN STORM MOTION HAS MAINTAINED A
WEST-SOUTHWESTWARD TRAJECTORY. ANIMATED WATER VAPOR IMAGERY
CONTINUES TO DEPICT EXCELLENT SELF-CONTAINED RADIAL OUTFLOW ALOFT
WITH TRANSVERSE BANDING IN ALL QUADRANTS. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE SMALL DIAMETER EYE AND THE
CENTER OF THE EYE IN RADAR IMAGERY. THE INITIAL INTENSITY OF 90 KTS
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE SPREAD OF AGENCY
DVORAK FIXES ON THE HIGHER END AND CIMSS OBJECTIVE INTENSITY
ESTIMATES ON THE LOWER END. THE ENVIRONMENT IS CHARACTERIZED AS
FAVORABLE, WITH HIGH SEA SURFACE TEMPERATURES, LOW VERTICAL WIND
SHEAR (VWS), AND EXCELLENT RADIAL OUTFLOW. WEAK DRY AIR ENTRAINMENT
DOES NOT APPEAR TO BE PENETRATING THE CENTRAL CORE BUT MAY BE
OFF-SETTING THE OTHERWISE FAVORABLE CONDITIONS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWESTERN FLANK OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED OVER HONSHU 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T5.5 - 102 KTS
   CIMSS SATCON: 84 KTS AT 071800Z
   CIMSS ADT: 87 KTS AT 071800Z
   CIMSS AIDT: 90 KTS AT 071800Z
   CIMSS D-MINT: 70 KTS AT 071730Z
   CIMSS D-PRINT: 73 KTS AT 071800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: 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: TYPHOON (TY) 12W (DOLPHIN) HAS CONTINUED TO
TRACK WEST-SOUTHWESTWARD (MEAN STORM MOTION) WITH A NOTABLE
SOUTHWARD DIP OVER THE PAST 6 HOURS AS THE COMPACT CENTRAL CORE
OSCILLATES WITHIN THE BROADER CIRCULATION. THE STEERING RIDGE
CENTERED OVER HONSHU HAS WEAKENED SLIGHTLY BUT AN EXTENSION OF A
SEPARATE RIDGE OVER MAINLAND CHINA HAS BUILT IN FROM THE WEST AND
AIDED IN MAINTAINING THE WEST-SOUTHWESTWARD TRAJECTORY. THE TRACK
IS FORECAST TO RECURVE POLEWARD OVER THE NEXT 48 HOURS AS THE
PRIMARY STEERING RIDGE ROTATES SOUTHEASTWARD. LANDFALL SOUTH OF
SHANGHAI IN EASTERN CHINA IS EXPECTED AROUND TAU 48, AFTER WHICH
THE TRACK INLAND TAKES ON A NORTHWESTWARD TRAJECTORY. TY DOLPHIN
HAS MANAGED TO REINVIGORATE OVER THE PAST 18 HOURS TO AN INTENSITY
OF 90 KTS AND IS FORECAST TO GRADUALLY WEAKEN AS IT APPROACHES
EASTERN CHINA. AFTER LANDFALL, RAPID DECAY OVER TERRAIN IS
EXPECTED, WITH DISSIPATION BY TAU 96.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN OVERALL GOOD AGREEMENT
ABOUT THE RECURVING TRACK SCENARIO BUT HAS AN 85 NM CROSS-TRACK
SPREAD AT TAU 48 AS A RESULT OF UNCERTAINTY IN THE STRENGTH AND
DISPOSITION OF THE TWO INFLUENTIAL RIDGES. THE PREVIOUSLY NOTED
OSCILLATION OF THE CENTRAL CORE ALSO INTRODUCES SOME UNCERTAINTY.
THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE MULTI-MODEL
CONSENSUS WITH A BIAS TOWARD THE CONSENSUS OF AI MODELS THAT HAS
STATISTICALLY PERFORMED VERY WELL FOR TY 12W. THE INTENSITY GUIDANC
REMAINS WITHIN A 10 KT ENVELOPE THROUGH TAU 48 AND ALL MODELS
DEPICT THE SAME GRADUAL WEAKENING TREND FOLLOWED BY RAPID DECAY
OVER LAND. THE JTWC INTENSITY FORECAST IS PLACED ON THE HIGHER END
OF THE GUIDANCE ENVELOPE WITH MEDIUM CONFIDENCE GIVEN RECENT
INTENSITY TRENDS.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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