WDPN31 PGTW 270900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 01W (EWINIAR) WARNING NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.2N 123.5E
   INITIAL INTENSITY: 95 KTS
   GEOGRAPHIC REFERENCE: 663 NM SOUTH-SOUTHWEST OF KADENA AB,
OKINAWA
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 8 KTS
   SIGNIFICANT WAVE HEIGHT: 27 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS WARMING
CLOUD TOPS AS MODERATE VERTICAL WIND SHEAR (VWS) FROM THE NORTHWEST
HAS ERODED THE VERTICAL STRUCTURE OF TYPHOON (TY) 01W. THE
LOW-LEVEL CIRCULATION CENTER (LLCC) IS OBSCURED BY CLOUD COVER IN
ANIMATED MULTISPECTRAL IMAGERY. A 270537Z ATMS 89GHZ MICROWAVE
IMAGE DEPICTS ASYMMETRICAL CONVECTIVE BANDING TO THE SOUTHEAST OF
THE LLCC, INDICATING A SOUTHEASTWARD VERTICAL TILT WITH HEIGHT. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON ANIMATED
MSI, EIR, AND RADAR FROM THE PHILIPPINES. THE INITIAL INTENSITY OF
95 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY AND
OBJECTIVE FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T5.0 - 90 KTS
   KNES: T5.0 - 90 KTS
   CIMSS SATCON: 78 KTS AT 270536Z
   CIMSS ADT: 82 KTS AT 270530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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: TY 01W WILL CONTINUE TO TRACK NORTHEASTWARD
UNDER THE STEERING INFLUENCE OF A STR POSITIONED TO THE EAST. BY
TAU 72, THE SYSTEM WILL COMMENCE EXTRATROPICAL TRANSITION AS IT
BECOMES IMPACTED BY A MID-LATITUDE TROUGH. THE TRACK SPEED WILL 
INCREASE AS EXTRATROPICAL TRANSITION COMPLETES. MODERATE
VWS IS EXPECTED TO IMPACT THE SYSTEM AS IT MOVES THROUGH AN
OTHERWISE FAVORABLE ENVIRONMENT, GENERATING UNCERTAINTY IN THE
INTENSITY FORECAST. BASED ON THESE OFFSETTING FACTORS IT APPEARS
LIKELY THAT THE SYSTEM COULD MAINTAIN INTENSITY OR POTENTIALLY
INTENSIFY SLIGHTLY IN THE NEAR-TERM, BUT THE SMALL SYSTEM IS
VULNERABLE TO SHIFTS IN THE UPPER-LEVEL FLOW AND COULD WEAKEN IF
MODERATE NEAR-TERM SHEAR PERSISTS. AFTER TAU 36, VWS OF 20KTS OR
GREATER WILL RESULT IN CONTINUOUS WEAKENING THROUGH THE END OF THE
FORECAST. THE PEAK INTENSITY IS SLIGHTLY LOWER THAN REPRESENTED IN
THE PREVIOUS FORECAST DUE TO STRONGER THAN PREVIOUSLY EXPECTED VWS.


MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GOOD AGREEMENT
THAT THE SYSTEM WILL CONTINUE TO BE STEERED NORTHEASTWARD FOR THE
REMAINDER OF THE FORECAST. A FEW DETERMINISTIC AND ENSEMBLE MODEL
SOLUTIONS INDICATE THAT THE SYSTEM CENTER COULD TRACK SLIGHTLY
NORTH OF THE MULTI-MODEL CONSENSUS AND THE CLOSELY ALIGNED JTWC
FORECAST, BRINGING IT SLIGHTLY NEARER TO MAINLAND JAPAN, DUE TO
VARYING REPRESENTATIONS OF STORM INTERACTION WITH THE MID-LATITUDE
TROUGH DURING EXTRATROPICAL TRANSITION. INTENSITY GUIDANCE IS
SPREAD FOR THE FIRST 48 HOURS, REFLECTING UNCERTAINTY ASSOCIATED
WITH THE OFFSETTING INFLUENCES OF PASSAGE OVER WARM WATER, MODERATE
UPPER-LEVEL OUTFLOW, AND MODERATE VERTICAL WIND SHEAR. THE CURRENT
JTWC FORECAST LIES NEAR THE MULTI-MODEL CONSENSUS WITH LOW
CONFIDENCE IN THE NEAR-TERM AND MEDIUM CONFIDENCE IN THE EXTENDED
RANGE AS MODEL SOLUTIONS CONVERGE DURING THE EXTRATROPICAL
TRANSITION PERIOD.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: LOW
   INTENSITY 72-120 HR: MEDIUM//
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