179 

WDPN31 PGTW 172100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 04W (SINLAKU) WARNING NR 036//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.3N 146.5E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 356 NM SOUTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 34 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SLOWLY
WEAKENING CYCLONE WITH DECREASING DEEP CONVECTION AROUND THE
CENTRAL CORE OVER THE PAST 6 HOURS. ANIMATED WATER VAPOR IMAGERY
DISPLAYS ROBUST POLEWARD OUTFLOW AIDED BY THE PROXIMITY TO THE
DEEP-LAYER WESTERLIES TO THE NORTH OF THE SYSTEM. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE ANIMATED EIR
AND AGENCY DVORAK FIXES, HOWEVER, CONFIDENCE IS REDUCED BY A LACK
OF RECENT MICROWAVE IMAGERY AND CENTRAL DENSE OVERCAST OBSCURING
THE LOW-LEVEL CIRCULATION CENTER. THE INITIAL INTENSITY OF 70 KTS
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES
AND THE WEAKENING TREND OBSERVED IN CIMSS INTENSITY ESTIMATES, ALL
OF WHICH ARE LISTED BELOW. DESPITE THE EXCELLENT UPPER-LEVEL
OUTFLOW, THE ENVIRONMENT IS CHARACTERIZED AS UNFAVORABLE WITH
CONTINUED DRY AIR ENTRAINMENT, INCREASED (20 KTS) WESTERLY VERTICAL
WIND SHEAR (VWS), AND COOLING (25-26 C) SEA SURFACE TEMPERATURES
(SST).

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF THE SUBTROPICAL
RIDGE (STR) CENTERED TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T4.0 - 65 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T4.0 - 65 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 88 KTS AT 171800Z
   CIMSS ADT: 65 KTS AT 171800Z
   CIMSS AIDT: 68 KTS AT 171800Z
   CIMSS D-MINT: 74 KTS AT 171800Z
   CIMSS D-PRINT: 74 KTS AT 171800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: SIGNIFICANT DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TYPHOON (TY) 04W (SINLAKU) IS FORECAST TO
ACCELERATE ON A NORTHEASTWARD, BECOMING EAST-NORTHEASTWARD, TRACK
UNDER THE INFLUENCE OF THE STEERING RIDGE TO THE SOUTHEAST AND THE
MIDLATITUDE WESTERLIES TO THE NORTH. TY SINLAKU IS EXPECTED TO
BEGIN EXTRATROPICAL TRANSITION (ETT) AROUND TAU 36 AS IT TRANSITS
OVER MUCH COOLER (20-21 C) SEA SURFACE TEMPERATURES AND BECOMES
EMBEDDED IN THE MIDLATITUDE WESTERLIES. ETT IS EXPECTED TO COMPLETE
AROUND TAU 48 AS VWS APPROACHES 50 KTS AND THE SYSTEM GAINS
BAROCLINICITY. A STEADY WEAKENING TREND IS FORECAST THROUGH THE
ENTIRE FORECAST PERIOD, DECREASING TO 50 KTS AT TAU 48 UNDER THE
INCREASINGLY HOSTILE ENVIRONMENTAL CONDITIONS. IN SPITE OF THE
WEAKENING TREND, 04W IS EXPECTED TO MAINTAIN A BROAD AREA OF
GALE-FORCE WINDS AS IT ACCELERATES INTO THE NORTHERN PACIFIC AS AN
EXTRATROPICAL CYCLONE.

MODEL DISCUSSION: MODEL TRACK GUIDANCE HAS COME INTO VERY GOOD
AGREEMENT ABOUT THE TRAJECTORY OF TY SINLAKU WITH THE LATEST MODEL
RUNS. THE CROSS-TRACK SPREAD OF 65 NM AT TAU 48 INCLUDES ALL
GUIDANCE WITH NO OUTLIERS. THE JTWC TRACK FORECAST IS PLACED CLOSE
TO THE MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE. MODEL INTENSITY
GUIDANCE IS LIKEWISE IN GOOD AGREEMENT ABOUT THE WEAKENING TREND
THROUGH TAU 48. THE JTWC INTENSITY FORECAST IS PLACED SLIGHTLY
ABOVE THE MULTI-MODEL CONSENSUS THROUGH TAU 24 AND CLOSE TO THE
HAFS-A SOLUTION THEREAFTER WITH OVERALL HIGH CONFIDENCE.

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