WDPN32 PGTW 081500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 28W (HALONG) WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 31.5N 138.5E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 229 NM SOUTH OF CAMP FUJI
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 40 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEPICTS
TYPHOON (TY)  28W (HALONG) WITH AN EVIDENT EYE FEATURE THAT HAS
BECOME LESS SYMMETRICAL OVER THE PAST 6 HOURS. THE ASSOCIATED
CONVECTION OUTSIDE OF THE EYEWALL HAS SUSTAINED TEMPERATURES BETWEEN 
-73 AND -75 C. STRONG RADIAL OUTFLOW PERSISTS. ENVIRONMENTAL 
CONDITIONS ARE NOW MARGINAL WITH THE SYSTEM REACHING AN AREA OF 
MODERATE (20-25 KTS) VERTICAL WIND SHEAR, SLIGHTLY COOLER SEA 
TEMPERATURES (27-28 C), AS WELL AS DRY AIR IN THE VICINITY, THOUGH 
NOT YET PENETRATING THE CORE. THE INITIAL POSITION IS PLACED WITH 
HIGH CONFIDENCE BASED ON THE OBSERVABLE EYE FEATURE ON ANIMATED EIR. 
THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE BASED ON 
SUBJECTIVE AGENCY DVORAK ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: A 081211Z METOP-C ASCAT PASS

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T6.0 - 115 KTS
   KNES: T6.0 - 115 KTS
   CIMSS ADT: 115 KTS AT 081130Z
   CIMSS AIDT: 105 KTS AT 081130Z
   CIMSS D-PRINT: 103 KTS AT 081300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 28W IS FORECAST TO CONTINUE ON A
EAST-NORTHEASTWARD TRACK AROUND THE WESTERN-MOST EXTENT OF THE
DEEP-LAYER SUBTROPICAL RIDGE TO THE SOUTHEAST. THIS MOVEMENT WILL
CONTINUE THROUGH THE REMAINDER OF THE FORECAST WITH THE RIDGE
CONTINUING TO STEER THE SYSTEM NORTHEAST AS IT TRANSITIONS TO ITS
EXTRATROPICAL PHASE. WITH REGARD TO INTENSITY, TYPHOON HALONG HAS
ALREADY EXPERIENCED SOME WEAKENING IN THE NOW MARGINAL ENVIRONMENTAL 
CONDITIONS AND IS FORECAST TO DROP TO 115 KTS OVER THE NEXT 12 HOURS 
AND THEN START A MORE RAPID WEAKENING PHASE AS IT CONTINUES EAST-
NORTHEASTWARD. BY TAU 24, VWS (40+ KTS), DRY AIR WRAPPING INTO THE 
SOUTHERN SEMICIRCLE, AND COOLER SEA SURFACE TEMPERATURES (26-27 C) 
WILL BRING TY 28W DOWN TO 100 KTS. THE EXTRATROPICAL TRANSITION WILL 
RAPIDLY PROGRESS AND BY TAU 48, TY 28W IS FORECASTED TO BECOME FULLY 
EXTRATROPICAL WHILE MAINTAINING SURFACE INTENSITIES OF 50 KTS UNDER 
THE INFLUENCE OF THE MID-LATITUDE UPPER-LEVEL JET.

MODEL DISCUSSION: NUMERICAL WEATHER PREDICTION GUIDANCE REMAINS IN
GOOD AGREEMENT THAT TY 28W WILL CONTINUE ON A EAST-NORTHEASTWARD
TRACK WITH A CROSS-TRACK SPREAD OF 35 NM AT TAU 36. THE JTWC TRACK
FORECAST IS PLACED WITH HIGH CONFIDENCE THROUGHOUT THE ENTIRETY OF
THE FORECAST PERIOD AND ALIGNED CLOSELY WITH THE MULTI-MODEL
CONSENSUS. MOST OF THE JTWC INTENSITY GUIDANCE ENVELOPE MEMBERS
ILLUSTRATE STEADY WEAKENING OVER THE NEXT 12 HOURS, FOLLOWED BY A
SHARP WEAKENING PHASE UNTIL THE END OF THE FORECAST PERIOD. THE
JTWC INTENSITY FORECAST IS ASSESSED WITH HIGH CONFIDENCE BASED ON
THE MAJORITY OF CONSENSUS MEMBERS AND QUICK RATE OF DECAY AS THE
SYSTEM UNDERGOES EXTRATROPICAL TRANSITION.

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