WDPN32 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 28W (HALONG) WARNING NR 019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 33.0N 141.1E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 155 NM SOUTH-SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 39 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
(TY) 28W WITH A CONSIDERABLY LARGER EYE, EXPANDING BY APPROXIMATELY
25NM OVER THE LAST 6 HOURS. THE EYEWALL REPLACEMENT CYCLE (ERC) HAS 
COMPLETED, CONTRIBUTING TO THE DROP IN INTENSITY AND EXPANDING 
EYEWALL. POLEWARD OUTFLOW IS STILL ROBUST; HOWEVER, THE EQUATORWARD 
OUTFLOW CHANNEL HAS BEEN SUBSTANTIALLY DAMPENED. ANALYSIS INDICATES A 
MARGINALLY UNFAVORABLE ENVIRONMENT, CHARACTERIZED BY HIGH (30+ KTS) 
VERTICAL WIND SHEAR, MARGINAL (26-27 C) SEA SURFACE TEMPERATURES 
(SST), AND EXTENSIVE DRY AIR SURROUNDING 28W. THE INITIAL POSITION IS 
PLACED WITH HIGH CONFIDENCE BASED ON A COMBINATION OF THE LARGE EYE 
VISIBLE IN THE ANIMATED EIR, RADAR FIXES, AND A 082128Z WSFM 89GHZ 
COLOR COMPOSITE MICROWAVE IMAGE. THE INITIAL INTENSITY OF 105 KTS IS 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND 
OBJECTIVE INTENSITY AIDS LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T5.5 - 102 KTS
   KNES: T6.0 - 115 KTS
   CIMSS ADT: 112 KTS AT 090000Z
   CIMSS AIDT: 108 KTS AT 090000Z
   CIMSS D-PRINT: 90 KTS AT 090030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 30+ KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

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 28W (HALONG) WILL CONTINUE ITS EAST-
NORTHEASTWARD MOTION, WHILE ACCELERATING AS IT ROUNDS THE 
NORTHWESTERN PERIPHERY OF THE STEERING STR TO THE SOUTHEAST. 28W IS 
FORECAST TO BEGIN EXTRATROPICAL TRANSITION (ETT) AROUND TAU 12, 
THOUGH IT IS ALREADY BEGINNING TO SHOW INTERACTION WITH THE UPPER-
LEVEL JET. HALONG IS FORECAST TO COMPLETE ETT NO LATER THAN TAU 36. 
28W IS EXPECTED TO RAPIDLY DETERIORATE BEGINNING IMMINENTLY AND 
THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD DUE TO THE POOR 
ENVIRONMENTAL CONDITIONS, INCLUDING COOLING SST, SIGNIFICANT DRY AIR 
ENTRAINMENT, AND INTERACTION WITH THE UPPER-LEVEL WESTERLIES.

MODEL DISCUSSION: DETERMINISTIC TRACK MODEL GUIDANCE IS IN TIGHT
AGREEMENT FOR THE DURATION OF THE FORECAST PERIOD, WITH A 40NM
CROSS-TRACK SPREAD AT TAU 36. AS A RESULT, THE JTWC TRACK FORECAST
IS PLACED WITH HIGH CONFIDENCE. RELIABLE INTENSITY GUIDANCE IS IN
GOOD AGREEMENT ON A CONSISTENT AND RAPID WEAKENING TREND, LENDING
HIGH CONFIDENCE TO THE JTWC INTENSITY FORECAST.

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