WDPN31 PGTW 200900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 28W (RAI) WARNING NR 
030//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.3N 111.8E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 275 NM SOUTH-SOUTHWEST OF HONG KONG
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAPIDLY
DECAYING SYSTEM WITH THE MAIN CONVECTION GREATLY ERODED AND SHEARED
NORTHEASTWARD, FULLY EXPOSING A RAGGED LOW LEVEL CIRCULATION (LLC).
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
EXPOSED LLC IN THE MSI LOOP. THE INITIAL INTENSITY IS ASSESSED LOWER 
THAN THE MAJORITY OF AGENCY AND AUTOMATED DVORAK ESTIMATES BUT 
HIGHER THAN THAT OF PGTW TO REFLECT THE RAPID DECAY. TS 28W IS NOW 
IN A HIGHLY UNFAVORABLE ENVIRONMENT WITH STRONG POLEWARD OUTFLOW 
OFFSET BY HIGH VWS, COOLING SST, AND COLD DRY AIR INTRUSION 
ASSOCIATED WITH THE NORTHEASTERLY WIND SURGE IN THE SOUTH CHINA SEA. 
THE CYCLONE IS TRACKING WITH THE GRADIENT FLOW BETWEEN MID-LATITUDE 
TROUGH TO THE WEST AND WESTERN PERIPHERY OF THE STR TO THE EAST.

INITIAL WIND RADII BASIS: PERSISTENCE, ADJUSTED FOR RAPID
DETERIORATION. 

CURRENT STEERING MECHANISM: GRADIENT FLOW BETWEEN MID-LATITUDE 
TROUGH TO THE WEST AND WESTERN PERIPHERY OF THE LOW REFLECTION OF 
THE SUBTROPICAL RIDGE (STR) TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.0 - 25 KTS
   RJTD: T5.0 - 90 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 61 KTS AT 200251Z
   CIMSS ADT: 57 KTS AT 200540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 25-30 KTS
   SST: 24-25 CELSIUS
   OUTFLOW: STRONG 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: TS RAI WILL CONTINUE TO RAPIDLY DECAY AS IT 
DRIFTS NORTHEASTWARD IN THE SCS DUE TO THE AFOREMENTIONED HIGHLY
UNFAVORABLE ENVIRONMENT, LEADING TO DISSIPATION BY TAU 24. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT, LENDING
HIGH CONFIDENCE TO THE JTWC TRACK FORECAST.

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