WDPN31 PGTW 031500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 27W (NYATOH) WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.8N 142.3E
   INITIAL INTENSITY: 110 KTS
   GEOGRAPHIC REFERENCE: 81 NM SOUTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 21 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY AND A 031223Z
METOP-B MHS 89GHZ MICROWAVE IMAGE DEPICT A RAPIDLY WEAKENING SYSTEM
WITH DIMINISHED CORE CONVECTION SHEARED OVER THE NORTHERN QUADRANT.
THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE ALONG THE
SOUTHWESTERN EDGE OF THE DEEP CONVECTION BASED ON THE EIR IMAGERY.
THE INITIAL INTENSITY OF 110 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON A BLEND OF THE PGTW, KNES AND RJTD CURRENT INTENSITY
ESTIMATES. ENVIRONMENTAL ANALYSIS DEPICTS UNFAVORABLE CONDITIONS
WITH STRONG VERTICAL WIND SHEAR (40-50 KNOTS) OFFSET SOMEWHAT BY
ROBUST POLEWARD OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE
POSITIONED TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T6.5 - 127 KTS
   KNES: T5.5 - 102 KTS
   CIMSS SATCON: 115 KTS AT 030926Z
   CIMSS ADT: 115 KTS AT 031140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 40+ KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: 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: TY 27W IS WEAKENING RAPIDLY DUE TO STRONG VWS
WITH DEEP CONVECTION SHEARING TO THE NORTH. THE SYSTEM IS FORECAST
TO RAPIDLY WEAKEN THROUGH TAU 48 DUE TO PERSISTENT STRONG VWS AND
DRY AIR ENTRAINMENT. THE SYSTEM SHOULD CONTINUE TO TRACK
NORTHEASTWARD AND SLOW THROUGH TAU 24. AFTER TAU 24, TY 27W WILL
STALL AND BECOME QUASI-STATIONARY AS IT ENCOUNTERS LOW-LEVEL
NORTHEASTERLIES AND IS EXPECTED TO DISSIPATE BY TAU 48.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
THROUGH TAU 24 THEN DIVERGES WITH THE SEVERAL MODELS INDICATING A
SHARP EQUATORWARD TRACK CHANGE AND OTHERS INDICATING DISSIPATION
NEAR 30N. THE BULK OF THE ECMWF (EPS) AND GFS (GEFS) ENSEMBLE
SOLUTIONS SUPPORT THE JTWC FORECAST TRACK SCENARIO, HOWEVER, DUE TO
THE UNCERTAINTY IN THE EXACT TIMING OF THE STALL THERE IS LOW
CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: LOW
   INTENSITY 0 - 72 HR: LOW//
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