WDPN31 PGTW 021500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 27W (NYATOH) WARNING NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.2N 136.7E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 472 NM SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TY 27W HAS RAPIDLY INTENSIFIED 35 KNOTS OVER THE PAST 24 HOURS FROM
65 KNOTS TO THE INITIAL INTENSITY OF 100 KNOTS. ANIMATED ENHANCED
INFRARED SATELLITE IMAGERY (EIR) CONTINUES TO INDICATE RAPID
CONSOLIDATION WITH A PARTIALLY CLOUD-FILLED, RAGGED EYE EVIDENT
WITH INTENSE CORE CONVECTION. A 021242Z METOP-B MHS 89GHZ MICROWAVE
IMAGE INDICATES A 35-40NM DIAMETER MICROWAVE EYE FEATURE, WHICH
SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. THE COINCIDENT
021240Z EIR IMAGE INDICATES THE PARTIAL EYE FEATURE IS ROTATING
CYCLONICALLY WITHIN THIS LARGER EYE. DVORAK INTENSITY ESTIMATES
HAVE JUMPED AS HIGH AS T6.0 (115 KNOTS) WITH DATA-T ESTIMATES UP TO
6.5 (127 KNOTS). ADT ESTIMATES AT 021210Z WERE AT 5.5 (102 KNOTS)
SUPPORTING THE INITIAL INTENSITY ASSESSMENT OF 100 KNOTS BUT HAVE
INCREASED QUICKLY TO 6.1 (117 KNOTS) AT 021340Z. BASED ON THE RAPID
INTENSIFICATION AND INCREASE IN DVORAK ESTIMATES AND ADT ESTIMATES,
THERE IS MEDIUM CONFIDENCE IN THE INITIAL INTENSITY ESTIMATE.
UPPER-LEVEL OUTFLOW REMAINS ROBUST WITH A STRONG POLEWARD OUTFLOW
CHANNEL. HOWEVER, VERTICAL WIND SHEAR (VWS) VALUES HAVE INCREASED
TO 20-25 KNOTS WITH SIGNIFICANT DRY AIR PRESENT OVER THE WESTERN
SEMICIRCLE.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA (PARTIAL IMAGE
COVERING THE CENTER AND WESTERN SEMICIRCLE). 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T5.0 - 90 KTS
   KNES: T6.0 - 115 KTS
   CIMSS SATCON: 90 KTS AT 021025Z
   CIMSS ADT: 102 KTS AT 021210Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 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 27W HAS MAINTAINED A RAGGED, PARTIALLY
CLOUD-FILLED EYE WHILE RAPIDLY INTENSIFYING WITH A SIGNIFICANT JUMP
IN DVORAK ESTIMATES OVER THE PAST SIX HOURS. DESPITE INCREASING,
HIGH VWS, TY 27W SHOULD BE ABLE TO INTENSIFY TO A PEAK OF 105 KNOTS
OR HIGHER WITHIN THE NEXT 06-12 HOURS. AFTER TAU 12, THE SYSTEM
WILL BEGIN INTERACTING WITH THE WESTERLIES ON THE SOUTHEASTERN 
PERIPHERY OF A DEEP MAJOR SHORTWAVE TROUGH WITH VWS VALUES 
INCREASING TO 30-40 KNOTS AND SIGNIFICANT DRY AIR ENTRAINMENT, WHICH 
WILL LEAD TO A FAIRLY RAPID WEAKENING TREND FROM TAU 24 TO TAU 72. 
THE SYSTEM SHOULD CONTINUE TO TRACK NORTHEASTWARD THROUGH TAU 48 BUT 
WILL STALL AND TURN SHARPLY EQUATORWARD UNDER THE LOW-LEVEL 
NORTHEASTERLIES BY TAU 72. TY 27W WILL DISSIPATE BY TAU 72 DUE TO 
VERY STRONG VWS EXCEEDING 50 KNOTS AND SIGNIFICANT DRY AIR 
ENTRAINMENT.     

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
THROUGH TAU 48 THEN DIVERGES WITH THE BULK OF THE MODELS INDICATING
A SHARP EQUATORWARD TRACK CHANGE. HOWEVER, THERE ARE SIGNIFICANT
DIFFERENCES IN THE STALL POINT AND TIMING OF THE SOUTHWARD TURN.
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 TURN THERE IS MEDIUM
CONFIDENCE.

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