WDPN31 PGTW 030900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 27W (NYATOH) WARNING NR 016//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.5N 140.5E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 145 NM SOUTH-SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 23 KTS
   SIGNIFICANT WAVE HEIGHT: 40 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
40-45NM EYE WITH WEAKENING DEEP CONVECTION AND WARMING CLOUD TOP
TEMPERATURES. HOWEVER, A 030358Z AMSR2 89GHZ MICROWAVE IMAGE SHOWS
A WELL-DEFINED MICROWAVE EYE FEATURE WITH A SURROUNDING EYEWALL AND
DEEP CONVECTION SHEARING PRIMARILY OVER THE NORTHERN QUADRANT. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EIR
IMAGERY. THE INITIAL INTENSITY OF 120 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON A BLEND OF THE DATA-T ESTIMATES OF T6.0 (115
KNOTS) FROM PGTW AND RJTD, AND THE CURRENT INTENSITY ESTIMATES OF
6.5 (127 KNOTS). ALTHOUGH THE ADT CI REMAINS AT 6.7-6.9 (1320137
KNOTS), THE RAW T NUMBERS AND FINAL T NUMBERS ARE DECREASING
QUICKLY AS THE SYSTEM RAPIDLY WEAKENS. ENVIRONMENTAL ANALYSIS
DEPICTS MARGINAL 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: 6.5 - 127 KTS
   RJTD: 6.5 - 127 KTS
   KNES: 6.5 - 127 KTS
   CIMSS SATCON: 134 KTS AT 030412Z
   CIMSS ADT: 137 KTS AT 030540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 40+ 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 27W IS WEAKENING RAPIDLY DUE TO STRONG VWS
WITH DEEP CONVECTION SHEARING TO THE NORTH. EIR IMAGERY AFTER
030600Z CONTINUES TO INDICATE A WEAK EYE ON THE SOUTHERN EDGE OF
THE SHRINKING CONVECTIVE CORE. THE SYSTEM IS FORECAST TO RAPIDLY
WEAKEN THROUGH TAU 72 DUE TO PERSISTENT STRONG VWS AND DRY AIR
ENTRAINMENT. THE SYSTEM SHOULD CONTINUE TO TRACK NORTHEASTWARD AND
SLOW THROUGH TAU 36. AFTER TAU 36, TY 27W WILL STALL AND TURN
SHARPLY EQUATORWARD UNDER THE LOW-LEVEL NORTHEASTERLIES AND IS
EXPECTED TO DISSIPATED BY TAU 72.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
THROUGH TAU 24 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 LOW
CONFIDENCE.

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