WDPN31 PGTW 050300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (NURI) WARNING NR 21//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 20W (NURI), LOCATED APPROXIMATELY 213 NM WEST OF IWO 
TO, HAS TRACKED NORTHEASTWARD AT 10 KNOTS OVER THE PAST SIX HOURS.
ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A SLIGHT WEAKENING 
TREND; HOWEVER, THE SYSTEM HAS RETAINED TIGHTLY-CURVED BANDING (TCB) 
WRAPPING INTO A WELL-DEFINED LOW-LEVEL CIRCULATION CENTER. A 050055Z 
METOP-B 89GHZ IMAGE DEPICTS ORGANIZED, SYMMETRIC CORE CONVECTION 
WITH TCB WRAPPING INTO THE CENTER. THE INITIAL INTENSITY IS ASSESSED 
AT 100 KNOTS BASED ON DVORAK CURRENT INTENSITY ESTIMATES RANGING 
FROM 90 TO 102 KNOTS. UPPER-LEVEL ANALYSIS REVEALS A FAVORABLE 
ENVIRONMENT DUE TO VIGOROUS POLEWARD OUTFLOW INTO THE MIDLATITUDE 
WESTERLIES, WHICH IS OFFSETTING MODERATE VERTICAL WIND SHEAR (VWS). 
TY 20W IS CURRENTLY TRACKING POLEWARD AROUND THE NORTHWESTERN 
PERIPHERY OF THE SUBTROPICAL RIDGE. 
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TY 20W IS FORECAST TO ACCELERATE NORTHEASTWARD AS IT TRACKS 
POLEWARD OF THE SUBTROPICAL RIDGE AXIS, AND INTO THE STRONG 
MIDLATITUDE WESTERLIES. NEAR TAU 12, TY NURI SHOULD BEGIN EXTRA-
TROPICAL TRANSITION (ETT) AS IT INTERACTS WITH THE BAROCLINIC ZONE. 
TY 20W SHOULD COMPLETE ETT BY TAU 48 AS IT BECOMES EMBEDDED IN THE 
MIDLATITUDE WESTERLIES AND GAINS FRONTAL CHARACTERISTICS. DYNAMIC 
MODEL GUIDANCE IS IN TIGHT AGREEMENT, THEREFORE, THERE IS HIGH 
CONFIDENCE IN THE JTWC FORECAST TRACK, WHICH IS POSITIONED SLIGHTLY 
FASTER THAN THE MULTI-MODEL CONSENSUS. TY 20W IS FORECAST TO WEAKEN 
RAPIDLY AFTER TAU 12 DUE TO STRONG VWS AND INTERACTION WITH THE 
BAROCLINIC ZONE.//
NNNN