WDPN32 PGTW 112100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 19W (CHANTHU) WARNING NR 023//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.8N 122.0E
   INITIAL INTENSITY: 110 KTS
   GEOGRAPHIC REFERENCE: 386 NM SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 45 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TY 19W CONTINUES TO EXPERIENCE A SERIES OF FAIRLY QUICK EYEWALL
REPLACEMENT CYCLES (ERC) INCLUDING THE ONGOING ERC, WHICH HAS
RESULTED IN THE RE-DEVELOPMENT OF A SMALL EYE AND CORE. ANIMATED
ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SMALL CORE OF
INTENSE CONVECTION SURROUNDING AN 8NM EYE WITH EXTENSIVE SPIRAL
BANDING OVER THE SOUTHERN SEMICIRCLE. POLEWARD AND EQUATORWARD
OUTFLOW HAVE REMAINED ROBUST WITH LOW VERTICAL WIND SHEAR (VWS) AND
WARM SST. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED
ON EIR IMAGERY. THE INITIAL INTENSITY OF 110 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE PGTW AND KNES DVORAK ESTIMATES AND 
THE RECENT SATCON ESTIMATE. THE 112100Z PGTW DVORAK ESTIMATE IS SET 
AT A DT 5.5 (102 KNOTS) BASED ON A DG EYE AND SURROUNDING BLACK RING
WITH A CURRENT INTENSITY OF 6.0 (115 KNOTS). THE HIGHER RESOLUTION
UW-CIMSS EIR IMAGERY INDICATES A WARMER EYE TEMPERATURE OF -14.7C SO
THERE IS SOME UNCERTAINTY IN THE INITIAL INTENSITY, WHICH COULD BE
CLOSER TO A T6.0 (115 KNOTS) WITH A BANDING FEATURE.

INITIAL WIND RADII BASIS: PERSISTENCE FROM RECENT ASCAT IMAGERY. 

CURRENT STEERING MECHANISM: DEEP-LAYERED, NORTH-SOUTH ORIENTED
SUBTROPICAL RIDGE (STR) ENTRENCHED TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T7.0 - 140 KTS 
   KNES: T6.0 - 115 KTS
   CIMSS SATCON: 110 KTS AT 111351Z
   CIMSS ADT: 102 KTS AT 111740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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 19W WILL TRACK POLEWARD ALONG THE WESTERN
PERIPHERY OF THE STR THROUGH TAU 72. THE SYSTEM SHOULD STEADILY
WEAKEN AS IT INTERACTS WITH TAIWAN AND UPPER-LEVEL DIVERGENCE 
DECREASES AS THE SYSTEM BEGINS TO INTERACT WITH AN UPPER-LEVEL 
SUBTROPICAL TROUGH EXPECTED TO DEEPEN OVER EASTERN CHINA OVER THE 
NEXT TWO DAYS. IN THE EXTENDED PERIOD, TY 19W IS FORECAST TO TRACK 
SLOWLY EASTWARD WITHIN WEAK WESTERLY FLOW AND WILL WEAKEN TO TS 
STRENGTH (45 KNOTS) BY TAU 120. NUMERICAL MODEL GUIDANCE INDICATES A 
FAIRLY ATYPICAL MIDLATITUDE PATTERN WITH WEAK SUBTROPICAL WESTERLIES 
AND THE FRONTAL ZONE TO THE NORTH OVER THE KOREAN PENINSULA, 
THEREFORE, EXTRATROPICAL TRANSITION IS NOT LIKELY. ADDITIONALLY, 
TRACK SPEEDS SHOULD BE UNUSUALLY SLOW.   

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT
THROUGH TAU 48 WITH A 45NM SPREAD IN SOLUTIONS AT TAU 48. AFTER TAU
48, THERE IS INCREASING UNCERTAINTY WITH WEAKER STEERING FLOW THUS 
MEDIUM OVERALL TRACK CONFIDENCE. IN THE EXTENDED PERIOD, THERE IS LOW
CONFIDENCE IN THE JTWC TRACK FORECAST WITH LARGE SPREAD IN MODEL
SOLUTIONS. THERE IS LOW CONFIDENCE IN THE JTWC INTENSITY FORECAST
DUE TO THE COMPLEX INTERACTIONS WITH THE AFOREMENTIONED TROUGH AND
SUBTROPICAL WESTERLIES AS WELL AS INTERACTION WITH TAIWAN AND
EASTERN CHINA.   

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: LOW
   INTENSITY 72-120 HR: LOW//
NNNN