WDPN32 PGTW 072100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 19W (CHANTHU) WARNING NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.3N 133.5E
   INITIAL INTENSITY: 125 KTS
   GEOGRAPHIC REFERENCE: 690 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
COMPACT, SYMMETRIC CORE OF INTENSE CONVECTION SURROUNDING A 6-NM
PINHOLE EYE. OBJECTIVE ADT ESTIMATES ARE NOT HANDLING THE INTENSITY
WELL DUE TO THE PINHOLE EYE AND ARE VASTLY UNDERESTIMATING THE
INITIAL INTENSITY. EIR ALSO INDICATES TROCHOIDAL MOTION (WOBBLE) AS
THE SYSTEM TRACKS GENERALLY WESTWARD UNDER THE STEERING INFLUENCE
OF THE SUBTROPICAL RIDGE POSITIONED TO THE NORTH. UPPER-LEVEL
CONDITIONS ARE VERY FAVORABLE WITH RADIAL OUTFLOW AND LOW VERTICAL
WIND SHEAR. ADDITIONALLY, SST VALUES ARE CONDUCIVE AND OCEAN HEAT
CONTENT VALUES ARE VERY HIGH SUPPORTING THE RECENT EXTREME RAPID
INTENSIFICATION EVENT. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE PINHOLE EYE. THE INITIAL INTENSITY OF 125
KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE PGTW ESTIMATE AS
WELL AS THE KNES DATA-T ESTIMATE OF 6.5.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T6.0 - 115 KTS
   KNES: T6.0 - 115 KTS
   CIMSS SATCON: 89 KTS AT 071713Z
   CIMSS ADT: 84 KTS AT 071740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL
   OTHER FACTORS: HIGH, VERY FAVORABLE OCEAN HEAT CONTENT VALUES.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: TY 19W HAS UNDERGONE EXTREME RAPID
INTENSIFICATION WITH AN 80-KNOT INCREASE IN INTENSITY OVER THE PAST
24 HOURS.

FORECAST DISCUSSION: TY 19W IS FORECAST TO TRACK GENERALLY WESTWARD
TO WEST-NORTHWESTWARD THROUGH TAU 72 UNDER THE STEERING INFLUENCE
OF THE DEEP-LAYERED STR ENTRENCHED TO THE NORTH. TY 19W WILL
INTENSIFY TO SUPERTYPHOON (STY) STRENGTH (PEAK 135 KNOTS) SHORTLY
AND WILL MAINTAIN STY INTENSITY FOR AT LEAST THE NEXT 36 HOURS WITH
SOME POTENTIAL FOR AN EYEWALL REPLACEMENT CYCLE WHICH COULD PRODUCE
SOMEWHAT ERRATIC INTENSITIES THROUGH TAU 72. AFTER TAU 72, THE 
SYSTEM SHOULD TURN NORTHWESTWARD ALONG THE SOUTHWEST PERIPHERY OF 
THE STR WHILE WEAKENING STEADILY DUE TO LAND INTERACTION. UPPER-
LEVEL FLOW IS EXPECTED TO REMAIN ZONAL OVER THE EAST CHINA SEA WITH 
NO DEEP MIDLATITUDE SHORTWAVE TROUGHS EXPECTED TO WEAKEN THE 
SUBTROPICAL STEERING RIDGE THUS RECURVATURE IS ASSESSED AS UNLIKELY.

MODEL DISCUSSION: THERE IS HIGH CONFIDENCE IN THE JTWC TRACK
FORECAST THROUGH TAU 72 WITH A 60NM TO 90NM SPREAD IN SOLUTIONS
FROM TAU 48 TO TAU 60. JGSM IS THE LONE OUTLIER WITH A MORE
POLEWARD, UNREALISTIC TRACK OVER NORTHERN TAIWAN INTO THE STR.
AFTER TAU 72, THERE IS INCREASING UNCERTAINTY AND MEDIUM CONFIDENCE
IN THE JTWC TRACK, HOWEVER, THE BULK OF THE DETERMINISTIC AND ECMWF
ENSEMBLE SOLUTIONS INDICATE A HIGH PROBABILITY TRACK OVER OR SOUTH
OF TAIWAN. INTENSITY GUIDANCE, IN GENERAL, HAS STRUGGLED WITH THIS
SYSTEM AND CONTINUES TO INDICATE A LARGE SPREAD IN INTENSITY
GUIDANCE. THE JTWC INTENSITY FORECAST IS PLACED HIGHER THAN THE
INTENSITY CONSENSUS (ICNW). THE LIKELIHOOD OF BINARY INTERACTION
WITH TS 18W REMAINS LOW AS THE TWO SYSTEMS CLOSE WITHIN 500NM AT
TAU 60, WHICH IS BORDERLINE AND UNLIKELY DUE TO THE COMPACT NATURE
OF EACH SYSTEM.  

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