WDPN32 PGTW 032100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 06W (KHANUN) WARNING NR 031//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.8N 124.3E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 189 NM WEST OF KADENA AB, OKINAWA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 29 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS TY KHANUN
REMAINED QUASI-STATIONARY IN THE EAST CHINA SEA, CAUGHT BETWEEN THE
SUBTROPICAL RIDGE (STR) TO THE NORTH AND THE NEAR EQUATORIAL RIDGE
(NER) TO THE SOUTH. THERE IS REDUCED POLEWARD AND EQUATORWARD 
OUTFLOW, EVIDENT IN THE EIR LOOP. CONVECTION AROUND THE CORE 
ESPECIALLY ALONG THE NORTHWEST PERIPHERY HAS SIGNIFICANTLY ERODED; 
HOWEVER, AN OUTLINE OF A REMNANT EYE IN THE MIDDLE OF THE CORE IS 
STILL DISCERNIBLE. THE INITIAL POSITION IS PLACED WITH HIGH 
CONFIDENCE BASED ON THE REMNANT EYE. THE INITIAL INTENSITY IS ALSO 
PLACED WITH HIGH CONFIDENCE BASED ON OVERALL ASSESSMENT OF AGENCY AND 
AUTOMATED DVORAK ESTIMATES AND REFLECTS THE SIGNIFICANT 6-HR 
WEAKENING. ANALYSIS INDICATES A DEGRADED, UNFAVORABLE ENVIRONMENT 
MOSTLY CAUSED BY COOLING SST DUE TO UPWELLING BROUGHT ON BY THE 
QUASI-STATIONARY MOTION AND BY THE DIMINISHED UPPER LEVEL 
VENTILATION.

INITIAL WIND RADII BASIS: PERSISTENCE AND PRORATED FROM LAST
WARNING.  

CURRENT STEERING MECHANISM: QUASI-STATIONARY BETWEEN THE STR TO THE 
NORTH AND THE NER TO THE SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS
   CIMSS ADT: 69 KTS AT 031730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 06W WILL SLOWLY TRANSITION FROM BEING QUASI-
STATIONARY AND TRACK WESTWARD AS THE NER BUILDS AND BECOMES THE 
PRIMARY STEERING MECHANISM. AROUND TAU 48, A SECONDARY STR TO THE 
EAST-NORTHEAST WILL ASSUME STEERING AND DRIVE THE SYSTEM POLEWARD 
TOWARD SHIKOKU,JAPAN. THE UNFAVORABLE ENVIRONMENT WILL PREVAIL AND 
CONTINUE TO ERODE THE SYSTEM DOWN TO 55KTS BY TAUS 36-48. AFTERWARD, 
INCREASING POLEWARD OUTFLOW AS IT APPROACHES THE PREVAILING 
WESTERLIES WILL INVIGORATE THE DYING CONVECTION AND PROMOTE ANOTHER 
INTENSIFICATION PHASE, AND BY TAU 120, WILL REACH 70KTS AS IT 
APPROACHES SHIKOKU.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN OVERALL GOOD AGREEMENT
WITH A GRADUAL AND EVEN SPREAD TO 185NM BY TAU 120 WITH JGSM ON THE
LEFT MARGIN AND NAVGEM ON THE RIGHT MARGIN OF THE ENVELOPE. HOWEVER, 
DUE TO THE UNCERTAINTIES WITH THE ALONG-TRACK STORM MOTION AS THE 
CYCLONE COMES OUT OF ITS QUASI-STATIONARY PHASE, THERE IS ONLY MEDIUM 
CONFIDENCE IN THE JTWC TRACK FORECAST THAT IS LAID VERY CLOSE TO THE 
MODEL CONSENSUS.  

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