WDPN32 PGTW 172100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 19W (CHANTHU) 
WARNING NR 047//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 33.9N 134.3E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 280 NM WEST-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: EASTWARD AT 23 KTS
   SIGNIFICANT WAVE HEIGHT: 0 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE SYSTEM
RAPIDLY COLLAPSED AND UNRAVELED AS IT DRAGGED ACROSS SOUTHWESTERN
HONSHU AND SHIKOKU, JAPAN. A COMPOSITE RADAR LOOP FROM JMA DEPICTED
THUNDERSTORMS THAT MOMENTARILY TRIGGERED DOWNBURSTS OF OVER 40KTS,
REPORTED BY SURFACE OBSERVATIONS IN SHIKOKU, THAT HAVE SINCE
SUBSIDED. THE INITIAL POSITION AND INTENSITY ARE ASSESSED WITH HIGH
CONFIDENCE BASED ON TRIANGULATION FROM NUMEROUS 171800Z WIND AND
SEA LEVEL PRESSURE OBSERVATIONS NEARBY, INCLUDING MORUTOMISAKI AND
FUKUSHIMA AB. ANALYSIS INDICATES TD 19W IS NOW UNDRGOING
EXTRA-TROPICAL TRANSITION (ETT) IN AN UNFAVORABLE ENVRONMENT WITH
DRY NORHTWESTERLY AIR ENTRAINMENT, FRICTIONAL EFFECTS OVER LAND,
AND STRONG VWS, WITH A STRONG POLEWARD OUTFLOW GREATLY OFFSET BY
THE STRONG VWS. THE CYCLONE IS TRACKING ALONG THE NORTHERN
PERIPHERY OF THE STR TO THE SOUTH.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR )TO THE SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS ADT: 35 KTS AT 171730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: OVER LAND
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TD CHANTHU WILL CONTINUE EASTWARD UNDER THE
STR AND EXIT INTO THE PACIFIC OCEAN AROUND TAU 06, AND BY TAU 36
WILL BE 161NM EAST-SOUTHEAST OF YOKOSUKA. THE UNFAVORABLE CONDITIONS
WILL CONTINUE TO ERODE THE SYSTEM AND ITS ASSOCIATED REMNANT
CONVECTION. HOWEVER, CONCURRENT ETT AND INFUSION INTO THE BAROCLINIC 
ZONE WILL RESULT IN A SLOWER AND MORE HOMOGENEOUS REDUCTION OF 
CENTRAL 
WIND SPEED. TD 19W IS EXPECTED TO TRANSFORM INTO A COLD-CORE LOW BY 
TAU 24 AND DISSIPATE BY TAU 36, OR SOONER. 
  
MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT WITH AFUM
AND GFS THE NOTABLE LEFT OUTLIERS, LENDING HIGH CONFIDENCE TO THE
JTWC TRACK FORECAST THAT IS LAID JUST TO THE RIGHT OF THE MODEL
CONSENSUS TO OFFSET THE OUTLIERS.  

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