WDPN32 PGTW 290900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (SHANSHAN) WARNING NR 032//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 32.9N 130.5E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 42 NM EAST-SOUTHEAST OF SASEBO, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 10 KTS

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY AND A COMPOSITE
RADAR LOOP SHOW RAPID EROSION AND UNRAVELING OF CONVECTIVE TOPS AND
FEEDER BANDS AFTER THE SYSTEM MADE LANDFALL INTO KYUSHU, 
APPROXIMATELY 40NM EAST-SOUTHEAST OF SASEBO. THE INITIAL POSITION
IS PLACED WITH HIGH CONFIDENCE BASED ON THE DEFINED CIRCULATION ON
THE RADAR LOOP THAT WAS CONCENTRIC WITH THE TIGHT AGENCY AND RADAR
FIX CLUSTER. THE INITIAL INTENSITY IS BASED ON THE HIGH END OF
AGENCY AND AUTOMATED DVORAK INTENSITIES. ANALYSIS INDICATES THE
ENVIRONMENT HAS BECOME HIGHLY UNFAVORABLE DUE TO INTERACTION WITH THE
RUGGED TERRAIN.

INITIAL WIND RADII BASIS: RECENT SAR DATA AND SURFACE WIND
OBSERVATIONS. 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   RJTD: T4.0 - 65 KTS
   CIMSS SATCON: 61 KTS AT 290438Z
   CIMSS ADT: 59 KTS AT 290530Z
   CIMSS AIDT: 63 KTS AT 290530Z
   CIMSS DMNT: 61 KTS AT 290530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: FORECAST REDUCED TO TAU 72 IN
ANTICIPATION OF EARLY DISSIPATION OVER LAND. 

FORECAST DISCUSSION: TYPHOON SHANSHAN WILL TRACK MORE NORTHEASTWARD
THEN EASTWARD ALONG THE EDGE OF A SHALLOWER REFLECTION OF A
RECEDING STEERING STR, AND MOSTLY OVER LAND AS IT DRAGS ACROSS THE
ISLANDS OF KYUSHU INTO SHIKOKU, AND HONSHU. THE HIGHLY UNFAVORABLE
ENVIRONMENT WILL RAPIDLY ERODE THE SYSTEM TO DISSIPATION BY TAU 72. 
HOWEVER, THERE IS A POSSIBILITY, AS INDICATED BY A FEW NUMERICAL 
TRACK MODELS, THAT THE SYSTEM WILL MAKE A TIGHT U-TURN BACK INTO THE 
PACIFIC OCEAN AND RE-INTENSIFY. 

MODEL DISCUSSION: THE NUMERICAL TRACK MODELS ARE IN GOOD AGREEMENT
UP TO TAU 36; AFTERWARD, NVGM, GFS, AND AEMN LOOP THE VORTEX
CLOCKWISE BACK OVER WATER. THE MAJORITY OF THE MODELS SLOW DOWN THE
VORTEX UP TO TAU 72 BEFORE ACCELERATING IT NORTHEASTWARD THROUGH
HONSHU. IN VIEW OF THESE, THERE IS ONLY MEDIUM CONFIDENCE IN THE
JTWC TRACK FORECAST. GIVEN THE VARIABILITY OF A LAND TRACK AND
THE POSSIBILITY OF A RETURN TO WATER, THERE IS LOW CONFIDENCE IN
THE JTWC INTENSITY FORECAST.  

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