WDPN32 PGTW 300900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (SHANSHAN) WARNING 
NR 036//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 33.9N 132.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 25 NM SOUTH-SOUTHEAST OF IWAKUNI, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 04 KTS

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY AND A COMPOSITE
RADAR LOOP SHOW CONTINUED EROSION AND UNRAVELING OF CONVECTIVE 
TOPS AND FEEDER BANDS AS THE SYSTEM MADE LANDFALL OVER IWAKUNI IN
WESTERN HONSHU. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE DEFINED LOW LEVEL CIRCULATION (LLC) ON THE RADAR LOOP
THAT WAS CONCENTRIC WITH THE EXPOSED LLC IN THE EIR LOOP. THE
INITIAL INTENSITY IS PLACED WITH MEDIUM CONFIDENCE BASED ON
EXTRAPOLATION FROM NEARBY WIND AND SEA LEVEL PRESSURE OBSERVATIONS
AND SUPPORTED BY THE HIGH END OF RJTD AND AUTOMATED DVORAK
ESTIMATES. ANALYSIS INDICATES AN UNFAVORABLE ENVIRONMENT DUE TO
INTERACTION WITH THE RUGGED TERRAIN.

INITIAL WIND RADII BASIS: EXTRAPOLATED SURFACE WINDS.

CURRENT STEERING MECHANISM: SHALLOW LAYER OF SOUTHWEST EXTENSION OF
THE SUBTROPICAL
RIDGE (STR) TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   RJTD: T2.0 - 30 KTS
   CIMSS SATCON: 36 KTS AT 300445Z
   CIMSS ADT: 33 KTS AT 300530Z
   CIMSS DPRNT: 33 KTS AT 300500Z
   CIMSS DMNT: 36 KTS AT 300420Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 10-15 KTS
   SST: OVER LAND
   OUTFLOW: STRONG POLEWARD

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: TROPICAL STORM SHANSHAN WILL TRACK MORE
EASTWARD ALONG THE NORTHERN PERIPHERY OF THE STEERING STR AND
QUICKLY CROSS THE SETO INLAND SEA, THEN MAKE ANOTHER LAND CROSSING
ACROSS SHIKOKU, EXIT INTO AND DRIFT ACROSS THE KII CHANNEL BEFORE
MAKING A FINAL LANDFALL OVER SOUTHERN HONSHU NEAR WAKAYAMA BY TAU
24. AFTERWARD, A SECONDARY STR TO THE WEST WILL COMPETE FOR
STEERING AND PLACE THE SYSTEM IN A QUASI-STATIONARY MODE AS IT
APPROACHES THE CENTRAL JAPANESE ALPS. THE UNFAVORABLE ENVIRONMENT
WILL EVENTUALLY ERODE THE SYSTEM TO DISSIPATION BY TAU 48, POSSIBLY
SOONER.

MODEL DISCUSSION: THE NUMERICAL TRACK MODELS ARE IN GOOD AGREEMENT
UP TO TAU 24; AFTERWARD, THE MEMBERS DIVERGE SIGNIFICANTLY ALONG A
NORTHEASTWARD TRAJECTORY. IN VIEW OF THIS, THERE IS ONLY MEDIUM
CONFIDENCE IN THE JTWC TRACK FORECAST. GIVEN THE VARIABILITY OF A 
LAND TRACK AND THE POSSIBILITY OF AN EARLY DISSIPATION, THERE IS LOW 
CONFIDENCE IN THE JTWC INTENSITY FORECAST. 

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