WDPN33 PGTW 191500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (NANMADOL) WARNING 
NR 028//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 36.1N 134.3E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 153 NM NORTHEAST OF IWAKUNI, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 20 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A BROAD
SHIELD OF CONVECTION SHEARING DOWNSTREAM FROM AN PROGRESSIVELY LESS
ORGANIZED CIRCULATION CENTER. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON RECENT SATELLITE FIXES FROM PGTW, RJTD
AND KNES AS WELL AS ANIMATED RADAR IMAGERY AND SYNOPTIC
OBSERVATIONS FROM JAPAN. THE INITIAL INTENSITY OF 50 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON SYNOPTIC OBSERVATIONS
AROUND THE CIRCULATION CENTER AND PERSISTENCE. TS 16W HAS CONTINUED
TO UNDERGO EXTRATROPICAL TRANSITION AND HAS STEADILY WEAKENED DUE
TO INCREASING VERTICAL WIND SHEAR, LAND INTERACTION WITH THE
SOUTHERN PORTION OF THE CIRCULATION, AND PASSAGE OVER UNFAVORABLY
COOL WATER.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK AND PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR) TO
THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   CIMSS ADT: 39 KTS AT 191140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 30+ KTS
   SST: 25-26 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 16W IS ACCELERATING EAST-NORTHEASTWARD
WITHIN A STRENGTHENING GRADIENT BETWEEN THE CURRENT STEERING RIDGE
AND A MID-LATITUDE TROUGH TO THE NORTH. THE SYSTEM WILL CONTINUE TO
MOVE QUICKLY EAST-NORTHEASTWARD, MERGE WITH THE AFOREMENTIONED
MID-LATITUDE TROUGH, AND COMPLETE EXTRATROPICAL TRANSITION BY TAU
12. STEADY WEAKENING IS ANTICIPATED THROUGHOUT THE FORECAST PERIOD
DUE TO PERSISTENT VERTICAL WIND SHEAR, LAND INTERACTION, PASSAGE
OVER COOLER WATER AND AN INFUSION OF DRY AIR FROM THE NORTH AND
WEST. DESPITE THE WEAKENING TREND, GALE FORCE WINDS ARE POSSIBLE
ACROSS HONSHU IN THE NEAR-TERM, PARTICULARLY IN AREAS THAT ARE
EXPOSED TO ONSHORE FLOW AND PRONE TO TERRAIN-INDUCED FUNNELING.

MODEL DISCUSSION: NUMERICAL MODEL TRACK FORECASTS REMAIN IN GOOD
AGREEMENT THOUGH TAU 24, WITH THE GFS AND GEFS ENSEMBLE MEAN
PREDICTING A TRACK SLIGHTLY TO THE SOUTH OF THE PRIMARY MODEL
GROUPING. AMONG SOLUTIONS IN THE PRIMARY GROUPING, TRACK SPREAD IS
MOST PRONOUNCED IN THE ALONG-TRACK DIRECTION. THERE IS HIGH 
CONFIDENCE IN THE ORIENTATION OF THE FORECAST TRACK ALONG THE 
NORTHERN COAST OF HONSHU AND MEDIUM CONFIDENCE IN THE TRACK OVERALL 
DUE TO NOTED TRACK SPEED UNCERTAINTY. NUMERICAL MODELS REMAIN IN VERY 
GOOD AGREEMENT WITH RESPECT TO THE ANTICIPATED INTENSITY, LENDING 
HIGH CONFIDENCE TO THAT ASPECT OF THE FORECAST. 

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