WDPN31 PGTW 220900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (SEVENTEEN) 
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.9N 136.5E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 288 NM WEST-NORTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC), WITH DEEP PERSISTENT
CONVECTION DISPLACED TO THE NORTHERN SECTOR OF THE SYSTEM. AN
EARLIER BULLSEYE 220102Z METOP-C ASCAT IMAGE REVEALED A TIGHTLY
WOUND 30KT SYSTEM. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE MSI IMAGERY. THE INITIAL INTENSITY OF 30
KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE PREVIOUS ASCAT,
ALONG WITH THE AGREEMENT OF THE AGENCY DVORAK INTENSITY ESTIMATES,
PGTW T2.0, RJTD T1.5 AND THE OBJECTIVE INTENSITY ESTIMATES LISTED 
BELOW.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA FROM 220102Z METOP-C
ASCAT.

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
NORTHEAST 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 36 KTS AT 220416Z
   CIMSS ADT: 33 KTS AT 220620Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: ENVIRONMENTAL CONDITIONS REMAIN MARGINALLY
FAVORABLE AS CHARACTERIZED BY WARM SEA SURFACE TEMPERATURES (SSTS)
(28-29C), AND STRONG POLEWARD OUTFLOW INDUCED BY AN UPPER LEVEL
TROUGH, SITUATED TO THE NORTHWEST OF 17W. AS TD 17W TRACKS POLEWARD
ALONG THE WESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE
(STR), TD 17W WILL BEGIN TO ROUND THE RIDGE AXIS BETWEEN TAUS 12
AND 24 AND INCREASE IN TRACK SPEED AND ONLY INCREASE INTENSITY TO A
PEAK OF 40KTS AS AN APPROACHING UPPER-LEVEL TROUGH MOVES IN FROM
THE WEST. AS THE SYSTEM NEARS THE COAST OF JAPAN, IT WILL BEGIN TO
ENCOUNTER STRONGER LOW-LEVEL SHEAR JUST BEFORE MAKING LANDFALL ON
MAINLAND HONSHU, NEAR THE CITY OF TAHARA, AICHI PREFECTURE, JAPAN
JUST AFTER TAU 36. TD 17W WILL CONTINUE ON A NORTHEAST TRACK OVER
LAND AND ENCOUNTER THE RUGGED TERRAIN, WHEREBY IT WILL QUICKLY
DECREASE IN INTENSITY AND LIKELY DISSIPATE BETWEEN TAU 48 AND TAU
72 OVER LAND, HOWEVER, A SLIGHT CHANCE REMAINS FOR THE SYSTEM TO
DISSIPATE OVER WATER.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN OVERALL TIGHT
AGREEMENT EXCEPT FOR JGSM AND NAVGEM, WHICH ARE THE WESTERN OUTLIERS 
THROUGH TAU 36, THEN QUICKLY CROSSES RIGHT OF ALL TRACKS. EXCLUDING 
JGSM AND NAVGEM, FROM THE TRACK ENVELOPE THERE IS ONLY A 57NM SPREAD 
IN THE SOLUTIONS UNTIL TAU 48. AFTER TAU 48 THE CIRCULATION BECOMES 
VERY WEAK AND THE ALONG-TRACK AND CROSS TRACK SPREAD WIDENS TO 320NM 
INDUCING A LACK OF CONFIDENCE BETWEEN TAU 48 AND 72. THE MOST LIKELY 
CAUSE OF THE LARGER SPREAD IS POSSIBLY DUE THE LAND INTERACTION AND 
SHORTWAVE TROUGH INTERACTION. THEREFORE, THE JTWC OFFICIAL TRACK 
FORECAST IS PLACED WITH MEDIUM CONFIDENCE THROUGH TAU 36 AND IS LOW 
THEREAFTER AS MODEL GUIDANCE LOSES THE LOW-LEVEL CIRCULATION OVER THE 
JAPANESE ALPS. THE JTWC INITIAL INTENSITY CONFIDENCE IS MEDIUM UP TO 
TAU 36, BUT DECREASES TO LOW AFTER LANDFALL DURING THE LAND 
INTERACTION.

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