WDPN31 PGTW 081500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (LAN) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.5N 148.1E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 323 NM WEST OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY CONTINUES TO
DEPICT A CONSOLIDATING SYSTEM WITH IMPROVED CONVECTIVE BANDING OVER
THE NORTHERN AND EASTERN SEMICIRCLES OBSCURING LOW LEVEL CIRCULATION
CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON A GROUPING OF AGENCY POSITION FIXES.
ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE FOR INTENSIFICATION DUE
TO WARM (30-31C) SEA SURFACE TEMPERATURES (SSTS), LOW (5-10 KTS)
VERTICAL WIND SHEAR (VWS), AND GOOD EQUATORWARD OUTFLOW. THE
INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON A COMBINATION OF AGENCY DVORAK ESTIMATES FROM PGTW, KNES,
RCTP, RJTD ALONG WITH AUTOMATED DVORAK ESTIMATES. ADDITIONALLY, A
081058Z ASCAT WHICH SHOWS 40-45 KTS OVER THE EASTERN SEMICIRCLE.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 34 KTS AT 081140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

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 07W IS FORECAST TO TRACK WEST-NORTHWESTWARD
ALONG THE SOUTHERN AND SOUTHWESTERN PERIPHERIES OF THE STR THROUGH
TAU 36. AFTER TAU 36, 07W WILL SLOW SLIGHTLY AND TURN NORTHWESTWARD
AS A MID-LATITUDE TROUGH TO THE NORTH WILL WEAKEN THE STR. BY TAU
48, THE STR IS EXPECTED TO POSITION TO A NORTH-SOUTH ORIENTATION
SUPPORTING A MORE NORTH-NORTHWESTWARD TRACK. AFTER TAU 72, TS 07W
IS EXPECTED TO ACCELERATE NORTHWESTWARD TOWARD HONSHU THROUGH THE
END OF THE FORECAST. TS 07W WILL INTENSIFY OVER THE NEXT 12 HOURS
AS IT CONSOLIDATES UNDER GENERALLY FAVORABLE CONDITIONS. BY TAU 24,
THE FORECAST CALLS FOR A STEEPER RATE OF INTENSIFICATION AND THE
POSSIBILITY OF RAPID INTENSIFICATION AS POLEWARD OUTFLOW IMPROVES.
AFTER WHICH A PEAK INTENSITY OF 85 KNOTS IS EXPECTED TO OCCUR NEAR
TAU 72.


MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE ARE IN OVERALL GOOD
THROUGH TAU 72, WITH ONLY A 75 NM SPREAD IN MODEL TRACK SOLUTIONS.
BY TAU 120 THE MODEL GUIDANCE INCREASES IN UNCERTAINLY WITH A
GRADUAL SPREAD TO 200 NM. THEREFORE, THE JTWC TRACK FORECAST IS
ASSESSED WITH MEDIUM CONFIDENCE TO ACCOUNT FOR THE CROSS TRACK
SPREAD AT TAU 120. INTENSITY GUIDANCE REMAINS FAIR AGREEMENT AND
SUPPORTS A RAPID INTENSIFICATION PHASE WITH HAFI INDICATING A
STEADY INTENSIFICATION PHASE TO A PEAK OF 95 KNOTS, WHILE AVNI
SHOWS A MORE MODEST INTENSIFICATION WITH A PEAK OF 75 KNOTS.
ADDITIONALLY, RAPID INTENSIFICATION (RI) GUIDANCE IS TRIGGERED
LENDING ADDITIONAL SUPPORT TO THE IMMINENT RI PHASE. FOR THESE
REASONS THE JTWC INTENSITY FORECAST IS ASSESSED WITH MEDIUM
CONFIDENCE AND FOLLOWS CLOSELY TO THE MULTI-MODEL CONSENSUS.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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