WDPN31 PGTW 080900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (LAN) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.4N 148.5E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 301 NM WEST OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
OBSCURED LOW LEVEL CIRCULATION CENTER (LLCC) WITH A BULK OF THE
CONVECTION ON THE EASTERN PERIPHERY. A 080521Z SSMIS 91 GHZ
MICROWAVE IMAGE REVEAL DEEP CONVECTIVE BANDS ON THE SOUTHERN AND
EASTERN SEMICIRCLES. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC. THE INITIAL
INTENSITY IS ALSO PLACED WITH MEDIUM CONFIDENCE BASED ON OVERALL
ASSESSMENT OF AGENCY AND AUTOMATED DVORAK ESTIMATES. ENVIRONMENTAL
ANALYSIS INDICATES 07W IS IN A FAVORABLE ENVIRONMENT FOR
INTENSIFICATION DUE TO WARM (30-31C) SEA SURFACE TEMPERATURES
(SSTS), LOW (5-10 KTS) VERTICAL WIND SHEAR (VWS), AND GOOD
EQUATORWARD OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 34 KTS AT 080238Z
   CIMSS ADT: 32 KTS AT 080230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

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: TS 07W IS FORECAST TO TRACK ALONG THE OUTER
PERIPHERY OF THE SUBTROPICAL RIDGE (STR) TO THE NORTHEAST, AS THE 
SYSTEM CONTINUES TO DO SO THE STR WILL REPOSITION TO A NORTHWEST TO 
SOUTHEAST ORIENTATION. AFTER TAU 36, A MID-LATITUDE TROUGH TO THE 
NORTH WILL WEAKEN THE STR ALLOWING TS 07W TO ACCELERATE NORTHWESTWARD 
TOWARD HONSHU. AS THE SYSTEM TRANSITS NORTHWESTWARD, THE ENVIRONMENTAL 
CONDITIONS WILL REMAIN FAVORABLE WITH DECREASING VWS AND INCREASING 
POLEWARD OUTFLOW WHICH WILL ALLOW 07W TO STEADILY INTENSIFY TO A 
MAXIMUM INTENSITY OF 75 KTS BY TAU 120. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE ARE IN OVERALL GOOD
THROUGH TAU 36, WITH ONLY A 83 NM SPREAD IN MODEL TRACK SOLUTIONS.
BY TAU 120 THE MODEL GUIDANCE INCREASES IN UNCERTAINLY WITH A
GRADUAL SPREAD TO 275 NM. THEREFORE, THE JTWC TRACK FORECAST IS
ASSESSED WITH MEDIUM CONFIDENCE TO ACCOUNT FOR THE CROSS TRACK
SPREAD AT TAU 120. INTENSITY GUIDANCE REMAINS MIXED WITH HAFI BEING
AGGRESSIVE WITH A STEADY INTENSIFICATION TO A PEAK OF 85 KNOTS,
WHILE AVNI SHOWS A MORE MODEST INTENSIFICATION WITH A PEAK OF 75
KNOTS. 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: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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