WDPN31 PGTW 090900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (LAN) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.5N 146.0E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 257 NM EAST OF IWO TO
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SPIRAL BANDS
OF DEEP CONVECTION WRAPPING INTO AND OBSCURING THE LOW-LEVEL
CIRCULATION CENTER (LLCC). MSI ALSO SHOWS EXTENSIVE WELL-DEFINED
LOW-LEVEL CLOUD LINES WRAPPING IN ON THE SOUTHERN SEMICIRCLE. THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE
GROUPING OF AGENCY POSITION FIXES. ENVIRONMENTAL CONDITIONS REMAIN
FAVORABLE FOR INTENSIFICATION DUE TO WARM (30-31C) SEA SURFACE
TEMPERATURES (SSTS), LOW (0-5 KNOTS) VERTICAL WIND SHEAR (VWS), AND
GOOD DUAL OUTFLOW ALOFT. THE INITIAL INTENSITY OF 55 KNOTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK
ESTIMATES FROM PGTW AND KNES AND AUTOMATED DVORAK ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

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


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 45 KTS AT 090540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG EQUATORWARD
   OTHER FACTORS: STRONG EASTWARD OUTFLOW INTO A TUTT CELL. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: OVER THE NEXT 24 HOURS, TS 07W IS FORECAST TO
TRACK NORTHWESTWARD ON THE SOUTHWESTERN PERIPHERY OF THE
DEEP-LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST.
BY TAU 36, TS 07W WILL SLOW AND TURN NORTH-NORTHWESTWARD AS A
MID-LATITUDE TROUGH TO THE NORTH WILL WEAKEN AND REORIENT THE
DEEP-LAYERED STR. BY TAU 48, THE STR IS EXPECTED TO EXTEND WESTWARD
WHICH WILL ACCELERATE AND STEER 07W NORTHWESTWARD TOWARD YOKOSUKA,
JAPAN. IN TERMS OF INTENSITY, THE FAVORABLE ENVIRONMENT WILL FUEL A
STEADY INTENSIFICATION TO A PEAK OF 90KTS BETWEEN TAUS 36-48.
AFTERWARD, COOLING SSTS DUE TO UPWELLING IN RELATIVELY SHALLOW
WATERS NEAR THE COAST OF HONSHU WILL GRADUALLY WEAKEN THE SYSTEM,
DOWN TO 75 KNOTS BY TAU 120.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE ARE IN OVERALL GOOD
AGREEMENT THROUGH TAU 72, WITH ONLY A 103 NM SPREAD IN MODEL TRACK
SOLUTIONS. BY TAU 120 THE MODEL TRACK SPREAD INCREASES SLIGHTLY TO
200 NM. THIS LENDS OVERALL HIGH CONFIDENCE TO THE JTWC TRACK
FORECAST THROUGH TAU 72, WITH MEDIUM CONFIDENCE BY TAU 120.
INTENSITY GUIDANCE REMAINS IN FAIR AGREEMENT WITH A STEADY
INTENSIFICATION TO A PEAK OF 90 KNOTS. OVERALL, 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: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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