WDPN31 PGTW 132100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 07W (LAN) WARNING NR 025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 31.2N 138.1E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 283 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (HM9 CIRA PROXY VIS)
SHOWS AN ENVIRONMENTALLY CONSTRAINED TROPICAL CYCLONE WITH FAIRLY
SYMMETRICAL NARROW BANDING WRAPPING INTO A RAGGED, ELLIPTICAL EYE 
(SEMI MAJOR AXIS OF APPROX 55NM). THE CIRRUS CANOPY HAS EXPANDED 
GREATLY OVER THE PAST 6 HOURS, INCREASING FROM APPROX 265NM TO 365NM. 
DEEP FLARING CONVECTION IS MOST CONCENTRATED IN THE FRONT RIGHT 
QUADRANT BUT IS PRESENT AROUND THE ENTIRE CIRCULATION. SSTS (27-29 
DEGREES CELSIUS) AND OCEAN HEAT CONTENT REMAIN MARGINAL. THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A 131800Z HM9 IR BD 
IMAGE. THE INITIAL INTENSITY OF 80KTS IS PLACED WITH MEDIUM 
CONFIDENCE BASED ON GROWTH OF THE CIRRUS CANOPY AND IS SUPPORTED BY 
AGENCY DVORAK ESTIMATES (AVG 4.5). ANALYSIS INDICATES A MARGINALLY 
FAVORABLE ENVIRONMENT WITH LOW VWS AND MODERATE OUTFLOW OFFSET BY 
LOCALIZED LOW SST AND OHC VALUES DUE TO UPWELLING ASSOCIATED WITH THE 
SLOWER STORM SPEED AS WELL AS DRY AIR WRAPPING INTO THE CIRCULATION 
FROM THE OUTERMOST WESTERN PERIPHERY.

INITIAL WIND RADII BASIS: PERSISTENCE

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   CIMSS ADT: 92 KTS AT 131430Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 0-5 KTS
   SST: 27-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TYPHOON LAN WILL CONTINUE ON ITS CURRENT TRACK
TOWARD CENTRAL HONSHU, JAPAN, MAKING LANDFALL BETWEEN TAU 24 AND
TAU 36. DURING THIS PERIOD, SLIGHT INTENSIFICATION MAY OCCUR AS THE
SYSTEM BEGINS TO PICK UP SPEED, MOVING AWAY FROM UPWELLED SEAS AND
ROUNDING THE AXIS OF THE STR POSITIONED TO THE NORTHEAST. A WEAKENING
PHASE IS EXPECTED AS THE SYSTEM TRACKS OVER CENTRAL JAPAN AND THE
KYOTO REGION AND UNDERGOES THE EFFECTS OF LAND INTERACTION THROUGH
TAU 48, AFTER WHICH THE SYSTEM IS FORECAST TO RETURNS OVER WATER IN 
THE SEA OF JAPAN AT TROPICAL STORM INTENSITY.  AFTER TAU 48, THE 
SYSTEM WILL CONTINUE TO TRACK NORTHEASTWARD AROUND THE RIDGING TO THE 
EAST AND DRAMATICALLY ACCELERATE TOWARD THE NORTHEAST DUE TO A DEEP, 
SHARP MIDLATITUDE TROUGH THAT IS EXPECTED TO DIG TO THE WEST.  THE 
SYSTEM IS ANTICIPATED TO COMPLETE EXTRATROPICAL TRANSITION BETWEEN 
TAU 96 AND TAU 120, STARTING THE TRANSITION AS EARLY AS TAU 72.

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, NUMERICAL MODELS
ARE IN VERY GOOD AGREEMENT WITH CROSS-TRACK ERROR OF 24NM AT
LANDFALL AND 113NM AT TAU 72, LENDING HIGH CONFIDENCE TO THIS
PORTION OF THE JTWC TRACK FORECAST. DUE TO THE UNCERTAINTIES
INHERENT WITH EXTRATROPICAL TRANSITION AND MID-LATTIUDE TROUGH
VARIABILITY TO THE WEST, THERE IS MEDIUM CONFIDENCE IN THE EXTENDED
PORTION OF THE TRACK FORECAST.

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