WDPN31 PGTW 131500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 07W (LAN) WARNING NR 024//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.7N 138.5E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 283 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET

SATELLITE ANALYSIS, INITIAL POSITION, AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (GOES H-8 PROXY VIS)
SHOWS A MEDIUM-SIZED SYMMETRICAL CYCLONE THAT HAS MOSTLY MAINTAINED
ITS OVERALL CONVECTIVE AND WRAP STRUCTURE WITH A LARGE 60X40-NM
BANDING EYE, EXPOSING A RAGGED BUT DEFINED LOW LEVEL CIRCULATION
CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE EXPOSED LLCC FEATURE. THE INITIAL INTENSITY OF 75KTS
IS ALSO PLACED WITH HIGH CONFIDENCE BASED ON A 130851Z SAR PASS,
SUPPORTED BY AGENCY DVORAK ESTIMATES, AND REFLECTS THE MOSTLY
SUSTAINED STRUCTURE. ANALYSIS INDICATES A MARGINALLY FAVORABLE
ENVIRONMENT WITH LOW VWS AND MODERATE OUTFLOW OFFSET BY LOCALIZED
LOW SST AND OHC VALUES DUE TO OCEANIC UPWELLING AND DRY AIR
INTRUSION.

INITIAL WIND RADII BASIS: SAR DATA.

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: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 81 KTS AT 131149Z
   CIMSS ADT: 90 KTS AT 131140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 0-5 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: HIGH

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 JUST BEFORE TAU 36
NEAR WAKAYAMA PREFECTURE. AFTERWARD, IT WILL TRACK MORE NORTHWARD
AS THE STR RECEDES IN RESPONSE TO A MID-LATITUDE TROUGH APPROACHING
FROM THE NORTHWEST, EXIT INTO THE SEA OF JAPAN (SOJ), CREST THE STR
AXIS BY TAU 60, THEN ACCELERATE NORTHEASTWARD ON THE POLEWARD SIDE
OF THE STR, CLIPPING THE NORTHERN TIP OF HOKKAIDO JUST BEFORE TAU
120. THE MARGINALLY FAVORABLE ENVIRONMENT WILL PROMOTE A MODEST
INTENSIFICATION TO A PEAK OF 80KTS AT TAUS 12-24; AFTERWARD, 
INCREASING VWS, DRY AIR INTRUSION, THEN LAND INTERACTION WILL REDUCE 
IT TO 50KTS BY TAU 48. DESPITE THE RELATIVELY WARM SST IN THE SOJ, 
INCREASING VWS, THEN INTERACTION WITH THE BAROCLINIC ZONE AS TY 07W 
BEGINS EXTRA-TROPICAL TRANSITION AROUND TAU 72 WILL GRADUALLY ERODE IT 
TO A 45-KT COLD CORE LOW BY TAU 120.  

MODEL DISCUSSION: NUMERICAL MODELS ARE IN VERY GOOD AGREEMENT WITH
A GRADUAL AND EVEN SPREAD TO JUST 140NM BY TAU 72, LENDING HIGH
CONFIDENCE TO THIS PORTION OF THE JTWC TRACK FORECAST. AFTERWARD,
THE MODELS REMAIN FAIRLY TIGHT BUT DUE TO THE UNCERTAINTIES INHERENT
WITH EXTRA-TROPICAL TRANSITION THERE IS ONLY MEDIUM CONFIDENCE IN
THE EXTENDED PORTION OF THE TRACK FORECAST. THERE IS MEDIUM
CONFIDENCE IN THE JTWC INTENSITY FORECAST UP TO TAU 72 THEN LOW
AFTERWARD FOR THE SAME REASON. 

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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