WDPN31 PGTW 102100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 07W (LAN) WARNING NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.3N 142.9E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 565 NM SOUTH-SOUTHEAST OF YOKOSUKA, JA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TYPHOON 07W (LAN) SURGED DURING THE DIURNAL MAX PERIOD AND IS NOW
UP TO TRIPLE DIGITS. DEEP CONVECTION ORGANIZED TIGHTLY AROUND A
24NM EYE, AND THE SYMMETRY IMPROVED SUBSTANTIALLY. LAN IS A SMALL
SYSTEM OVERALL, BUT THE EYE AND EYEWALL ARE BROAD AND DEEP. A
101904Z SSMIS SERIES VERIFIES EYEWALL INTEGRITY DESPITE DRYING AT
THE EDGE OF THE NORTHWEST QUADRANT. THERE IS IMPINGEMENT UPSTREAM
THAT IS AFFECTING THE PERIPHERY OF THE NORTHWEST QUADRANT, WHICH IS
REVEALED IN A SHARP LINE ON BOTH ANIMATED WATER VAPOR IMAGERY AND
THE PROXYVIS FROM CIMSS. THE IMPINGEMENT IS ASSOCIATED WITH DRY AIR
AND SUBSIDENCE UPSTREAM. NONETHELESS, IN THE SHORT TERM THE STORM
IS MANAGING TO COCOOON ITSELF FROM THE HARSHER ENVIRONMENT
UPSTREAM. THE CURRENT INTENSITY IS ASSESSED BASED ON DVORAKS FROM
JTWC AND JMA. OBJECTIVE ASSESSMENTS FROM CIMSS ARE GENERALLY RIDING
HIGHER BUT THE GAP BETWEEN DVORAKS AND THE OBJECTIVE TOOLS HAS
CLOSED CONSIDERABLY OVER THE PAST 24 HOURS. LAN IS TRACKING THROUGH
A MIXED ENVIRONMENT CHARACTERIZED BY LOW VERTICAL WINDSHEAR, AND
WARM SEA SURFACE TEMPERATURES, BUT LOW OCEAN HEAT CONTENT AND VERY
DRY AIR, ESPECIALLY NORTH OF THE 30TH LATITUDE. THE STORM IS
ENTERING THE 24 HOUR PERIOD WHERE IT IS EXPECTED TO PEAK IN
INTENSITY. IT IS BENEFITING FROM A POLEWARD OUTFLOW CHANNEL 
ORIGINATING IN A TUTT CELL CURRENTLY NEAR 34N 146E. THE CELL IS 
KICKING TO THE WNW FAIRLY RAPIDLY. EQUATORWARD OUTFLOW HAS NOT 
COMPLETELY CUT OFF, BUT IT HAS BEEN REDUCED SUBSTANTIALLY OVER THE 
PAST 24 HOURS.  AN ENTRENCHED ANTICYCLONE ANCHORED IN A 596DM H500 
HGT CENTER NEAR 30N 175W IS FORCING LAN ON A POLEWARD TRACK.

INITIAL WIND RADII BASIS: SCATTEROMETRY DATA FROM 101201Z.

CURRENT STEERING MECHANISM: THE WESTERN FLANK OF THE SUBTROPICAL
RIDGE. THE RIDGE EXTENDS ACROSS NORTHERN HONSHU, WHICH WILL ACT TO
SLOW MOVEMENT AND PREVENT RECURVATURE. THUS, THE TRACK RUNS DIRECTLY
OVER THE JAPANESE ALPS. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T5.0 - 90 KTS
   KNES: T6.0 - 115 KTS
   CIMSS SATCON: 92 KTS AT 101420Z
   CIMSS ADT: 115 KTS AT 101730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT AND A GENERALLY VERY DRY
ENVIRONMENT NORTH OF THE 30TH LATITUDE WILL BE A MAJOR INFLUENCE ON
THIS STORM. 

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: ALTHOUGH THE INTENSITY FORECAST WAS
RAISED 15 KNOTS, THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST
PHILOSOPHY. 

FORECAST DISCUSSION: TYPHOON LAN WILL CONTINUE ON ITS POLEWARD
TRACK AND PEAK DURING THE NEXT 24 HOURS. THE ALREADY HIGH LATITUDE
AND MIXED ENVIRONMENT UPSTREAM WILL CAP DEVELOPMENT BELOW SUPER
TYPHOON STRENGTH. AS THE SYSTEM TRACKS POLEWARD IT WILL BE NUDGED A
LITTLE FURTHER NORTHWEST DUE TO THE INFLUENCE OF AN UPPER LEVEL
RIDGE ENTRENCHED OVER NORTHERN HONSHU. ALTHOUGH THE KUROSHIO IS
RUNNING VERY CLOSE TO THE COAST AND WARM WATERS EXIST ALL THE WAY
ALONG THE TRACK, THE PRESENCE OF INORDINATELY DRY AIR AND
DETERIORATING OUTFLOW CONDITIONS WILL BEGIN WEAKENING THE STORM AS
IT CROSSES THE 30TH LATITUDE, MAKING FOR A GRADUAL DECREASE IN
INTENSITY FROM TAU 36 UNTIL LANDFALL. GUIDANCE HAS BEEN FOCUSING ON
A STRIKE EAST OF OSAKA AND WEST OF TOKYO FOR SOME TIME NOW, WITH A
TRACK DIRECTLY OVER THE JAPANESE ALPS AND INTO THE SEA OF JAPAN. 
THE UPSTREAM RIDGE OVER NORTHERN HONSHU IS TOO WELL ENTRENCHED TO
ALLOW FOR RECURVATURE. OPERATORS AND EMERGENCY MANAGERS SHOULD BE
HAPPY TO NOTE THAT THE WINDFIELDS ASSOCIATED WITH THE STORM ARE
TIGHTER THAN AVERAGE.  

MODEL DISCUSSION: THE JTWC FORECAST LEANS TOWARDS THE AMERICAN AND
EUROPEAN ENSEMBLE GUIDANCE BUT DOES NOT DEVIATE FAR FROM CONSENSUS.
GUIDANCE HAS BEEN QUALITATIVELY STABLE AS FAR AS FOCUSING ON THE
AREA OF THE LAND STRIKE, BUT THERE REMAINS RUN TO RUN VARIATION
ESPECIALLY IN ALONG TRACK SPEEDS. THE INTENSITY FORECAST IS HEAVILY
WEIGHTED TO THE STATISTICAL-DYNAMICAL GUIDANCE, WHICH DOES WELL IN
CAPTURING DECREASES IN UPPER LEVEL DIVERGENCE AND FALLING MOISTURE
CONTENT. WINDFIELDS ARE EXTRAPOLATED USING THE RVCN GUIDANCE. 

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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