Tropical Storm LAN Advisory Thu Oct 19

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (LAN)
WARNING NR 12//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 25W (LAN), LOCATED APPROXIMATELY 321 NM NORTH-NORTHWEST
OF KAYANGEL, HAS TRACKED NORTHWARD AT 10 KNOTS OVER THE PAST SIX
HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY AND A 180536Z 85
GHZ SSMI IMAGE DEPICTS BROAD DEEP CONVECTIVE BANDING MOST PREVALENT
ON THE SOUTHERN PERIPHERY WRAPPING INTO A PARTIALLY-EXPOSED LOW-
LEVEL CIRCULATION CENTER (LLCC). THERE IS HIGH CONFIDENCE IN THE
INITIAL POSITION BASED ON THE EXPOSED LLCC EVIDENT IN BOTH
MULTISPECTRAL AND MICROWAVE IMAGERY. THE INITIAL INTENSITY IS
ASSESSED AT 65 KNOTS AND IS BASED ON DVORAK ESTIMATES FROM ALL
AGENCIES REPORTING T4.0 (65 KNOTS). UPPER-LEVEL ANALYSIS SHOWS A
POINT SOURCE SLIGHTLY OFFSET TO THE EAST OF THE LLCC, BUT OTHERWISE
A STRONG POLEWARD OUTFLOW CHANNEL IS ESTABLISHED FEEDING INTO A TUTT
CELL SOME DISTANCE TO THE EAST. SSTS IN THE REGION ARE EXTREMELY
WARM NEAR 30 TO 31 CELSIUS WITH NOTABLY HIGH OCEAN HEAT CONTENT.
CURRENTLY TY 25W IS TRACKING NORTHWARD ALONG THE WESTERN BOUNDARY OF
A NORTH-SOUTH ORIENTED SUBTROPICAL RIDGE BUILDING TO THE EAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE. HOWEVER, THE EXTENDED FORECAST TRACK
WAS SLOWED DOWN TO REFLECT LATER INTERACTION WITH THE MID-LATITUDE
WESTERLIES.
   B. TY 25W IS FORECAST TO TRACK NORTH-NORTHWESTWARD OVER THE NEXT
36 HOURS AS THE SUBTROPICAL RIDGE CONTINUES TO BUILD. ENVIRONMENTAL
CONDITIONS WILL REMAIN VERY FAVORABLE WITH ROBUST UPPER-LEVEL
OUTFLOW AND NOTABLY HIGH OCEAN HEAT CONTENT, TY 25W IS FORECAST TO
INTENSIFY RAPIDLY TO SUPER TYPHOON STRENGTH BY TAU 48. DYNAMIC MODEL
GUIDANCE SHOWS VERY GOOD AGREEMENT IN THE SYSTEM TRACK UP TO TAU 72,
LENDING HIGH CONFIDENCE IN THIS PORTION OF THE FORECAST TRACK.
   C. IN THE EXTENDED PERIOD, TY 25W WILL TURN NORTHEASTWARD AROUND
THE RIDGE AXIS AS THE MID-LATITUDE WESTERLIES BEGIN TO EXERT
INFLUENCE ON THE SYSTEM. A SHORT-WAVE TROUGH IS EXPECTED TO DEVELOP
AROUND THIS TIME; INITIALLY ENHANCING UPPER-LEVEL EXHAUST BUT LATER
RESTRICTING IT LEADING TO A WEAKENING TREND. GALE FORCE WINDS ARE
FORECAST TO EXTEND AN UNUSUALLY FAR FROM THE SYSTEM CENTER, ENHANCED
BY A COLD SURGE EVENT OVER THE EAST CHINA SEA. TY 25W IS EXPECTED TO
BEGIN ACCELERATING NORTH OF 30 DEGREES AS IT INTERACTS WITH THE
WESTERLIES AND SOMETIME BETWEEN TAU 96 AND 120 THE SYSTEM WILL BEGIN
EXTRATROPICAL TRANSITION. MODEL GUIDANCE SHOWS GENERAL AGREEMENT AND
RELATIVELY HIGH CONFIDENCE ON THE TRACK TRAJECTORY, HOWEVER THERE
ARE SIGNIFICANT DIFFERENCES ON THE SPEED OF THE SYSTEM AFTER IT
TURNS TO THE NORTHEAST. THERE IS APPROXIMATELY 710 NM OF SEPARATION
IN THE WIDEST MODEL TRACKERS AT TAU 120. DUE THE UNCERTAINTY IN THE
EXTENDED FORECAST TRACK SPEED, THERE IS LOW CONFIDENCE IN THE
EXTENDED FORECAST TRACK.//
NNNN
NNNN