Tropical Storm LAN Advisory Wed Oct 18

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (LAN)
WARNING NR 11//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 25W (LAN), LOCATED APPROXIMATELY 314 NM NORTH-
NORTHWEST OF KOROR, HAS TRACKED NORTHWARD AT 10 KNOTS OVER THE PAST
SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS BROAD
DEEP CONVECTIVE BANDING WRAPPING INTO A PARTIALLY-EXPOSED LOW-LEVEL
CIRCULATION CENTER (LLCC). HOWEVER, A 172159Z SSMIS 37GHZ COLOR
IMAGE DEPICTS CONVECTIVE BANDING WRAPPING TIGHTLY INTO A WELL-
DEFINED CENTER, WHICH INDICATES A STRENGTHENING LLCC. CONSEQUENTLY,
THE INITIAL INTENSITY IS ASSESSED AT 65 KNOTS BASED ON DVORAK
INTENSITY ESTIMATES OF T4.0 FROM ALL AGENCIES. UPPER-LEVEL ANALYSIS
SHOWS AN EXCELLENT ENVIRONMENT WITH LOW VERTICAL WIND SHEAR, STRONG
POLEWARD OUTFLOW ENHANCED BY THE TUTT, WARM SST (30C) AND HIGH OCEAN
HEAT CONTENT VALUES. AFTER A BRIEF PERIOD OF QUASI-STATIONARY MOTION
ASSOCIATED WITH THE WEAKENING SUBTROPICAL RIDGE TO THE NORTH, TY 25W
CONTINUES TO TRACK NORTHWARD UNDER THE STEERING INFLUENCE OF THE
BUILDING STEERING RIDGE TO THE EAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 25W IS FORECAST TO TRACK NORTHWARD UNDER THE STEERING
INFLUENCE OF THE BUILDING SUBTROPICAL RIDGE TO THE EAST. DESPITE THE
COMPLEX, EVOLVING SYNOPTIC STEERING PATTERN, DYNAMIC MODEL GUIDANCE
REMAINS IN TIGHT AGREEMENT WITH MINOR DIFFERENCES IN TRACK SPEED. TY
LAN IS FORECAST TO INTENSIFY STEADILY THROUGH TAU 72 TO A PEAK
INTENSITY OF 130 KNOTS DUE TO THE VERY FAVORABLE CONDITIONS.
   C. IN THE EXTENDED PERIOD, TY 25W WILL WEAKEN SLIGHTLY AS THE
SYSTEM BEGINS EXTRA-TROPICAL TRANSITION (ETT) NEAR TAU 96 AND
INTERACTS WITH UPPER-LEVEL WESTERLIES. TY 25W WILL REMAIN A VERY
LARGE SYSTEM WITH EXTENSIVE GALE-FORCE WINDS, ENHANCED BY A COLD
SURGE OVER THE RYUKYU ISLANDS AND A STRONG BAROCLINIC SYSTEM OVER
JAPAN. THE SYSTEM WILL COMPLETE ETT JUST PRIOR TO MAKING LANDFALL
OVER HONSHU BUT WILL REMAIN A STRONG TYPHOON STRENGTH EXTRA-TROPICAL
LOW. OVERALL, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
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