Tropical Storm LAN Advisory вт, 17.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (LAN)
WARNING NR 06//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 25W (LAN), LOCATED APPROXIMATELY 239 NM NORTH-
NORTHWEST OF KOROR, HAS TRACKED WESTWARD AT 10 KNOTS OVER THE PAST
SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A
CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC) WITH INCREASING
CENTRAL CONVECTION. A 161638Z NPP IMAGE INDICATES THE SYSTEM CENTER
IS LIKELY DISPLACED JUST WEST OF THIS CENTRAL DEEP CONVECTION,
THEREFORE, THERE IS FAIR CONFIDENCE IN THE INITIAL POSITION. THE
INITIAL INTENSITY IS ASSESSED AT 40 KNOTS BASED ON AN AVERAGE OF THE
DVORAK INTENSITY ESTIMATES, WHICH RANGE FROM T2.5 TO T3.0 (35 TO 45
KNOTS). 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. TS 25W IS
TRACKING WESTWARD UNDER THE STEERING INFLUENCE OF THE SUBTROPICAL
RIDGE (STR) POSITIONED TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE. THE 34-KNOT WIND RADII OVER THE
EASTERN SEMI-CIRCLE HAVE BEEN ADJUSTED BASED ON A DETAILED ANALYSIS
OF RECENT ASCAT IMAGERY. ADDITIONALLY, PEAK INTENSITY IS NOW SET AT
130 KNOTS (SUPERTYPHOON STRENGTH) AT TAU 96.
   B. TS 25W IS FORECAST TO SLOW AND BECOME QUASI-STATIONARY OVER
THE NEXT 24 HOURS AS THE STR TO THE NORTH WEAKENS IN REPONSE TO
STRENGTHENING WESTERLY FLOW OVER THE EAST CHINA SEA. THIS WILL RE-
ORIENT THE STR IN A POLEWARD FLOW CONFIGURATION, ESSENTIALLY A NORTH-
SOUTH ORIENTATION, WHICH WILL PRODUCE A GRADUAL NORTHWARD TRACK
ACCELERATION THROUGH TAU 72. DESPITE THE COMPLEX, EVOLVING SYNOPTIC
STEERING PATTERN, DYNAMIC MODEL GUIDANCE IS IN TIGHT AGREEMENT WITH
MINOR DIFFERENCES IN TRACK SPEED. TS LAN IS FORECAST TO INTENSIFY
STEADILY THROUGH TAU 24 BUT IS THEN EXPECTED TO RAPIDLY INTENSIFY
THROUGH TAU 72 DUE TO THE VERY FAVORABLE CONDITIONS.
   C. IN THE EXTENDED PERIOD, TS 25W WILL INTENSIFY TO A PEAK OF 130
KNOTS BY TAU 96 THEN WEAKEN SLIGHTLY EAST OF OKINAWA AS IT BEGINS
EXTRA-TROPICAL TRANSITION (ETT) AND INTERACTS WITH UPPER-LEVEL
WESTERLIES. TS 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. DUE TO POSITIONAL
UNCERTAINTY AND UNCERTAINTY IN THE TIMING OF THE NORTHWARD TURN,
THERE IS LOW OVERALL CONFIDENCE IN THE JTWC FORECAST TRACK.//
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