Tropical Storm MAYSAK Advisory 30.08.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (MAYSAK) WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 10W (MAYSAK), LOCATED APPROXIMATELY 566 NM SOUTH
OF KADENA AB, OKINAWA, HAS TRACKED NORTHWESTWARD AT 03 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
DEPICTS TIGHTLY-CURVED BANDING WRAPPING INTO A CONSOLIDATING LOW-
LEVEL CIRCULATION CENTER (LLCC). A 292150Z GMI 37GHZ COLOR COMPOSITE
IMAGE DEPICTS A THICK CYAN RING, INDICATIVE OF AN IMMINENT RAPID
INTENSIFICATION PHASE, AND A WELL-DEFINED MICROWAVE EYE FEATURE,
WHICH SUPPORTS THE INITIAL POSITION AND RECENT TRACK MOTION WITH
GOOD CONFIDENCE. UPPER-LEVEL ANALYSIS INDICATES A VERY FAVORABLE
ENVIRONMENT WITH AN ENHANCED POLEWARD OUTFLOW CHANNEL INTO A BROAD
UPPER LOW POSITIONED TO THE NORTHEAST, GOOD EQUATORWARD OUTFLOW AND
LOW VERTICAL WIND SHEAR (VWS). ADDITIONALLY, SST VALUES (30-31C) AND
HIGH OCEAN HEAT CONTENT VALUES ARE CONDUCIVE FOR FURTHER
DEVELOPMENT. THE 29/12Z 500MB ANALYSIS INDICATES AN UPPER LOW NEAR
25N 135E ASSOCIATED WITH THE AFOREMENTIONED BROAD 200MB LOW; THIS
SYNOPTIC ENVIRONMENT HAS LED TO A WEAK STEERING ENVIRONMENT WITH
SLOW / QUASI-STATIONARY TRACK MOTION OVER THE PAST DAY. CURRENTLY,
THE SYSTEM HAS TURNED ONTO A SLOW NORTHWESTWARD TRACK.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. THE UPPER LOW TO THE NORTHEAST IS FORECAST TO TRACK WESTWARD
WHILE WEAKENING OVER THE NEXT SIX HOURS AS IT TRACKS ALONG THE
NORTHERN PERIPHERY OF TY 10W. THIS WILL ALLOW THE STEERING
SUBTROPICAL RIDGE (STR) TO BUILD EAST OF THE SYSTEM SUPPORTING A
STEADY NORTHWARD TO NORTH-NORTHWESTWARD TRACK THROUGH TAU 48. THE
PRESENCE OF AN EXTENSION OF THE STR TO THE NORTH, OVER WESTERN JAPAN
AND THE KOREAN PENINSULA WILL ALSO INFLUENCE THE FORECAST TRACK
PRODUCING A NORTH-NORTHWESTWARD TRACK THROUGH TAU 60 AS THE SYSTEM
SKIRTS TO THE WEST OF OKINAWA. THE STR EXTENSION SHOULD ERODE AFTER
TAU 60 WITH THE APPROACH OF A DEEP MIDLATITUDE SHORTWAVE TROUGH OVER
EASTERN CHINA THEREFORE TY 10W SHOULD TRACK MORE POLEWARD. WITH THE
EXCEPTION OF AFUI, NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT AT
TAU 60 (WEST OF OKINAWA) WITH A 90NM SPREAD IN SOLUTIONS. UNDER
VERY FAVORABLE CONDITIONS, TY 10W IS FORECAST TO RAPIDLY INTENSIFY
OVER THE NEXT 36 HOURS WITH A PEAK INTENSITY OF 120 KNOTS AT TAU 36.
SLIGHT WEAKENING IS ANTICIPATED BY TAU 72 AS SST VALUES COOL
SLIGHTLY TO 28-29C.
   C. IN THE EXTENDED PERIOD, TY 10W IS FORECAST TO ACCELERATE NORTH-
NORTHEASTWARD AS IT BEGINS EXTRA-TROPICAL TRANSITION (ETT) AND
BEGINS TO INTERACT WITH THE AFOREMENTIONED MIDLATITUDE SHORTWAVE
TROUGH. SIGNIFICANT WEAKENING WILL OCCUR AFTER TAU 90 AS THE SYSTEM
TRACKS OVER THE MOUNTAINOUS KOREAN PENINSULA AND ENCOUNTERS
INCREASING VWS ASSOCIATED A MIDLATITUDE JET. TY 10W WILL COMPLETE
ETT BY TAU 120 AS IT GAINS FRONTAL CHARACTERISTICS AND TRACKS UNDER
THE JET. NUMERICAL MODELS DIVERGE WITH A 185NM SPREAD IN SOLUTIONS
AT TAU 120. THE JTWC FORECAST TRACK IS POSITIONED NEAR THE
MULTI-MODEL CONSENSUS, CLOSER TO THE ECMWF / EEMN SOLUTIONS. OVERALL
THERE IS FAIR CONFIDENCE IN THE JTWC FORECAST TRACK DUE TO THE
ERRATIC INITIAL MOTION AND UNCERTAINTY IN EXTENDED PERIOD.//
NNNN
NNNN