Tropical Storm MAYSAK Advisory 8月30日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (MAYSAK) WARNING NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 10W (MAYSAK), LOCATED APPROXIMATELY 584 NM SOUTH OF
KADENA AB, OKINAWA, HAS TRACKED WEST-NORTHWESTWARD AT 03 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
DEPICTS A CONSOLIDATING SYSTEM WITH A CENTRAL DENSE OVERCAST
OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC). A 291640Z AMSR2
36GHZ MICROWAVE IMAGE, HOWEVER, REVEALS TIGHTLY-CURVED BANDING
WRAPPING INTO AN OBLONG 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 WEST-NORTHWESTWARD OR PERHAPS 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 12 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 125NM 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 48.
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 96 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 255NM SPREAD IN SOLUTIONS
AT TAU 120. THE JTWC FORECAST TRACK IS POSITIONED JUST EAST OF 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.//
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