Tropical Storm MAYSAK Advisory 8月31日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (MAYSAK) WARNING NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 10W (MAYSAK), LOCATED APPROXIMATELY 344 NM SOUTH OF
KADENA AB, OKINAWA, HAS TRACKED NORTHWARD AT 13 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). HOWEVER, A TIMELY 301721Z AMSR2
36GHZ MICROWAVE IMAGE DEPICTS A SMALL, WELL-DEFINED MICROWAVE EYE
FEATURE THAT SUPPORTS THE INITIAL POSITION AND RECENT TRACK MOTION
WITH HIGH CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 90 KNOTS
BASED ON DVORAK INTENSITY ESTIMATES OF T5.0 (90 KNOTS) FROM ALL
AGENCIES. UPPER-LEVEL ANALYSIS INDICATES A FAVORABLE ENVIRONMENT
WITH AN ENHANCED POLEWARD OUTFLOW CHANNEL INTO A WEAKENING UPPER LOW
POSITIONED TO THE NORTH, GOOD EQUATORWARD OUTFLOW AND LOW VERTICAL
WIND SHEAR (VWS). ADDITIONALLY, SST VALUES (29-30C) AND FAVORABLE
OCEAN HEAT CONTENT VALUES ARE CONDUCIVE FOR FURTHER DEVELOPMENT. THE
30/00Z-30/12Z 500MB ANALYSES INDICATE THAT THE SUBTROPICAL RIDGE
(STR) HAS BUILT EAST OF THE SYSTEM OVER THE PAST 24 HOURS AS
FORECASTED WITH AN EXTENSION OF THE STR MAINTAINING TO THE NORTH
(OVER EASTERN CHINA AND WESTERN JAPAN). A MIDLATITUDE SHORTWAVE
TROUGH HAS DEEPENED AND SHIFTED SOUTHEASTWARD OVER CENTRAL CHINA
NEAR 105E. AS A CONSEQUENCE OF THE CURRENT STATE OF THE STR, TY 10W
IS ACCELERATING NORTHWARD (RADIAL 350 DEGRESS) ALONG THE WESTERN
PERIPHERY OF THE STR POSITIONED TO THE EAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 10W IS EXPECTED TO CONTINUE TRACKING NORTHWARD TO NORTH-
NORTHWESTWARD THROUGH TAU 36 THROUGH THE COMBINED STEERING INFLUENCE
OF THE STR TO THE EAST AND THE STR EXTENSION TO THE NORTH. WITH THE
EXCEPTION OF AFUM, WHICH HAS STRUGGLED AND REMAINS THE SOLE OUTLIER,
NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT (50NM SPREAD IN
SOLUTIONS AT TAU 36). THE ECMWF ENSEMBLE IS ALSO IN GOOD AGREEMENT
WITH ALL SOLUTIONS WEST OF OKINAWA, HOWEVER, THERE IS STILL SOME
UNCERTAINTY IN THE EXACT CPA FROM OKINAWA. THE SYSTEM IS EXPECTED TO
STEADILY INTENSIFY TO A PEAK INTENSITY OF 120 KNOTS BY TAU 36 UNDER
FAVORABLE CONDITIONS. THE STR EXTENSION SHOULD ERODE AFTER
TAU 36 WITH THE APPROACH OF THE AFOREMENTIONED DEEP MIDLATITUDE
SHORTWAVE TROUGH OVER EASTERN CHINA THEREFORE TY 10W SHOULD TRACK
MORE POLEWARD THEN TURN NORTH-NORTHEASTWARD THROUGH TAU 72 AS IT
APPROACHES SOUTH KOREA. MODEL SPREAD (UNCERTAINTY) INCREASES TO 90NM
NEAR SASEBO, JAPAN AS THE SYSTEM BEGINS EXTRA-TROPICAL TRANSITION
AND INTERACTS WITH THE MIDLATITUDE TROUGH. TY 10W SHOULD WEAKEN
STEADILY AFTER TAU 48 AS IT ENCOUNTERS INCREASING VWS AND INTERACTS
WITH LAND.
   C. IN THE EXTENDED PERIOD, TY 10W IS FORECAST TO ACCELERATE
POLEWARD WHILE RAPIDLY WEAKENING AS IT BECOMES EMBEDDED WITHIN
STRONG SOUTHERLY FLOW AND COMPLETES EXTRA-TROPICAL TRANSITION AND
GAINS FRONTAL CHARACTERISTICS. THE JTWC FORECAST TRACK IS HIGHLY
CONSISTENT WITH THE PREVIOUS JTWC FORECAST AND IS POSITIONED NEAR
THE MULTI-MODEL CONSENSUS. OVERALL, THERE IS HIGH CONFIDENCE IN THE
JTWC FORECAST TRACK.//
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