Tropical Storm MAYSAK Advisory So, 30.08.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (MAYSAK) WARNING NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 10W (MAYSAK), LOCATED APPROXIMATELY 242 NM SOUTH
OF KADENA AB, OKINAWA, HAS TRACKED NORTHWARD AT 17 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS AN
IRREGULAR EYE WITH SPIRAL BANDING OVER THE SOUTHERN SEMICIRCLE,
WHICH SUPPORTS THE INITIAL POSITION AND RECENT TRACK MOTION WITH
HIGH CONFIDENCE. BASED ON AN UNOFFICIAL PGTW ESTIMATE OF T5.5 (102
KNOTS) AT 310200Z, THE INITIAL INTENSITY OF 95 KNOTS IS HEDGED ABOVE
THE 310000Z 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 DEGREES) 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 24 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 (60NM SPREAD IN
SOLUTIONS AT TAU 24). 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 24 UNDER
FAVORABLE CONDITIONS. THE STR EXTENSION SHOULD ERODE AFTER
TAU 24 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 AND TRACKS OVER SOUTH KOREA. MODEL SPREAD (UNCERTAINTY)
HAS DECREASED AND IS NOW 55NM NEAR SASEBO, JAPAN AS THE SYSTEM
BEGINS EXTRA-TROPICAL TRANSITION AND INTERACTS WITH THE MIDLATITUDE
TROUGH. TY 10W SHOULD WEAKEN STEADILY AFTER TAU 36 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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