Tropical Storm MEGI Advisory 9月26日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (MEGI) WARNING NR 12//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 20W (MEGI), LOCATED APPROXIMATELY 355 NM SOUTH OF KADENA
AB, HAS TRACKED WEST-NORTHWESTWARD AT 10 KNOTS OVER THE PAST SIX
HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS SEVERAL
DEEP CONVECTIVE RADIAL BANDS WRAPPING TIGHTLY INTO THE LOW LEVEL
CIRCULATION CENTER WITHOUT MUCH CHANGE OVER THE LAST SIX HOURS. A
DEFINED EYE FEATURE IS STILL ABSENT FROM SATELLITE IMAGERY DESPITE
THE INITIAL INTENSITY ASSESSMENT OF 90 KNOTS, WHICH IS BASED ON
CURRENT INTENSITY DVORAK ESTIMATES OF T5.0 (90 KNOTS) FROM ALL
AGENCIES. THE INITIAL POSITION IS PLACED WITH GOOD CONFIDENCE BASED
ON SATELLITE FIXES FROM PGTW AND RJTD. UPPER-LEVEL ANALYSIS SHOWS
EXCELLENT RADIAL OUTFLOW OVER THE SYSTEM, TAPPING INTO THE WESTERLY
MID-LATITUDE JET TO THE NORTH AND A LARGE TUTT CELL TO THE EAST.
VERTICAL WIND SHEAR IS VERY LOW (5 TO 10 KNOTS) AND SSTS ARE ALSO
FAVORABLE, NEAR 30 CELSIUS. CURRENTLY TY MEGI IS TRACKING NORTHWEST
ALONG THE PERIPHERY OF A BUILDING DEEP-LAYERED SUBTROPICAL RIDGE
POSITIONED TO THE NORTHEAST.
3. FORECAST REASONING.
    A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING BULLETIN, HOWEVER, THE FORECAST TRACK REFLECTS
A SLIGHT SHIFT NORTHWARD.
    B. TY MEGI WILL CONTINUE ITS NORTHWESTERN TRACK ALONG THE
CURRENT STEERING RIDGE THAT WILL CONTINUE TO BUILD THROUGHOUT THE
FORECAST PERIOD. SLIGHT INTENSIFICATION IS EXPECTED THROUGH TAU 24
REACHING A PEAK INTENSITY OF 100 KNOTS UNDER FAVORABLE ENVIRONMENTAL
CONDITIONS. RAPID WEAKENING WILL ENSUE FOLLOWING LANDFALL OVER THE
MOUNTAINOUS REGION OF CENTRAL TAIWAN AROUND TAU 36. TY MEGI IS
EXPECTED TO EMERGE OVER WATER OFF THE WESTERN SHORE OF TAIWAN
REORGANIZING AS A TROPICAL STORM, THEN MAKE LANDFALL AGAIN OVER
CHINA NEAR TAU 60. RAPID DISSIPATION IS EXPECTED AS TY MEGI TRACKS
FURTHER INLAND FULLY DISSIPATING BY TAU 96. DYNAMIC MODEL GUIDANCE
IS IN VERY GOOD AGREEMENT WITH ONLY MINOR DIFFERENCES IN TRACK
LOCATION AND SPEED. THE FORECAST TRACK IS PLACED NEAR THE MULTI-
MODEL CONSENSUS WITH HIGH CONFIDENCE.//
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