簽到天數: 868 天 [LV.10]以壇為家III
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jrchang5|2019-9-17 16:32
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JTWC 17/06Z再度提升評級至Medium。
(1) THE AREA OF CONVECTION (INVEST 95W) PREVIOUSLY LOCATED
NEAR 23.8N 132.6E IS NOW LOCATED NEAR 20.2N 128.8E, APPROXIMATELY
376 NM SOUTH OF OKINAWA, JAPAN. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS A BROAD SYSTEM WITH MULTIPLE MESOVORTICES ROTATING
CYCLONICALLY AROUND A POORLY-DEFINED CENTER WITH LIMITED DEEP
CONVECTION SHEARED TO THE SOUTHWEST. THE SYNOPTIC ENVIRONMENT
REMAINS VERY COMPLEX AND ATYPICAL WITH A GYRE-SIZE LOW PRESSURE AREA
SITUATED SOUTH OF JAPAN AND A STRONG BAROCLINIC ZONE OVER AND JUST
SOUTH OF JAPAN, ALONG THE NORTHERN PERIPHERY OF THE GYRE.
ADDITIONALLY, STRONG SOUTHWESTERLY LOW-LEVEL FLOW PERSISTS ALONG THE
SOUTHERN PERIPHERY OF THE GYRE WITH NUMEROUS OUTFLOW BOUNDARIES
INTERACTING WITH, AND DISRUPTING THE LOW-LEVEL STRUCTURE. THIS IS
EVIDENT IN A 170446Z AMSR2 89GHZ COMPOSITE MICROWAVE IMAGE SHOWING
DEFINED, SHALLOW, FRAGMENTED BANDS WRAPPING AROUND THE BROAD, ILL-
DEFINED CENTER. A 170019Z ASCAT IMAGE SHOWS 25-30 KNOT WINDS OVER
THE SOUTHERN SEMICIRCLE AND 20-25 KNOT NORTHERLY WINDS OVER THE
WESTERN SEMICIRCLE, HOWEVER, WINDS ARE SIGNIFICANTLY WEAKER
ELSEWHERE. UPPER-LEVEL ANALYSIS DEPICTS A HOSTILE ENVIRONMENT WITH
STRONG (30-50 KNOTS) VERTICAL WIND SHEAR AND BROAD DIFFLUENCE.
DYNAMIC GLOBAL MODELS INDICATE A QUASI-STATIONARY MOTION OVER THE
NEXT 1-2 DAYS, PERSISTENT MARGINAL UPPER-LEVEL CONDITIONS, AND WEAK
DEVELOPMENT. IN SUMMARY, GLOBAL MODELS HAVE STRUGGLED WITH THIS
COMPLEX SYSTEM, WHICH HAS YET TO CONSOLIDATE AS A WARM-CORE TROPICAL
CYCLONE. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 20 TO 25
KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 997 MB.
BASED ON THE SURFACE WIND FIELD AND STRONG WESTERLIES, THE POTENTIAL
FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE
NEXT 24 HOURS IS UPGRADED TO MEDIUM. 
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