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本帖最後由 霧峰追風者 於 2018-4-1 09:17 編輯
JTWC 18Z評級提升至Medium
(1) THE AREA OF CONVECTION (REMNANTS OF TC 17P) PREVIOUSLY
LOCATED NEAR 16.1S 150.8E, IS NOW LOCATED NEAR 14.9S 149.6E,
APPROXIMATELY 250 NM EAST-NORTHEAST OF CAIRNS, AUSTRALIA. ANIMATED
ENHANCED INFRARED SATELLITE IMAGERY AND A 311159Z AMSU-B 89GHZ IMAGE
SHOW A FULLY EXPOSED, WELL DEFINED LOW LEVEL CIRCULATION CENTER WITH
LIMITED FLARING CONVECTION DISPLACED TO THE PERIPHERY IN THE NORTH.
A 311200Z ASCAT PASS SHOWS A BROAD SWATH OF 20 KT WINDS ENCIRCLING
THE DISTURBANCE, AND PATCHES OF 25 KT WINDS TO THE SOUTH OF THE
CENTER. THE DISTURBANCE IS CURRENTLY LOCATED IN A MARGINAL
ENVIRONMENT, WITH LIMITED DIVERGENCE ALOFT, AND AN AREA OF
CONVERGENCE TO THE SOUTH SUPPRESSING CONVECTION, AND MODERATE TO
HIGH VERTICAL WIND SHEAR (15-30 KNOTS). HOWEVER, SEA SURFACE
TEMPERATURES (28-30 CELSIUS) ARE WARM. THE SYSTEM IS CURRENTLY
ASSESSED AS SUBTROPICAL DUE TO ITS EXPANSIVE BUT CONTRACTING WIND
FIELD AND AN AMSU RADIAL CROSS-SECTION DEPICTING A COLD OVER WARM
OVER COLD ANOMALY PATTERN. HOWEVER, THE TOTAL PRECIPITABLE WATER
CONTENT HAS BEEN INCREASING OVER RECENT HOURS IN THE CENTER OF THE
DISTURBANCE, WHICH COULD BE INDICATIVE OF INCREASING TROPICAL
CHARACTERISTICS. IN THE NEAR TERM, GLOBAL MODELS AGREE THAT THE
REMNANTS OF 17P WILL TRACK SOUTHEASTWARD. HOWEVER, AFTER SEVERAL
DAYS, THERE IS SIGNIFICANT SPREAD IN THE MODEL GUIDANCE; SOME DEPICT
MODERATE DEVELOPMENT IN LATER TAUS, WHILE OTHER MODELS MAINTAIN THE
SYSTEM AROUND 34 KTS OF WIND SPEED. ADDITIONALLY, A COMPLICATED
STEERING ENVIRONMENT MAKES THE PREDICTED DIRECTION OF MOVEMENT
UNCLEAR AFTER SEVERAL DAYS. MAXIMUM SUSTAINED SURFACE WINDS ARE
ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED
TO BE NEAR 999 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A
SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS UPGRADED TO
MEDIUM.
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