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Subtropical Storm Beryl Forecast Discussion Number 19
2018-07-15 10:35:08| National Hurricane Center (Atlantic)
Issued at 500 AM AST Sun Jul 15 2018 149 WTNT42 KNHC 150835 TCDAT2 Subtropical Storm Beryl Discussion Number 19 NWS National Hurricane Center Miami FL AL022018 500 AM AST Sun Jul 15 2018 Water vapor imagery indicates that Beryl has become fully entangled with and embedded within an upper-level cold low, causing the small cyclone to slow down considerably over the warm waters of the Gulfstream. Beryl's appearance in satellite imagery consists of a small donut ring of shallow to moderate convection that fully encircles an eye-like feature. Most of the cloud tops in the ring are around -15C to -20C with a few overshooting towers of -35C to -45C, or about 28,000 to 38,000 ft, in the southeastern quadrant. Although that doesn't sound very impressive, those cloud heights are fairly typical for a subtropical cyclone given the low altitude of the tropopause in the inner core of cold upper-lows at high latitudes. The initial intensity is being maintained at 35 kt based on the tight ring appearance and a subtropical classification of T2.5/35 kt from TAFB. The initial motion estimate is slowly northeastward or 050/03 kt. Now that Beryl has become embedded within the upper-low, its future motion depends heavily on the motion of the now parent upper-low. For the next 48 hours, the new NHC models guidance shows Beryl and the upper-low moving northeastward toward Newfoundland within the mid-latitude westerlies, accompanied by a gradually increasing forward speed of about 10-15 kt by 36 and 48 hours. The new NHC forecast track is again slower than the previous advisory track, and lies between the HCCA and FSSE consensus track forecast models. The center of Beryl is moving slowly over North Atlantic Gulfstream waters of about 27.5C and the entire cyclone lies between the 26-deg-C isotherms, which are only about 60 nmi apart from north to south. The new forecast track keeps Beryl over these warmer waters a little longer than previous forecasts, which could result in the regeneration of convection a slight delay in Beryl weakening and eventually degenerating into a remnant low pressure system than what is currently forecast. But for now, the new NHC intensity forecast maintains continuity with the previous advisory, and closely follows a blend of the HCCA, FSSE, and IVCN intensity consensus models, which have Beryl dissipating just before reaching Newfoundland in about 72 hours. FORECAST POSITIONS AND MAX WINDS INIT 15/0900Z 38.3N 65.2W 35 KT 40 MPH 12H 15/1800Z 39.1N 64.0W 35 KT 40 MPH 24H 16/0600Z 40.5N 62.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 16/1800Z 42.6N 59.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 17/0600Z 45.0N 57.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 18/0600Z...DISSIPATED $$ Forecaster Stewart
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