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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