1. A non-tropical low pressure system located over the central Atlantic
about midway between Bermuda and the Azores Islands is producing an
area of gale-force winds to the west of the center. This low is
currently producing only limited shower activity, but environmental
conditions could favor additional development and this system has
some potential to become a subtropical cyclone over the next day or
so as it moves generally eastward. The next Special Tropical
Weather Outlook will be issued by 2 PM EDT Tuesday. For additional
information on this system, please see High Seas Forecasts issued by
the National Weather Service.
* Formation chance through 48 hours...low...30 percent
* Formation chance through 5 days...low...30 percent
Subtropical Depression One Discussion Number 1
NWS National Hurricane Center Miami FL AL012017
1100 AM AST Wed Apr 19 2017
The non-tropical low over the north central Atlantic which has
been tracked by NHC for the past few days has developed organized
convection mainly in a curved band southeast of the center. The
system is still embedded within an upper-low, the outflow is minimal
and the strongest winds are removed from the center of circulation.
Consequently, the low is being classified as a subtropical
depression with an initial intensity of 30 kt. These winds are based
on recent ASCAT data. It is anticipated that shear and cold waters
will not allow intensification, and the subtropical depression is
expected to become absorbed by a large extratropical cyclone in
about 36 hours or sooner.
The subtropical depression is moving toward the north-northeast at
about 10 kt. A gradual turn to the north and north-northwest
around the approaching extratropical low is forecast for the next
24 hours or so.
Tropical Depression One Discussion Number 5
NWS National Hurricane Center Miami FL AL012017
1100 AM AST Thu Apr 20 2017
Conventional satellite imagery indicate that the convection,
although not very deep, has become more symmetric around the center,
suggesting that the subtropical cyclone has transitioned into a
tropical depression. This is supported by AMSU data this morning
that shows that the system has developed a weak, but warm core. This
transition is a common process, and does not change the previous
intensity or track forecasts that call for the depression to
become a remnant low later today, and become absorbed by a larger
low tonight or early Friday. It is estimated that the depression is
producing winds of 30 kt within some convective bands. Since the
circulation is already becoming elongated, a weakening trend is
likely to begin soon.
The depression is moving toward the northwest at 12 kt, and this
general motion with a gradual increase in forward speed is expected
to continue until dissipation.
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