簽到天數: 1620 天
WTNT44 KNHC 111452
Subtropical Storm Melissa Discussion Number 1
NWS National Hurricane Center Miami FL AL142019
1100 AM AST Fri Oct 11 2019
Convection increased near the center of the nor'easter centered
southeast of New England overnight. First-light visible satellite
imagery briefly showed an eye-like feature before the convection
around the immediate center began to weaken. However, a large
convective band still persists over the northern semicircle, and
this structure indicated the system has transitioned to a
subtropical cyclone. The latest Hebert-Poteat classification from
TAFB indicates an initial intensity of 55 kt, and this is also
supported by an earlier scatterometer overpass showing a large area
of winds near 50 kt in the northwest quadrant.
Melissa is currently located underneath an upper-level trough,
resulting in a light shear environment. This trough will begin to
lift northeastward later today, and strong upper-level westerlies
should begin to affect the storm by tonight. This pattern is
expected to cause a weakening trend, and Melissa is forecast to
become post-tropical by Saturday night. The post-tropical cyclone is
then expected to be absorbed by an approaching front in 3 to 4 days.
Melissa is currently embedded in weak steering flow under the upper-
level trough, and little net motion is expected today. Later
tonight, an approaching mid-latitude trough currently crossing
the upper Midwest will begin to force an east-northeastward
motion at a faster forward speed. This motion will continue until
the cyclone is absorbed by the cold front. The NHC track forecast is
closest to the ECMWF ensemble mean.
Ongoing hazards from wind and coastal flooding will continue be
covered by non-tropical products from local National Weather Service
Gale-force winds that extend well northeastward of Melissa into the
central Atlantic that are not included in the wind radii, since they
are associated with a frontal boundary.
1. While the nor'easter centered southeast of New England has become
Subtropical Storm Melissa, the expected magnitude of wind and
coastal flooding impacts along portions of the U.S. east coast from
the mid-Atlantic states to southeastern New England has not changed.
For information on these hazards, see products issued by local
National Weather Service forecast offices at weather.gov.
2. Melissa is expected to gradually weaken and begin moving away
from the U.S. east coast by tonight, resulting in a gradual decrease
in wind and coastal flooding impacts.
FORECAST POSITIONS AND MAX WINDS
INIT 11/1500Z 38.5N 69.6W 55 KT 65 MPH
12H 12/0000Z 38.2N 69.3W 45 KT 50 MPH
24H 12/1200Z 38.4N 67.7W 35 KT 40 MPH
36H 13/0000Z 39.0N 65.1W 30 KT 35 MPH...POST-TROPICAL
48H 13/1200Z 39.9N 61.0W 30 KT 35 MPH...POST-TROPICAL
72H 14/1200Z 41.3N 52.6W 30 KT 35 MPH...POST-TROPICAL