Subtropical Storm Melissa Forecast Discussion Number 5

By | October 12, 2019

Issued at 1100 AM AST Sat Oct 12 2019


000
WTNT44 KNHC 121449
TCDAT4

Subtropical Storm Melissa Discussion Number   5
NWS National Hurricane Center Miami FL       AL142019
1100 AM AST Sat Oct 12 2019

A small area of deep convection has persisted for the past several
hours over and around the center of Melissa.  Recent AMSU microwave
temperature data indicate that a warm core exists at least above 550
mb.  It is uncertain, however, if this warm core is due to the
intrusion of warmer temperatures aloft embedded in the upper trough
over Melissa, or if the warming was induced by convective feedback.
If deep convection persists into the afternoon, then it is more
likely that the warm core is due to the convection, and Melissa
could transition to a tropical cyclone by that time.  Based on
nearby surface observations, the wind field immediately surrounding
Melissa has contracted, with no evidence of gale-force winds beyond
150 n mi from the center.  Given the convection near the center, the
strongest winds are now most likely occurring in that region.  The
latest Hebert-Poteat subtropical satellite intensity estimate from
TAFB is 45-50 kt, and UW-CIMSS ADT and SATCON tropical estimates are
41 kt and 42 kt, respectively. Therefore, the initial intensity is
being held at 45 kt.

The upper trough over Melissa is forecast to weaken and lift
northeastward through tonight, which would remove the upper-level
support for the subtropical storm.  Increasing westerly wind shear
and progressively cooler SSTs should weaken the cyclone over the
next few days, with Melissa moving over waters of 23-24 C tonight.
This should cause the cyclone to lose its convection and transition
to a remnant low by Sunday.  The post-tropical cyclone is expected
to persist for a couple of days just ahead of a frontal zone before
it is finally absorbed by the front in 3-4 days.  The NHC forecast
is near the consensus aids at 12 hours, but a little below that
guidance through Sunday, as the global models appear to be capturing
the strongest winds in a frontal zone well-removed to the northeast
of Melissa, and not directly associated with the cyclone itself.

Melissa is now moving east-northeastward, or 070/08 kt. Increasing
westerly flow will cause the cyclone to accelerate tonight through
Monday. This motion will continue until the cyclone is absorbed by
a frontal zone. The new NHC track forecast is close to the previous
one and in the middle of the various consensus aids.

Ongoing hazards from coastal flooding will continue to be covered by
non-tropical products from local National Weather Service forecast
offices.

Gale-force winds that extend from offshore of Nova Scotia eastward
over the Atlantic are not included in the wind radii since they are
associated with a frontal boundary.

Key Messages:

1. Melissa is expected to slowly weaken and move away from the
U.S. east coast today, resulting in a gradual decrease in wind and
coastal flooding impacts.

2. Minor to moderate coastal flooding is still expected along
portions of the U.S. Mid-Atlantic and southeastern New England
coasts around times of high tide today.  For more information,
see products issued by local National Weather Service forecast
offices at weather.gov.


FORECAST POSITIONS AND MAX WINDS

INIT  12/1500Z 38.1N  67.0W   45 KT  50 MPH
 12H  13/0000Z 38.7N  65.2W   40 KT  45 MPH
 24H  13/1200Z 39.6N  62.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 36H  14/0000Z 40.3N  58.2W   30 KT  35 MPH...POST-TROP/REMNT LOW
 48H  14/1200Z 41.0N  54.3W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  15/1200Z 42.2N  45.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  16/1200Z...ABSORBED BY A FRONTAL ZONE

$$
Forecaster Latto

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