EPAC: MARIE - Post-Tropical

[cycloneye]

Tropical Storm Marie Discussion Number 28
NWS National Hurricane Center Miami FL EP182020
500 PM HST Mon Oct 05 2020

Marie is making one last grasp at holding on to tropical cyclone
status. Convection has both deepened and moved closer to the center
of the cyclone since the last advisory. Although this convection is
still displaced well to the north of Marie's center, it appears to
be sufficient to maintain advisories for the moment. The initial
intensity of 40 kt is based on earlier ASCAT data, assuming gradual
weakening since then. This assessment may be generous, but we will
likely get more scatterometer data before the next advisory.

Despite its recent marginal convective resurgence, Marie is still
moving over cold SSTs and through a hostile environment. It is
therefore forecast to become a remnant low within 12 h. The
aforementioned ASCAT data showed Marie was still producing a wide
area of 35 kt or greater winds, and it will take a little while for
the large circulation to spin down. Most of the models indicate that
Marie will degenerate into a trough of low pressure in about 4 days,
and this is reflected in the NHC forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 06/0300Z 21.4N 133.5W 40 KT 45 MPH
12H 06/1200Z 21.9N 134.7W 35 KT 40 MPH...POST-TROP/REMNT LOW
24H 07/0000Z 22.5N 136.2W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 07/1200Z 22.9N 137.3W 30 KT 35 MPH...POST-TROP/REMNT LOW
48H 08/0000Z 23.1N 138.2W 30 KT 35 MPH...POST-TROP/REMNT LOW
60H 08/1200Z 23.0N 139.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 09/0000Z 22.9N 140.3W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 10/0000Z...DISSIPATED

$$
Forecaster Zelinsky

[cycloneye]

Tropical Storm Marie Discussion Number 30
NWS National Hurricane Center Miami FL EP182020
800 AM PDT Tue Oct 06 2020

Marie continues to gradually spin down this morning, and the
impressive burst of convection that developed near the surface
center last night, now consists of a shrinking cloud mass with
significantly warming cloud tops. Assuming some weakening since
the last night's METOP-A and B scatterometer passes indicating
peak winds of 40 kt, the initial intensity is lowered to 35 kt
which is also supported by a blend of the Dvorak intensity estimates
from TAFB and SAB.

Marie is moving over cool oceanic sea surface temperatures and
through a high statically stable air mass. The persistent, harsh
vertical shear environment has displaced what remains of the
cyclone's associated deep convection well to the northeast of the
center. The Statistical-dynamical intensity guidance and the
large-scale models are in general agreement with Marie degenerating
into a trough of low pressure in 3 days, and the NHC intensity
forecast follows suit.

The initial motion estimate is estimated to be west-northwestward,
or 295/8 kt. There are no significant changes to the previous
forecast track or reasoning. The cyclone should continue moving
toward the west-northwest through Wednesday evening. Through the
remaining portion of the period, the post-tropical remnant low
should continue to gradually spin down while moving westward within
the low-level easterlies and open up into a trough of low pressure
by Friday.


FORECAST POSITIONS AND MAX WINDS

INIT 06/1500Z 22.1N 135.1W 40 KT 45 MPH
12H 07/0000Z 22.5N 136.2W 35 KT 40 MPH...POST-TROPICAL
24H 07/1200Z 22.9N 137.3W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 08/0000Z 23.2N 138.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
48H 08/1200Z 23.2N 138.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 09/0000Z 23.2N 139.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 09/1200Z...DISSIPATED

$$
Forecaster Roberts

[cycloneye]

Post-Tropical Cyclone Marie Discussion Number 32
NWS National Hurricane Center Miami FL EP182020
500 PM HST Tue Oct 06 2020

Patchy shower activity continues nearly 250 n mi to the northeast
of Marie's center--way too far away and way too weak for the system
to still be classified as a tropical cyclone. Marie has therefore
become a remnant low, with maximum winds set at 30 kt since an
ASCAT-C pass around 1800 UTC did not register any winds of tropical
storm force. The remnant circulation is expected to gradually spin
down during the next few days due to cold waters, dry air, and
southwesterly shear of about 40 kt. The global models generally
show the remnant low hanging around for the next 3 days and then
opening up into a trough by day 4, and that is reflected in this
last NHC advisory.

Marie continues moving toward the west-northwest, or 300/7 kt.
A fairly weak low- to mid-level ridge to the north should keep
Marie on a west-northwestward heading for the next 24 hours,
followed by a westward motion with a gradual decrease in speed from
36 to 72 hours. Most of the track models seem to pull the remnant
low too far to the north during the next day or so, and the NHC
track forecast is therefore near the southern side of the guidance
envelope, between HCCA and the previous interpolated official
forecast.

This is the last advisory on Marie. For additional information on
the remnant low please see High Seas Forecasts issued by the
National Weather Service, under AWIPS header NFDHSFEPI, WMO header
FZPN02 KWBC, and on the web at ocean.weather.gov/shtml/NFDHSFEPI.php


FORECAST POSITIONS AND MAX WINDS

INIT 07/0300Z 22.5N 136.2W 30 KT 35 MPH...POST-TROP/REMNT LOW
12H 07/1200Z 22.9N 137.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
24H 08/0000Z 23.2N 137.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 08/1200Z 23.3N 138.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 09/0000Z 23.3N 139.4W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 09/1200Z 23.3N 140.1W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 10/0000Z 23.3N 140.7W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 11/0000Z...DISSIPATED

$$
Forecaster Berg