Issued at 1100 PM AST Mon Oct 19 2020

000
WTNT42 KNHC 200239
TCDAT2

Tropical Storm Epsilon Discussion Number

4
NWS National Hurricane Center Miami FL

AL272020
1100 PM AST Mon Oct 19 2020

Water vapor imagery indicates that Epsilon has been interacting with
a shear line/dissipating cold front from the north and with a
negatively tilted upper-level trough from the south. Furthermore, a
pronounced dry slot has developed in the eastern semicircle, which
has severed the convective band that had been wrapping about
three-fourths of the way around the circulation. Overall, the cloud
pattern more closely resembles that of an occluded extratropical
low, with a small inner-core tropical feature. A 20/0025Z ASCAT-A
pass indicated a small fetch of mostly straight-flow 40-kt winds
located 60-90 nmi northeast of the well-defined surface center.
Given the distance from the low-level center and lack of any
significant curvature to those winds, undersampling is probably not
occurring. Therefore, the initial intensity is being held at 40 kt
for this advisory, which is consistent with satellite
classifications of T2.5/35 kt from TAFB, SAB, and UW-CIMSS ADT, and
a 19/2202Z SATCON estimate of 42 kt. Epsilon is a large cyclone with
gale-force or tropical-storm-force winds extending outward more than
250 nmi in the northern semicircle.

The initial motion estimate is 360/02 kt. No significant changes
were made to the previous track forecast or reasoning. Epsilon is
expected to meander within weak steering currents well to the
southeast of Bermuda for the next 12 h or so. By late Tuesday, a
ridge is forecast to build to the north and east of the cyclone,
forcing Epsilon generally toward the northwest through Friday. As an
upper-level trough and associated frontal system approach the
cyclone, Epsilon is expected to turn sharply northeastward between
the trough and the ridge by late Friday, and accelerate
northeastward thereafter over over the north Atlantic. The latest
NHC model guidance is coming into better agreement, with a tight
clustering of he various consensus models lying essentially along
the previous advisory track. On the forecast track, Epsilon should
make its closest approach to Bermuda on Friday.

Epsilon is forecast to remain over sea-surface temperatures (SST) of
at least 27C the next 36 h or so and, when coupled with 200-mb
temperatures of -55C, sufficient instability will exist to continue
to allow for deep convection to be generated both in the inner- and
outer-core regions of the cyclone. Thus, gradual strengthening is
forecast during that time. However, by 48 h and continuing through
72 h, SSTs cool to near 26.5C and the depth of the relatively warm
water becomes quite shallow, as indciated by upper-ocean heat
content values dropping to near zero by 72 h. The large and
expansive wind field should result in cold upwelling both ahead of
and beneath the inner-core wind field, which is likely to temper the
intensification process. This may be reflected in the past couple of
HRWF runs which no longer make Epsilon a hurricane by the time the
cyclone approaches Bermuda on Friday. For now, the intensity
forecast has only been lowered slightly since there may be some
baroclinic interaction with an approaching upper-level trough that
could offset the cooler waters. Epsilon could be undergoing
extratropical transition by the 120-h forecast period, but for now
the system will be shown as still being tropical since it will be
located over marginal SSTs near 26C at that time.

Key Message:

1. Epsilon is forecast to be at or near hurricane strength when
it approaches Bermuda late this week. While it is too soon to
determine the exact details of Epsilon's track and intensity near
the island, there is a risk of direct impacts from wind, rainfall,
and storm surge on Bermuda, and interests there should closely
monitor the progress of Epsilon.

FORECAST POSITIONS AND MAX WINDS

INIT 20/0300Z 25.3N 55.3W

40 KT 45 MPH
12H 20/1200Z 26.1N 55.5W

45 KT 50 MPH
24H 21/0000Z 27.5N 56.7W

50 KT 60 MPH
36H 21/1200Z 28.3N 58.5W

55 KT 65 MPH
48H 22/0000Z 29.1N 59.8W

60 KT 70 MPH
60H 22/1200Z 30.4N 60.8W

65 KT 75 MPH
72H 23/0000Z 31.3N 61.5W

70 KT 80 MPH
96H 24/0000Z 32.9N 62.5W

75 KT 85 MPH
120H 25/0000Z 36.4N 60.3W

75 KT 85 MPH

$$
Forecaster Stewart

Click here to read more at The National Hurricane Center