ATL: ERNESTO - Advisories

[cycloneye]

Hurricane Ernesto Discussion Number 33
NWS National Hurricane Center Miami FL AL052024
500 PM AST Mon Aug 19 2024

Ernesto is maintaining its intensity at high latitudes. The
hurricane continues to have an eye feature, especially in the
mid-levels, and thunderstorms remain most organized north of the
center. Recent microwave images indicate that the circulation has
become titled from southwest to northeast with height, an indication
of increasing southwesterly vertical wind shear. The initial
intensity is held at 80 kt, in general agreement with the subjective
and objective Dvorak estimates.

Ernesto has likely peaked in strength. Since the hurricane has now
crossed the north wall of the Gulf Stream and moving into an
environment of increasing shear and drier air, steady or rapid
weakening is expected to begin soon. The environmental factors
should also cause extratropical transition, which will likely be
complete Tuesday morning. The NHC intensity forecast is the same as
the previous one and in line with the bulk of the guidance.

The hurricane is gradually accelerating to the northeast, or 35
degrees at 23 kt. The strong flow between an approaching mid- to
upper-level trough over the eastern U.S. and a ridge over the
subtropical central Atlantic should cause the cyclone to accelerate
even more and turn to the northeast and east-northeast during the
next couple of days. The NHC track forecast remains near the middle
of the tightly clustered models.


Key Messages:

1. Swells generated by Ernesto will continue to affect the coasts
of Bermuda, the northeast U.S., and Atlantic Canada during the next
day or so. Beach goers should be aware that there is a significant
risk of life-threatening surf and rip currents, and should stay out
of the water if advised by lifeguards.

2. Ernesto will likely bring some wind, wave, and rain impacts to
portions of southeastern Newfoundland tonight into Tuesday morning.
Breaking waves could bring the possibility of coastal flooding,
particularly along southwest-facing shorelines from Bunin east to
Avalon regions. For additional impact specific information, please
see statements issued by the Canadian Hurricane Centre.


FORECAST POSITIONS AND MAX WINDS

INIT 19/2100Z 43.8N 56.1W 80 KT 90 MPH
12H 20/0600Z 46.4N 51.2W 65 KT 75 MPH
24H 20/1800Z 49.2N 42.0W 55 KT 65 MPH...POST-TROP/EXTRATROP
36H 21/0600Z 51.5N 30.4W 45 KT 50 MPH...POST-TROP/EXTRATROP
48H 21/1800Z 53.8N 18.4W 40 KT 45 MPH...POST-TROP/EXTRATROP
60H 22/0600Z...DISSIPATED

$$
Forecaster Cangialosi

[cycloneye]

Hurricane Ernesto Discussion Number 34
NWS National Hurricane Center Miami FL AL052024
1100 PM AST Mon Aug 19 2024

Satellite imagery shows that the convective structure of Ernesto is
decaying due to increasing shear and passage over colder water,
with most of the remaining convection now in the northeastern
quadrant. However, Canadian radar shows the remaining convection
still has a good tropical cyclone banding pattern. Satellite
intensity estimates were mostly near 75 kt at 00Z, and based on the
loss of organization since that time the initial intensity is
decreased to 70 kt.

Ernesto should continue steady to rapid weakening due to shear and
cold water. The new intensity forecast has the cyclone losing its
remaining convection and becoming a post-tropical low by 24 h.
However, this could be generous, and the system could become
post-tropical at any time. After 24 h, Ernesto is going to become
involved with a large baroclinic low developing near Iceland, and
as this occurs it is likely to develop or merge with a frontal zone
to become extratropical. The system is expected to degenerate to a
trough on the south side of the larger low by 48 h.

The hurricane is now accelerating northeastward with the initial
motion of 050/30 kt. The strong flow between an approaching mid- to
upper-level trough over the eastern U.S. and a ridge over the
subtropical central Atlantic should cause the cyclone to accelerate
even more during the next 24 h, and a rapid east-northeastward
motion should continue as the baroclinic low becomes the
predominant steering influence. The NHC track forecast remains near
the middle of the tightly clustered models and has no significant
change since the previous advisory.


Key Messages:

1. The effects of swells generated by Ernesto on the coasts of
Bermuda, the northeast U.S., and Atlantic Canada should diminish
during the next day or so. Until then, beach goers should be aware
that there still could be a significant risk of life-threatening
surf and rip currents and should stay out of the water if advised by
lifeguards.

2. Ernesto will likely bring some wind, wave, and rain impacts to
portions of southeastern Newfoundland during the next several hours.
Breaking waves could bring the possibility of coastal flooding,
particularly along southwest-facing shorelines from Bunin east to
Avalon regions. For additional impact specific information, please
see statements issued by the Canadian Hurricane Centre.


FORECAST POSITIONS AND MAX WINDS

INIT 20/0300Z 45.7N 53.1W 70 KT 80 MPH
12H 20/1200Z 48.0N 47.2W 60 KT 70 MPH
24H 21/0000Z 50.6N 36.3W 50 KT 60 MPH...POST-TROPICAL
36H 21/1200Z 52.8N 24.1W 45 KT 50 MPH...POST-TROP/EXTRATROP
48H 22/0000Z...POST-TROP/EXTRATROP

$$
Forecaster Beven

[abajan]

Hurricane Ernesto Discussion Number 35
NWS National Hurricane Center Miami FL AL052024
500 AM AST Tue Aug 20 2024

Increasingly strong westerly vertical wind shear is affecting the
cyclone, displacing most of the remaining deep convection to the
east of the low-level center. The system's cloud pattern is
already taking on a less tropical-looking appearance, making
intensity estimates via the Dvorak technique somewhat problematic.
However, a couple of ship reports of winds of 58 and 51 kt to the
east of the center indicate that Ernesto is still near hurricane
strength. Thus, the advisory intensity is set at 65 kt.

The hurricane has been accelerating northeastward and the initial
motion estimate is 050/31 kt. Ernesto is embedded within a strong
deep-layer flow between a large trough over the northeastern U.S.
and a ridge over the central subtropical Atlantic. In a day or so,
an even faster motion toward the northeast and east-northeast is
likely as the cyclone comes more under the influence of a large
deep-layer cyclone over the northeastern Atlantic. The official
track forecast is close to the previous NHC prediction, and follows
the multi-model consensus solution.

Continued weakening is likely as Ernesto moves over cold water and
remains under the influence of strong shear. Based on current
trends and simulated satellite imagery from the global models, the
system's deep convection should be disrupted to the point that
Ernesto will have become a post-tropical cyclone in about 12 hours.
In 24 hours, the guidance shows a frontal appearance indicating
extratropical transition. In 36 hours or so, Ernesto is predicted
to open up into a trough over the northeastern Atlantic.


Key Messages:

1. The effects of swells generated by Ernesto on the coasts of
Bermuda, the northeast U.S., and Atlantic Canada should diminish
during the next day or so. Until then, beach goers should be aware
that there still could be a significant risk of life-threatening
surf and rip currents and should stay out of the water if advised by
lifeguards.


FORECAST POSITIONS AND MAX WINDS

INIT 20/0900Z 47.3N 50.0W 65 KT 75 MPH
12H 20/1800Z 49.5N 42.0W 55 KT 65 MPH...POST-TROPICAL
24H 21/0600Z 52.0N 30.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
36H 21/1800Z...DISSIPATED

$$
Forecaster Pasch

[cycloneye]

Post-Tropical Cyclone Ernesto Discussion Number 36
NWS National Hurricane Center Miami FL AL052024
300 PM GMT Tue Aug 20 2024

Strong southwesterly vertical wind shear and cold sea-surface
temperatures have caused Ernesto to lose tropical characteristics
this morning. The cyclone lacks organized convection, and the
low-level center is becoming exposed as dry air wraps into the
circulation. Also, GFS phase diagrams indicate Ernesto no longer has
a warm-core structure. Thus, it appears the cyclone has completed
its transition to a post-tropical cyclone. Despite these structural
changes, nearby ship observations indicate Ernesto remains a
powerful cyclone with storm-force winds in its southern semicircle.
Based on these observations, the initial intensity is set at 60 kt.

The post-tropical cyclone is moving quickly northeastward (055/32
kt) within the flow between a deep-layer trough over the north
Atlantic and a subtropical ridge over the central Atlantic. An even
faster east-northeastward motion is forecast through Wednesday as
the cyclone remains embedded within strong steering currents. The
system is forecast to merge with a frontal system and become
extratropical by tonight, and the low should dissipate on Wednesday
over the northeastern Atlantic. Although some weakening is expected
during the next day or so, the cyclone will maintain a large wind
field to the south of its center.

This is the last NHC advisory on Ernesto. Additional information on
this system can be found in High Seas Forecasts issued by the
National Weather Service, under AWIPS header NFDHSFAT1, WMO header
FZNT01 KWBC, and online at ocean.weather.gov/shtml/NFDHSFAT1.php


FORECAST POSITIONS AND MAX WINDS

INIT 20/1500Z 49.0N 44.7W 60 KT 70 MPH...POST-TROPICAL
12H 21/0000Z 50.5N 36.0W 50 KT 60 MPH...POST-TROP/EXTRATROP
24H 21/1200Z 52.8N 23.3W 40 KT 45 MPH...POST-TROP/EXTRATROP
36H 22/0000Z...DISSIPATED

$$
Forecaster Reinhart