ATL: ERNESTO - Post-Tropical

[Hammy]

You wouldn't guess based on the activity in this thread but this has a good chance at becoming Ernesto based on latest trends.

I've largely been quiet on this thread because nobody else is posting, ironic as that is.

[somethingfunny]

You wouldn't guess based on the activity in this thread but this has a good chance at becoming Ernesto based on latest trends.

I do think it has a good shot at being Ernesto. For some reason these subtropical systems don't draw nearly as much attention as a deep tropics system would. It's really weird that we could see yet another subtropical storm in the Atlantic, in August too (a month which is mostly deep tropics development).

I would not be surprised either if we got Ernesto out of it.

In general the Atlantic folks (not all but many) aren't really into the satellite watching of systems in the middle of nowhere unless it's going to effect someone's backyard. That's when you get the most activity. STS or even tropical converts that gets caught up in the westerlies and leaves off generally do not spark the general poster's interests. The weather nerds that likes to watch storms in the middle of nowhere are on the Pacific side generally

These types of storms tend not to be much to look at. A similar storm in the Pacific probably wouldn't get any more attention - probably less actually - than this will get. Then again, these types of systems usually don't get named in the Pacific. Supertyphoon Lionrock being an exception.

[galaxy401]

Sometimes one of these swirls pulls a surprise and becomes something like Michael in 2012. BTW the chances have been increased to 80/80.

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 AM EDT Wed Aug 15 2018

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

Satellite images indicate that the circulation of a low pressure
system located about 750 miles south-southeast of Cape Race,
Newfoundland has become better defined. In addition, the
associated showers and thunderstorms are now well organized. If
the current trends continue, the low will likely become a
subtropical depression or subtropical storm overnight. Some
additional development of the low is likely during the next day or
two before it moves northeastward over colder water and merges with
a frontal zone over the northern Atlantic by the end of the week or
this weekend.
* Formation chance through 48 hours...high...80 percent.
* Formation chance through 5 days...high...80 percent.

$$
Forecaster Cangialosi

[Sciencerocks]

684
WTNT45 KNHC 150839
TCDAT5

Subtropical Depression Five Discussion Number 1
NWS National Hurricane Center Miami FL AL052018
500 AM AST Wed Aug 15 2018

The low pressure system that the National Hurricane Center has been
monitoring over the central Atlantic Ocean has developed
sufficently organized deep convection and a well-defined center.
Since the system has a large radius of maximum wind and is
co-located with an upper-level low, it is being classified as a
subtropical depression. The initial intensity is set to a possibly
conservative 30 kt based on an earlier ASCAT pass. This value
is slightly below the latest satellite intensity estimate from TAFB.
It is interesting to note that so far this hurricane season, four of
the five systems have been a subtropical cyclone at some point in
their lifetimes.

Slow strengthening is possible during the next 24 hours or so while
the system remains over warm SSTs and in fairly low wind shear
conditions. After that time, sharply colder waters, drier air, and
a significant increase in wind shear should cause extratropical
transition in about 48 hours, or sooner, and a gradual weakening.
The models show the post-tropical system merging with a frontal zone
in 3 to 4 days.

The subtropical depression is moving slowly northward at about 4
kt. A north to north-northeastward motion is expected today as the
system moves on the western periphery of a mid-level ridge. A mid-
to upper-level trough currently over the northeastern U.S. is
anticipated to approach the cyclone, and that feature should cause
the system to accelerate northeastward on Thursday and Friday.
The models are in good agreement, and the NHC track forecast lies
near the middle of the guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT 15/0900Z 37.6N 45.6W 30 KT 35 MPH
12H 15/1800Z 38.5N 45.4W 35 KT 40 MPH
24H 16/0600Z 40.2N 44.4W 45 KT 50 MPH
36H 16/1800Z 42.5N 41.9W 45 KT 50 MPH
48H 17/0600Z 45.1N 37.9W 45 KT 50 MPH...POST-TROP/EXTRATROP
72H 18/0600Z 51.0N 24.0W 40 KT 45 MPH...POST-TROP/EXTRATROP
96H 19/0600Z...DISSIPATED

$$
Forecaster Cangialosi

[Sciencerocks]

[euro6208]

Wish JTWC would follow NHC in upgrading these kind of systems in the WPAC. That will put up the numbers even more!

[TheStormExpert]

Oh look! Another Subtropical Cyclone.

[wxman57]

Looks like it's attached to a cold front.

[cycloneye]

Best Track upgrades to SS ERNESTO.

AL, 05, 2018081512, , BEST, 0, 378N, 459W, 35, 1008, SS

[MGC]

North Atlantic the new MDR....likely Ernesto soon...MGC

[cycloneye]

Subtropical Storm Ernesto Discussion Number 2
NWS National Hurricane Center Miami FL AL052018
1100 AM AST Wed Aug 15 2018

Convection associated with the subtropical cyclone became better
organized after the release of the previous advisory, but
cloud tops have warmed recently with the convection becoming
somewhat fragmented. An Hebert-Potent subtropical classification of
T2.5 from TAFB suggests that they system is producing gale-force
winds, and recent scatterometer data that passed over the far
eastern portion of the circulation revealed 30-kt winds. Since the
instrument missed the radius of maximum winds, it is assumed that
stronger winds exist over the eastern portion of the circulation,
and the initial intensity is increased to 35 kt, making the system
a subtropical storm.

Ernesto has about 24 hours over marginally warm SSTs and in a low-
shear environment in which to strengthen. After that time, the
cyclone will be moving over much colder water which should cause it
to become post-tropical within 48 hours. The post-tropical cyclone
is forecast to merge with a frontal zone associated with a larger
extratropical cyclone over the North Atlantic in 3 to 4 days.

The cyclone is moving northward at about 6 kt. A mid-level trough
that is moving off the east coast of the United States should cause
Ernesto to turn north-northeastward later today, and the cyclone is
forecast to accelerate northeastward by late Thursday as it becomes
embedded within the mid-latitude westerlies. The dynamical model
guidance continues to be in good agreement, and the new NHC track
forecast remains in the middle of the guidance envelope.


FORECAST POSITIONS AND MAX WINDS

INIT 15/1500Z 38.1N 46.0W 35 KT 40 MPH
12H 16/0000Z 39.3N 45.3W 40 KT 45 MPH
24H 16/1200Z 41.3N 43.5W 45 KT 50 MPH
36H 17/0000Z 43.6N 40.3W 45 KT 50 MPH
48H 17/1200Z 46.4N 35.2W 45 KT 50 MPH...POST-TROPICAL
72H 18/1200Z 52.3N 21.0W 40 KT 45 MPH...POST-TROPICAL
96H 19/1200Z...MERGED WITH LARGER EXTRATROPICAL LOW

$$
Forecaster Brown

[OuterBanker]

Whoever thought that the new MDR would be north of 35?

[Sciencerocks]

Whoever thought that the new MDR would be north of 35?

Within a year that isn't even a nino.

Hell, it started out a la nina but the Atlantic seems to be acting like there's a moderate to strong nino for some reason.

[MississippiWx]

I know it’s not a popular opinion, but I happen to believe these systems are interesting. It’s rather fun watching them evolve from a cold-core low to a tropical low.

[cycloneye]

Subtropical Storm Ernesto Discussion Number 3
NWS National Hurricane Center Miami FL AL052018
500 PM AST Wed Aug 15 2018

Recent visible satellite imagery has shown a slight increase in
convection near and to the east of the center of Ernesto this
afternoon, but there has been little change in the overall
organization of the subtropical storm. The satellite intensity
estimate from TAFB remains an ST2.5, so the initial wind speed
remains 35 kt for this advisory. Ernesto is forecast to remain over
marginally warm SSTs and in a low wind shear environment during the
next 12-24 hours, and some modest strengthening is anticipated.
After that time, the cyclone will be moving over SSTs below 20C and
into an area of increasing vertical wind shear. As a result,
Ernesto is forecast to become a post-tropical cyclone in about 36
hours, and merge with a frontal zone near Ireland and the United
Kingdom in 3 to 4 days.

Ernesto is moving northward or 005/8 kt. The cyclone should turn
north-northeastward tonight ahead of a mid-level trough that is
located off the coast of the eastern United States. Ernesto is
forecast to become embedded within the mid-latitude westerlies by
late Thursday and it is expected to accelerate northeastward at
that time. The track guidance remains in good agreement, and the
NHC forecast is again near the center of the guidance envelope.


FORECAST POSITIONS AND MAX WINDS

INIT 15/2100Z 39.0N 45.7W 35 KT 40 MPH
12H 16/0600Z 40.4N 44.6W 40 KT 45 MPH
24H 16/1800Z 42.6N 42.1W 45 KT 50 MPH
36H 17/0600Z 45.1N 37.9W 45 KT 50 MPH...POST-TROPICAL
48H 17/1800Z 48.0N 31.8W 45 KT 50 MPH...POST-TROPICAL
72H 18/1800Z 53.0N 15.8W 40 KT 45 MPH...POST-TROP/EXTRATROP
96H 19/1800Z...MERGED WITH FRONTAL ZONE

$$
Forecaster Brown

[cycloneye]

Subtropical Storm Ernesto Discussion Number 4
NWS National Hurricane Center Miami FL AL052018
1100 PM AST Wed Aug 15 2018

Although inner-core convection has increased since the previous
advisory, outer banding features have become more fragmented and
the overall cloud pattern has become elongated north-to-south.
There are also no signs of any upper-level anticyclonic outflow,
an indication that Ernesto is still a subtropical cyclone. The
initial intensity is being maintained at 35 kt based on a 2328Z
ASCAT pass that showed peak winds of 32 kt in the southeastern
quadrant, along with a radius of maximum winds of 70-80 nmi. This
intensity is consistent with a ST2.5/35 kt classification from TAFB.

The initial motion is now north-northeastward or 025/09 kt. Ernesto
has rounded the subtropical ridge axis to its south, and the
cyclone should gradually get caught up in the mid-latitude
westerlies and turn northeastward during the next 12 hours or so.
A northeastward motion along with a steadily increasing forward
speed is expected through Friday. The track guidance is tightly
packed around the previous advisory track, so the new NHC forecast
track is essentially just an extension of the previous advisory, and
lies near the track consensus models HCCA and TVCN. On the forecast
track, Ernesto is expected to approach Ireland as an extratropical
gale area on Saturday.

Ernesto is expected to remain over sea-surface temperatures (SST)
of 25 deg C or warmer for the next 18-24 hours, along with low
vertical shear conditions of less than 10 kt. These conditions
should allow for some slight strengthening during that short time
window. By 36 hours, Ernesto is forecast to be moving over SSTs of
20 deg C and colder and into a more stable airmass, resulting in a
degeneration of the inner-core convection. As a result, Ernesto is
expected to become a post-tropical cyclone by 36 hours, and become
an extratropical gale area after merging with a frontal zone near
Ireland and the United Kingdom in about 3 days.

FORECAST POSITIONS AND MAX WINDS

INIT 16/0300Z 39.7N 45.1W 35 KT 40 MPH
12H 16/1200Z 41.3N 43.4W 40 KT 45 MPH
24H 17/0000Z 43.7N 40.0W 40 KT 45 MPH
36H 17/1200Z 46.3N 34.9W 40 KT 45 MPH...POST-TROPICAL
48H 18/0000Z 49.0N 27.9W 40 KT 45 MPH...POST-TROP/EXTRATROP
72H 19/0000Z 54.0N 12.1W 40 KT 45 MPH...POST-TROP/EXTRATROP
96H 20/0000Z...DISSIPATED

$$
Forecaster Stewart

[toad strangler]

I know it’s not a popular opinion, but I happen to believe these systems are interesting. It’s rather fun watching them evolve from a cold-core low to a tropical low.

I guess I’ll make the rebuttal to this mindset.

LOL

[cycloneye]

Subtropical Storm Ernesto Discussion Number 5
NWS National Hurricane Center Miami FL AL052018
500 AM AST Thu Aug 16 2018

Ernesto has generally changed little during the past several hours.
The subtropical storm continues to produce patches of convection in
curved bands around the center. The circulation of the system is
becoming a little elongated from north to south, and dry air is
wrapping into the western portion of the system. The initial
wind speed is again held at 35 kt, in agreement with the satellite
intensity estimate from TAFB.

The subtropical storm has a limited amount of time to strengthen as
it will remain over marginally warm waters and in a low wind
shear environment for only another 12 hours. After that time,
the cyclone is expected to cross over a sharp SST gradient and move
into an environment of higher shear. These conditions should cause
Ernesto to lose its tropical characteristics in about 24 hours, when
the SSTs beneath the cyclone are expected to be near 20 deg C. The
post-tropical system will likely maintain its intensity, due in part
to its fast forward speed, until it merges with a frontal zone near
the United Kingdom this weekend.

The storm continues to gradually speed up, and it is now moving
north-northeastward at 11 kt. A turn to the northeast with a
significant increase in forward speed is expected later today and
Friday as a pair of shortwave troughs approach the storm, causing
the system to become embedded in the mid-latitude westerlies. The
models remain in fairly good agreement, and this track forecast is
largely an update of the previous one.

FORECAST POSITIONS AND MAX WINDS

INIT 16/0900Z 40.8N 44.1W 35 KT 40 MPH
12H 16/1800Z 42.4N 41.9W 40 KT 45 MPH
24H 17/0600Z 45.0N 37.7W 40 KT 45 MPH...POST-TROPICAL
36H 17/1800Z 47.8N 31.6W 40 KT 45 MPH...POST-TROP/EXTRATROP
48H 18/0600Z 50.6N 23.4W 40 KT 45 MPH...POST-TROP/EXTRATROP
72H 19/0600Z...DISSIPATED

$$
Forecaster Cangialosi

[cycloneye]

Subtropical Storm Ernesto Discussion Number 6
NWS National Hurricane Center Miami FL AL052018
1100 AM AST Thu Aug 16 2018

Convection developed closer to the center of Ernesto early this
morning, suggesting that the system was attempting to make the
transition to a tropical cyclone, but that area of convection has
weakened within the past couple of hours. Patches of deep
convection continue over the outer portion of the circulation, and
a very recent ASCAT overpass continues to show a rather large radius
of maximum winds, indicating that Ernesto remains a subtropical
cyclone. The ASCAT data showed a large area of 35-40 kt winds over
the eastern and southeastern portions of the circulation, so the
initial wind speed has been increased to 40 kt.

Ernesto has likely reached its peak intensity since it will be
moving over much cooler SSTs later today, and the cyclone is
expected to lose its subtropical characteristics late tonight or
early Friday. The post-tropical cyclone should be able to maintain
its intensity due in part to its expected fast forward speed over
the North Atlantic. The global models indicate that the system will
merge with a frontal zone as it approaches Ireland and the United
Kingdom late Saturday.

Ernesto has turned northeastward and is beginning to accelerate,
and is now moving at around 14 kt. The cyclone should be fully
embedded within the mid-latitude westerlies within the next 24
hours, and a significantly faster northeastward to
east-northeastward motion is expected over the next couple of days.
The track guidance continues to be in good agreement, and the new
NHC official forecast is essentially an update of the previous
advisory.

FORECAST POSITIONS AND MAX WINDS

INIT 16/1500Z 42.0N 43.2W 40 KT 45 MPH
12H 17/0000Z 43.9N 40.4W 40 KT 45 MPH
24H 17/1200Z 46.7N 35.0W 40 KT 45 MPH...POST-TROPICAL
36H 18/0000Z 49.5N 28.0W 40 KT 45 MPH...POST-TROP/EXTRATROP
48H 18/1200Z 52.0N 19.5W 40 KT 45 MPH...POST-TROP/EXTRATROP
72H 19/1200Z...DISSIPATED

$$
Forecaster Brown

[CyclonicFury]

ATCF now lists this as a tropical storm