ATL: GERT - Post-Tropical - Discussion

[xironman]

Looks like Gert has started to have a nice moist envelope to develop in.

[floridasun78]

we catching up to epac now i think i heard their on 10 name system 7for Atlantic if not mistaking

[Kingarabian]

Looks nice on visible but with fairly shallow convection. Doesn't look exactly stacked or else it will be firing much deeper convection considering it's over sufficiently warm SSt's. Also looks like it's got quite a bit of dry air mixed in.

[NDG]

Looks nice on visible but with fairly shallow convection. Doesn't look exactly stacked or else it will be firing much deeper convection considering it's over sufficiently warm SSt's. Also looks like it's got quite a bit of dry air mixed in.

It looks better than any system in the EPac right now

In all seriousness it has plenty of convection considering the time of the day, its structure looks better than it did this morning.

[Kingarabian]

Looks nice on visible but with fairly shallow convection. Doesn't look exactly stacked or else it will be firing much deeper convection considering it's over sufficiently warm SSt's. Also looks like it's got quite a bit of dry air mixed in.

It looks better than any system in the EPac right now

In all seriousness it has plenty of convection considering the time of the day, its structure looks better than it did this morning.

That's because there is none .

[emeraldislenc]

Looks pretty good

[xironman]

Looks nice on visible but with fairly shallow convection. Doesn't look exactly stacked or else it will be firing much deeper convection considering it's over sufficiently warm SSt's. Also looks like it's got quite a bit of dry air mixed in.

It has had a dry air problem for a while, knocking down the convection. Now that it has a nice circulation it will be interesting what dbmax brings.

[cycloneye]

00z Best Track:

AL, 08, 2017081400, , BEST, 0, 285N, 718W, 40, 1009, TS

[txwatcher91]

Is it me or does Gert haves an eye-like feature forming?

[Sciencerocks]

[cycloneye]

Forecast to become a Hurricane.

Tropical Storm Gert Discussion Number 5
NWS National Hurricane Center Miami FL AL082017
1100 PM EDT Sun Aug 13 2017

Gert continues to gradually become better organized on satellite
imagery. A large curved band feature has formed in the eastern
semicircle, with very deep convection. It still appears the center
is on the northwest side of the convection, somewhat displaced to
the north of the mid-level center. Intensity estimates are a little
higher than the last advisory, so the wind speed is raised to 40 kt.
Gert should remain in a light-to-moderate northerly wind shear
environment for the next couple of days, with anomalously warm SSTs
and increasing mid-level moisture in the forecast path. Almost all
of the historically reliable guidance now show Gert becoming a
hurricane in a couple of days under these moderately favorable
conditions, and so does the official forecast. The latest NHC
prediction is raised from the previous one but remains below the
model consensus, closest to the LGEM model. Gert should rapidly
weaken as it undergoes extratropical transition in 3-4 days over the
cold north Atlantic waters.

Gert is moving north-northwestward at 8 kt on the southwestern
periphery of a subtropical ridge. A northward turn is expected
on Monday while the system rounds the western side of the ridge, and
Gert is expected to be about midway between Bermuda and North
Carolina on Tuesday. After that time, a progressively faster motion
to the northeast and east-northeast is forecast as the system
becomes embedded in the mid-latitude westerlies until it dissipates
in about 5 days. The guidance has shifted a little bit to the west
after recurvature, so the official forecast is moved in that
direction.

FORECAST POSITIONS AND MAX WINDS

INIT 14/0300Z 28.8N 71.9W 40 KT 45 MPH
12H 14/1200Z 30.0N 72.1W 50 KT 60 MPH
24H 15/0000Z 31.6N 72.1W 55 KT 65 MPH
36H 15/1200Z 33.6N 71.2W 60 KT 70 MPH
48H 16/0000Z 36.0N 68.5W 65 KT 75 MPH
72H 17/0000Z 41.0N 55.5W 65 KT 75 MPH
96H 18/0000Z 48.0N 41.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 19/0000Z...DISSIPATED

$$
Forecaster Blake

[MississippiWx]

18z Best Track up to Tropical Storm.

AL, 08, 2017081318, , BEST, 0, 277N, 716W, 35, 1011, TS

No doubt a tropical storm. Spiral banding is impressive and continuing to improve. If it can wrap a strong band into the core, it may make a run at hurricane strength.

I think this is what is happening currently. The strong band in the eastern semicircle is beginning to wrap into the core of the system. Can't rule out even a Cat 2 with the way Gert is organizing currently. She's setting herself up for a quicker bout of strengthening with the improving core...

[Steve]

I thought it would be post tropical by the time it deepened that much. 5 ACE?

[Hammy]

Looks like northerly shear is already starting to move in, about a day earlier than forecast.

[TheStormExpert]

 https://twitter.com/ericblake12/status/896940216400982017

[northjaxpro]

Well. our old lady Gert is putting on a show this early pre dawn hour. Impressive banding features and she is in the process currently of developing an eyewall

She will be a hurricane shortly. She battled dry air and shear relentlessly on her long and rugged trek to this point. However, in the end, Lady Gert has become quite a formidable tropical cyclone. Could make a run at Cat 2 before exiting the scene!

[Hammy]

We need either recon or ASCAT because it appears NHC is going to keep the wind at 45mph for the 5am but it looks closer to 60. I have a feeling this is going to reach hurricane intensity and end up being classified much lower than that when it happens.

[GCANE]

Very-large tower firing now just before DMAX, just SE of the CoC

[cycloneye]

Tropical Storm Gert Discussion Number 6
NWS National Hurricane Center Miami FL AL082017
500 AM EDT Mon Aug 14 2017

Although Gert's asymmetric convective cloud pattern has improved
slightly since the previous advisory, the system remains sheared
with the low-level center located near the far northwestern edge of
the deepest convection due to deep-layer and mid-level northerly
shear of 15 kt. Although the satellite intensity estimates are a
consensus T3.0/45 kt from TAFB, SAB, and UW-CIMSS ADT, the initial
intensity is being held at 40 kt due to the low-level center having
become more exposed since those 0600 UTC intensity estimates.

Gert has maintained a north-northwestward motion or 345/08 kt. There
are significant changes to the previous track forecast or reasoning.
The small cyclone is expected to turn northward shortly and then
turn toward the north-northeast by tonight, moving through a break
in the subtropical ridge roughly midway between the U.S. east coast
and Bermuda on Tuesday. By 48 h, Gert is forecast to steadily
accelerate northeastward over the north Atlantic through the
remainder of the forecast period ahead of a strong deep-layer
trough. The latest guidance has again shifted a little bit to the
west after recurvature, so the official forecast was nudged in that
direction slightly, but remains on the far eastern edge of the
guidance envelope.

Gert should continue to be affected by moderate northerly vertical
wind shear and dry mid-level air for the next 24-30 h, so only
slight strengthening is anticipated despite the very warm SSTs
beneath the cyclone. By 36-48h, a window of opportunity for more
significant strengthening is expected when the shear decreases to
less than 10 kt after the cyclone begins to recurve, with Gert
possibly becoming a hurricane by 48 h. However, the intensification
trend is expected to be short-lived due to the vertical wind shear
shifting to southwesterly and increasing to more than 30 kt by 60 h
and beyond. By 72 h, Gert will be moving over ocean temperatures of
20 deg C and colder, which should induce and sustain extratropical
transition. Gert's intensity is held to near-hurricane strength at
72 h due to the system getting a baroclinic kick when the cyclone
moves underneath a favorable region of the upper-level jetstream.
However, rapid weakening is expected by 96 h when the cyclone is
moving over 15 deg C SSTs, with the system being absorbed on day 5
by a larger extratropical low pressure system over the far north
Atlantic. The official intensity forecast is similar to the previous
advisory, and is lower than the consensus models IVCN and HCCA.
This is due to the HWRF model creating a high bias in those models
caused by an unrealistic forecast of Gert becoming a category 4
hurricane in 72 h when the cyclone will be moving over SSTs of 25
deg C or colder and in shear conditions greater than 35-40 kt.

FORECAST POSITIONS AND MAX WINDS

INIT 14/0900Z 29.7N 72.2W 40 KT 45 MPH
12H 14/1800Z 30.9N 72.3W 45 KT 50 MPH
24H 15/0600Z 32.7N 71.9W 50 KT 60 MPH
36H 15/1800Z 34.9N 70.0W 55 KT 65 MPH
48H 16/0600Z 37.3N 66.0W 65 KT 75 MPH
72H 17/0600Z 42.7N 52.1W 60 KT 70 MPH...POST-TROP/EXTRATROP
96H 18/0600Z 49.0N 38.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 19/0600Z...ABSORBED BY LARGER EXTRATROPICAL LOW

$$
Forecaster Stewart

[xironman]

Impressive looking 40kt storm.