ATL: JULIA - Post-Tropical - Discussion

[cycloneye]

TROPICAL DEPRESSION JULIA DISCUSSION NUMBER 6
NWS NATIONAL HURRICANE CENTER MIAMI FL AL112016
500 AM EDT THU SEP 15 2016

Westerly shear of about 25 knots has advected dry air over Julia
and removed all of the deep convection from the cyclone center, with
the coldest cloud tops now more than 100 n mi to the east. Coastal
observations have shown the winds decreasing overnight, with most
locations now reporting sustained winds of 20 to 25 kt. Based on
these data, Julia is downgraded to a depression with an initial
intensity of 30 kt, which is in agreement with a blend of the latest
Dvorak Final-T and CI numbers from TAFB and SAB. Despite the
cyclone being situated over warm SSTs, persistent shear and dry air
should result in little change in intensity during the next few
days. Remnant low status is forecast at 72 hours, but this could
occur much sooner if organized deep convection does not return. The
remnant low is forecast to dissipate in 4-5 days, consistent with
the latest GFS and ECMWF solutions.

Julia has moved little overnight, and the initial motion estimate is
a slow eastward drift at 2 kt. The shallow cyclone is expected to
continue drifting eastward today and then meander in weak steering
currents until dissipation. This forecast is based on the latest
GFS and ECMWF tracks and is similar to the previous official
forecast.

FORECAST POSITIONS AND MAX WINDS

INIT 15/0900Z 32.0N 79.6W 30 KT 35 MPH
12H 15/1800Z 32.0N 79.3W 30 KT 35 MPH
24H 16/0600Z 32.0N 78.9W 30 KT 35 MPH
36H 16/1800Z 32.0N 78.9W 30 KT 35 MPH
48H 17/0600Z 31.9N 79.0W 30 KT 35 MPH
72H 18/0600Z 31.9N 79.3W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 19/0600Z 32.0N 79.3W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 20/0600Z...DISSIPATED

$$
Forecaster Brennan

[Kazmit]

:uarrow:
That's no cone my friend, that's a perfect circle!!

When it's a circle, you know the cone of uncertainty is very uncertain!

[hipshot]

Looks like it was tropical and then sub-tropical between the 3 day and 5 day

[xironman]

The word of the day is shear

[Alyono]

It's also moving east far more than NHC and the MU/EC are forecasting

This is why one should not ignore the mesoscale models for small systems near the USA

[xironman]

I was going to upset everyone and say the RGEM has done a pretty good job with it.

[wxman57]

It's also moving east far more than NHC and the MU/EC are forecasting

This is why one should not ignore the mesoscale models for small systems near the USA

The HRRR & 4K NAM are not indicating much change from the current status. HRRR indicates a slowly increasing pressure. NAM indicates steady between 1007-1009mb. Only the Canadian is indicating strengthening, and I never trust the Canadian.

[Alyono]

It's also moving east far more than NHC and the MU/EC are forecasting

This is why one should not ignore the mesoscale models for small systems near the USA

The HRRR & 4K NAM are not indicating much change from the current status. HRRR indicates a slowly increasing pressure. NAM indicates steady between 1007-1009mb. Only the Canadian is indicating strengthening, and I never trust the Canadian.

4km NAM shows this regaining TS status. It makes it far enough east to escape the shear

We should not discount the Canadian as it is the only model to have performed somewhat well on this storm. I wouldn't trust the MU or the EC as they have been brutal with Julia

[wxman57]

I don't think a couple millibar drop for a short period of time (4k NAM) is very significant. One thing to consider is that the NHC is now no longer forecasting strengthening, indicating that they're not inclined to call it a TS again. Interesting that I found the very first measured 35kt wind in Julia last night right before the NHC downgraded it.

Relatively strong wind shear should persist off the SE U.S. coast, with only a slight decrease in the shear Sat/Sun. I think Julia will continue to spin off the coast for another 2-3 days. At times, the convection may pop up close to the low-level swirl. It's possible winds could increase a little now and then, but the threat of significant strengthening appears low. The Canadian model is developing it in a high shear area, typical of that model's failings. Heavy rainfall threat along the SC coast may be decreasing.

[LarryWx]

It's also moving east far more than NHC and the MU/EC are forecasting

This is pretty much what I was saying yesterday ("clueless" models as I said not being east enough except possibly the CMC) though I thought it would be moving more like ENE (more on that below). Per the visible loop with lat/long grid, it is very easy to see that it is well east of even the 5AM NHC track. This track didn't have it crossing 79W til this evening. But it is already near 78.6W and with a still decent eastward component. The NHC track only had it making it as far eastward as 78.9 and that being not til after midnight.

The one thing that I've missed this morning is that it has actually been moving south of due east. It has dropped down to 31.8N from 32.1N last night and still has some S of due E component of motion. The NHC had it still at 32.0N into tomorrow and never getting below 31.9N even afterward. This may allow it to get in lower shear earlier down the road, which could be significant to the SE US later IF its eastward motion actually does end and it comes back westward later. But that's kind of a longshot for now. We may be following this for a long time to come if it does finally stop moving eastward. I can hear the cries of "die already" coming later from wx hobbyists.

Edit: I think it is now near 31.7N, 78.4W, per my eyeballing the visible loop. The NHC 5 AM track had it near 32.0N, 79.4W as of now. That means it is currently about 60 miles ESE of the 5AM track prog. The 11AM NHC track update will be interesting.

[JaxGator]

I don't think a couple millibar drop for a short period of time (4k NAM) is very significant. One thing to consider is that the NHC is now no longer forecasting strengthening, indicating that they're not inclined to call it a TS again. Interesting that I found the very first measured 35kt wind in Julia last night right before the NHC downgraded it.

Relatively strong wind shear should persist off the SE U.S. coast, with only a slight decrease in the shear Sat/Sun. I think Julia will continue to spin off the coast for another 2-3 days. At times, the convection may pop up close to the low-level swirl. It's possible winds could increase a little now and then, but the threat of significant strengthening appears low. The Canadian model is developing it in a high shear area, typical of that model's failings. Heavy rainfall threat along the SC coast may be decreasing.

That is funny how the NHC downgraded it, when you found those readings. Julia left quick mark here though. There were Tropical Storm conditions in the rainband associated with the center from St. Augustine-Jax Beach when she hit this past Tusday. Even a part of an Chevron gas station awning in Atlantic Beach got blown off. The station is still open thankfully.

[wxman57]

Over the last 3 hours, I measured a movement due east of 35nm, which is a speed of about 11.7 kts (13.4mph). In addition, the LLC appears to be opening up - not a sign of strengthening. We may be talking about remnant low Julia sooner rather than later. The swirl may persist offshore for days, as did Hermine's remnant low.

[xironman]

There is still a plane going in today, right?

[LarryWx]

It's also moving east far more than NHC and the MU/EC are forecasting

I think it is now near 31.7N, 78.4W, per my eyeballing the visible loop. The NHC 5 AM track had it near 32.0N, 79.4W as of now. That means it is currently about 60 miles ESE of the 5AM track prog. The 11AM NHC track update will be interesting.

The NHC 11AM position (probably based on a 10:30ish position) turned out to be 31.8N, 78.2W vs my estimated position per visible loops as of the 9:15 AM vis pic of 31.7N, 78.4W. So, it is still steadily moving eastward.

[wxman57]

I can't see any possible benefit from having recon in Julia. It's clear where the low centers are (yeah "centers), and there are plenty of surface obs around Julia. Nothing to learn with recon. Take a look at a recent visible. As the convection continues to collapse, a second center has appeared. The two centers are rotating counter-clockwise around a central point. This is NOT a sign of something that is going to strengthen any time soon. Julia is looking like a remnant low now.

[LarryWx]

The original center is per visible satellite as of 12:45 PM EDT near 32.0N, 77.7 W vs the ~10:30 AM NHC position of 31.8N, 78.2 W. So, over that just over two hour period it moved ENE (vs the earlier ESE and then E) about 30 miles. So, it moved a good 13 mph or so to the ENE. This about 250 miles due east of where the 5 AM advisory had it now thanks to very poor model progs.

[Fishing]

Fwiw recon is flying into her now. I have no idea why. The skies are clearing up quite nicely here in Charleston, soccer practice is still on so the town apparently isn't expecting any rains this afternoon. We still have a few fast moving grey clouds cruising through but all in all for us Julia is remnant history
Now over to keeping an eye on TD 12. I am not liking the models that show it cruising so far west.

[LarryWx]

I can't see any possible benefit from having recon in Julia. It's clear where the low centers are (yeah "centers), and there are plenty of surface obs around Julia. Nothing to learn with recon. Take a look at a recent visible. As the convection continues to collapse, a second center has appeared. The two centers are rotating counter-clockwise around a central point. This is NOT a sign of something that is going to strengthen any time soon. Julia is looking like a remnant low now.

I see the second one but I think the original one will remain the primary one. Let's see.

Upon further review of the visible loop, Julia looks to me like she is, indeed, looping around and may be about to halt her eastward progress. During the next few hours, it will be interesting to track her.

[xironman]

I can't see any possible benefit from having recon in Julia. It's clear where the low centers are (yeah "centers), and there are plenty of surface obs around Julia. Nothing to learn with recon. Take a look at a recent visible. As the convection continues to collapse, a second center has appeared. The two centers are rotating counter-clockwise around a central point. This is NOT a sign of something that is going to strengthen any time soon. Julia is looking like a remnant low now.

That kind of looks like what the RGEM predicted... 1007 mb is lower than I thought they would find. 35kt SFMR. Oops missed the 40kt.

[wxman57]

Original vortex (east one) appears to be dissipating. Now there's another one to the north and one to the south. I don't buy those SFMR reports from the plane. 20-25kt FL winds and 35-38kt SFMR???