ATL: LEE - Models

[REDHurricane]

Regardless of eventual track, it's pretty remarkable to see basically one-third of Euro ensemble members (16 out of 50) forecasting a sub-940mb major hurricane eight full days out, and half (26 out of 50) predicting sub-950mb!

[gatorcane]

Overnight runs have largely trended toward a powerful hurricane recurving not impacting the islands nor the CONUS (save the GFS which still has the hurricane getting close or impacting the NE CONUS like just one of its ensembles does). The ECMWF 500MB pattern screams recurve and the EPS and GEFS does as well. Check out that signal on the GEFS!

[MEANINGLESS_NUMBERS]

Overnight runs have largely trended toward a powerful hurricane recurving not impacting the islands nor the CONUS (save the GFS which still has the hurricane getting close or impacting the NE CONUS like just one of its ensembles does). The ECMWF 500MB pattern screams recurve and the EPS and GEFS does as well. Check out that signal on the GEFS!

https://i.postimg.cc/Fzz28pW1/ec-fast-z500a-Norm-atl-fh0-240-2.gif
https://i.postimg.cc/1trq2cnx/gfs-ememb-lowlocs-atl-fh132-240.gif

A classic Bermuda hurricane.

[jconsor]

Upper pattern across the eastern US and western Atlantic this weekend into next week is far from set in stone. Need to watch the potential for a trough split, which models often don't handle well until inside 5 days.

If the the southern piece of the trough cuts off across the SE US by this weekend, and the ridge over the NW Atlantic/SE Canada is strong enough to resist troughs in the northern stream from progressing eastward much, that could block a typical recurve out to sea.

6Z GEFS and past few GFS runs are now hinting at another trough split mid to late next week from the Great Lakes to the Lower Mississippi/Tennessee Valley. A trough in that position along with an anomalous NW Atlantic ridge has in the past steered many SW Atlantic hurricanes toward a landfall from NC to New England.

 https://twitter.com/yconsor/status/1698661249146384450




 https://twitter.com/yconsor/status/1698674338080149943




 https://twitter.com/yconsor/status/1698689260147126603




 https://twitter.com/yconsor/status/1698694330888687972

[aspen]

06z HWRF shows rapid genesis and a TS in only about 24-30 hours. While I would write this off as an overly aggressive run, it does initialize the current convective pattern of 95L quite well, so it’s not starting off from an aggressive initialization. The other hurricane models also show genesis in 24-48 hours. We’ll have to see how 95L puts itself together throughout the rest of the day.

[cheezyWXguy]

6z gfs with the Long Island express redux

[gatorcane]

Upper pattern across the eastern US and western Atlantic this weekend into next week is far from set in stone. Need to watch the potential for a trough split, which models often don't handle well until inside 5 days.

If the the southern piece of the trough cuts off across the SE US by this weekend, and the ridge over the NW Atlantic/SE Canada is strong enough to resist troughs in the northern stream from progressing eastward much, that could block a typical recurve out to sea.

6Z GEFS and past few GFS runs are now hinting at another trough split mid to late next week from the Great Lakes to the Lower Mississippi/Tennessee Valley. A trough in that position along with an anomalous NW Atlantic ridge has in the past steered many SW Atlantic hurricanes toward a landfall from NC to New England.

https://twitter.com/yconsor/status/1698661249146384450

Anything is possible this far out. We do note the EPS and the Euro OP are showing less doubt with pattern. EPS 500MB mean below with lower height anomalies down the entire east coast of the US and those combined with the fact it could be a major hurricane suggests it wouldn’t take much of a weakness to turn it north before it can get close to the US coastline:

[jconsor]

Hi Larry, very important point you make that the possibility of a rare event shouldn't be dismissed this far out.

When you say eastern MDR, what is the longitude cutoff you are using? I personally find that systems that didn't become a TS until 45W lead to significantly increased odds of at least making it west of 70W, meaning a decent chance of impacting Bahamas and typically a fairly close miss for the East Coast. Recent examples include Irene in 2011, Bertha in 2014, Maria in 2017, Dorian in 2019, and Fiona last year. Also included are several E Coast hurricane hits like Gloria in 1985, Fran in 1996, Bonnie in 1998 and Floyd in 1999.

The counter-examples which formed E of 40W and stayed at or east of 70W (with many staying E of 60W) include Bill 2009, Igor 2010, Katia 2011, Gaston 2016, Helene 2018, Lorenzo 2019, Teddy 2020, Larry and Sam 2021. Earl 2010 and Jose 2017 got to 75W and 73W, respectively, but still stayed off the East Coast.

0Z Euro fits in well with the consensus of the last couple of EPS runs with a recurve near 67W and no land hit though it might have gotten close to Bermuda might had the run continued.

yup, a safe recurve well east of the coast is looking more and more likely

Climo heavily favors a miss of the CONUS from a TCG in the E MDR in Sept, especially with it not La Niña. Climo based odds are somewhere around 80% of no CONUS hit, easily the best bet. However, the problem this far out, especially with no TC center to track yet, is that nobody knows for sure that this won't be one of the 20% that do hit. It isn't as if the chance were something tiny like 5%. Also, if TCG doesn't occur until the W MDR, then that 80% stat becomes irrelevant.

Over the next few days we should get a clearer picture. We need to make sure that this won't be a pretty rare long tracking Sep El Niño US hit like Florence of 2018, Ivan of 2004, and Frederic of 1979. Granted, those three were all during a weak El Niño. However, 2023's much stronger El Nino has yet to act much like one.

One thing I will say about the GFS is that it may have a left bias these days based on how it did with Ian and Idalia. Any thoughts about this?

Edit: 0Z UKMET (goes out 168 hours) is nearly identical to its prior run trackwise though it is weaker. 0Z EPS is pretty similar to its prior couple of runs strongly favoring no NE Caribbean, Bahamas, or CONUS hit.

[cycloneye]

 https://twitter.com/dmorris9661/status/1698652317594108248

[jlauderdal]

https://twitter.com/dmorris9661/status/1698652317594108248

Keeping it north for cycloneye, msbee and others, good trend today.

[Spacecoast]

06z EPS:

[Teban54]

This is quite ominous given how global models underestimated Franklin by like 20-30 mb.

... And then there's this.

[ScottNAtlanta]

The 6z GFS is the nightmare scenario for NYC. If the GFS were to verify, it would make Sandy look like a walk in the park. I have a very hard time buying into the Euro for the simple reason it has been horrid with the post-tropical Idalia evolution which the GFS has had a better handle on. This is still far out, but don't any of you for one second go calling this a fish or a hit. Both are possible, but in my opinion and from what I see, it is going to be a very close call for something extremely disruptive.

[LarryWx]

Hi Larry, very important point you make that the possibility of a rare event shouldn't be dismissed this far out.

When you say eastern MDR, what is the longitude cutoff you are using? I personally find that systems that didn't become a TS until 45W lead to significantly increased odds of at least making it west of 70W, meaning a decent chance of impacting Bahamas and typically a fairly close miss for the East Coast. Recent examples include Irene in 2011, Bertha in 2014, Maria in 2017, Dorian in 2019, and Fiona last year. Also included are several E Coast hurricane hits like Gloria in 1985, Fran in 1996, Bonnie in 1998 and Floyd in 1999.

The counter-examples which formed E of 40W and stayed at or east of 70W (with many staying E of 60W) include Bill 2009, Igor 2010, Katia 2011, Gaston 2016, Helene 2018, Lorenzo 2019, Teddy 2020, Larry and Sam 2021. Earl 2010 and Jose 2017 got to 75W and 73W, respectively, but still stayed off the East Coast.

yup, a safe recurve well east of the coast is looking more and more likely

Climo heavily favors a miss of the CONUS from a TCG in the E MDR in Sept, especially with it not La Niña. Climo based odds are somewhere around 80% of no CONUS hit, easily the best bet. However, the problem this far out, especially with no TC center to track yet, is that nobody knows for sure that this won't be one of the 20% that do hit. It isn't as if the chance were something tiny like 5%. Also, if TCG doesn't occur until the W MDR, then that 80% stat becomes irrelevant.

Over the next few days we should get a clearer picture. We need to make sure that this won't be a pretty rare long tracking Sep El Niño US hit like Florence of 2018, Ivan of 2004, and Frederic of 1979. Granted, those three were all during a weak El Niño. However, 2023's much stronger El Nino has yet to act much like one.

One thing I will say about the GFS is that it may have a left bias these days based on how it did with Ian and Idalia. Any thoughts about this?

Edit: 0Z UKMET (goes out 168 hours) is nearly identical to its prior run trackwise though it is weaker. 0Z EPS is pretty similar to its prior couple of runs strongly favoring no NE Caribbean, Bahamas, or CONUS hit.

Your thinking is similar. Last night I was analyzing those storms that had TCG (TD+) E of 40W during (incoming) El Niño seasons with most of their existence within Sep. I didn't count Frances of 2004 because it was already past 65W on Sep 1st. I didn't count David of 1979 because it was already over Haiti on Sep 1st. If it were to look like 95L were to wait til after 40W to become a TD, I might reanalyze by including, say, those with TCG between 40W and 50W.

[LarryWx]

06z EPS:
https://i.ibb.co/vCWT0hJ/ef68.jpg

Thanks for posting. These (as of 144 on 6Z EPS) are similar to 150 on 0Z EPS. The recurving members start mainly ~18-24 hours later.

[emeraldislenc]

It is almost like a game as who calls fish or recurve first! Let's see where it forms first.

[LarryWx]

It is almost like a game as who calls fish or recurve first! Let's see where it forms first.

As I see it, it isn't a game but more of an ongoing analysis that makes for good quality forecasting discussions. Due to inherent everpresent uncertainties, I like to use percentage chances this early on based on many decades of history as opposed to making a definitive call like fish, recurve, hit, dissipation over open water, or whatever. As the event gets closer and closer, these % chances continually change. If there weren't the inherent uncertainties, these forecast discussions wouldn't be nearly as interesting since there'd be little or nothing to discuss as regards what might happen.

[cycloneye]

ICON blows it up to cat 2 moving just north of islands.

[Hypercane_Kyle]

The last time I saw the intensity models this geared up over a MDR system was Sam in 2021.

[aspen]

12z GFS has a hurricane as early as Wednesday afternoon.