2021 Indicators: SST's / SAL / MSLP / Shear / Steering / Instability / Sat Images

[SFLcane]

https://i.postimg.cc/4N5ffdLZ/cfs-avg-mslpa-Norm-Mean-atl-1.png
https://i.postimg.cc/MGcqmYWK/cfs-avg-mslpa-Norm-Mean-atl-2.png
https://i.postimg.cc/fyvNR2v5/cfs-avg-mslpa-Norm-Mean-atl-3.png
https://i.postimg.cc/FHH9748S/cfs-avg-z500a-Mean-atl-1.png

https://i.postimg.cc/BvdsY165/cfs-avg-z500a-Mean-atl-2.png
https://i.postimg.cc/28zYKYzt/cfs-avg-z500a-Mean-atl-3.png

Yeah CFS is showing the same thing. Ridge weakens over the next 2-3 weeks

[Category5Kaiju]

I do have to wonder if that trough may actually not be entirely good news for the CONUS as any system that remains weak in the MDR and slips into the West Atlantic would not be steered right into Mexico or CA but rather be pulled toward the Gulf; although I would say that for trackers who love to see high ACE, the opportunity for harmless but strong fish storms could really help

[toad strangler]

500mb steering is so fluid. Have to take each wave one at a time. No matter what the models say.

[aspen]

The GFS wants the eastern part of the ridge to rebuild, and by September 1st, it extends to 50W despite the massive break caused by Ida. The Euro also has strong ridging, but IIRC, it likes to over-estimate ridging while the GFS under-estimates. A blend of the two suggests there could be an escape route for MDR systems in early September, but probably not until 50-60W. This immediately makes me think of Igor’s track.

We’ll have to see what Ida does up in the subtopics before we can confidently say what the ridge will be like for the August 31st MDR system on the Euro/EPS/CMC, and the possible second one behind it. This could be a train of strong recurves like 2010, or it’ll be a mix of tracks like 2017 and 2004; both had strong ridging but saw systems recurve or get into the subtropics like Karl and Lee.

[Woofde]

500mb steering is so fluid. Have to take each wave one at a time. No matter what the models say.

Yep, we saw this with Elsa, Fred, Grace and Henri. Models showed them curling North much earlier than they did in actuality. If models struggle with the 5 day forecast of ridging, then no way should they be trusted weeks in advance.

[chaser1]

It's also interesting to note that of the 4 recorded Cat 5 CONUS landfalls, Andrew was the only one that formed and originated in the MDR. 1935, Camille, and Michael were homegrown; while n=4 is a very small sample size to look at, perhaps there's something about starting near land and blowing up that proves more durable and advantageous for a storm to make landfall at such strength in the CONUS as opposed to being a long tracker?

This is correct. I have said for years here on this forum, it's not about the eye-candy way off to the east.... it's not about "how many" either. In terms of potential for landfall and destruction, what's most relevant for any given geographic point are those conditions and the steering which are most apt to lead to potential impact for "that given region". That naturally means different things to those in the Islands verses Bermuda. and especially to the many different points along the U.S. coastline. For every Hurricane Allen that might threaten the Texas coastline, how many other storms have struck Texas that actually developed much further west. The same applies for those in Florida. The majority if significant storms impacting Florida have ultimately developed in the Western Atlantic basin. Meanwhile, those CV origin tropical cyclones that don't veer out to sea have posed the greatest threat to the Caribbean and perhaps the mid-Atlantic Seaboard.

[chaser1]

500mb steering is so fluid. Have to take each wave one at a time. No matter what the models say.

Yep, we saw this with Elsa, Fred, Grace and Henri. Models showed them curling North much earlier than they did in actuality. If models struggle with the 5 day forecast of ridging, then no way should they be trusted weeks in advance.

This is why I think there may be significant risk for the Carolina's over the coming 2-3 weeks. This broad scale steering pattern thus far has suggest strong mid level ridging over Eastern Canada and U.S. East coast. Sure, 'climo" will generally play into things with Fall troughs causing weaknesses at differing points and longitudes. I just think that one net result will be for some storm tracks to veer more poleward north of the Antilles yet still being steered WNW to NW under predominant W. Atlantic ridging. While this may lead to a few storms veering harmlessly out to sea, this may also pose a significant risk to South Carolina and North Carolina as well. Especially this year, it is those tropical storms where models suggest "short-fuse" development west of 60W in the Caribbean or just north of the Greater Antilles that will require those in the N. Gulf, Bahamas, and Florida to keep their heads on a swivel during the weeks to come.

[aspen]

500mb steering is so fluid. Have to take each wave one at a time. No matter what the models say.

Yep, we saw this with Elsa, Fred, Grace and Henri. Models showed them curling North much earlier than they did in actuality. If models struggle with the 5 day forecast of ridging, then no way should they be trusted weeks in advance.

This is why I think there may be significant risk for the Carolina's over the coming 2-3 weeks.

I really hope not. My grandparents will be down in SC from September 10th to 20th, unfortunately right in the middle of peak season.

[Shell Mound]

Fish parade coming...2010 2.0

High-latitude ridging but troughing underneath

https://i.postimg.cc/7hNJXRrf/8501882-A-A1-FD-4-CEA-9-B10-54909-A34-C31-F.png

Models were highlighting this possibility as early as mid July. So this is not unforeseen and could be great news for the mainland U.S. (see below).

It's also interesting to note that of the 4 recorded Cat 5 CONUS landfalls, Andrew was the only one that formed and originated in the MDR. 1935, Camille, and Michael were homegrown; while n=4 is a very small sample size to look at, perhaps there's something about starting near land and blowing up that proves more durable and advantageous for a storm to make landfall at such strength in the CONUS as opposed to being a long tracker?

This is correct. I have said for years here on this forum, it's not about the eye-candy way off to the east.... it's not about "how many" either. In terms of potential for landfall and destruction, what's most relevant for any given geographic point are those conditions and the steering which are most apt to lead to potential impact for "that given region". That naturally means different things to those in the Islands verses Bermuda. and especially to the many different points along the U.S. coastline. For every Hurricane Allen that might threaten the Texas coastline, how many other storms have struck Texas that actually developed much further west. The same applies for those in Florida. The majority if significant storms impacting Florida have ultimately developed in the Western Atlantic basin. Meanwhile, those CV origin tropical cyclones that don't veer out to sea have posed the greatest threat to the Caribbean and perhaps the mid-Atlantic Seaboard.

Of the thirty hurricanes to strike the CONUS as Category-4+ cyclones since 1851, twenty (two-thirds or 67%) originated as depressions or stronger in the MDR.

So if the upcoming pattern during peak season favours OTS, it means that the seasonal risk of a Category-4+ LF on the CONUS could be greatly diminished.

Of course, our potential system in the W Caribbean could always prove to be one of the exceptions, similar to 1961’s Carla...



Credit: Wikipedia

Compared to 2010, 2021 thus far seems to have featured stronger and more zonal ridging. The 500-mb composites confirm this general pattern:




So maybe those model runs for the peak of the 2021 season will end up being incorrect, at least to some degree. 2021 is certainly not 2010.

[weeniepatrol]

Atlantic heard the bell ring, for sure.

[toad strangler]

Giddy Up!

 http://twitter.com/EricBlake12/status/1430349278841561093

[SFLcane]

Wow!

[AutoPenalti]

Atlantic heard the bell ring, for sure.

https://i.imgur.com/2Rp31LH.gif

That looks like the COVID market crash, jesus.

[Shell Mound]

Fish parade coming...2010 2.0

High-latitude ridging but troughing underneath

https://i.postimg.cc/7hNJXRrf/8501882-A-A1-FD-4-CEA-9-B10-54909-A34-C31-F.png

Models were highlighting this possibility as early as mid July. So this is not unforeseen and could be great news for the mainland U.S. (see below).

It's also interesting to note that of the 4 recorded Cat 5 CONUS landfalls, Andrew was the only one that formed and originated in the MDR. 1935, Camille, and Michael were homegrown; while n=4 is a very small sample size to look at, perhaps there's something about starting near land and blowing up that proves more durable and advantageous for a storm to make landfall at such strength in the CONUS as opposed to being a long tracker?

This is correct. I have said for years here on this forum, it's not about the eye-candy way off to the east.... it's not about "how many" either. In terms of potential for landfall and destruction, what's most relevant for any given geographic point are those conditions and the steering which are most apt to lead to potential impact for "that given region". That naturally means different things to those in the Islands verses Bermuda. and especially to the many different points along the U.S. coastline. For every Hurricane Allen that might threaten the Texas coastline, how many other storms have struck Texas that actually developed much further west. The same applies for those in Florida. The majority if significant storms impacting Florida have ultimately developed in the Western Atlantic basin. Meanwhile, those CV origin tropical cyclones that don't veer out to sea have posed the greatest threat to the Caribbean and perhaps the mid-Atlantic Seaboard.

https://i.ibb.co/9gwJwFz/Ska-rmavbild-2021-08-24-kl-19-15-19.png

Of the thirty hurricanes to strike the CONUS as Category-4+ cyclones since 1851, twenty (two-thirds or 67%) originated as depressions or stronger in the MDR.

So if the upcoming pattern during peak season favours OTS, it means that the seasonal risk of a Category-4+ LF on the CONUS could be greatly diminished.

Of course, our potential system in the W Caribbean could always prove to be one of the exceptions, similar to 1961’s Carla...

https://upload.wikimedia.org/wikipedia/commons/thumb/d/d6/2021_Atlantic_hurricane_season_summary_map.png/600px-2021_Atlantic_hurricane_season_summary_map.png
https://upload.wikimedia.org/wikipedia/commons/thumb/0/0b/2010_Atlantic_hurricane_season_summary_map.png/600px-2010_Atlantic_hurricane_season_summary_map.png
Credit: Wikipedia

Compared to 2010, 2021 thus far seems to have featured stronger and more zonal ridging. The 500-mb composites confirm this general pattern:

https://i.ibb.co/d2jKk4j/2010-Jul-Aug-1.gif
https://i.ibb.co/x8bxDSr/2021-Jul-Aug-1.gif

So maybe those model runs for the peak of the 2021 season will end up being incorrect, at least to some degree. 2021 is certainly not 2010.

How accurate are the CFSv2's and EC's weeklies' 500-mb forecasts?

[NDG]

IMO, not smart to call for an OTS parade of storms during September, the NAO has been negative for the past 2 weeks, how has that turned out for us in the western Basin?
What comes out of Africa and quickly organizes that would be another story.

[AlphaToOmega]

The NAO was negative during ASO of 2017. I want you to guess how that turned out

[NDG]

The pattern since the NAO went negative around Aug 10th, the PNA went negative which pumped up ridging across the western Atlantic Basin and SE Canada.
I don't see a +PNA returning any time soon.

[SFLcane]

The pattern since the NAO went negative around Aug 10th, the PNA went negative which pumped up ridging across the western Atlantic Basin and SE Canada.
I don't see a +PNA returning any time soon.

https://i.imgur.com/DuBjX7x.gif

What’s your take on the over 500mb steering long range?

[SFLcane]

The NAO was negative during ASO of 2017. I want you to guess how that turned out

In 2017 it was a totally different pattern though. I have yet to see any kinda of substantial ridging on the modeling to get this wave even close to the islands. We shall see

[NDG]

The pattern since the NAO went negative around Aug 10th, the PNA went negative which pumped up ridging across the western Atlantic Basin and SE Canada.
I don't see a +PNA returning any time soon.

https://i.imgur.com/DuBjX7x.gif

What’s your take on the over 500mb steering long range?

The pattern is already set, what we’ve been seeing is what we will continue to see through at least October.