Absolute Vorticity

Welcome everyone to our annual thread where we begin to discuss ENSO, some very long range model data, SST's, winter forecasts from outside outlets, etc. etc. in terms of how all of these things may impact our upcoming winter. After 3 consecutive La Nina winters, this winter looks to break that trend with an El Nino. As we all know, the strength of the event, where the warmest and coolest SST's are, and where the best tropical forcing exists, all contributes to the overall jet stream pattern over North America.

We have also been seeing a stagnant 500 MB pattern which so far, as refused to change. Ridging has persisted over the Western half of North America all the way up into the higher latitudes. This has kept the persistent heat at bay well to the SW of our local area. We've had a persistent trough instead with bouts of storminess from time to time as well as below normal temps. Sure we had those few days of 90s and high humidity but that didn't last long as we expected. We've reverted right back to the same ole pattern we've had for most of the summer. As of this writing, that looks to continue for the month of August. It'll be interesting to see how long the pattern lasts. If it can hold into the winter then you know it'll be a cold and stormy affair. It is just too early for us to know right now since it is only August.

The one thing that I am confident on, is that we should NOT see the usual typical El Nino effects. That is a mild northern half of the country and a cooler southern half (due to clouds / rain from the subtropical jet). The polar jet typically is off to our north keeping the cold air locked in over the arctic regions. However, how strong will this Nino get? I've seen model solutions that range from high end moderate to low end strong... to a weak Nino meaning that the SST's aren't going to continue warming all that much. Take a look at the Global SST Anomalies from 8/1.


Several things should stick out. First, the El Nino itself. You can clearly see that it is an East based Nino right now since the warmest SST's continue to be in ENSO region 1+2 off of the South American Coast. I'd like to see this become more centralized or more basin wide then it is now. So that is my first concern along with its strength (which we don't yet know). Second, the well above avg SST's in the North Pacific. This is known as a +PDO and that can be a good thing in conjunction with an El Nino. Lastly, look at the Atlantic. We have no analogs to cover an El Nino, +PDO, and a very warm Atlantic Ocean. The Atlantic honestly has never been this warm in the modern era. So to be completely honest with all of you, I have no idea how that will impact the pattern. Do we get a big Western Atlantic Ridge or a SE Ridge as a result? Or will the warmer waters aide in feeding bigger storm systems? Both of these scenarios are on the table in my mind.

This is just the tip of the iceberg folks. As most of you know that have been on our forum for a while now, we track these things in the coming months as well as a whole host of other things, which we will be discussing in future posts. For now, I just wanted to get the discussion started.

Great Post Les!!! Going to be tons of talk over the next several months and as we know many things will change over time. What really sticks out so far is how warm the waters are off the east coast of Asia and North America. Not sure what this means down the line but you made a good point about the waters off the Atlantic and will that help in forming a strong southeast ridge or will this just strengthen the storms in that area. Normally with and El Nino it should be stormier than normal especially across the southern USA but many other factors will be involved. Anything beats last winter which was almost over by January 1st lol.

tpweather wrote: ↑Thu Aug 03, 2023 10:14 am Great Post Les!!! Going to be tons of talk over the next several months and as we know many things will change over time. What really sticks out so far is how warm the waters are off the east coast of Asia and North America. Not sure what this means down the line but you made a good point about the waters off the Atlantic and will that help in forming a strong southeast ridge or will this just strengthen the storms in that area. Normally with and El Nino it should be stormier than normal especially across the southern USA but many other factors will be involved. Anything beats last winter which was almost over by January 1st lol.

I knew you'd be the first person to respond. I can't wait to really get into it with you guys in the weeks and months to come! It's almost time for some classic weather geek posts!

The Farmer's Almanac is out with their annual prediction and each year it gets sillier and sillier!

Great discussion Les. Looking forward to the posts and comments here as we go toward Fall and Winter.

Snowbrain2 wrote: ↑Fri Aug 04, 2023 7:21 am Great discussion Les. Looking forward to the posts and comments here as we go toward Fall and Winter.

Thank you Jeff! I always love seeing your LES pics and videos also. Keep it up!

I checked the QBO at 30 MB and recall last winter how it was positive. The QBO started to fall back in April and it really dropped in June and July. It is now negative for the July reading. Here are the numbers from January thru July of this year. We shall see how negative it goes during the autumn months.

Jan: 12.50
Feb: 9.80
Mar: 10.93
April: 12.89
May: 9.26
June: 0.72
July: -5.96

Data Source: https://psl.noaa.gov/data/correlation/qbo.data

Euro Seasonal model is out for DJF. This is the August run from Weather Bell. Below are 500 MB Maps for each month as well as precip anomalies. As usual, we shall see! One other thing to note... if the Nino's forcing develops more Central or even West based then we could be in for a nice winter (cold and stormy). CAN SIPS model is showing that which is a good thing if correct. Remember it's not so much the strength of the Nino but where the warmest SST's are and tropical forcing. That is of the utmost importance. The last couple of strong / super Nino's were very East based... the warmest waters were off the South American Coast. We want that to be Central or better yet in the Western Pacific. Plenty of time to see how this Nino develops and matures. Okay enough rambling, on to those maps!


My interpretation of those maps are of a classic El Nino winter that could be more West based vs East based. You can see the blocking over the top with an active STJ underneath,. Warmer over the N Plains and cooler over the SE. I suspect December will be milder then avg as has been the norm but Jan and Feb should be colder based on those maps. Drier then avg too but that could mean that most of our precip falls in the form of snow which is a good thing! Could also mean a lot of Nor Easters too esp in Feb.

Here is the CAN SIPS model in terms of the El Nino forcing that I just mentioned. If correct, this would be awesome for winter over the Eastern US. Of course, this is all model speculation and it's only August. But for now, things look decent to me.

Les if we can get the trough in the pacific and the southern USA then we are in big time business. Again that is a pipe dream but so far models are showing a basic El Nino but we know many other items are involved and way too early to make any kind of forecast.

tpweather wrote: ↑Sat Aug 05, 2023 1:09 pm Les if we can get the trough in the pacific and the southern USA then we are in big time business. Again that is a pipe dream but so far models are showing a basic El Nino but we know many other items are involved and way too early to make any kind of forecast.

Great post Tim! Exactly right. Every ENSO event behaves differently despite our best efforts to get it right. If the Nino can become more West based then I think we have a good chance here combined with a falling QBO (at this time anyway it continues to fall. That will be something else to monitor as you know I do). Also wondering how long the +PNA / -EPO pattern can persist. Keeping an eye on those North Pacific SST's also and as of now, that is looking good. Like we talked about the other day with the very warm Atlantic, that is going to be a wild card. Whether it's good or bad remains to be seen.

My folks and I are moving to a catalpa-style house by Oct 1st at the Brethren Ret Community (BRC) Village in south Greenville and my Dad and I won't miss nearly the amount of shoveling / snowblower blowing that we've had at our current one. We'll be able to have BRC maintenance e.g. do ours or we can do it ourselves after a storm event. The way the neighborhood is set up, each property has their own short driveway and short front door walkway.

MVWxObserver wrote: ↑Sat Aug 05, 2023 3:43 pm My folks and I are moving to a catalpa-style house by Oct 1st at the Brethren Ret Community (BRC) Village in south Greenville and my Dad and I won't miss nearly the amount of shoveling / snowblower blowing that we've had at our current one. We'll be able to have BRC maintenance e.g. do ours or we can do it ourselves after a storm event. The way the neighborhood is set up, each property has their own short driveway and short front door walkway.

So you'll be rooting for snow this winter then since you won't have to shovel much, correct? If I am wrong about this, then please send it my way. Thank you!

tron777 wrote: ↑Sat Aug 05, 2023 4:11 pm

MVWxObserver wrote: ↑Sat Aug 05, 2023 3:43 pm My folks and I are moving to a catalpa-style house by Oct 1st at the Brethren Ret Community (BRC) Village in south Greenville and my Dad and I won't miss nearly the amount of shoveling / snowblower blowing that we've had at our current one. We'll be able to have BRC maintenance e.g. do ours or we can do it ourselves after a storm event. The way the neighborhood is set up, each property has their own short driveway and short front door walkway.

So you'll be rooting for snow this winter then since you won't have to shovel much, correct? If I am wrong about this, then please send it my way. Thank you!

I'll be rooting for it Bro as we won't have to shovel as much property-wise.

MVWxObserver wrote: ↑Sat Aug 05, 2023 6:38 pm

tron777 wrote: ↑Sat Aug 05, 2023 4:11 pm

MVWxObserver wrote: ↑Sat Aug 05, 2023 3:43 pm My folks and I are moving to a catalpa-style house by Oct 1st at the Brethren Ret Community (BRC) Village in south Greenville and my Dad and I won't miss nearly the amount of shoveling / snowblower blowing that we've had at our current one. We'll be able to have BRC maintenance e.g. do ours or we can do it ourselves after a storm event. The way the neighborhood is set up, each property has their own short driveway and short front door walkway.

So you'll be rooting for snow this winter then since you won't have to shovel much, correct? If I am wrong about this, then please send it my way. Thank you!

I'll be rooting for it Bro as we won't have to shovel as much property-wise.

That's the Spirit!!!

I dont have any thoughts about it yet or this upcoming winter I just hope we have an average fall or a slightly below avg would be okay also.

airwolf76 wrote: ↑Tue Aug 08, 2023 6:31 am I dont have any thoughts about it yet or this upcoming winter I just hope we have an average fall or a slightly below avg would be okay also.

I'll 100% agree with this with regards to Fall! Last year I don't think was all that bad. It was a little more typical for us, but it has been a while since we've had a cold fall, no doubt about that.

I have renewed my Accuwx Pro subscription for another year so we will have model text data again for the winter.

tron777 wrote: ↑Tue Aug 08, 2023 8:06 pm I have renewed my Accuwx Pro subscription for another year so we will have model text data again for the winter.

Yeah baby!!!! Thanks Les!

snowbo wrote: ↑Tue Aug 08, 2023 10:10 pm

tron777 wrote: ↑Tue Aug 08, 2023 8:06 pm I have renewed my Accuwx Pro subscription for another year so we will have model text data again for the winter.

Yeah baby!!!! Thanks Les!

Not a problem, Bo! Hopefully, we'll be tracking more wintry storms this season instead of cold rain makers.

I found an interesting post on another forum that I would like to share with you guys. The poster is from the TN Valley. The post talks about the -EPO, -QBO / El Nino combo.

Right now, the EPO has went negative, it's at -12, and is in the East descending phase. In 2021-22 it fell into the negative in May and stayed deeply negative until the following May. So it should descend throughout winter.

Below, average pressure anomalies over NH when the QBO is negative. Higher in the PNA/NAO region, lower over the south and eastern U.S. (These maps may initially appear confusing, since they greens are positive numbers. It just means that the they are higher by those margins over those areas or lower by those margins over those areas when there isn't a -QBO in place. Just keep in mind green = lower pressure and cooler temps during -QBO years)

QBO1.png

QBO2.png

There tends to be higher pressure over the North Pole during a -QBO, which results in a weaker jet stream/polar vortex on average.

QBO3.png

During an El Nino/-QBO combination our forum region is slightly BN for temps DJF and pressures are quite a bit lower across the Southeast (our storm track). The map doesn't look unlike this for temps, but BN for Texas, Tennessee, North Carolina and up the east coast is more prominent than the CPC map here. Especially over Texas.

NOAATempOutlook.gif

An interesting tweet from Ben Noll with regards to our ongoing El Nino. We definitely want to see this become a basin wide event or more Centrally or West based. East based is No Bueno.

Hi Les,

Does that 33-40% slightly above for the OV mean like a slightly above normal mild winter?

MVWxObserver wrote: ↑Fri Aug 11, 2023 6:32 pm Hi Les,

Does that 33-40% slightly above for the OV mean like a slightly above normal mild winter?

I hate those percentages Eric that NOAA uses because you could interpret it several different ways. If NOAA thinks there is a third of a chance of being above normal, then you could also say that there is 2/3rd of a chance we are normal or below normal. Equal chances is even worse! A 50% chance you are above, normal, or below. It's just plain silly! Using those percentages means that your forecast truly is never wrong and that's why I cannot stand how NOAA issues those maps.

JMA for November shows a trough West / Ridge East pattern. Usually, Novembers are cold in El Ninos, but as you all know, our weather patterns usually don't follow any particular script anymore.