Terpeast's 2023-24 Winter Outlook - Overall Grade: C

[Terpeast]

I put my outlook in a PDF, so I'll put the "tl,dr" here:

There are a lot of mixed signals leading into this winter. But I have seen enough signs to raise my confidence for an interesting winter across the Mid-Atlantic and Southeast U.S. This year is the best chance for a big winter or a top 10 KU since 2015-16 or even 2009-10.

However, I have also seen other signs that confound the potential for big snowfall, like Hunga Tonga, continuation of a negative PDO base state, and abnormally warm SSTs everywhere except for a few cool spots. I relied on factors such as the MEI, PDO, preceding Pacific "base state", AMO, QBO and solar cycle. 

Instead of giving one range for snowfall, I went with a probabilistic forecast instead. 

So for the mid-atlantic, here's what I think will happen:

• +2 degrees F above normal (medium confidence)
• 10-20% wetter than normal (high confidence)
• 60% chance we beat climo for snowfall (low-medium confidence)
• 15-30% chance we get a top 10 HECS

Probabilistic snowfall forecast*:

• 0 to 10 inches: 10% chance
• 10 to 20 inches: 30% chance
• 20 to 40 inches: 45% chance
• 40” or more: 15% chance

*if you're in the mountains, you can double or triple these numbers depending on your elevation/upslope activity and the same probabilities will apply

And now the temp & precip DJF maps:

 

You can read the attached PDF to see how I arrived at my outlook.

Or you can just click here: https://drive.google.com/file/d/10gF1EktEgErvpJ_pIgmN-OTLpz0VRLRe/view?usp=sharing

I don’t expect you to read the whole thing, so I created a linkable table of contents on the next page so you can jump to the parts that you care about.

But I’d be ecstatic if you actually read the whole thing!

Terpeast's 2023-24 Winter Outlook.pdf

[NorthArlington101]

You had me at ‘09-‘10 being the most common analog!

Awesome job - read the whole thing and it was very digestible even for someone who hasn’t picked up the fancier terms over their years here. Thanks for putting this together for everyone!

[brooklynwx99]

amazing job. we’re in pretty good agreement

[rjvanals]

@TerpeastThanks for putting in the effort to produce such a in-depth outlook! 

[clskinsfan]

Those January analogs you used are straight up weenine heaven. I am with you. I am going big this year for just about everyone as well. Delmarva could be more rainy than they have been lately with storms hugging the coast. Excellent write up. Thanks for sharing. 

[Terpeast]

Glad you all enjoyed reading this. I wanted to make it easy to skim and digest, while being as comprehensive as possible. 

Now let’s see where the chips fall…

[mattie g]

19 minutes ago, Terpeast said:

Glad you all enjoyed reading this. I wanted to make it easy to skim and digest, while being as comprehensive as possible. 

Now let’s see where the chips fall…

Agreed with the comments about it being very easy to digest. Really well researched and written!

[GramaxRefugee]

15 hours ago, NorthArlington101 said:

You had me at ‘09-‘10 being the most common analog!
...

quote from the report:

Below are the analogs that scored at least 2 points are as follows:
✓ 1951-52 (3 points)
✓ 1958-59 (2 points)
✓ 1965-66 (3 points)
✓ 1972-73 (2 points)
✓ 1976-77 (3 points)
✓ 1986-87 (2 points)
✓ 2002-03 (2 points)
✓ 2006-07 (2 points)
✓ 2009-10 (5 points)
✓ 2018-19 (2 points)

--------------------------

The others aren't even in the same ballpark.  

I'm only half serious, and there is a disclaimer, and all that, but...I can't wait for @Jebman to see this.

(Thanks @Terpeast, for the nice work.)

[MN Transplant]

Great writeup and analysis.  I certainly hope this comes to fruition.

IMO, only a 10% chance of less than 10" is really aggressive.  5 of the last 7 winters have been sub-10" in my backyard, and I'm not even in a river like DCA.  

[Eskimo Joe]

1 hour ago, Terpeast said:

Glad you all enjoyed reading this. I wanted to make it easy to skim and digest, while being as comprehensive as possible. 

Now let’s see where the chips fall…

I read your entire discussion. Really well done. If there is one area that could tilt in our favor for a snowier season, what do you think it would be?

[mattie g]

48 minutes ago, MN Transplant said:

Great writeup and analysis.  I certainly hope this comes to fruition.

IMO, only a 10% chance of less than 10" is really aggressive.  5 of the last 7 winters have been sub-10" in my backyard, and I'm not even in a river like DCA.  

The post-super Nino era hasn't been kind to us:

Nina
Nina
Nino
Neutral
Nina
Nina
Nina

Obviously there's ore to it than that, but that ENSO stretch isn't helpful to our snow chances. A strong basin-wide Nino should help alleviate that it his year.

[Maestrobjwa]

1 hour ago, mattie g said:

The post-super Nino era hasn't been kind to us:

Nina
Nina
Nino
Neutral
Nina
Nina
Nina

Obviously there's ore to it than that, but that ENSO stretch isn't helpful to our snow chances. A strong basin-wide Nino should help alleviate that it his year.

And the one Niño wasn't even a legit nino...so having 5 of the last 7 years be your historically least conducive ENSO certainly did not help, even with some of the other stuff going on. It'll be good to get a good niño to see where we're at overall.

[Terpeast]

2 hours ago, Eskimo Joe said:

I read your entire discussion. Really well done. If there is one area that could tilt in our favor for a snowier season, what do you think it would be?

One area, you mean within the MA forum? 

The mountains would be the easy answer. 

East of the blue ridge, I don't know. It's like trying to work out the exact location of mesoscale banding on a 384 hour storm this far out. We just have to see how the cookie crumbles...

[Stormchaserchuck1]

I liked the outlook. Easy to read or browse through. 

One point I would like to make is that things like PNA or NAO impact PDO and AMO in now-time. In other words, a +PNA Winter Dec-Feb is more likely to produce +PDO. Because of this, unless there is some alter pattern happening with the future progression of water currents, the Fall period is these best to roll forward future 500mb patterns. I think I found in the past that Sept-Nov PDO had higher than random correlation to Winter PNA, but I'm not 100% sure. 

I mostly agree with your temperatures, snowfall, and precip, although snowfall could go higher, given how it's solidly El Nino/max -QBO (together), and our above average precip pattern this year and for the last few years. I average 32" and the El Nino/max -QBO gives me a 40-60" range to start with, using years like 14-15. 

[Jebman]

5 hours ago, GramaxRefugee said:

quote from the report:

Below are the analogs that scored at least 2 points are as follows:
✓ 1951-52 (3 points)
✓ 1958-59 (2 points)
✓ 1965-66 (3 points)
✓ 1972-73 (2 points)
✓ 1976-77 (3 points)
✓ 1986-87 (2 points)
✓ 2002-03 (2 points)
✓ 2006-07 (2 points)
✓ 2009-10 (5 points)
✓ 2018-19 (2 points)

--------------------------

The others aren't even in the same ballpark.  

I'm only half serious, and there is a disclaimer, and all that, but...I can't wait for @Jebman to see this.

(Thanks @Terpeast, for the nice work.)

I am so happy for you all this winter, I want to shout this from the housetops, until I am hoarse!

[Terpeast]

4 hours ago, MN Transplant said:

Great writeup and analysis.  I certainly hope this comes to fruition.

IMO, only a 10% chance of less than 10" is really aggressive.  5 of the last 7 winters have been sub-10" in my backyard, and I'm not even in a river like DCA.  

Thanks MN. Yeah - I'm pretty bullish about our chances at reaching at least climo or above in our area. Still, a 10% chance is a non-zero chance. It can still happen. 1972-73 kept popping up in my analog research...

[winter_warlock]

6 hours ago, GramaxRefugee said:

quote from the report:

Below are the analogs that scored at least 2 points are as follows:
✓ 1951-52 (3 points)
✓ 1958-59 (2 points)
✓ 1965-66 (3 points)
✓ 1972-73 (2 points)
✓ 1976-77 (3 points)
✓ 1986-87 (2 points)
✓ 2002-03 (2 points)
✓ 2006-07 (2 points)
✓ 2009-10 (5 points)
✓ 2018-19 (2 points)

--------------------------

The others aren't even in the same ballpark.  

I'm only half serious, and there is a disclaimer, and all that, but...I can't wait for @Jebman to see this.

(Thanks @Terpeast, for the nice work.)

Oh man to have a repeat of the 2009-2010  winter would be a dream for alot of us!!!!

[Stormchaserchuck1]

The last 6 Winter's, we have had -PNA's a greater % of the time, in 3 month periods, then the last 7 months, since the El Nino developed. (I'm quantifying that 1/10 chance, and saying if you base on current probability for PNA it's about 1/3 of the 5/7 recently (5/21). 

[Jebman]

1 hour ago, winter_warlock said:

Oh man to have a repeat of the 2009-2010  winter would be a dream for alot of us!!!!

Bank on this, it is gonna happen to the Mid Atlantic this winter! I'll be cheering all of you right on!

[Jebman]

Good analysis Terpeast.

I think however that you are underestimating western MD for snow. Those communities will get Palisaded by snows.

[winter_warlock]

39 minutes ago, Jebman said:

Bank on this, it is gonna happen to the Mid Atlantic this winter! I'll be cheering all of you right on!

   It does appear as the biggest analog .   Most of us in northern mid Atlantic  are due brother!! 

[winter_warlock]

3 hours ago, Jebman said:

I am so happy for you all this winter, I want to shout this from the housetops, until I am hoarse!

Shout it  bro!!! Lol

[das]

On 11/1/2023 at 10:05 PM, Terpeast said:

I put my outlook in a PDF, so I'll put the "tl,dr" here:

There are a lot of mixed signals leading into this winter. But I have seen enough signs to raise my confidence for an interesting winter across the Mid-Atlantic and Southeast U.S. This year is the best chance for a big winter or a top 10 KU since 2015-16 or even 2009-10.

Nice writeup.  I am prepared to watch storm after storm cruise by just to my east from my warm(ish), dry perch up here in Vermont.  It'll be maddening.

[raindancewx]

I enjoyed reading your outlook. PowerPoint style setups really do wonders for flipping through ideas quickly.

I used to do what you do, where you take 4-8 factors and see which years have those factors. Then you grab the overall years in the most categories.

What I found though is the blend from doing that makes the overall match much worse than the individual years. You really want the blend to match everything - that's what I've found anyway. Like, you could probably blend 1997 and 1954 in the right situation and get the pattern in a weak El Nino if the blend is correctly combined to generate all the important variables.

[Terpeast]

23 minutes ago, raindancewx said:

I enjoyed reading your outlook. PowerPoint style setups really do wonders for flipping through ideas quickly.

I used to do what you do, where you take 4-8 factors and see which years have those factors. Then you grab the overall years in the most categories.

What I found though is the blend from doing that makes the overall match much worse than the individual years. You really want the blend to match everything - that's what I've found anyway. Like, you could probably blend 1997 and 1954 in the right situation and get the pattern in a weak El Nino if the blend is correctly combined to generate all the important variables.

Yeah, ideally I want my blend to match everything but this year it was difficult to find a good blend for it. That’s why I wanted to temper expectations that a year like 09-10 isn’t necessarily a great match despite it having commonalities within the factors I looked at.

Sensible weather analogs is another good way to do it, but I’m not well versed in that method like you are. I have a lot to learn in that area. 

[Terpeast]

December 11 Update - No change to outlook

New MEI came in at ~0.6 today after a restrengthening of the El Nino. The PDO remains slightly negative with an unfavorable pacific profile dominated by a GOA low. 

However, the GOA low should retrograde and the pacific jet retracts sometime between Christmas and Jan 5, while the MJO weakens into COD. 

December will likely finish above normal for the Mid-Atlantic, which was to be expected. January and February might end up closer to normal, if not slightly above. February may end up being the colder month if the SSW event were to pan out, too.

Last month, when the MEI came in much lower than expected at 0.3, I started to reconsider my snowfall probabilistic forecast. However, with the MEI increasing again, and the mid-Atlantic region having gotten on the board with last night's snowfall, I am leaving my outlook unchanged. 

I still maintain that we have a 60% chance of beating climo with 20-40" area-wide (lean towards higher end the more NW, and lower the more SE and/or within the cities). 

[Terpeast]

January 6 Update - Slightly Lower Expectations in the lowlands and/or east of Route 15

While I would never cancel an El Nino winter for the mid-Atlantic, as of Jan 6, we've missed a big opportunity in the lowlands to get towards my expectations of an above-climo winter. West of route 15, however, is still very much on track and can meet or even exceed my snowfall forecast. But east of 15 in the low lands and coastal plan, we're facing an uphill battle to even reach climo.

Of course we can still reach it in one big storm. The chances of 1 big KU is still higher as it's ever been. The STJ is on steroids and is as relentless as I have ever seen it. But we've lacked cold air and while we might get some more of that in the coming weeks, our window of opportunity is shrinking and fast. Especially with a projected late-Jan thaw, before a February reload with the SSWE. 

We NEED February to go on an absolute tear to get above climo, and if it doesn't happen, we will fall short. Maybe not in the mountains, which will still do fine, but definitely for the low lands east of 15. 

Sorry if my thoughts seem disorganized, I'm writing this while watching my 2 year old daughter run circles around me. She's going stir crazy. We need snow... BAD.

While I'm going to officially grade myself on my original forecast, I created a new map to reflect my expectations going forward. No change west of 15, but east of 15 I'm cutting amounts by 25-30% (with an extra 20% siting penalty on DCA).

Whether we reach climo at the main airport sites is now 50/50.

 

[Terpeast]

Grading my 23-24 winter outlook vs actual results

Temperatures: Decent match spatially, but off on the magnitude of the warmth. It's not just us being really warm, it's everywhere. Including Canada. Grade: B-

Precipitation: Good match spatially and magnitude, a little bit off on the precip maxes though both midwest and east coast. I was highly confident of a wet winter, and that did happen. Grade: A-

Snowfall: Truth is, I had at least one big storm baked into my snowfall outlook even through I cited only a 15-30% chance of a HECS. Well, that didn't happen obviously, so my snowfall guess was shot to hell. Grade: F

Overall: I think my methodology and use of MEI led to an OK outlook, but was a little overconfident on blocking. We did get blocking, but each episode was either too brief, or occurred in the wrong places. Unfortunately, the MEI is no more, and I will have to either use RONI or a different method altogether for next year's outlook. Overall grade: C