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Wintry Winter Discussion 2023/24

We had 3 winters in a row over a foot of snow in the late 80s wow and one year has been a big analog for this winter here

I mean 2009-2011 did it here but still to see that again would be quite something ?
 
Here's why I'm really intrigued by this bout of -NAO we're seeing the next few weeks:

Does early winter NAO behavior tell us anything about its behavior later in winter (Jan-Mar) during El Niños?! ?

The data says yes! ?


The relationship is positive (they reinforce each other) & it's significant-very significant.

This means that a more negative/or less positive NAO in December begets an even more negative NAO in January-March when an El Niño is present. This is objectively a very good early sign for cold/snowy winter in the SE US & mid-Atlantic states.


Below is the December vs January-March averaged 500mb correlation (R) for El Niño winters only, since 1855 in NOAA's 20th Century Reanalysis Version 3 (NOAA 20CRv3). I applied a 30-year sliding base period that lagged by 20 years to . Notice that areas contoured and stippled in white are where the correlations are significant at the 99% level. This basically says that there's a < 1 % probability that the correlation between December NAO & January-March NAO in El Niño winters occurs simply by chance.


Dec_JFM_Nhem_500mb_El_Nino_Correlation_crop.png


Dec-Mar 500mb correlation w/ the -NAO (for a sanity check & comparison purposes).
Dec_JFM_Nhem_500mb_NAO_Correlation_crop.png





I've also looked at MSLP data in NOAA 20CRv3, because it's directly assimilated into the reanalysis model & thus tends to be the most reliable variable to look at. Not surprisingly, it supports the 500mb data w/ very significant correlation between Greenland & Scandinavia. This corresponds pretty well w/ the SLP loadings for the -NAO too (like the 500mb data).


Dec_JFM_Nhem_SLP_El_Nino_Correlation_crop.png




Dec-Mar MSLP correlation w/ the -NAO.

Dec_JFM_Nhem_SLP_NAO_Correlation_crop.png
 
Well my first chance at some flakes at least maybe

Saturday Night
Rain in the evening, then rain and snow likely after midnight. Cold with lows in the lower 30s. Northeast winds around 5 mph, becoming northwest 10 to 15 mph after midnight. Chance of precipitation 90 percent.
 
Itryatgolf said:
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I think this is just preliminary but what are yalls thoughts so far?
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It’s showing warming high in the stratosphere which is a good thing, but it will take multiple rounds of warming in order to hit the Strat PV really hard. Can see here on the chart the predicted weakening of the zonal winds at 10mb at 60 deg N latitude. This would have to weaken much further to 0 in order for it to be considered an official SSW. But again, attacks on the SPV and weakening are a good thing

0F44CBF6-5804-4BF5-9880-513516F141A2.png
 
griteater said:
It’s showing warming high in the stratosphere which is a good thing, but it will take multiple rounds of warming in order to hit the Strat PV really hard. Can see here on the chart the predicted weakening of the zonal winds at 10mb at 60 deg N latitude. This would have to weaken much further to 0 in order for it to be considered an official SSW. But again, attacks on the SPV and weakening are a good thing

View attachment 138146
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So I guess the ensembles and op runs that have been showing warming is what happens throughout late fall /winter that leads to more of a STRETCHING of the pv that if the warming continues, it could lead to a SSW event later? Want to make sure I understand that correctly lol.
 
CaryWx said:
Maybe not that soon but a Happy New Year could be in the works
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Imo its entirely possible that the MA up to the NYC metro or even inland areas like Charleston to Pittsburgh through Albany could see a good storm before the solstice, even the mountains of Virginia and NC could cash in.

Us in the south outside of the mountains will probably wait until New Years like you said.
 
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Itryatgolf said:
So I guess the ensembles and op runs that have been showing warming is what happens throughout late fall /winter that leads to more of a STRETCHING of the pv that if the warming continues, it could lead to a SSW event later? Want to make sure I understand that correctly lol.
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Correct. It’s akin to seeing a strong hurricane that is wound up tight weaken. Things like dry air entrainment, wind shear, and interactions with land masses weaken hurricanes. A strong hurricane will encounter those along its path and weaken, but in between those encounters, it will recover some or all of its strength back. In comparison, periodic heat flux coming from the troposphere and up into the stratosphere are the obstacles for the Strat PV trying to gain and maintain its strength.,,and the stronger and more prolonged the heat flux is, the weaker the Strat PV will be
 
LukeBarrette said:
GFS is definitely picking up on a wave around the Dec 5th timeframe. Last 3 runs it shows a shortwave moving towards the east coast from the center of the country.
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The only thing I’m having a hard time with the gfs lately is the 2m temps. The 6z this morning was about 10 or so degrees off with what verified. Then you have the CMC which will probably verify too cold. I don’t have much faith in any of them at a day much less 10.
 
jeremyt said:
The only thing I’m having a hard time with the gfs lately is the 2m temps. The 6z this morning was about 10 or so degrees off with what verified. Then you have the CMC which will probably verify too cold. I don’t have much faith in any of them at a day much less 10.
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The CMC has been horrible in the 8-10 day range lately. For example 9 days before Thanksgiving it had highs in the 30s to low 40s for most of the Carolinas outside of the mountains. Then last weekend it was saying this cold shot that we have coming up was going to be a full on Arctic blast with most of the Midwest having their first sub-zero lows of the season and the much of the Piedmont dropping to the low to mid teens.
 
Chazwin said:
The CMC has been horrible in the 8-10 day range lately. For example 9 days before Thanksgiving it had highs in the 30s to low 40s for most of the Carolinas outside of the mountains. Then last weekend it was saying this cold shot that we have coming up was going to be a full on Arctic blast with most of the Midwest having their first sub-zero lows of the season and the much of the Piedmont dropping to the low to mid teens.
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Agreed, but the GFS seems too warm lately, based off runs and what’s happened or local forecast temps. I don’t have the euro so I can only see what people post here.
 
iGRXY said:
The GFS has been too warm dating back to Summer at least. It is consistently busting high on temps at least around my neck of the woods
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Which is interesting because it seems like for a number of years the GFS has had a warm bias in the summer and cold bias the further we get into fall and winter.
 
Interesting graphic on CNN.com today showing differences in snowfall from the 70s to now. Surprised to see the big increases along the coast, but I guess warmer waters means more amped coastal lows?

Worrisome trend when you think about the ski resorts in WV, VA, NC, and TN
 

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ajr said:
Interesting graphic on CNN.com today showing differences in snowfall from the 70s to now. Surprised to see the big increases along the coast, but I guess warmer waters means more amped coastal lows?

Worrisome trend when you think about the ski resorts in WV, VA, NC, and TN
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Interesting. Tend to think most of the differences between the Rockies and Apps can be attributed to the PDO/AMO combination in the 60s/70s/80s vs now. Think you're right on warmer water temps boosting storms for the coastal areas.
 
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ajr said:
Interesting graphic on CNN.com today showing differences in snowfall from the 70s to now. Surprised to see the big increases along the coast, but I guess warmer waters means more amped coastal lows?

Worrisome trend when you think about the ski resorts in WV, VA, NC, and TN
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The NC numbers are down the most. WV still doing well.
 
Miracle snow

gfs_mslp_pcpn_frzn_us_60.png
 
If the teleconnections and ensembles are on to how the first 10 days of December play out, there might really be a lot of busted monthly forecasts. While it’s not showing anything extremely cold, the biggest takeaway when looking at them is that there is nothing to indicate an extended stretch of above to well above average temperatures.
 
Experimenting with something new tonight. Having one of those very late night coding sessions (usually when I do my best work).

This is what the historical tercile summaries look like for El Niño events since 1855, weighted more heavily towards analogous events that were accompanied by a positive Indian Ocean Dipole (+IOD), negative Pacific Decadal Oscillation (-PDO), early winter -NAO, and a positive Atlantic Multidecadal Oscillation (+AMO), or warm Atlantic.

In essence, this provides you with a true apples-to-apples comparison of Climate Prediction Center (CPC) probabilistic winter outlooks to what has historically occurred in El Niño winters like this over the last 150+ years or so.

The plots will look a little noisier than the ones I've shown previously because I'm looking at finer-scale details in the local probability distribution at each point.
(i.e. splitting the data into thirds/3 parts instead of 2 equal halves yields slightly noisier data).

Here I've only looked at February, but I'd be curious about what other months show.

I plan to take a look at ERA-5 reanalysis monthly snowfall data (which goes back to 1940) at some point tomorrow and perform the same analysis (or in this case I guess today because it's already past local midnight here).
Feb_Nhem_500mb_CPC_Prob_Nino_Analog_crop.png


Feb_Analog_CPC_Temp_Prob_Composite_crop.png
 
Webberweather53 said:
Now the map that most everyone here has probably been waiting for:

Snowfall tercile summaries (CPC-like probabilities) across the CONUS for El Niño winters since 1940 using ERA-5 reanalysis:

View attachment 138182
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Same analysis, but over the entire Northern Hemisphere. It tends to get quite snowy over much of Eurasia during El Niños, esp over the Tibetan Plateau of western China.


NHEM_NDJFM_CPC_Snow_Prob_El_Nino_Composite_crop.png
 
Brent said:
Well my first chance at some flakes at least maybe

Saturday Night
Rain in the evening, then rain and snow likely after midnight. Cold with lows in the lower 30s. Northeast winds around 5 mph, becoming northwest 10 to 15 mph after midnight. Chance of precipitation 90 percent.
Click to expand...

Well it did snow in the cityScreenshot_2023-11-26-11-07-33-46_a23b203fd3aafc6dcb84e438dda678b6.jpg
 
Fwiw, these are the (weighted) analogs I came up w/ for this winter & posted about on twitter/"X" a few days ago. I weighed more intense El Niños, El Niños accompanied by a positive Indian Ocean Dipole (+IOD), negative Pacific Decadal Oscillation (-PDO), a neutral - negative NAO in December, and a warm Atlantic (+AMO) more heavily than other Ninos.

Even when you account for things like long-term climate change and changes in instrumentation/measurement & sampling techniques over the record, this subset of years paints a rather cool/stormy picture across the southern tier of the US.

Snow is obviously a whole different animal. While I didn't factor the background warming of the climate into the ERA-5 (CPC-like) probability composite shown below, you definitely get the idea that things are really leaning in our favor this year regardless.

F_okICbXsAA77Mb.jpeg




F_okN9XWkAAKCTt.jpeg


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F_okPUcWUAErVMm.jpeg


F_4wheiWgAAppqF.jpeg
 
Webberweather53 said:
Fwiw, these are the (weighted) analogs I came up w/ for this winter & posted about on twitter/"X" a few days ago. I weighed more intense El Niños, El Niños accompanied by a positive Indian Ocean Dipole (+IOD), negative Pacific Decadal Oscillation (-PDO), a neutral - negative NAO in December, and a warm Atlantic (+AMO) more heavily than other Ninos.

Even when you account for things like long-term climate change and changes in instrumentation/measurement & sampling techniques over the record, this subset of years paints a rather cool/stormy picture across the southern tier of the US.

Snow is obviously a whole different animal. While I didn't factor the background warming of the climate into the ERA-5 (CPC-like) probability composite shown below, you definitely get the idea that things are really leaning in our favor this year regardless.

View attachment 138185




View attachment 138187


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View attachment 138186


View attachment 138191
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Here's what precipitation looks like in ERA-5 for all El Niños (top) and these analogs (bottom).


F_5vpfiWMAADdB7.jpeg




F_5zD-gW0AACa-i.jpeg



Not all that far off from the latest CPC and C3S Ensemble Mean Forecasts.

off01_prcp.gif



ps2png-worker-commands-76898cbbf-bq7dx-6fe5cac1a363ec1525f54343b6cc9fd8-2OmAb_.png
 
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