February Medium/Long Range Thread

[mitchnick]

Storm on the Eps for the 20/21st heading east.

[mitchnick]

Just now, mitchnick said:

Storm on the Eps for the 20/21st heading east.

 

[Stormchaserchuck1]

13 minutes ago, brooklynwx99 said:

personally, I find it very hard to believe that there isn't a large storm when a four sigma west-based -NAO breaks down

That's called a -AO.  NAO is a North Atlantic sea-level pressure measurement. 

[Stormchaserchuck1]

41 minutes ago, mitchnick said:

Overcoming the February Niña climo in medium range forecasts is a bigger biatch than the models/ensembles seem to think, or so it seems.

What do you mean, you think the models are warm biased because of Nina? 

[mitchnick]

1 minute ago, Stormchaserchuck1 said:

What do you mean, you think the models are warm biased because of Nina? 

No. They don't figure it in and base state too hard to overcome. 

[mitchnick]

Eps looks to favor the north dor the 20/21, though this is not an exact method I'll admit.

[mitchnick]

Just now, mitchnick said:

Eps looks to favor the north dor the 20/21, though this is not an exact method I'll admit.

12 hours later

[Stormchaserchuck1]

3 minutes ago, mitchnick said:

No. They don't figure it in and base state too hard to overcome. 

I think they have it included. I was wondering about the string of High pressures, and if it was going to break down allowing storms to track more north again.. so far that looks to be the case. It will be hard to have so many rainstorms though with the AO at -4 and nothing really unfavorable in the Pacific/Atlantic mid latitudes.

For the data collected on -AO being our snowstorm pattern.. know that a ridge at 90N is rare. Usually the NAO/AO overlap, and they are just talking about Greenland block.. I wonder if the Arctic circle is actually too far north to have substantial effect on our precip type. 

[psuhoffman]

51 minutes ago, frd said:

If it does hold then its time for that conversation that @psuhoffman mentioned.  

On to the EPS

From a 30k foot view we NEED blocking to start working again. And I think it will as the extreme -pdo cycle ends. 

I think because the one anomaly was not that long ago there seems to be a notion that EPO driven patterns can be a vehicle to snow but the fact is our snow climo has always been heavily reliant on anomalous big snow years with a bunch of below “avg” lean snow years in between. And those big years are driven by one thing. Blocking. 
 

9 of the last 10 40” winters in Baltimore are from a blocking regime. The one exception was 2014!  That was a unicorn anomaly. We get maybe one snowy winter that way every 50 years!  If that’s the only way for us to get a snowy winter we’re pretty much screwed as history says that that kind of thing happens once a lifetime. 
 

This is the h5 comp of the other 9 40” winters.  We NEED this to work!  

The issue lately has been blocks have not caused the depth of mid latitude response we need. Look at the depth of the troughs in the mid latitudes under that blocking!  The depth is greater than the high latitude heights!  Lately the mid latitude heights have not been nearly as low as the blocks heights are high. That’s a problem!
 

To simplify we aren’t getting cold enough under the blocks to make the equation work. Look at 3 recent blocks and the mid latitude response!  

Where’s the cold!!??  Seriously where is the mid latitude response we need?  And forget worrying about here.  Where is the depth of cold anywhere in the mid latitudes under any of those blocks!?  Compare those to the analogs above of what we need the response to a block to look like!   Lately the only time the mid latitudes get truly cold is with epo driven cross polar directly discharged arctic air but that’s not a snowy pattern. It’s just cold. Snowy patterns here are from domestic cold stuck under a block not cross polar arctic shots. 
 

Now I’ve said I think the PDO has been 80-90% of the issue. The other 20% is you know what. I’m banking that as the PDO cycle ends we have more luck again. Hopefully I’m not to fast to expect that. The last block did deliver the cold!  
 

But if in the next few years the pdo flips and we continue to see this phenomenon it’s time to have a very depressing conversation about our new reality. One I really hope we don’t have to have yet. 

[Stormchaserchuck1]

15 minutes ago, psuhoffman said:

This is the h5 comp of the other 9 40” winters.  We NEED this to work!  

Yeah, but include 2014 because there's no reason why not to include it.. +NAO/-EPO is actually a pattern that has happened in tandem more since 2013.. I'm surprised we don't get more -EPO driven snow, maybe there's a lot of ice instead. 

Here's the 10 analogs you came up with

This doesn't scream blocking to me. This screams mid latitude cold. Last year I ran a composite of December's before DCA's most snowy Winter.. in those composites 90% of the N. Hemisphere was below average in December. This isn't a -NAO signal as much as general mid-latitude trough/below average.. -NAO is the 3rd strongest anomaly in that ^ map. A cold trough over western Europe is actually a greater anomaly by almost double! Wow (in the upper latitudes there is more volatility, so that's even more impressive)! +PNA too..  And the Arctic circle/North Pole might actually be too far north for a block to correlate with snow (I guess unless you're at 45N). 

[psuhoffman]

2 minutes ago, Stormchaserchuck1 said:

Yeah, but include 2014 because there's no reason why not to include it.. +NAO/-EPO is actually a pattern that has happened in tandem more since 2013.. I'm surprised we don't get more -EPO driven snow, maybe there's a lot of ice instead. 

Here's the 10 analogs you came up with

This doesn't scream blocking to me. This screams mid latitude cold. Last year I ran a composite of December's before DCA's most snowy Winter.. in those composites 90% of the N. Hemisphere was below average in December. This isn't a -NAO signal as much as general mid-latitude trough/below average.. -NAO is the 3rd strongest anomaly in that ^ map. A cold trough over western Europe is actually a greater anomaly by almost double! Wow (in the upper latitudes there is more volatility, so that's even more impressive)! +PNA too.. Actually the -NAO is the 4th strongest anomaly in that map, 3 troughs (Pacific/Atlantic/US) are all more powerful.  And the Arctic circle/North Pole might actually be too far north for a block to correlate with snow. 

I mentioned 2014 but that is the ONLY time that this pattern lead to a huge snow year in my lifetime.  It’s happened once in 50 years!  That isn’t going to adequately replace blocking as a viable path to our big snowfalls. You said yourself epo is more ice than snow signal. AO/nao are snow signals. 

[Stormchaserchuck1]

2 minutes ago, psuhoffman said:

I mentioned 2014 but that is the ONLY time that this pattern lead to a huge snow year in my lifetime.  It’s happened once in 50 years!  That isn’t going to adequately replace blocking as a viable path to our big snowfalls. You said yourself epo is more ice than snow signal. AO/nao are snow signals. 

Yeah but it happened. We had a real strong -EPO that Winter. EPO is more of a rare pattern, and you see it usually run in 7-12 day cycles vs longer periods, so you generally don't get it in a full Winter composite (a lot of + and - periods in a Winter). It wasn't like some tropical pattern that lead to an anomalous snowfall that Winter.. it was Pacific driven cold, legit imo. 

[psuhoffman]

@Stormchaserchuck1 you’re 100% right in your observation of trends the last 8 years but have you thought maybe that’s why it’s been by far the least snowy 8 year period in our recorded history!   Yes the last 8 years you’re right blocks haven’t been working and guess what that’s a big part of WHY it’s not been snowy!  If blocks continue to fail we will continue to underperform our historical snow climo. Doesn’t mean we won’t snow. Yes epo patterns will lead to snow. But not enough!  We won’t get many 30” or 40”+ seasons that way!  

[Stormchaserchuck1]

About AO/NAO being snow signals.. If you base them solely on High pressure, I don't think so. The mid latitude cold is a stronger pattern. You see -50 anomaly in the Pacific and <-40dm anomaly off of western Europe, but the whole northern latitude AO/NAO blocking only reaches +35dm.  A lot of times when we are talking about the NAO, we are talking about a Greenland block. But the mid latitude needing to be cold (50/50 low, +PNA) is actually more important, according to those maps. 

[Stormchaserchuck1]

5 minutes ago, psuhoffman said:

@Stormchaserchuck1 you’re 100% right in your observation of trends the last 8 years but have you thought maybe that’s why it’s been by far the least snowy 8 year period in our recorded history!   Yes the last 8 years you’re right blocks haven’t been working and guess what that’s a big part of WHY it’s not been snowy!  If blocks continue to fail we will continue to underperform our historical snow climo. Doesn’t mean we won’t snow. Yes epo patterns will lead to snow. But not enough!  We won’t get many 30” or 40”+ seasons that way!  

PNA might be a little underrated.. In your maps, its signal beats out the NAO and AO.  Also, for a 90N block to work, you should be at 45N. So the composite also shows 80N blocking (northern Alaska/Greenland) as the strongest signal for 40N here... something to keep in mind because this coming block is right up over the Arctic circle. 

But +PNA is strong, and the 8-year period is most -PNA on record by 150% over any #2 (at least for Feb-March)! Greenland blocking recently has disconnected somewhat, but when we have a strong +PNA/-EPO pattern it generally doesn't disconnect (I know we had -epo in Dec 2022 and March 2023, but that's the only time it didn't correlate with cold).  If you believe the CPC, it's also been +NAO in the Winter something like 41/46 Winter months since 2013.. and record -PNA.. it's no surprise our snowfall is record low (although I think they base a lot of NAO calculation on mid-latitudes - the ability for a Greenland ridge/block to produce a trough underneath of it)! 

[Stormchaserchuck1]

17 minutes ago, psuhoffman said:

@Stormchaserchuck1 you’re 100% right in your observation of trends the last 8 years but have you thought maybe that’s why it’s been by far the least snowy 8 year period in our recorded history!   Yes the last 8 years you’re right blocks haven’t been working and guess what that’s a big part of WHY it’s not been snowy!  If blocks continue to fail we will continue to underperform our historical snow climo. Doesn’t mean we won’t snow. Yes epo patterns will lead to snow. But not enough!  We won’t get many 30” or 40”+ seasons that way!  

I think -EPO/+NAO would produce a 30" or 40" Winter, because NAO is strongly correlated to precip, and the positive phase has 3x more precip than negative phase (+0.50 correlation vs -0.50 correlation, is that 3x?)! EPO is neutral precip and the coldest pattern of all indexes.. so with the EPO having slightly more cold correlation than NAO, we would be below average temps with above average precip in that pattern! Only thing is EPO is loosely related to H5, so some of the cold precip could be ice. 

I also think it's just a general point - mid latitude cold, not necessarily related to upper latitude High pressure, is the snow pattern. So us losing mid latitude cold is the generality that is correlating with less snow.  It doesn't always have to stack. 

[Ralph Wiggum]

2 hours ago, stormtracker said:

Buncha rainstorms on the Euro too.   Imagine if that holds, lol

Nina climo ftw?

[Scarlet Pimpernel]

So...we're canceling the PSU window now? 

[Ralph Wiggum]

1 hour ago, brooklynwx99 said:

personally, I find it very hard to believe that there isn't a large storm when a four sigma west-based -NAO breaks down

There probably will be a big storm. But climo in a Nina late Feb says probably not for the immediate East Coast generally speaking.

[frd]

1 minute ago, Ralph Wiggum said:

There probably will be a big storm. But climo in a Nina late Feb says probably not for the immediate East Coast generally speaking.

SE "Tropical "Ridge on roids.  More expansive then the block.  

[aldie 22]

It's a battle of the multiple paragraphs! Taking forever to scroll this page

[Scarlet Pimpernel]

2 minutes ago, Ralph Wiggum said:

There probably will be a big storm. But climo in a Nina late Feb says probably not for the immediate East Coast generally speaking.

Wow, the mood in here seems to have deflated faster than a Tom Brady football!  We've been following the later February into March time frame as being a very favorable time for good opportunities, for a little while now.  Yeah, the 06Z GFS with the crazy 40" amounts is not going to happen and I don't think anyone truly took that to heart.  But it showed the potential, as have other similar storms that have shown up in that time frame a handful of times.  Now, everyone semi-loses it because the GFS and Euro ops show rainers, and now we're talking like, "well, it's a Nina, so we're doomed regardless" or "what if the blocking doesn't work", etc.  Of course there is no guarantee with a favorable setup, but I would think there will be several chances to score all the same.  If people are looking for a top-5 HECS system here, you're likely going to be disappointed even though that could happen, sure.  If you're looking for some solid MECS events, that's a better shot in this environment (i.e., yes, a Nina!).

[Scarlet Pimpernel]

1 hour ago, mitchnick said:

No. They don't figure it in and base state too hard to overcome. 

I kind of understand what you're saying here, but this isn't exactly how models work.  At least not dynamical models that compute a complex set of dynamic/thermodynamic equations through time, given a set of input initial conditions.  Now, the AI-type models might be able to do this.  Does the Euro AI use some historical database of the Nino state (or any other factor, like MJO), in its forecasts?  You can argue that perhaps the dynamical models don't respond as well as they should to the overall atmospheric state, but it's not a situation of where some "base state" is ignored; it would be sort of indirectly factored in by the input data.  If you ran the GFS in the Jurassic era (using those observations the dinosaurs took, hahaha!), it would still work and it would respond to what the atmospheric state was at that time, within the confines of the model biases and such.  Regardless of the atmospheric state, the physical and thermodynamic laws are still the same.  Of course, as I said, one can look into how well any particular model or ensemble can handle that or how well those equations are represented.  But that's a different conversation.

[psuhoffman]

45 minutes ago, Stormchaserchuck1 said:

I think -EPO/+NAO would produce a 30" or 40" Winter, because NAO is strongly correlated to precip, and the positive phase has 3x more precip than negative phase (+0.50 correlation vs -0.50 correlation, is that 3x?)! EPO is neutral precip and the coldest pattern of all indexes.. so with the EPO having slightly more cold correlation than NAO, we would be below average temps with above average precip in that pattern! Only thing is EPO is loosely related to H5, so some of the cold precip could be ice. 

First of all I love and value our back and forth dialogues.  I learn a lot. Sorry if I ever come off confrontational. 
 

Recently most of our snow has come that way. But recently we’ve been in a horrific snow drought. And this historical data would suggest why. 
 

This is a chart I compiled back in 2019 for every 5” snow at BWI going back to 1948. 88 events. And to be transparent I used a mean of the pattern the 5 days leading up to the snow. That’s because we had some events from blocking where it was flipping positive and by the day of the snow was neutral or positive but the storm was set up by the block. IMO the loading pattern 5 days leading up is more important then the includes the day of the snow. 
 

here was the results. 

Only 12 of the 88 snows were from a -epo +nao. It’s one of the least common snowfall index combos.  Overall the epo had no correlation to snow. We had the exact same number of 5” snows with a + as - epo. 
 

Also of note the PNA was not the death sentence to snow historically.  Yes when a -PDO was combined with other hostile long wave features like a +epo nao ao it was rare. But it was rare to get snow when any of the other 3 indexes were hostile also. A pna alone was a rare way to snow absent other favorable pattern drivers. And if other factors were favorable a -pna didn’t seem to make snow less likely. 
 

Actually the most common index setting for snow was -epo, -pna, -AO, -nao. Our most common big snow look was in a -pna!!!!  This is because with blocking the troughs in the west would historically slide east under the block not amplify and cut into the block like is happening lately.  I theorize that’s been partly the fault of the crazy -pdo cycle amplifying everything out west.  

The take away though is by far the two most important factors was AO and NAO. The 4 most common snowfall settings was when those were both negative regardless of the value of the epo pna. And it was rare to get a 5” snow in a +AO NAO no matter what the PNA and EPO was also. 
 

The data just doesn’t support the idea that epo pna patterns are a likely way to her big snowstorms. 
 

It is more murky if you start to look at 2-4” snows. I started that and had to abandon it for time reasons and never got back but prelim results indicated there is more of a correlation between pna epo and those minor snowfalls. But frankly ok a big game hunter and not that concerned with the locating pattern for a 2” snow. Plus almost every one of our 30” winters!includes some 5” snows so we aren’t getting a snowy winter with those 1-4” event patterns anyways. 2014 was the one exception. Actually that one season made up a few of those rare examples on that chart. If you took out 2014 it would look even worse and there would be a negative correlation overall between -epo and snow!  The historical data says that season was an anomaly and not something to bank on as a way to get a lot of snow. 

[psuhoffman]

40 minutes ago, Scarlet Pimpernel said:

So...we're canceling the PSU window now? 

I ain’t cancelled shit. Im just having dialogue I find educational and interesting with Chuck about effective snowstorm loading patterns overlayed with hypothesizing about how climate factors “could” impact blocking. But this discussion does not mean I’ve changed my mind about the pattern. 
 

BTw keep something in mind. For the last 10 days I was kinda debbing next week despite models spitting out crazy stupid snow. The reason was the pattern just didn’t look like a snowy one. I said the guidance at range when it’s not aligned with historical analogs for a pattern usually adjust to the climo for that pattern once inside day 5. And what happened!  
 

Well that works both ways!  Remember 10 days before Jan 6 when it was a cutter and Ji and I said that made no sense and should adjust. It ended up adjusting so much it fringed me. I’m not worried about what the surface Synoptics are on model runs at 300 hours. I’m way more worried about what the longwave pattern is. The surface will adjust to it 90% of the time. 

[Stormchaserchuck1]

PNA has a big precip correlation like the NAO. It's actually equal to temps. So if we are +0.5 in -PNA (75% chance of above average temps), we are also +0.5 precip (75% chance of above average precip). You can see how if other things are favorable, that could possibly align with more snow... but I would say in the 1960s we not only had some -NAO blocks, but there was a much stronger relative [underneath] mid level trough... maybe that was from -AMO

-AMO ibb.co/bR3LvKW

+AMO ibb.co/KctZCPm

-AMO ibb.co/wKX4YCC

+AMO ibb.co/sFSwm0j

Thanks for your input about our discussions.. like I said before, you discuss these things and do research on it.. that's more than people can ask for. 

The thing I like about +PNA is it has lower pressure correlation on the coast, despite being 75/25 drier. So +PNA in the Winter can be more fun, because it's more associated with stronger low pressure and windstorms. -PNA's are just overrunning events.. 

I'm surprised you have 13 cases associated with +EPO. I think that's in part because of how it's calculated. A trough in the Gulf of Alaska is actually a BIG factor in East coast snowstorms.. that and a 50/50 low. 8"+ composite has like a -120dm anomaly in the Gulf of Alaska... that in some cases is called +EPO. I consider the EPO to be more a 500mb over Alaska and north of, and sometimes going NE Of Alaska into NW Canada and the Arctic circle. The CPC calculates the EPO much further south. Some blizzards may have technically had +EPO because of this, but when I think of +EPO, that pattern is shut the blinds, blowout, mid Winter 50s and 60s. I think the overlap between PNA/EPO is where the weakness in your snow data is. 

I see your clear cut correlation with NAO and AO in your data. Half of the NAO is calculated in the mid latitudes. Sometimes the mid latitude will be cold, and there will be none or a weak High pressure over top of it.. that's called a -NAO. We had a lot of that in the 1960s. We've had the opposite lately. NAO remember is North Atlantic sea level pressure differences between ~Iceland and ~The Azores. If there is neutral over the Azores, that's a 0 to half the NAO index. And of course, that mid-latitude trough extends to us.. so by default us having a trough is actually more of a -NAO pattern. See? If you separate out the high latitude High pressures it's probably a weaker correlation.  We haven't had those mid latitude troughs lately, so the CPC has said 41/46 Winter months since 2013 have been +NAO (16/16 NAO cases monthly >1.11 in that time have all been positive!)! 

[psuhoffman]

How many times the last 8 years would we have killed to see this across all guidance.

 

I think it’s a combo of discontent with this week and the fact it’s still forever away which is my fault because I started hyping the window when it was like 30 days out.  Also I think some bought into the idea we would be colder and get a lot of snow during the period BEFORE that, which makes this feel like a can kick but imo the failure is the -epo -pna +NAO pattern this week has no bearing on what will happen in the next -AO driven pattern.  

[psuhoffman]

@Stormchaserchuck1 I think you’re saying the same thing but in different terms. I agree our biggest issue is the mid latitudes have warmed. The indexes are just a way of measuring the pattern. It’s a 6 v half dozen debate. But the bottom line is we’re not seeing the level of mid latitude troughs or cold that we need at this latitude as often. Could be AMO. PDO. Some combo. And some is it’s climate change. I don’t have all the answers either just like doing my best to study and guess 

 

Wrt the +epo snows I think a decent number of them fell into this grouping which I termed “Hudson bay ridge storms”.  This is a composite of those 16 events. 

[psuhoffman]

@Stormchaserchuck1 oh also remember I studied the loading pattern not the day of. Yes a lot of our big snows come with a trough in GOA. But that’s also why we warm up right after. The loading pattern to that big storm was what happened a week before that to establish cold over us then as the pattern breaks down and sends some wave at us with cold in place…that’s how we get the big ones often. 

[Stormchaserchuck1]

3 minutes ago, psuhoffman said:

@Stormchaserchuck1 I think you’re saying the same thing but in different terms. I agree our biggest issue is the mid latitudes have warmed. The indexes are just a way of measuring the pattern. It’s a 6 v half dozen debate. But the bottom line is we’re not seeing the level of mid latitude troughs or cold that we need at this latitude as often. Could be AMO. PDO. Some combo. And some is it’s climate change. I don’t have all the answers either just like doing my best to study and guess 

 

Wrt the +epo snows I think a decent number of them fell into this grouping which I termed “Hudson bay ridge storms”.  This is a composite of those 16 events. 

That's actually a pretty good -WPO surprisingly and also surprisingly because it correlates with Canada, neutral 500mb over and NE of Alaska.  I'd like to see the +EPO snowstorm composite sometime if you ever see it, because a true +EPO, with the strongest anomaly in the Northern Hemisphere over Alaska... there is pretty much almost no chance of snow in that pattern.