Ending out December with a Potential Pattern Change

[TalcottWx]

hey give me a positive AO,NAO EPO,negative PNA,hostile Atlantic,mega SE ridge and I'll show you how it snows, not. The pattern of course matters

I think he is just trying to suggest that some obsess over the perfect setup or long range etc. He's right. I think some do get caught up in that. The pattern doesn't need to be perfect, but seems like were rounding the corner into something better. The right direction is all you can ask for. I don't even understand all the global indices fully but it's pretty easy to look at 850 and 500mb's to see what is good and what is bad. 

 

We've had several instances were a pattern was poo-pooed but it snowed pretty significantly despite that in the end. 

[eduggs]

hey give me a positive AO,NAO EPO,negative PNA,hostile Atlantic,mega SE ridge and I'll show you how it snows, not. The pattern of course matters

Temperature gradients drive mid-latitude weather.  Those indices you list don't cause weather, they describe its state at a specific time.  The causal sequence is easily misunderstood.

 

If you can predict what the indices will look like in two weeks, then you can have a pretty good idea what the large scale atmospheric circulations will look like.  In other words, you could predict the overall weather "pattern."  But that's the tricky part.  It's not very easy to predict those things.

[eduggs]

Getting half of that equation correct is where skill in the long range exists. We can predict cold with at least some skill. We can't forecast storms that far out.

This is the definition of probabilistic forecasting. We have two variables that are important. If one of those variables goes into a favorable state for snow while the other remains unknown, then you would elevate the chances for snow during that period.

Except it's not really that simple, right?  Because in many places in the northeast, snow has a better correlation with QPF than with temperature.  In other words, sometimes warm and wet ultimately leads to more snow than cold alone.  Marginal airmasses and/or storm tracks can be best overall.  And rooting for cold might not be the best thing if you want an active, snowy pattern.

[CoastalWx]

Instead it's dry and warm

The idea is there though. That's what I mean. Big EPO cold dump is always west first.

[Ginx snewx]

Temperature gradients drive mid-latitude weather. Those indices you list don't cause weather, they describe its state at a specific time. The causal sequence is easily misunderstood.

If you can predict what the indices will look like in two weeks, But that's the tricky part. It's not very easy to predict those things.

interesting flip on your original post on the subject

[leo1000]

Is the -EPO ridge is looking strong in the long range?. Any signs of blocking?.

[leo1000]

The idea is there though. That's what I mean. Big EPO cold dump is always west first.

 Do you think that EPO will move east with time?.

[jamesnichols89]

The 30th event is still on the GFS, but its weak.  NAM has a secondary wave of low pressure for the 30th, but is out to sea still based upon H5 configuration and wave of northern stream energy.  January 3-5th looks interesting as the southern stream shortwave moves out of the Southwest US.

[CoastalWx]

Except it's not really that simple, right? Because in many places in the northeast, snow has a better correlation with QPF than with temperature. In other words, sometimes warm and wet ultimately leads to more snow than cold alone. Marginal airmasses and/or storm tracks can be best overall. And rooting for cold might not be the best thing if you want an active, snowy pattern.

Well SE ridges would elevate QPF chances. Are you assuming suppression?

[ORH_wxman]

Except it's not really that simple, right? Because in many places in the northeast, snow has a better correlation with QPF than with temperature. In other words, sometimes warm and wet ultimately leads to more snow than cold alone. Marginal airmasses and/or storm tracks can be best overall. And rooting for cold might not be the best thing if you want an active, snowy pattern.

Of course it isn't that simple. But QPF is not forecastable at long lead. There's the unknown variable. If you are in northern VT or something, then cold might be worse with a somewhat inverse correlation to snow in January at the peak of winter climo, but not in SNE.

We know that the cold is still important because snowy patterns happen with cold around.

[Ginx snewx]

Oddly enough this is very readable despite some thinking not

[eduggs]

I think he is just trying to suggest that some obsess over the perfect setup or long range etc. He's right. I think some do get caught up in that. The pattern doesn't need to be perfect, but seems like were rounding the corner into something better. The right direction is all you can ask for. I don't even understand all the global indices fully but it's pretty easy to look at 850 and 500mb's to see what is good and what is bad. 

 

We've had several instances were a pattern was poo-pooed but it snowed pretty significantly despite that in the end. 

But how do we even know if we are rounding the corner?  You could guess it will be colder next week just based on the time of year.  But how do we know a brief cold snap won't transition right back into warmth?  The longwave trof axis could easily set up too far west.  And even if it's cold, how do we know it won't be dry?  Cold and dry is the worst!

 

Maybe we should wait until we can really see the improvement before we start proclaiming its arrival.  Model skill is low beyond 7 days.

[TalcottWx]

The 30th event is still on the GFS, but its weak. NAM has a secondary wave of low pressure for the 30th, but is out to sea still based upon H5 configuration and wave of northern stream energy. January 3-5th looks interesting as the southern stream shortwave moves out of the Southwest US.

I'd forget much excitement about the 30th. The 3rd worries me with the possibility of another warm solution. I'm worried for the board more than anything else, lol.

[Ginx snewx]

But how do we even know if we are rounding the corner? You could guess it will be colder next week just based on the time of year. But how do we know a brief cold snap won't transition right back into warmth? The longwave trof axis could easily set up too far west. And even if it's cold, how do we know it won't be dry? Cold and dry is the worst!

Maybe we should wait until we can really see the improvement before we start proclaiming its arrival. Model skill is low beyond 7 days.

so you are saying Meteorology is an inexact science, thanks for the relevation

[eduggs]

Of course it isn't that simple. But QPF is not forecastable at long lead. There's the unknown variable. If you are in northern VT or something, then cold might be worse with a somewhat inverse correlation to snow in January at the peak of winter climo, but not in SNE.

We know that the cold is still important because snowy patterns happen with cold around.

I would be curious to look at the data.  For snow it doesn't need to be frigid... just cold enough.  And at our latitude, when it snows, the warm air is usually close by.  That baroclinicity drives most of our big events.

[40/70 Benchmark]

I'd forget much excitement about the 30th. The 3rd worries me with the possibility of another warm solution. I'm worried for the board more than anything else, lol.

I've essentially thrown in the towel through 1/4.

The 30th is dead, regardless of what some may think.

The 1/3-4 will  event cut.

 

It's hopeless until after 1/5.

[TalcottWx]

But how do we even know if we are rounding the corner? You could guess it will be colder next week just based on the time of year. But how do we know a brief cold snap won't transition right back into warmth? The longwave trof axis could easily set up too far west. And even if it's cold, how do we know it won't be dry? Cold and dry is the worst!

Maybe we should wait until we can really see the improvement before we start proclaiming its arrival. Model skill is low beyond 7 days.

There is pattern improvement within 7 days... there is undoubtedly a cooler pattern moving in. That SE ridge might offer brief warmer shots into SNE but everything is better moving forward. As Will and Scott say "I'd take my chances" on this pattern over the current one. There will be opportunities for snow coming soon.

is there a potential that we get plain screwed and it doesn't work out? Yes.

[CT Valley Snowman]

The models certainly are not trending in our favor through 1/4 although reversals can and have happened before, it's not a promising look right now.

[weathafella]

Won't look it though

Won't is deterministic and dangerous to assert. May not would have been better.

[Zeus]

Pattern looks like a loaded gun!

[CT Valley Snowman]

That being said, I still think it's too early to throw in the towel on the next storm despite the lack of model support right now but we certainly do need to see some more positive trends sooner rather than later

[weathafella]

The models certainly are not trending in our favor through 1/4 although reversals can and have happened before, it's not a promising look right now.

I don't agree. Did you look at all the ensemble products including GEFS, ecmwf eps, cmc ensembles and NAEFS?

[TalcottWx]

I've essentially thrown in the towel through 1/4.

The 30th is dead, regardless of what some may think.

The 1/3-4 will event cut.

It's hopeless until after 1/5.

Euro as one red tag said the other day is obsessed with cutters at the end of runs. Still a week plus out but II'm not feeling that storm. I think I like jan 5-10 as our flip, praise ullr.

[CT Valley Snowman]

I don't agree. Did you look at all the ensemble products including GEFS, ecmwf eps, cmc ensembles and NAEFS?

honestly just looked at the operational models and the Euro ensembles, is there something different you're seeing?

[weathafella]

honestly just looked at the operational models and the Euro ensembles, is there something different you're seeing?

Yes. There may be a lot of spread but the GEFS mean for the big cutter doesn't look bad. That is a big storm signal and I wouldn't automatically count on no snow. It's a decent swfe signal.

[Ginx snewx]

I don't agree. Did you look at all the ensemble products including GEFS, ecmwf eps, cmc ensembles and NAEFS?

possible Miller B setup, deep layered cold HP. Seems to me that total cutter look is going to change. Perhaps the myth of modeled cutters never changing goes down in flames.

[CT Valley Snowman]

yes I posted earlier in the January discussion how I thought cold air in the lower levels would at least create a front end event for the interior but it's going to be hard to have a true classic type snowstorm in the set up with the positive nao and the south east ridge

[TalcottWx]

Yes. There may be a lot of spread but the GEFS mean for the big cutter doesn't look bad. That is a big storm signal and I wouldn't automatically count on no snow. It's a decent swfe signal.

its been fluctuating between cutter and swfe.

[Ginx snewx]

Wiz cancelled winter on FB, oh lord

[weathafella]

its been fluctuating between cutter and swfe.

Well a swfe is a system where the mid levels cut but the surface gets squeezed under us so I'm not sure they are different.