January Medium/Long Range Discussion

[Thanatos_I_Am]

You need to look at the upper levels. In this case, the trough has a positive tilt as it passes and confluence (w-e oriented height contours) so the steering flow is more easterly instead of northerly. 



 

Negative tilted troughs will bring low pressure up north quickly and easily. Negative tilt is when the height contours are bent "backwards". I'll see if I can find something that shows it visually. 

Thanks Bob, love learning on here.

[psuhoffman]

4 minutes ago, Thanatos_I_Am said:

Alright PSU, question. I know this is fantasy land (I'm really just trying to learn here lol) but why would that low just slide off the coast? Why not move north?

The flow is pretty progressive although looking at the h5 there is some room for it to move north a bit your talking details though on a day 11 storm. A 100 mile shift at that range is like if a horse farts while facing north kind of stuff.  It's a darn good setup that's all we need to take from that. And I get fringed so that's a good sign too. But if you want to analyze why it moves east below see how the h5 trough opens up and flattens out a bit. If it holds together more or is a bit stronger it's probably a low tucked into the coast. I'm not sure how north it can get but I could see it being closer to the coast but again the whole setup could be wrong and look nothing like that anyways. 

[psuhoffman]

6 minutes ago, Bob Chill said:

You need to look at the upper levels. In this case, the trough has a positive tilt as it passes and confluence (w-e oriented height contours) so the steering flow is more easterly instead of northerly. 

 

Negative tilted troughs will bring low pressure up north quickly and easily. Negative tilt is when the height contours are bent "backwards". I'll see if I can find something that shows it visually. 

Ninja'd me

its a darn good setup details aside. And looking at h5 probably had room to be an even better result. 

[Bob Chill]

Here's a panel from the jan blizzard. Trough is negative and the upper level low is closed off. This is what a big storm looks like in the upper levels.

 

[CAPE]

15 minutes ago, soadforecaster said:

all you need to do is look at last year hecs, we tanked the nao and as it went to neutral we got the storm. I feel like a lot of our classic big storms come as the nao is on the rise from negative

Yes I believe this is absolutely the case- its the rate of change as the NAO transitions from negative to positive, but I am not sure if this applies when the NAO dips negative relatively briefly then heads back towards positive. Be interesting to see some data on storm occurrence when NAO is rising from strongly negative/sustained blocking pattern vs something weaker and more transient.

[Bob Chill]

Thanatos, the absolute best panels to become well versed in for winter storms are the 500mb vorticity and height anomaly plots. Surface panels look pretty and all but the real mechanism behind winter storms happens way up high. 

[showmethesnow]

46 minutes ago, psuhoffman said:

Since negativity seems to be the rule of the day I'll share two things that I keep seeing that does bother me. The first is the strength persistence of the eastern ridge even when the pattern as a whole isn't that bad. The ridge in the east just seems to want to be even stronger then I would expect given the overall pattern at times. It's amazing that the first look below which isn't that bad (-nao) somehow morphs into that ridge 48 hours later and 3 cutters back to back. Yea the nao is east based and the AK ridge is slightly west of ideal but we're in trouble if the only way to beat down the ridge is with an absolutely perfect setup in every detail. 

 

Call me skeptical but I doubt this is what we end up with in the Atlantic. We have seen this look on the models several times already this year but when it came time for verification we saw the SE ridge but little to no sign of a -NAO. Which makes sense because it is somewhat rare to have these in conjunction even with an east based -NAO. So the question is, which one wins out? If we can go against persistence of the pattern and we see the SE ridge beat down this would be a very good look. 

[showmethesnow]

45 minutes ago, Bob Chill said:

There is a good side to transient blocks. Many of our events happen as a -nao (bootleg or classic) is on the retreat. I have a bunch of NAO bar graphs I made from previous events and the majority came as the NAO was moving towards neutral. I'll try and dig them up and post if I can find them. 

Have you ever looked into the the transitioning of a +NAO to a negative state. Though rare we have had some good events with that as well if I recall correctly.

[poolz1]

Pretty tasty 500 D12 look on the 12z gefs. Much better ridge orientation in GL....should be some pretty snowy members. 

[psuhoffman]

7 minutes ago, showmethesnow said:

Call me skeptical but I doubt this is what we end up with in the Atlantic. We have seen this look on the models several times already this year but when it came time for verification we saw the SE ridge but little to no sign of a -NAO. Which makes sense because it is somewhat rare to have these in conjunction even with an east based -NAO. So the question is, which one wins out? If we can go against persistence of the pattern and we see the SE ridge beat down this would be a very good look. 

The -nao I'm referring too is developing now and peaks in only 3-4 days. I'm not talking about the long range. Maybe the models bust that bad but I do belive the nao is going negative right now. It just doesn't help us enough. It's east of where we want and not as sustained but still combined with the AK ridge I'm a bit shocked how stubborn the ridge is.  

[WxUSAF]

Based on that GEFS mean, there's certainly some support for the op's solution on days 9-12. Several waves of precipitation over that time frame which, based on the MSLP plots make it look like the shortwave is getting ejected at different times in the different members or they're keying on different waves. 

[psuhoffman]

8 minutes ago, showmethesnow said:

Have you ever looked into the the transitioning of a +NAO to a negative state. Though rare we have had some good events with that as well if I recall correctly.

Archambault events. It's been researched. But we tend to get rain most often. We usually need the cold in place first. That's why we do better with phase changes out of the nao. 

[psuhoffman]

17 minutes ago, showmethesnow said:

Call me skeptical but I doubt this is what we end up with in the Atlantic. We have seen this look on the models several times already this year but when it came time for verification we saw the SE ridge but little to no sign of a -NAO. Which makes sense because it is somewhat rare to have these in conjunction even with an east based -NAO. So the question is, which one wins out? If we can go against persistence of the pattern and we see the SE ridge beat down this would be a very good look. 

This is only 72 hours away. I think it's safe to say the nao is going negative for a time.  A negative nao doesn't mean snow and no snow doesn't mean a positive nao. 

[BristowWx]

yes.  I often equate -AO to the cold and -NAO to the storm.  -NAO allows storms to slow and deepen while the cold air is kept in place...the -AO allows the cold to be there in the first place. Do ever see a raging +AO but a raging -NAO? 

[psuhoffman]

Very good gefs run 

[Bob Chill]

2 minutes ago, psuhoffman said:

Very good gefs run 

 

Agreed man. That broad conus trough is money. It opens the door for a lot of different scenarios unlike a big +pna where there's always high inherent risk of late development or lack of moisture. With the GEFS look there are equal chances of overrunning, west track/front end thump, and even a progressive coastal. 

[CAPE]

The latest GEFS run looks a lot like yesterday's EPS runs, esp 12z, which was killer.

[usedtobe]

41 minutes ago, WxUSAF said:

Based on that GEFS mean, there's certainly some support for the op's solution on days 9-12. Several waves of precipitation over that time frame which, based on the MSLP plots make it look like the shortwave is getting ejected at different times in the different members or they're keying on different waves. 

That's my take on it and they probably don't offer a complete spectrum of possibilities.  I wrote a CWg article yesterday and noted that the GFS was jumping around from run to run and that hasn't stopped as last night's 06Z run takes a low west of after missing us to the south with the initial wave and then today hits us with one of the waves.  The ensembles have mostly liked the more southern track like today's but with different timing to the wave.   The Euro last night also liked that idea.  The pattern is the best we've seen this winter..  As you know, let's hope it actually delivers.  Lots can still go wrong. 

[H2O]

Wes just said its going to snow

 

 

 

 

 

 

 

 

 

 

 

 

i didn't say where he said it was going to snow

[WinterWxLuvr]

1 hour ago, Thanatos_I_Am said:

 

Thanks Bob, love learning on here.

 

To piggyback on what Bob said, to get it "more" up the coast we just need those height lines to be more vertical in front.  A neutral trough would put us in business on the 288 solution.

If you want a massive storm then you need that negative tilt.

[Bob Chill]

4 minutes ago, WinterWxLuvr said:

To piggyback on what Bob said, to get it "more" up the coast we just need those height lines to be more vertical in front.  A neutral trough would put us in business on the 288 solution.

If you want a massive storm then you need that negative tilt.

One of the first things I learned when I joined eastern was the basic rule of thumb: Positive tilt west of the MS river, neutral @ the MS river, and negative no earlier than the TN valley. Of course there are a million variations and endless details that don't fit this mold but early on in the learning stages it's a good way to learn h5 looks and what we like and don't like. 

[WinterWxLuvr]

1 minute ago, Bob Chill said:

One of the first things I learned when I joined eastern was the basic rule of thumb: Positive tilt west of the MS river, neutral @ the MS river, and negative no earlier than the TN valley. Of course there are a million variations and endless details that don't fit this mold but early on in the learning stages it's a good way to learn h5 looks and what we like and don't like. 

I love to watch the next h5 run when tracking.  Of course 288 is way too far out to do that but if I was going to I'd want see just a tad deeper sw and that area of low heights to the north be just a tad west.  If this was 72/96 out we could have some fun doing that.

[WhiteoutMD]

3 minutes ago, Bob Chill said:

One of the first things I learned when I joined eastern was the basic rule of thumb: Positive tilt west of the MS river, neutral @ the MS river, and negative no earlier than the TN valley. Of course there are a million variations and endless details that don't fit this mold but early on in the learning stages it's a good way to learn h5 looks and what we like and don't like. 

Close for 12 days out (fingers crossed) 

[Windman18]

Looks pretty good, rather miss south than north at this range.

[WinterWxLuvr]

One weather bell product that I wish they had, and it seems it would be easy to do, is 6 hour snow and precip maps for both the op and ens for gfs/euro

 

[BristowWx]

Euro is cooking up an overrunning stew for next weekend.  I have to wonder if we will be too far north however. 

[Bob Chill]

Man, euro is cooking up another excellent big real estate overrunning setup. 

[Bob Chill]

2 minutes ago, BristowWx said:

Euro is cooking up an overrunning stew for next weekend.  I have to wonder if we will be too far north however. 

With the way every single event has gone this season pretty much everywhere on the EC, being north @ d8-10 is preferable. 

[WinterWxLuvr]

At least the folks in the se can be happy for a while.

[usedtobe]

1 minute ago, Bob Chill said:

With the way every single event has gone this season pretty much everywhere on the EC, being north @ d8-10 is preferable. 

I agree plus note that the Euro track of the vort would give us at least light snow in the 6 to 12 hours after 240.