Dec 11-13 MW/Lakes/OV Snow Event? Part III

[buckeye]

Clipperish

uk is driving it southeast while developing another low in the carolinas....i would imagine it would go boom somewhere over WV. too bad it's a severe outlier

[Hoosier]

yup stubborn little guy. possibly a tad north of 12z but basically same idea. Absolutely amazing considering it's 60 hrs out

Yeah it seems to be somewhat farther north so this may be a case where the trend is more important than the run verbatim.

[Stebo]

Yeah it seems to be somewhat farther north so this may be a case where the trend is more important than the run verbatim.

Yeah it seemed to trend closer to the GGEM's idea.

[buckeye]

It did track it a decent amount N, and that is meaningful. Numerical models use the previous forecast as the first guess analysis field. 0Z will prolly be even farther N.

You can see it better when you open the same forecast times up and switch back and forth.

here ya go

[Chicago WX]

Good discussion by many on here today...kudos to all of you.

That being said if I see any more one-liners, without backing it up, of "storms always go NW"...I'm going to puke. Can we get "NW trend" added to the word filter?

[csnavywx]

This can be discussed a lot, but satellites are quite advanced and can sufficiently sample upper tropospheric waves. I don't disagree with your point as I too have seen systems over the ocean change, but a pretty consistent height field trend is coming in line with both the control runs and the SREF runs. If you were a forecaster, you simply can not keep "waiting" to alert the public to potential storms. That is what makes forecasting hard, and I always advocate that all mets should consider that when they look at weather.

Satellites are nice, but imo, still not as good as balloons. One doesn't have to look any further than verification scores of the relatively RAOB rich Nrn. Hemisphere vs the RAOB sparse Srn. Hemisphere to see some of the positive impacts of balloons. Throw in the fact that there's far less land-sea interaction and differential heating in the Srn. Hemisphere to "mess up" the models, and the difference is even more noticeable. I can tell you personally from forecasting in the Middle East that not having good surface and upper air observations around me were hell on the models (and myself, haha) in the winter time.

Having said that, I'm completely with you on throwing out the warning early. In this situation, waiting until it was over land would mean it's almost too late.

[Thundersnow12]

Good discussion by many on here today...kudos to all of you.

That being said if I see any more one-liners, without backing it up, of "storms always go NW"...I'm going to puke. Can we get "NW trend" added to the word filter?

there was one winter when I swear all i read was "NW trend ftw" lol

and yes some very good discussion going on today, this is why I love these forums and what I have learned the most from since joining years ago.

[Omahawx]

http://moe.met.fsu.e...ukm/2010120918/

none of those images are working for me...is there another link ?

[Stebo]

Satellites are nice, but imo, still not as good as balloons. One doesn't have to look any further than verification scores of the relatively RAOB rich Nrn. Hemisphere vs the RAOB sparse Srn. Hemisphere to see some of the positive impacts of balloons. Throw in the fact that there's far less land-sea interaction and differential heating in the Srn. Hemisphere to "mess up" the models, and the difference is even more noticeable. I can tell you personally from forecasting in the Middle East that not having good surface and upper air observations around me were hell on the models (and myself, haha) in the winter time.

Having said that, I'm completely with you on throwing out the warning early. In this situation, waiting until it was over land would mean it's almost too late.

No I agree we should be throwing out watches soon too, but for what areas, if you go by the models you essentially probably put a watch out from 80 north. The problem is there is a high potential some of those areas don't end up going to a warning.

[tornadotony]

there was one winter when I swear all i read was "NW trend ftw" lol

and yes some very good discussion going on today, this is why I love these forums and what I have learned the most from since joining years ago.

That was the winter of 2007-2008. The reasoning is simple. With La Ninas, especially mdt-strong (that winter was right on the cusp between the two), you favor a stronger subtropical ridge in the western Atlantic, off the southeast coast. The models often handle that ridge poorly, allowing for storms to travel farther south and east on projections than they would if the strength of the ridge were accurately depicted. The models often end up having to play catchup within 48h or so of the event, with storm tracks being depicted as being farther NW. Thus the "NW trend."

[Srain]

Satellites are nice, but imo, still not as good as balloons. One doesn't have to look any further than verification scores of the relatively RAOB rich Nrn. Hemisphere vs the RAOB sparse Srn. Hemisphere to see some of the positive impacts of balloons. Throw in the fact that there's far less land-sea interaction and differential heating in the Srn. Hemisphere to "mess up" the models, and the difference is even more noticeable. I can tell you personally from forecasting in the Middle East that not having good surface and upper air observations around me were hell on the models (and myself, haha) in the winter time.

Having said that, I'm completely with you on throwing out the warning early. In this situation, waiting until it was over land would mean it's almost too late.

Awesome post. I'd like to also comment the level of discussion as well. Kudos for a civil, readable dialog.

[csnavywx]

Going to have to really watch the low-level temps across the Canadian high plains over the next 24 hours and see if that arctic air is seeping south further than progged as that will have a pretty big downstream impact on the low track.

[Harry]

That was the winter of 2007-2008. The reasoning is simple. With La Ninas, especially mdt-strong (that winter was right on the cusp between the two), you favor a stronger subtropical ridge in the western Atlantic, off the southeast coast. The models often handle that ridge poorly, allowing for storms to travel farther south and east on projections than they would if the strength of the ridge were accurately depicted. The models often end up having to play catchup within 48h or so of the event, with storm tracks being depicted as being farther NW. Thus the "NW trend."

Since the model upgrades though it has not been seen much if at all. Thus the issue with it.

[WxMidwest]

Going to have to really watch the low-level temps across the Canadian high plains over the next 24 hours and see if that arctic air is seeping south further than progged as that will have a pretty big downstream impact on the low track.

It should be fun watching the 3 hour pressure falls Late Tomorrow/Saturday.. See what Actually happens with this system..

[baroclinic_instability]

No I agree we should be throwing out watches soon too, but for what areas, if you go by the models you essentially probably put a watch out from 80 north. The problem is there is a high potential some of those areas don't end up going to a warning.

The forecasting challenge

I totally know where you are coming from Stebo, but after forecasting for what seems like forever (3 years haha), you have to make those decisions. When you have clients who demand to know and are paying good money, you have to make decisions. It forces you to become a better forecaster. Big difference between forecasting and simply observing weather and waiting to see what happens.

[Stebo]

Going to have to really watch the low-level temps across the Canadian high plains over the next 24 hours and see if that arctic air is seeping south further than progged as that will have a pretty big downstream impact on the low track.

Yeah the further south that cold air/baroclinic zone sets up the more this thing will deviate from the current projection.

[Hoosier]

No I agree we should be throwing out watches soon too, but for what areas, if you go by the models you essentially probably put a watch out from 80 north. The problem is there is a high potential some of those areas don't end up going to a warning.

I don't think there's much doubt there's going to be near blizzard conditions in a lot of areas and possibly blizzard criteria in some places. The wind fields that are being progged certainly support it, and if we get a surface low that deepens more rapidly than progged, then it would only increase the threat. This looks like a serious event and watches should be out. They are only watches and can be cancelled/downgraded.

[Chicago WX]

That was the winter of 2007-2008. The reasoning is simple. With La Ninas, especially mdt-strong (that winter was right on the cusp between the two), you favor a stronger subtropical ridge in the western Atlantic, off the southeast coast. The models often handle that ridge poorly, allowing for storms to travel farther south and east on projections than they would if the strength of the ridge were accurately depicted. The models often end up having to play catchup within 48h or so of the event, with storm tracks being depicted as being farther NW. Thus the "NW trend."

Definitely noted Tony and good discussion/explanation about it. Maybe I'm making a mountain out of a mole hill, but it's the one line posts by some...without adding anything meaningful otherwise...of "storms always go NW", "congrats U.P.". That stuff adds little to the discussion and is just weenie fodder IMO. That being said, I will drop it as of now. Let us continue with the good discussion about this storm.

[Stebo]

I don't think there's much doubt there's going to be near blizzard conditions in a lot of areas and possibly blizzard criteria in some places. The wind fields that are being progged certainly support it, and if we get a surface low that deepens more rapidly than progged, then it would only increase the threat. This looks like a serious event and watches should be out. They are only watches and can be cancelled/downgraded.

Yes thats true, I would be shocked if there isn't watches out by tomorrow mornings packages even with the question marks at hand.

[csnavywx]

No I agree we should be throwing out watches soon too, but for what areas, if you go by the models you essentially probably put a watch out from 80 north. The problem is there is a high potential some of those areas don't end up going to a warning.

Yeah, only thing you can do at this point is move on known biases and adjust accordingly.

What I can say is that the air mass coming down is very cold and shallow, check out the sleet observation with an 8F surface temp:

CYYC 092300Z 06004KT 5SM -PL FEW010 SCT120

BKN210 M13/M16 A2971 RMK SC2AC1CI0 SLP134

Forecasting around cA boundaries is always tricky business, but the one consistent thing you can typically count on is models not quite being aggressive enough in movement with it. We're not talking about a rapidly moving boundary initially here, but they do have a tendency to "seep" or "creep" south along the ground pretty effectively.

[ValpoVike]

The one thing that has me intrigued with this is the Euro's insistence on a powerful, long-duration LES event here Sunday afternoon-Monday afternoon. It has a 24h+ period of persistent northerly flow down the fetch of LM...

I noticed that as well. We can certainly hope

[baroclinic_instability]

Yeah, only thing you can do at this point is move on known biases and adjust accordingly.

What I can say is that the air mass coming down is very cold and shallow, check out the sleet observation with an 8F surface temp:

CYYC 092300Z 06004KT 5SM -PL FEW010 SCT120

BKN210 M13/M16 A2971 RMK SC2AC1CI0 SLP134

Forecasting around cA boundaries is always tricky business, but the one consistent thing you can typically count on is models not quite being aggressive enough in movement with it. We're not talking about a rapidly moving boundary initially here, but they do have a tendency to "seep" or "creep" south along the ground pretty effectively.

Yes, definitely a good point regarding shallow cold air. A question worth asking, in this case, would it result in an even more enhanced baroclinic zone in the low levels and a stronger cyclone, or would it result in a surface low shunted southward (if the cold air retreated farther S)? It could be argued both ways it seems

[ArmyGreens]

I don't think there's much doubt there's going to be near blizzard conditions in a lot of areas and possibly blizzard criteria in some places. The wind fields that are being progged certainly support it, and if we get a surface low that deepens more rapidly than progged, then it would only increase the threat. This looks like a serious event and watches should be out. They are only watches and can be cancelled/downgraded.

Very important for the public to know! From what I read a few times is that it is extremely difficult for pro mets to be as accurate as possible while getting notice out in a reasonable manner. For those that do this . This storm is especially frustrating with the current spread and small window. My question is with the winds that are progged as well as cold temperatures, how many will be covered with warnings? Even if you only get a couple of inches out of this, you could still get some nasty ground blizzard conditions.

[baroclinic_instability]

Very important for the public to know! From what I read a few times is that it is extremely difficult for pro mets to be as accurate as possible while getting notice out in a reasonable manner. For those that do this . This storm is especially frustrating with the current spread and small window. My question is with the winds that are progged as well as cold temperatures, how many will be covered with warnings? Even if you only get a couple of inches out of this, you could still get some nasty ground blizzard conditions.

Absolutely! Alberta Clippers up in MN and ND often times can produce ground blizzards with only 1-3" of light snow. Also remember extreme cold air advection results in strong subsidence and that enhances vertical mixing of air and subsequent wind gusts. Also, air will have a downward component and it is more apt to "kick" up snow from the ground. UND has a "blowing snow" algorithm used for road weather and it is part of the "MDSS" system. This storm will have a ton of CAA as well as vertical shear in the low levels due to the rather tight low level baroclinic zone NAM suggest potential for 45+ to mix down. For now I think NWS fine with Winter Storm Warning, but as it gets closer upgrade to blizzard possible for localized areas.

[csnavywx]

Yes, definitely a good point regarding shallow cold air. A question worth asking, in this case, would it result in an even more enhanced baroclinic zone in the low levels and a stronger cyclone, or would it result in a surface low shunted southward (if the cold air retreated farther S)? It could be argued both ways it seems

And I've seen it work both ways, so you're right about it being a double edged sword, imo. It seems to me that if the cA air mass is moving more rapidly, it has the tendency to shunt, whereas a slower one seems to help with cyclogenesis up to the point where it's being advected more quickly. That little problem seems to be playing out on the NAM and GGEM to a degree. They both agree on spinning it up in similar fashion, but when the cA airmass really gets moving, the deepening rate slows and it gets shunted to the south a bit. Much more so on the GEM past 42 hrs though, as it seems to be more aggressive with the CAA than the NAM despite similar SLP/gradient strength.

[baroclinic_instability]

And I've seen it work both ways, so you're right about it being a double edged sword, imo. It seems to me that if the cA air mass is moving more rapidly, it has the tendency to shunt, whereas a slower one seems to help with cyclogenesis up to the point where it's being advected more quickly. That little problem seems to be playing out on the NAM and GGEM to a degree. They both agree on spinning it up in similar fashion, but when the cA airmass really gets moving, the deepening rate slows and it gets shunted to the south a bit. Much more so on the GEM past 42 hrs though, as it seems to be more aggressive with the CAA than the NAM despite similar SLP/gradient strength.

Should be interesting to see. Good points though. 09 to 15Z SREF trended nearly identical with track but with a more intense cyclone. In playing "lets try to beat the model", given latest trends, I think CMC will trend ever so slightly more north and a tad more intense with 0Z. Interested to see what 21Z SREF does...if they keep the intensification trend going.

[Stevo6899]

If mets are going to take the time to explain things, take the time to read it through.

I did read it through and I asked a question to verify that I understood it. Is that alright? Not everyone is as intelligent with weather as you may be and I would think you would respect that. Just finished a finance degree and I am thinking about attending Penn State to study meteorology. As you may see it's not going to be easy for me.

[ArmyGreens]

If mets are going to take the time to explain things, take the time to read it through.

I did read it through and I asked a question to verify that I understood it. Is that alright? Not everyone is as intelligent with weather as you may be and I would think you would respect that. Just finished a finance degree and I am thinking about attending Penn State to study meteorology. As you may see it's not going to be easy for me.

Get that degree now! Don't wait until you are like me, sitting with a half finished criminal justice degree that won't be used until I am 46. At which point I will be bald, with both knees shot, unable to enter the police force! I will have a pointless degree that will only solidify the fact that I have to work two shifts handing out stickers to bratty kids coming into the local walmart! For the love of God get your Met degree!!!

That is all.

[dilly84]

Get that degree now! Don't wait until you are like me, sitting with a half finished criminal justice degree that won't be used until I am 46. At which point I will be bald, with both knees shot, unable to enter the police force! I will have a pointless degree that will only solidify the fact that I have to work two shifts handing out stickers to bratty kids coming into the local walmart! For the love of God get your Met degree!!!

That is all.

haha, you could always be a security guard lol

[prinsburg_wx]

21Z sref mean 36 & 48