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Bob Chill

December 2017 Long Range Disco

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Dec is now coming into focus. 12z eps and now the 18z Gefs are both showing Dec kicking off with a -epo. Early Dec still requires legit cold to support snow and if the ens have the right idea, it looks like legit cold is on the way. 

It's an interesting pattern showing up and one that would support snowfall in our area. Unlike 13-14 and 14-15, there isn't a strong +nao or WAR in the panels. That will help with storm track. Not as prone to cut west.

The nao is neutral on the means but I'm not sure a -epo coincides with a -nao very often. I'd have to look through previous years to be sure but it makes sense that having an epo ridge pushing poleward wouldn't support ridging in the nao region due to wavelengths in the high latitudes. A -epo would have a much easier time coinciding with a -ao though because they share some domain space. 

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This looks a lot like the eps. Nice trough axis, plenty of cold available, and confluence near the 50/50 region. I can easily envision several ways to get some snow out of this. Not a big storm pattern but a clipper or progressive wave would work just fine. I'm getting a little excited about our prospects right now honeslty. 

gfs-ens_z500a_nhem_65.png

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gfsgwo_1.png

gfs1.png 

 

 

 

This is what I don't like, the progression favors a break in -EPO/N Pacific ridging action. Maybe a dampening pattern, or faster Pacific Jet in December. It will be hard to suppress the SE ridge enough for snow, I think, in this.

Maybe a +AO propagation by late December. 

prev60.thumb.png.dc8e34efeba467cc75eecda88eeeb43f.png

 

It's also a signal that doesn't assure the return of arctic cold. 

 

 

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1 hour ago, Bob Chill said:

This looks a lot like the eps. Nice trough axis, plenty of cold available, and confluence near the 50/50 region. I can easily envision several ways to get some snow out of this. Not a big storm pattern but a clipper or progressive wave would work just fine. I'm getting a little excited about our prospects right now honeslty. 

gfs-ens_z500a_nhem_65.png

I agree with your thinking. When I did my outlook in the Philly forum I noted that I felt the pattern was going to feature a return to more Alberta Clippers this year which we lacked severely the past few and this look is one way we see that come to light. Now as you said, there are a few ways both of our respective regions could see frozen out of this pattern....I am merely mentioning one as the fast N Jet via Nina coupled with a dip in the East thanks to the upstream -epo would lend credence to the clipper scenario as we head down the road. I like this look for early Dec....hope it holds.

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50 minutes ago, StormchaserChuck said:

gfsgwo_1.png

gfs1.png 

 

 

 

This is what I don't like, the progression favors a break in -EPO/N Pacific ridging action. Maybe a dampening pattern, or faster Pacific Jet in December. It will be hard to suppress the SE ridge enough for snow, I think, in this.

Maybe a +AO propagation by late December. 

prev60.thumb.png.dc8e34efeba467cc75eecda88eeeb43f.png

 

It's also a signal that doesn't assure the return of arctic cold. 

 

 

I claim to know very little ("yes", I probably should just stop here!) about the consequences of a basement dwelling AAM. However, your forecast is from the Gfs ensembles good through day 10. Yet, the forecast Bob posted is alao off the Gfs ensembles out to day 16. It seems that despite the AAM forecast from the GEFS, the GEFS look good come day 16. So either 1) There is a favorable disconnect between the AAM and a decent 500mb forecast over N America (possibly unique to this year due to unknown factors,  or 2) GEFS forecast beyond day 10 is wrong. Problem with option 2 is that the GEFS forecast is currently supported by the Euro and Canadian ensembles. That said, I ain't worrying about it until medium range guidance shows your concerns Chuck.

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17 hours ago, Bob Chill said:

Dec is now coming into focus. 12z eps and now the 18z Gefs are both showing Dec kicking off with a -epo. Early Dec still requires legit cold to support snow and if the ens have the right idea, it looks like legit cold is on the way. 

It's an interesting pattern showing up and one that would support snowfall in our area. Unlike 13-14 and 14-15, there isn't a strong +nao or WAR in the panels. That will help with storm track. Not as prone to cut west.

The nao is neutral on the means but I'm not sure a -epo coincides with a -nao very often. I'd have to look through previous years to be sure but it makes sense that having an epo ridge pushing poleward wouldn't support ridging in the nao region due to wavelengths in the high latitudes. A -epo would have a much easier time coinciding with a -ao though because they share some domain space. 

The pattern advertised by the ensemble guidance for the next 15 days could be a lot worse, thats for sure. It will be interesting to see how cold we can initially get in our area. There isn't a bunch of super cold air available in Canada, the NA blocking weakens, and it looks like we could have some weak ridging in the east for a time.

The PV appears to be on the move- it's projected to be on the other side of the pole by day 15 on the GEFS, although the Euro has some different ideas(through day 10) as it seems to be in the process of stretching and splitting it into 2 lobes, leaving a piece in N Canada. 

If the -EPO is real, and hangs around for a while, there should be a mechanism for cross polar flow and cold air delivery into our source region going forward. Hopefully any relaxation in the (negative)AO is brief, and the NAO stays neutral or heads back into slightly negative territory.

Overall, no complaints. With the advertised look, we have a chance to see actual winter weather in December, unlike recent years.

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2 hours ago, mitchnick said:

6z gfs has our 12/5 snowfall on it. Lol

It is going to be a challenge to get a storm to track underneath during that period if the ensembles are correct. If there is a trough in the SW, and we lose the -NAO, which seems likely, we will be fighting the tendency for a SE ridge and an unfavorable storm track. I think during the first part of December NE will probably see some snow chances. Maybe mid to late month the MA will see a legit chance if the good look in the NPAC persists and we can get a little -NAO action. But who knows, all of this is subject to change lol.

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20 minutes ago, C.A.P.E. said:

It is going to be a challenge to get a storm to track underneath during that period if the ensembles are correct. If there is a trough in the SW, and we lose the -NAO, which seems likely, we will be fighting the tendency for a SE ridge and an unfavorable storm track. I think during the first part of December NE will probably see some snow chances. Maybe mid to late month the MA will see a legit chance if the good look in the NPAC persists and we can get a little -NAO action. But who knows, all of this is subject to change lol.

I don't take it seriously,  I just thought that it was awfully coincidental how the Gfs gets into range of the 12/5 date and boom, there's a storm. 

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2 minutes ago, mitchnick said:

I don't take it seriously,  I just thought that it was awfully coincidental how the Gfs gets into range of the 12/5 date and boom, there's a storm. 

Yeah I kinda forgot about the 12/5 snowstorm thing. Its been awhile. :yikes:

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GEFS has been pretty consistent in keeping at least some +heights near GL into early December. 12z continues that trend. That could make a pretty significant difference, especially if there is a trough in the southwest like the EPS is suggesting(it also has neutral or slightly +NAO). A -NAO would tend to inhibit ridging along the east coast, keep us on the chilly side and the storm track a bit more favorable. Something to keep an eye on, for those hoping for a winter storm chance in early December.

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23 minutes ago, StormchaserChuck said:

Classic Northern Hemipshere -AAM signal now on models long range. This is completely different from the last few weeks and months of trend. Could be a completely different idea, like Mod-Strong La Nina actually being the main player this Winter. 

f348.gif

Mod-Strong Niña?  Sorry Chuck, or whoever you are,  you've gone off the deep end now. This will be lucky to get official Niña status. Troll on man.

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2 minutes ago, mitchnick said:

Mod-Strong Niña?  Sorry Chuck, or whoever you are,  you've gone off the deep end now. This will be lucky to get official Niña status. Troll on man.

Saying moderate-strong is crazy but there is definitely going to be an official weak La Niña this winter. Unanimous model agreement now. Region 3.4 has dropped below -1.0C now: nino34.png

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9 minutes ago, snowman19 said:

Saying moderate-strong is crazy but there is definitely going to be an official weak La Niña this winter. Unanimous model agreement now. Region 3.4 has dropped below -1.0C now: nino34.png

Its been pretty evident for a while now that this winter will feature a weak Nina.

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9 hours ago, C.A.P.E. said:

Its been pretty evident for a while now that this winter will feature a weak Nina.

It has yes. I don’t know what has gotten into Chuck but his posts are completely erratic and off the wall the last month. It’s like Dr. Jekyll and Mr. Hyde. He completely changes his forecasts like the wind, literally hours apart. Either it’s flat out trolling/joking or he has some problems within the old coconut...

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37 minutes ago, mitchnick said:

Mod-Strong Niña?  Sorry Chuck, or whoever you are,  you've gone off the deep end now. This will be lucky to get official Niña status. Troll on man.

Mitch,  I am looking for a more Nino like weather pattern in December versus a La Nina . As for your Dec 5 th snow  :-)   I love that,  but I feel that snow is more likely near Christmas versus early in the month.     

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40 minutes ago, mitchnick said:

Mod-Strong Niña?  Sorry Chuck, or whoever you are,  you've gone off the deep end now. This will be lucky to get official Niña status. Troll on man.

Hadley cell placement is strongly evident on the Ensemble mean, the smoothing makes it easier to see averaged between the individual members. If nothing less, this year has been fascinating on the climate front.

JetStreamBoth.jpg

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36 minutes ago, snowman19 said:

Saying moderate-strong is crazy but there is definitely going to be an official weak La Niña this winter. Unanimous model agreement now. Region 3.4 has dropped below -1.0C now: nino34.png

It's a 3-month average used to calculate the official status.  In 3 months temps will rising per the vast majority of the models. So there's just not enough time to get the 3-month average that low, and then remember you need 5 tri-monthly Niña averages to even qualify. The most current number is -.4, not cold enough. And if you look at today's 850 wind anomaly forecast, trades are on and off for next 10 days. More importantly,  there's a several month lag between SSTA and resulting weather, so again that argues against a hard and fast Niña forecast.

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26 minutes ago, mitchnick said:

It's a 3-month average used to calculate the official status.  In 3 months temps will rising per the vast majority of the models. So there's just not enough time to get the 3-month average that low, and then remember you need 5 tri-monthly Niña averages to even qualify. The most current number is -.4, not cold enough. And if you look at today's 850 wind anomaly forecast, trades are on and off for next 10 days. More importantly,  there's a several month lag between SSTA and resulting weather, so again that argues against a hard and fast Niña forecast.

Exactly mitch. Good post. Enso is a factor this year but how much is up for debate. Especially if ssta's warm as we go through met winter. My guess is there will be times that the NH pattern resembles a Nina and other times other factors will overwhelm. 

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Ens spread must be pretty big right now. Eps has AN heights and BN temps in the east. 

Eps did trend towards not breaking down the -nao. Makes a comeback after a relaxation. Overall ens still look plenty workable going into Dec. I still strongly believe that blocking will last longer than modeled down the line. 

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19 minutes ago, Bob Chill said:

Ens spread must be pretty big right now. Eps has AN heights and BN temps in the east. 

Eps did trend towards not breaking down the -nao. Makes a comeback after a relaxation. Overall ens still look plenty workable going into Dec. I still strongly believe that blocking will last longer than modeled down the line. 

GEPS at day 16 are similar. 

https://www.tropicaltidbits.com/analysis/models/?model=gem-ens&region=namer&pkg=z500a&runtime=2017111912&fh=378&xpos=0&ypos=0

https://www.tropicaltidbits.com/analysis/models/?model=gem-ens&region=namer&pkg=T2ma&runtime=2017111912&fh=378&xpos=0&ypos=0

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21 minutes ago, mitchnick said:

Seems that what the ens are telling us is that the consistent barrage of cold fronts will continue for a while. Spread late in the runs is broad brushing the same general pattern that's in place now with BN days out numbering AN days. If my take is correct then snow chances will have to come within a couple days after a cold front. Some sort of trailing wave or stalled boundary. Not seeing many signs of an organized synoptic event approaching from the south over the next couple weeks. 

 

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33 minutes ago, mitchnick said:

Towards the end of the GEPS run almost coast to coast below normal . Do not see that very often these days. 

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Hmm , wonder what Ventrice has up his sleeve in terms of changes, colder ??  

I says odds of colder at this time. 

 

 

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