December 2017 Discussions & Observations Thread

[Rtd208]

December looks to start off a bit on the milder side but things look to turn colder and hopefully stormier by the 2nd week of the month. Discuss.

[snowman19]

59 minutes ago, bluewave said:

Perhaps the most interesting piece of information going into December is that the +NPM is in opposition to the La Nina. I know that people say that you can't get a sustained +PNA with a La Nina which is often the case. But the +NPM favors a +PNA pattern in December. So it's quite possible that we see a more neutral or even positive PNA in December. There was  a bit of conversation about the Euro monthly which came out around November 7th showing an odd looking +PNA for December. In fact, the highest one month skill for the Euro monthly is in determining the PNA phase. All the models are taking the PNA positive after December 5th as of 0z. The La Nina Decembers in the past which had a +NPM as seen in the chart below featured below normal temperatures here. There is also an enhanced chance for above normal snowfall in NYC along with a more -AO pattern.

 

Major eruption ongoing at Mount Agung. This may play a role in this winter’s AO. Tropical volcanic eruptions are huge players in the stratosphere (sulfate aerosols). 

 

[dmillz25]

43 minutes ago, snowman19 said:

Major eruption ongoing at Mount Agung. This may play a role in this winter’s AO. Tropical volcanic eruptions are huge players in the stratosphere (sulfate aerosols). 

 

It’s not major it’s a minor one, try again.

[PB GFI]

40 minutes ago, dmillz25 said:

It’s not major it’s a minor one, try again.

A major eruption would prob promote high latitude blocking.

Regardless Decembers blocking is already getting established.

I don't think many are questioning that part of the forecast 

[Eduardo]

3 hours ago, bluewave said:

Perhaps the most interesting piece of information going into December is that the +NPM is in opposition to the La Nina. I know that people say that you can't get a sustained +PNA with a La Nina which is often the case. But the +NPM favors a +PNA pattern in December. So it's quite possible that we see a more neutral or even positive PNA in December. There was  a bit of conversation about the Euro monthly which came out around November 7th showing an odd looking +PNA for December. In fact, the highest one month skill for the Euro monthly is in determining the PNA phase. All the models are taking the PNA positive after December 5th as of 0z. The La Nina Decembers in the past which had a +NPM as seen in the chart below featured below normal temperatures here. There is also an enhanced chance for above normal snowfall in NYC along with a more -AO pattern.

 

Very astute obs, as usual Chris.  Can't help but notice the divergence preceding the 95-96 winter in the second graph you posted.  Any thoughts as to whether that may have played a role in the magic we experienced that year?

[snowman19]

10 hours ago, dmillz25 said:

It’s not major it’s a minor one, try again.

Really? Minor huh? Smh. The eruption is spewing ash to over 4,600 meters and climbing and there’s magma showing now at the top of the crater

 

[dmillz25]

16 minutes ago, snowman19 said:

Really? Minor huh? Smh. The eruption is spewing ash to over 4,600 meters and climbing and there’s magma showing now at the top of the crater 

 

Meh talk to me when it hits the strat

[MJO812]

Earthlight on board for a wild mid December

 

https://mobile.twitter.com/jhomenuk/status/934519992858611715

[MJO812]

Gfs with weenie blocking

https://www.tropicaltidbits.com/analysis/models/gfs/2017112518/gfs_z500a_namer_45.png

[CIK62]

First 10 days of Dec. are a furnace nationwide.

Then we could be 10degs. BN around here for the remainder of the year.

[SnoSki14]

17 hours ago, Snow88 said:

Gfs with weenie blocking

https://www.tropicaltidbits.com/analysis/models/gfs/2017112518/gfs_z500a_namer_45.png

Always LR. Everytime we get close the blocking dissipates. December should be AN, that first half looks extremely torchy (+8).

[MJO812]

1 hour ago, SnoSki14 said:

Always LR. Everytime we get close the blocking dissipates. December should be AN, that first half looks extremely torchy (+8).

December will most likely be below normal with the pattern change around the 6th.

 

Gefs and EPS agree on the big change.

[SnoSki14]

1 hour ago, Snow88 said:

December will most likely be below normal with the pattern change around the 6th.

 

Gefs and EPS agree on the big change.

That seems very early, I'd be shocked at a big time change before the 10th. 

But if we're at +7 or better by that time, then it's going to very difficult to bring that down to BN especially in our much warmer background climate. 

And as for snow, my bet is still on January. I'm with Snowman on this one.

[Stormlover74]

27 minutes ago, SnoSki14 said:

That seems very early, I'd be shocked at a big time change before the 10th. 

But if we're at +7 or better by that time, then it's going to very difficult to bring that down to BN especially in our much warmer background climate. 

And as for snow, my bet is still on January. I'm with Snowman on this one.

Doesn't really matter though if we can manage some snow during our below average stretches. Or it can turn cold for 3 weeks and we have nothing to show for it.

[Neblizzard]

55 minutes ago, SnoSki14 said:

That seems very early, I'd be shocked at a big time change before the 10th. 

But if we're at +7 or better by that time, then it's going to very difficult to bring that down to BN especially in our much warmer background climate. 

And as for snow, my bet is still on January. I'm with Snowman on this one.

We don’t want a large scale pattern change at this time , so if the models are correct after December 8th that will be perfect timing .

[MJO812]

1 hour ago, SnoSki14 said:

That seems very early, I'd be shocked at a big time change before the 10th. 

But if we're at +7 or better by that time, then it's going to very difficult to bring that down to BN especially in our much warmer background climate. 

And as for snow, my bet is still on January. I'm with Snowman on this one.

Every model has the big change.  We will see snow with the pattern depicted for December.

[MJO812]

Insane blocking on the eps starting the 8th 

[dmillz25]

1 hour ago, SnoSki14 said:

That seems very early, I'd be shocked at a big time change before the 10th. 

But if we're at +7 or better by that time, then it's going to very difficult to bring that down to BN especially in our much warmer background climate. 

And as for snow, my bet is still on January. I'm with Snowman on this one.

Your trolling is ridiculous. ALL models have the pattern change around the 8th and it’s moving up in time. The SPV is being perturbed as we speak and the MJO is headed into colder phases around that time as well. Obviously snow is harder to predict than cold so thats a wait and see but December will likely end BN in temps. And one week of +4-6 would easily be erased by 2-3 weeks of -4 to -6. And wasn’t you just optimistic just a week ago?

[CIK62]

Straight from the CFS and directly into the trash can (lol) come these snow threat dates:

Dec. 09  and then the whole period from Dec. 19-27, which looks at least to be wet, while the 2M temps. hover near the freezing point.

[IntenseBlizzard2014]

1 minute ago, CIK62 said:

Straight from the CFS and directly into the trash can (lol) come these snow threat dates:

Dec. 09  and then the whole period from Dec. 19-27, which looks at least to be wet, while the 2M temps. hover near the freezing point.

Well at least it's understanding that change is "afoot". Huh? Huuuuh? I'll stop now. 

[MJO812]

1 hour ago, dmillz25 said:

Your trolling is ridiculous. ALL models have the pattern change around the 8th and it’s moving up in time. The SPV is being perturbed as we speak and the MJO is headed into colder phases around that time as well. Obviously snow is harder to predict than cold so thats a wait and see but December will likely end BN in temps. And one week of +4-6 would easily be erased by 2-3 weeks of -4 to -6. And wasn’t you just optimistic just a week ago?

Excellent post

The pattern is changing a December will be a fun month 

[SnowGoose69]

The biggest problem I see right now on the ensembles 11-16 is the continued hints on some members that the Pac jet is gonna try and ruin things.  You can see it to an extent easily on the 18Z Op GFs.  I do recall we had a winter recently (as you get older you forget which ones) where we had so-so blocking but the Pac Jet continually just messed things up every time it would appear we would get cold and snowy.

[leo2000]

9 minutes ago, SnowGoose69 said:

The biggest problem I see right now on the ensembles 11-16 is the continued hints on some members that the Pac jet is gonna try and ruin things.  You can see it to an extent easily on the 18Z Op GFs.  I do recall we had a winter recently (as you get older you forget which ones) where we had so-so blocking but the Pac Jet continually just messed things up every time it would appear we would get cold and snowy.

Wouldn't the negative EPO slow down the Pac Jet though?. 

[PB GFI]

20 minutes ago, SnowGoose69 said:

The biggest problem I see right now on the ensembles 11-16 is the continued hints on some members that the Pac jet is gonna try and ruin things.  You can see it to an extent easily on the 18Z Op GFs.  I do recall we had a winter recently (as you get older you forget which ones) where we had so-so blocking but the Pac Jet continually just messed things up every time it would appear we would get cold and snowy.

The ensembles show the evolution nicely where you hook the ridge from the west  coast over the top then all the way to east of Greenland.

Develops nicely after day  8

You're fine 

[Isotherm]

Since 1958, there have been several sudden stratospheric warming events in late November-December. They were as follows:

 

Vortex splits:

 

08 Dec 1987 west QBO   

 

Vortex displacements:

 

30 Nov 1958 east QBO           

08 Dec 1965 east QBO            

27 Nov 1968 east QBO           

04 Dec 1981 east QBO                        

15 Dec 1998 east QBO                     

16 Dec 2000 east QBO         

 

All of these winter seasons, save for one (1998-99), featured a negative AO average for Dec-Jan-Feb. Some of the winters, particularly the El Nino's, featured strong polar blocking through late winter.

 

However, if we extract the El Nino events -- 1987-88, 1965-66, 1968-69, 1958-59, as well as the one strong La Nina event -- 1998-99, the remaining analogs are:

 

1981-82 (neutral ENSO)

2000-01 (weak La Nina)

 

Their SSW events occurred on December 4th and December 16th respectively. Hypothetically speaking, if we were to see a SSW, it would likely be wave-1 induced displacement variety (as most have been early season), and occur between December 4th and 16th.

 

The ensuing AO propensity for those two analogs was as follows for DJF:

 

1981: -1.216

1982 -0.883  0.974

 

2000: -2.354

2001 -0.959 -0.622

 

The common denominator was strong AO blocking in December, less but still negative in January, and neutralizing to positive in February. The DJF means were negative AO.

 

The ensuing NAO propensity for the two analogs for DJF:

 

1981: -0.02

1982  -0.89   1.15

 

Slightly positive NAO mean

 

2000: -0.58

2001   0.25   0.45

 

Slightly positive NAO mean

 

 

The progression of those two winters - while a very small sample size - could provide a clue for the upcoming season, in the case of a SSW, which is not guaranteed. Remember that every event is unique and this is a highly non-linear process.

 

My thoughts continue to remain the same, namely, that we are going to see a -AO/NAO first third of winter with a colder and snowier than normal December. The Dec 15th-30th period is a time frame to consider for a possible major event.

 

The duration of the tropospheric blocking, regardless of official achievements in the stratosphere, will be highly contingent upon countervailing forces in the troposphere which destructively interfere w/ -NAM maintenance.

[North and West]

Meh talk to me when it hits the strat

FYI, just checked on it: “... According to CNN, the Indonesian National Disaster Management Agency estimates the cloud was at least 4,000 meters (13,120 feet) tall, though the Australian Bureau of Meteorology later estimated a height of 7,600 meters (24,930 feet).”


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[snowman19]

29 minutes ago, North and West said:

FYI, just checked on it: “... According to CNN, the Indonesian National Disaster Management Agency estimates the cloud was at least 4,000 meters (13,120 feet) tall, though the Australian Bureau of Meteorology later estimated a height of 7,600 meters (24,930 feet).”


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It’s also confirmed that the eruption is releasing sulfate aerosols into the ash plume. If this continues, it’s going to have marked climate impacts. 

 

[SnowLover22]

It’s also confirmed that the eruption is releasing sulfate aerosols into the ash plume. If this continues, it’s going to have marked climate impacts. 

 

True but the good news is the eruption is happening so close to winter that it won’t have a negative effect on this winter.


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[IntenseBlizzard2014]

59 minutes ago, Philadelphia Snow said:

True but the good news is the eruption is happening so close to winter that it won’t have a negative effect on this winter.


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It wouldn't have been negative. It would have made things more interesting. Gotta wait for next winter. 

[Ralph Wiggum]

Overnight ensemble means definitely took a step back in the LR. While not a bad look, clearly not the fantasy runs from last couple days. NAO is weaker and block is shifted farther East, ridging out West less extreme, trof out West slower to move due to decrease in ridging over British Columbia. GEPS which had been most aggressive with -NAO loses it completely in the LR and even attempts a shift to a +NAO. Hope these LR teases that are taken away arent a repeat of last year. Again, not a horrible look on the EPS/GEFS at all.....just not the same perfection from past few runs. Didnt expect that look to remain constant for next 10-16 days anyway.