December 2016 Discussion & Observations

[bluewave]

Discussion and observations for December.

 

 

 

 

 

 

 

 

 

 

 

 

[dmillz25]

We might as well start using this since December is 3 days away

[Zelocita Weather]

Early still on the models, but seems to me a step wise/gradual move towards a true-winter/below average temp regime over the next 10-20 days. 

First cold shot comes in Thursday (Dec 1), and brings us to near normal for the time of year from well above after a soaking rain

We moderate for a time between slightly below normal to above normal for another 5-10 days, then there is a chance for true arctic air to overwhelm the majority of the country. 

I think chances are good for a sustained below average temp pattern to be in place by Dec 10-15 and on...

[MJO812]

Eps snowmap has some snow for our area but nothing significant. Interior NY and New England get a good deal of snow with the 6th storm. We should still watch it to see where the secondary forms.

[bluewave]

Battle of the models for next Monday. The Euro is going with a phased heavy rain and wind event while the GFS has no storm.

 

 

 

 

[MJO812]

36 minutes ago, bluewave said:

Battle of the models for next Monday. The Euro is going with a phased heavy rain and wind event while the GFS has no storm.

 

 

 

 

Interesting storm to track. I wonder if it can transfer early and benefit everyone. We shall see.

Euro weeklies look nice moving forward

[bluewave]

11 hours ago, Snow88 said:

Interesting storm to track. I wonder if it can transfer early and benefit everyone. We shall see.

Euro weeklies look nice moving forward

It may be another case of the OP Euro past day 5 being too amplified since the other models are weaker.

In any event, temps look generally above normal for the first week or so of December here while the west gets cold.

Big question second week of December is how much cold can come east?

 

 

 

[CIK62]

CFS has turned hotter than a fireman's helmet for the next 30 days, in the last 24hrs.  What did it see?

[donsutherland1]

2 hours ago, CIK62 said:

CFS has turned hotter than a fireman's helmet for the next 30 days, in the last 24hrs.  What did it see?

Some big changes in recent days:

1) The forecast deep (AO) block now appears unlikely to develop. In fact, some of the GEFS forecast a positive-to-strongly positive AO down the road. That's an ominous sign, as there that portends a lower-than-climatological probability of a blocky January-February, on average. That should be taken with a lot of caution, as there remains no reliable method for forecasting the seasonal AO. Were the AO to spike to +3.000 or above, that would suggest a much reduced probability of a blocky January-February relative to climatology). The previously-touted SAI fared badly during the last two winters.

2) The EPO- ridge is now forecast to be less impressive than previously modeled.

The PNA- remains on the table. That tends to favor a SE ridge downstream.

Overall, I still think there will be enough opportunity for cold intrusions to allow for above average snowfall (probably 30" in the NYC area +/- a few inches), as the winter appears to be in line for a weak La Niña rather than a strong one. Whether the bulk of the snow falls in a compressed period of time remains to be seen.

[uncle W]

1 minute ago, donsutherland1 said:

Some big changes in recent days:

1) The forecast deep (AO) block now appears unlikely to develop. In fact, some of the GEFS forecast a positive-to-strongly positive AO down the road. That's an ominous sign, as there that portends a lower-than-climatological probability of a blocky January-February, on average. That should be taken with a lot of caution, as there remains no reliable method for forecasting the seasonal AO. Were the AO to spike to +3.000 or above, that would suggest a much reduced probability of a blocky January-February relative to climatology). The previously-touted SAI fared badly during the last two winters.

2) The EPO- ridge is now forecast to be less impressive than previously modeled.

The PNA- remains on the table. That tends to favor a SE ridge downstream.

Overall, I still think there will be enough opportunity for cold intrusions to allow for above average snowfall (probably 30" in the NYC area +/- a few inches), as the winter appears to be in line for a weak La Niña rather than a strong one. Whether the bulk of the snow falls in a compressed period of time remains to be seen.

the ao forecast took a turn for the worst...two members above +4...It could be a up and down AO this winter with periods of strong blocking and periods of no blocking...A +4 at the beginning of December would suggest at least to me that another mild December is on tap...one thing about these ao forecasts is it changes every day...

[PB GFI]

Judah Cohen 

Twitter , 

 

Climate models SUHKKKKKKK.

 

 

[HailMan06]

^That's a lot of orange and red.

[donsutherland1]

1 hour ago, uncle W said:

the ao forecast took a turn for the worst...two members above +4...It could be a up and down AO this winter with periods of strong blocking and periods of no blocking...A +4 at the beginning of December would suggest at least to me that another mild December is on tap...one thing about these ao forecasts is it changes every day...

The ECMWF Ensembles are still colder, but 10 days out is a long time. Perhaps the CFSv2 is overdoing things. I think we'll know more once we see how the AO and EPO are actually evolving.

[Brian5671]

3 minutes ago, donsutherland1 said:

The ECMWF Ensembles are still colder, but 10 days out is a long time. Perhaps the CFSv2 is overdoing things. I think we'll know more once we see how the AO and EPO are actually evolving.

The problem too-is we've seen several false starts-Mid Nov was cold, then it was late November and now we're getting to 12/5 or later....models go big on the cold and blocking and then back off as we get closer.  

[snowman19]

15 hours ago, Snow88 said:

Interesting storm to track. I wonder if it can transfer early and benefit everyone. We shall see.

Euro weeklies look nice moving forward

You need a stout west based -NAO Greenland block to hope to see any secondary low redevelopment off the coast with a cutter

[WEATHERBUFF]

Every month has been around 2 degrees above the so-called average, why would we expect anything different

[Stormlover74]

18 minutes ago, WEATHERBUFF said:

Every month has been around 2 degrees above the so-called average, why would we expect anything different

Yeah its a safe bet at this point. With the warm start to the month it will be very difficult to see Dec go below normal by 2 or 3 degrees

[Brian5671]

Just now, Stormlover74 said:

Yeah its a safe bet at this point. With the warm start to the month it will be very difficult to see Dec go below normal by 2 or 3 degrees

1st week of December is going to start off with +3 to maybe +5, agree, we'll be lucky to finish average with that head start and who knows if we get any sustained cold in December, models all over the place....

[Stormlover74]

2 minutes ago, Brian5671 said:

1st week of December is going to start off with +3 to maybe +5, agree, we'll be lucky to finish average with that head start and who knows if we get any sustained cold in December, models all over the place....

+3 seems more likely than -3 but if we do see an arctic outbreak mid to late month it could change.

[bluewave]

12z Euro caves to GFS on weaker storm early next week. This sets the stage for a second more powerful storm later next week to

really pump up the SE Ridge ahead of it.

 

New run

 

old run

 

 

 

 

[Allsnow]

Bad start for the new euro 

[Brian5671]

1 minute ago, Allsnow said:

Bad start for the new euro 

yeah how often do you see the Euro cave to the GFS.   

[SnowGoose69]

22 minutes ago, Brian5671 said:

yeah how often do you see the Euro cave to the GFS.   

This new one has been doing it often

[PB GFI]

4 hours ago, Brian5671 said:

1st week of December is going to start off with +3 to maybe +5, agree, we'll be lucky to finish average with that head start and who knows if we get any sustained cold in December, models all over the place....

 

 

hmmmmmmmm.

[WEATHERBUFF]

With the kind of set up we are talking about it is bad news for the coast. 

[bluewave]

26 minutes ago, PB GFI said:

 

 

hmmmmmmmm.

The very strong cutter that the GEFS and EPS have day 8-10 finally pulls the trough into the east D 11-15.

It will be interesting to see if models hold serve or back off the closer that we get.

[Brian5671]

16 minutes ago, bluewave said:

The very strong cutter that the GEFS and EPS have day 8-10 finally pulls the trough into the east D 11-15.

It will be interesting to see if models hold serve or back off the closer that we get.

if they back off, another positive departure is almost a sure bet.  

[dmillz25]

That was a cold EPS run

[qg_omega]

1 hour ago, PB GFI said:

 

 

hmmmmmmmm.

I still like +2 to +4 for December, which was also my forecast for November 

[PB GFI]

31 minutes ago, bluewave said:

That's true. The +NAO cold pool is a little weaker than it has been from December 2011 to 2015. Not sure if this is indicative yet of a more neutral or even

negative NAO potential going forward. We would need some - to neutral NAO help if there is any chance of that SE Ridge flattening out for even a brief interval.

 

 

 

 

The key is the Pacific.  The WPO/EPO turn Canada cold. 

I am not concerned about the Atlantic it's much better to buckle the Pacific Jet. 

 

You can see the cross polar flow start by day 5 / 6 .

That air comes into the CONUS, they key is how long will it take to break out of the west. 

Does a strong day 8 cutter pull it in ? 

I think so , then it's on .