December 2017 Discussions & Observations Thread

[qg_omega]

Did anyone forecast rain today?

[Ericjcrash]

5 minutes ago, qg_omega said:

Did anyone forecast rain today?

Sprinkles were possible.

[qg_omega]

2 minutes ago, Ericjcrash said:

Sprinkles were possible.

Had more than that, legit light to moderate rain.  Messed up my plans

[Manny]

I haven’t been this excited about December since 2010. That month was just great in terms of cold and snow. It seems we might have many similarities if all of the pieces come together at the right time.

[IntenseBlizzard2014]

Latest QBO Phase Value:

November 2017: -17.20

Previous months:

October 2017: -16.79

September 2017: -15.28

[CIK62]

Next 8 days down to an average of 41degs., but still about 2degs. AN.

[CIK62]

Cobb Method has Rain>>>>>Snow 12/08-09,    8" Snow with .53" LEQ.  Same output also shows no Snow and almost no rain either.    See-Saw went the wrong way this time.   Almost 20 more such Flip_Flops possible before event arrives, if it does.

The 8" run corresponds to this:

The next has subtle differences:

[Isotherm]

The longwave circulation structure is incontrovertibly auspicious for colder than normal temperatures, though, to the extent that baroclinicity will be displaced, the structure is relatively unfavorable for significant to major+ potential (not impossible, but lower likelihood). Eastern and northern New England are most likely to receive a significant event if it occurs (6" or greater) through D10. Hemispherically, mountain torque will increase, subsequently inducing a jet extension event and resultant Nino-esque regime in the medium term. Adjunctively, LF forcing will promote maintenance of poleward ridging extending into the Arctic. Stratospherically, ozone increases in critical areas and wave 1 convergence will continue to destructively interfere with PNJ intensification for the next 2 weeks at least. However, the structure will preclude significant blocking in the NAO domain. Further down the road, eastward propagating MJO will hit a wall in p7, but the upper divergence signal will traverse the EPAC and Atlantic, much like the last wave. I expect NAO domain geopotential heights will become increasingly positive again, after the ephemeral negative interlude week 2. As retrogression of the poleward ridging initiates contemporaneously with improving NAO heights, I continue to favor mid to late December for something bigger. I would narrow it further to the 18th-23rd period approximately. Prior to then, a light to moderate event is still possible for our region, with a lower likelihood of significant.

[snowman19]

5 minutes ago, Isotherm said:

The longwave circulation structure is incontrovertibly auspicious for colder than normal temperatures, though, to the extent that baroclinicity will be displaced, the structure is relatively unfavorable for significant to major+ potential (not impossible, but lower likelihood). Eastern and northern New England are most likely to receive a significant event if it occurs (6" or greater) through D10. Hemispherically, mountain torque will increase, subsequently inducing a jet extension event and resultant Nino-esque regime in the medium term. Adjunctively, LF forcing will promote maintenance of poleward ridging extending into the Arctic. Stratospherically, ozone increases in critical areas and wave 1 convergence will continue to destructively interfere with PNJ intensification for the next 2 weeks at least. However, the structure will preclude significant blocking in the NAO domain. Further down the road, eastward propagating MJO will hit a wall in p7, but the upper divergence signal will traverse the EPAC and Atlantic, much like the last wave. I expect NAO domain geopotential heights will become increasingly positive again, after the ephemeral negative interlude week 2. As retrogression of the poleward ridging initiates contemporaneously with improving NAO heights, I continue to favor mid to late December for something bigger. I would narrow it further to the 18th-23rd period approximately. Prior to then, a light to moderate event is still possible for our region, with a lower likelihood of significant.

Isotherm, do you agree with some of these other winter outlooks showing February as way warmer than normal? I know February in Niña climo is typically warmer to much warmer than normal

[Isotherm]

45 minutes ago, snowman19 said:

Isotherm, do you agree with some of these other winter outlooks showing February as way warmer than normal? I know February in Niña climo is typically warmer to much warmer than normal

I went warmer than normal for both January and February in my winter outlook, with the possibility of one of those two months featuring a > +1.5 departure. Initially, I thought January had a higher probability than February of achieving that, as a mid winter SPV intensification occurs with decreasing favorability in the ATL domain and a retrogression of the NPAC geopotential heights. I'm unsure of the exact magnitude, but yes, I see no objective evidence to abandon my forecast progression right now.

[SnoSki14]

As models are backing off the snow chances, it does look like cold & dry will be the rule. 

December 2010 was a long wait too.

[MJO812]

2 minutes ago, SnoSki14 said:

As models are backing off the snow chances, it does look like cold & dry will be the rule. 

December 2010 was a long wait too.

What models are backing off the snow chances?

[snowman19]

1 minute ago, SnoSki14 said:

As models are backing off the snow chances, it does look like cold & dry will be the rule. 

December 2010 was a long wait too.

If you look at the next 14 days, the tropospheric polar vortex becomes very strong and expansive and it sets up shop in central Canada. That causes suppressive fast flow and just shears everything apart well to the south of us in the flat flow

[Ginx snewx]

6 minutes ago, SnoSki14 said:

As models are backing off the snow chances, it does look like cold & dry will be the rule. 

December 2010 was a long wait too.

wait wut

[snowman19]

The EPS is much less impressive than the op through Sunday

[ILoveWinter]

14 minutes ago, snowman19 said:

The EPS is much less impressive than the op through Sunday

Lol man, if the EPS was much more impressive than Op, would you have posted that? Or perhaps you would have posted something earlier if the Op run showed nothing?

[Rtd208]

Earthlight

 

[redbanknjandbigbasslakepa]

3 hours ago, Rtd208 said:

 

Even earth light is off the snow train. With this long duration cold pattern it’ll snow in nyc, just not this weekend. Modeling started caving that way overnight and had continued the trend today.

[MJO812]

4 hours ago, snowman19 said:

The EPS is much less impressive than the op through Sunday

It's going to change a million times by then

 

[Eduardo]

14 minutes ago, redbanknjandbigbasslakepa said:

Even earth light is off the snow train. With this long duration cold pattern it’ll snow in nyc, just not this weekend. Modeling started caving that way overnight and had continued the trend today.

3 hours ago, Rtd208 said:

Earthlight

One potential synoptic feature to watch for in the upcoming pattern is the presence of a large TPV in Central Canada. Mid level flow and angular momentum could act to temporarily mitigate East Coast storm potential by limiting meridonial nature of troughs. pic.twitter.com/p8T8diliGS

— John Homenuk (@jhomenuk) December 4, 2017

With aid of ECMWF EPS, we can visualize ensemble spread for potential upcoming wintry events. There are several potential events on the horizon for the Northeast states, depicted here in 24hr snowfall on 51-member ensemble. Lots to iron out still! #natgas #nywx pic.twitter.com/lKu8cqzooy

— John Homenuk (@jhomenuk) December 4, 2017

 

Read before you troll....  Consensus seems to be that a fast-moving, complex pattern is evolving, but it's certainly one that can produce especially as it matures a bit.  Nobody is jumping "off the snow train" just by pointing out potential flies in the ointment, nor does anybody dispute that climo ordinarily requires a bit of luck in our region (of which we've had a copious amount in recent years).

Looking at the big picture, I cannot see how anyone can deny that we will have our chances, even possibly this weekend.  Some will land and others might not.  ETA: That's what makes this hobby so fun!

[IntenseBlizzard2014]

55 minutes ago, redbanknjandbigbasslakepa said:

Even earth light is off the snow train. With this long duration cold pattern it’ll snow in nyc, just not this weekend. Modeling started caving that way overnight and had continued the trend today.

This weekend's event could go either way. Can't dismiss it until Friday at 00Z (7th @7 PM EST).

[SnoSki14]

I'll be shocked if we don't get some light snow event in the next 10 days.

The expansive cold also tends to be an extension of the snow cover line if it locks in as we expect it to.

[forkyfork]

i could see the friday event trending a bit west at the last minute. it's a WAR situation 

[AfewUniversesBelowNormal]

phase potential Dec 10, Low bombing out NYC, moving onshore

[CIK62]

Next 8 days still averaging 41degs., or 2 to 3degs. AN.

Leaving out the first 3 days gives an average of 37degs., which about 2degs. BN.

[bluewave]

This is looking like one of the strongest blocks centered over the Pacific Northwest and British Columbia that we have ever seen in December. It  locks in for the whole 15 day EPS run which will produce one of our coldest Decembers in years here.

 

 

 

 

 

[donsutherland1]

This morning, the preliminary value of the Arctic Oscillation (AO) was -0.748. All five days of December have been negative with an average value of -0.691. Looking back to last December, the first five days also started out weakly negative with an average value of -0.196. Given the consistent guidance, December 6 will mark where winter 2017-18 diverges from the path taken last winter when it comes to the Arctic Oscillation. Starting December 6, the remainder of December 2016 saw the AO stay positive, and generally strongly positive. December 2016 finished with a monthly average AO value of +1.786. Following that, 30/31 days in January also saw a positive AO. Overall, 80% of days during meteorological winter had positive AO values.

A very different outcome appears increasingly likely this winter. The development of extreme blocking in November and forecast redevelopment of strong blocking in December suggest that winter 2017-18 will feature a lot more blocking than last winter. Moreover, the forecast long-duration of the current round of blocking favors a blocky winter overall. So, a colder and snowier winter than 2016-17 appears likely.

Through yesterday, NYC's December mean temperature was 45.3°. That is more than 3° above normal, but well below the monthly average of 50.8°, which was established in 2015. The coming regime change courtesy of an extended period of EPO-AO-PNA blocking will lead to negative monthly departures. December also has an increasing probability of above to possibly much above normal snowfall. A weak system could graze parts of the region late Friday into Saturday, bringing light accumulations to parts of the area. More light snow or flurries are possible on Sunday. A more meaningful storm could occur around the middle of next week (a feature that has periodically shown up on various runs of the computer models).

Overall, things remain on track for a colder and snowier than normal December. We are now near the point where the transition will take place.

 

 

 

[Morris]

Over +10 today...

[Paragon]

8 hours ago, bluewave said:

This is looking like one of the strongest blocks centered over the Pacific Northwest and British Columbia that we have ever seen in December. It  locks in for the whole 15 day EPS run which will produce one of our coldest Decembers in years here.

 

 

 

 

 

Is this why California is getting unprecedented wet season fires right now?

[Paragon]

5 hours ago, donsutherland1 said:

This morning, the preliminary value of the Arctic Oscillation (AO) was -0.748. All five days of December have been negative with an average value of -0.691. Looking back to last December, the first five days also started out weakly negative with an average value of -0.196. Given the consistent guidance, December 6 will mark where winter 2017-18 diverges from the path taken last winter when it comes to the Arctic Oscillation. Starting December 6, the remainder of December 2016 saw the AO stay positive, and generally strongly positive. December 2016 finished with a monthly average AO value of +1.786. Following that, 30/31 days in January also saw a positive AO. Overall, 80% of days during meteorological winter had positive AO values.

A very different outcome appears increasingly likely this winter. The development of extreme blocking in November and forecast redevelopment of strong blocking in December suggest that winter 2017-18 will feature a lot more blocking than last winter. Moreover, the forecast long-duration of the current round of blocking favors a blocky winter overall. So, a colder and snowier winter than 2016-17 appears likely.

Through yesterday, NYC's December mean temperature was 45.3°. That is more than 3° above normal, but well below the monthly average of 50.8°, which was established in 2015. The coming regime change courtesy of an extended period of EPO-AO-PNA blocking will lead to negative monthly departures. December also has an increasing probability of above to possibly much above normal snowfall. A weak system could graze parts of the region late Friday into Saturday, bringing light accumulations to parts of the area. More light snow or flurries are possible on Sunday. A more meaningful storm could occur around the middle of next week (a feature that has periodically shown up on various runs of the computer models).

Overall, things remain on track for a colder and snowier than normal December. We are now near the point where the transition will take place.

 

 

 

Wonder if this strong blocking will hold through January and possibly beyond?