December 2021

[SnoSki14]

19 minutes ago, MJO812 said:

Yes sir

You are missing the NAO, AO and EPO.

I'd take the PNA/EPO 10x over the NAO

[NEG NAO]

16 minutes ago, bluewave said:

Just returning the favor for him giving the weenie to my earlier post.

Realistically every previous post regarding next week is neither right or wrong . There is still mass confusion in the modeling as demonstrated by last nights and the early morning runs with the GFS and Euro Ops in complete disagreement ( GFS an intense coastal hugger and Euro a miss to the south and east ) . Like I mentioned last night IMO until we get several runs in a row of consistency and the ensembles start coming into a basic agreement from multiple models  - all options remain on the table ! IMO !

[donsutherland1]

34 minutes ago, MJO812 said:

Yes sir

You are missing the NAO, AO and EPO.

One caveat concerning the NAO when the PNA is negative in December. Once the NAO falls to or below -1, snowfalls tend to be smaller (biggest daily snowfall: 2.7”, December 27, 1976).  Measurable snow fell on 7.3% of days. Between-0.999 and -0.001, nearly 60% of daily snowfalls were 2” or more. The December 26-27, 2010 blizzard was the biggest such storm with 20.0”. This blizzard produced the only days with 6” or more snowfall for this NAO subset. Measurable snow fell on 8.6% of days.

Data was from 1950-2020. There were 137 days in the earlier subset (NAO -1 or below) and 267 days in the latter one. Snowfall was from Central Park.

[EastonSN+]

3 minutes ago, donsutherland1 said:

One caveat concerning the NAO when the PNA is negative in December. Once the NAO falls to or below -1, snowfalls tend to be smaller (biggest daily snowfall: 2.7”, December 27, 1976).  Measurable snow fell on 7.3% of days. Between-0.999 and -0.001, nearly 60% of daily snowfalls were 2” or more. The December 26-27, 2010 blizzard was the biggest such storm with 20.0”. This blizzard produced the only days with 6” or more snowfall. Measurable snow fell on 8.6% of days.

Data was from 1950-2020. There were 137 days in the earlier subset (NAO -1 or below) and 267 days in the latter one. Snowfall was from Central Park.

Thanks Don!

Even the smaller snowfalls would be welcome. Would imagine as the blocking broke down in those cases larger events occurred (NAO rise)? That may have led to the Feb. 69 blizzard.

[RippleEffect]

36 minutes ago, MJO812 said:

Hopefully the weeklies are right

If so then we will have plenty of chances in the upcoming weeks.

i'll be in mahopac for christmas hopefully we hit big there. hey whatever happened to yanks? and billy?

[EasternLI]

32 minutes ago, MJO812 said:

Hopefully the weeklies are right

If so then we will have plenty of chances in the upcoming weeks.

Well, I put very little faith in extended modeling these days. Just in general, regardless of what is shown. What is nice to see is someone like Paul Roundy saying something like that. He is an expert on tropical convection/MJO. 

[MJO812]

1 minute ago, EasternLI said:

Well, I put very little faith in extended modeling these days. Just in general, regardless of what is shown. What is nice to see is someone like Paul Roundy saying something like that. He is an expert on tropical convection/MJO. 

I follow him on Twitter

Very knowledgeable 

[donsutherland1]

2 minutes ago, EastonSN+ said:

Thanks Don!

Even the smaller snowfalls would be welcome. Would imagine as the blocking broke down in those cases larger events occurred (NAO rise)? That may have led to the Feb. 69 blizzard.

The data is only for December. Yes, as you noted, big storms have occurred as the NAO was rising. During January, an AO-/PNA+ pattern is most favorable for significant snowfalls.

I always welcome any snow. Hopefully, we’ll have one or two before December ends.

[MJO812]

Larry Cosgrove 

 

Beware of warmer, calmer forecasts this week and next.

I make this remark because many of the numerical models cannot correctly figure what will happen in situations where stronger high-latitude blocking ridges exist, concurrently with an equally impressive subtropical jet stream. The evolution of a Bering Sea and Greenland/Iceland couplet ridging is well underway. Positive height anomalies in those positions favor the formation of cold 500MB vortices in Alberta and below Newfoundland. The USA result is that colder than normal temperatures are probable in all but Texas and the Dixie states.

Climatology for this type of event allows for stronger cold frontal passages through the Midwest and the Eastern Seaboard above Interstate 40. With the active southern branch adding energy, there can be phased events off of the Mid-Atlantic shoreline. Much like what the GGEM panels show December 20-22. Not only is there the chance for a rogue snow event then (along and west of the major cities), but warm-ups will be hard to maintain.

I suspect that another risk for an important precipitation event may occur between Christmas and New Year's. That cold pool setting up east of Sable Island NS creates a window for redevelopment, which could be especially potent if the subtropical jet stream energy joins in the fray.

Be very careful when handling cold air and storm transitions over the next two or three weeks. Note that the heat ridge complex in the Gulf of Mexico and Florida gets suppressed after this week!

[bluewave]

53 minutes ago, NEG NAO said:

Realistically every previous post regarding next week is neither right or wrong . There is still mass confusion in the modeling as demonstrated by last nights and the early morning runs with the GFS and Euro Ops in complete disagreement ( GFS an intense coastal hugger and Euro a miss to the south and east ) . Like I mentioned last night IMO until we get several runs in a row of consistency and the ensembles start coming into a basic agreement from multiple models  - all options remain on the table ! IMO !

The only constant in this pattern has been disappointment when getting invested in individual model solutions for storms  beyond 5 days with such a fast Pacific flow. Sometimes I wish that they stopped making operational models available beyond 120 hrs and just had ensemble means. I have no idea why they run the GFS OP beyond 10 days. This really creates more public relations issues for the NWS than it’s worth. Way too much posting of long range snowfall charts on these forums and social media. It has the effect of eroding the public confidence in the weather forecasting profession. While ensembles do well with general 500 mb and temperature patterns, operational models  have almost no skill with snowfall forecasts beyond a few days.

[NEG NAO]

5 minutes ago, MJO812 said:

Larry Cosgrove 

 

Beware of warmer, calmer forecasts this week and next.

I make this remark because many of the numerical models cannot correctly figure what will happen in situations where stronger high-latitude blocking ridges exist, concurrently with an equally impressive subtropical jet stream. The evolution of a Bering Sea and Greenland/Iceland couplet ridging is well underway. Positive height anomalies in those positions favor the formation of cold 500MB vortices in Alberta and below Newfoundland. The USA result is that colder than normal temperatures are probable in all but Texas and the Dixie states.

Climatology for this type of event allows for stronger cold frontal passages through the Midwest and the Eastern Seaboard above Interstate 40. With the active southern branch adding energy, there can be phased events off of the Mid-Atlantic shoreline. Much like what the GGEM panels show December 20-22. Not only is there the chance for a rogue snow event then (along and west of the major cities), but warm-ups will be hard to maintain.

I suspect that another risk for an important precipitation event may occur between Christmas and New Year's. That cold pool setting up east of Sable Island NS creates a window for redevelopment, which could be especially potent if the subtropical jet stream energy joins in the fray.

Be very careful when handling cold air and storm transitions over the next two or three weeks. Note that the heat ridge complex in the Gulf of Mexico and Florida gets suppressed after this week!

So basically in his opinion take the models with a grain of salt the next few days - I totally agree ! Anybody else agree ?

[SnoSki14]

BTW MJO is now expected to halt in phase 7 so lagging effects do spell a period of colder weather & maybe snows after December 20th. 

It's probably a short window though, about 2 weeks before a more unfavorable pattern develops again.

If it does manage to get into 8-1 then January will be cooler but think that's unlikely right now.

[MJO812]

6 minutes ago, SnoSki14 said:

BTW MJO is now expected to halt in phase 7 so lagging effects do spell a period of colder weather & maybe snows after December 20th. 

It's probably a short window though, about 2 weeks before a more unfavorable pattern develops again.

If it does manage to get into 8-1 then January will be cooler but think that's unlikely right now.

Why is it unlikely ?

[NEG NAO]

8 minutes ago, SnoSki14 said:

BTW MJO is now expected to halt in phase 7 so lagging effects do spell a period of colder weather & maybe snows after December 20th. 

It's probably a short window though, about 2 weeks before a more unfavorable pattern develops again.

If it does manage to get into 8-1 then January will be cooler but think that's unlikely right now.

Remember we still have no idea what is going to happen next week ..........

[Stormlover74]

24 minutes ago, NEG NAO said:

Remember we still have no idea what is going to happen next week ..........

I'm pretty sure if we get a storm it'll be rain for the coast and snow well inland

[bluewave]

16 minutes ago, RippleEffect said:

anything over 5 days you shouldn't be even showing nevermind taking it serious. You should know that Chris. although they look like pretty colors these images are worth zero past 5 days!

Thats only true for OP run storm tracks and precipitation forecasts beyond 3-5 days. The ensemble mean 500 mb and temperature patterns forecasts have been doing pretty well through 6-10 days. But the longer range 11-15 day ran too cool for our area in  early December which verified warmer. The effective range for OP runs for storm tracks is only about 3-5 days. But the general ensemble means for 500 mb patterns and temperatures skill extends to 6-10 and sometimes 11-15 if we get lucky. People on these forums are well aware that extended runs beyond 15 days don’t have that much skill. But we still like to talk about them. We never use those longer range products  to try to pin down individual storm tracks. I would consider a model forecast beyond 2 weeks a success if it can identify at least one teleconnection pattern that has a significant influence.

[Eduardo]

1 minute ago, RippleEffect said:

you're probably right honestly. we have no luck!

I don't think it's about luck here (except insofar as it'd require massively good luck to get snow down to the coast).  It's more a matter of pattern recognition.  I can see us maybe getting a few slushy inches before a changeover.  For me, the upcoming pattern has a very mehhhh 08-09 feel to it.  Lil more -NAO help might give us what we need, but it's a close call.

[EastonSN+]

43 minutes ago, SnoSki14 said:

BTW MJO is now expected to halt in phase 7 so lagging effects do spell a period of colder weather & maybe snows after December 20th. 

It's probably a short window though, about 2 weeks before a more unfavorable pattern develops again.

If it does manage to get into 8-1 then January will be cooler but think that's unlikely right now.

Only halts on EC not GEFS. Better to look at the EC ensembles.

[EasternLI]

We take. 

 

[MJO812]

3 minutes ago, EasternLI said:

We take. 

 

Let the blocking get established

The models will adjust most likely 

[NEG NAO]

12Z GFS completely different from last nights 0Z regarding the 21st storm

 

[MJO812]

3 minutes ago, NEG NAO said:

12Z GFS completely different from last nights 0Z regarding the 21st storm

 

Let's see how many different outcomes the GFS will show 

[North and West]

12Z GFS completely different from last nights 0Z regarding the 21st storm

 

how much for philly


.

[RippleEffect]

has GFS become the worst model of all? 

[donsutherland1]

Four quick thoughts on the upcoming pattern change:

1. The MJO's push into Phase 7 (amplitude > 2) should trigger a circulation response that favors cooler than normal temperatures during the January 1-10 period overall.

2. The magnitude of the cold and its duration remains uncertain. MJO forecasts aren't very skillful beyond a week. Additional factors influence the hemispheric circulation. There remains a risk that severe cold remains largely confined to northwestern/central Canada and the U.S. Northwest/Northern Plains and, if it comes eastward, remains largely north of the U.S.-Canada border. One likely won't have a firm idea as to whether the colder pattern will last closer to two weeks or closer to four weeks  until late this month.

3. The December 21-31 period should be cooler than the December 11-20 period. It very likely won't be severely cold based on consistent teleconnections forecasts into the start of that period.

4. In January, an AO-/PNA+ pattern has accounted for a disproportionate share of significant Mid-Atlantic snowstorms. Teleconnections can't be reliably forecast beyond two weeks.

 

[Stormlover74]

24 minutes ago, RippleEffect said:

has GFS become the worst model of all? 

No but that's why you can't expect a model solution to be correct 7 days out

[NEG NAO]

12Z Canadian similar to 12Z GFS but beyond 21st storm lingers down south

[CIK62]

EURO for the last week of the year:      The snow is just the usual  0"-2", CTA(coverthyass)

[NEG NAO]

1 minute ago, CIK62 said:

EURO for the last week of the year:

That doesn't tell us much for NYC metro we are stuck in the middle - which usually means an active stormy pattern.......

[RippleEffect]

everything has been trending south. so expect a colder pattern down the road probably resulting drier also