December 2021

[thunderbolt]

National weather service at the Juno tweet :Juneau Forecast Office has been taking snowfall observations in the back of the valley since 2001. As of 12/7, the office has picked up 56.8" of snow since Nov 1st! This is the second highest snow amount recorded this early in the season at the office. #akwx Juneau Alaska tweet

[donsutherland1]

Tomorrow will be another cool day. Milder air will begin to overspread the region on Friday. Temperatures could soar to near record and record levels on Saturday in the Middle Atlantic region.

No Arctic blasts appear likely for the foreseeable future. Overall, through December 20th, temperatures will likely be warmer than normal in the means with some short-lived cool shots.

Out West, Denver has yet to see its first measurable snowfall through December 7. The previous record latest first measurable snowfall occurred on November 21, 1934. The progression of Denver's latest first measurable snowfall of the season is as follows:

November 11, 1882
November 16, 1894
November 19, 1931
November 21, 1934

The base case is that the closing 10 days of December could turn cooler, though not necessarily cold. Since 1950, there have been 7 cases where the AO averaged +2.000 or above during the first week in December, as has been the case this year. The mean December 21-31 temperature in New York City was 40.2°. The median temperature was 41.5°. The coldest was 35.3° (1951) and the warmest was 44.0° (1979). In short, this historic experience would suggest that there will be no severe Arctic outbreaks in the East this month. It also suggests that New York City will likely have an average temperature of 40° or above this month.

Although the MJO moved into Phase 6 at a very high amplitude in recent days, the sample size of cases where the MJO moved into Phase 6 at an amplitude of 1.75 or above during December 1-15 is very small (n=5). Moreover, just a single case occurred during a predominantly EPO+/AO+ pattern and none occurred during a La Niña. Among those five cases, two had a cold or very cold December 21-31 period, one saw near normal conditions, and two had warm conditions. In short, the current high amplitude MJO does not provide a clear signal where things are headed.

Following very wet July-September periods, winter (December-February) precipitation has typically been near or below normal. The most recent exception was winter 2018-19.

The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -0.9°C for the week centered around December 1. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.87°C and the ENSO Region 3.4 anomaly has averaged -0.92°C. La Niña conditions will likely persist into at least late winter.

The SOI was +10.43 today.

The preliminary Arctic Oscillation (AO) figure was +2.262 today

On December 6 the MJO was in Phase 6 at an amplitude of 1.977 (RMM). The December 5-adjusted amplitude was 1.930 (RMM).

Based on sensitivity analysis applied to the latest guidance, there is an implied 83% probability that New York City will have a warmer than normal December (1991-2020 normal). December will likely finish with a mean temperature near 42.2° (3.1° above normal).

 

[mattinpa]

6 minutes ago, donsutherland1 said:

Tomorrow will be another cool day. Milder air will begin to overspread the region on Friday. Temperatures could soar to near record and record levels on Saturday in the Middle Atlantic region.

No Arctic blasts appear likely for the foreseeable future. Overall, through December 20th, temperatures will likely be warmer than normal in the means with some short-lived cool shots.

Out West, Denver has yet to see its first measurable snowfall through December 7. The previous record latest first measurable snowfall occurred on November 21, 1934. The progression of Denver's latest first measurable snowfall of the season is as follows:

November 11, 1882
November 16, 1894
November 19, 1931
November 21, 1934

The base case is that the closing 10 days of December could turn cooler, though not necessarily cold. Since 1950, there have been 7 cases where the AO averaged +2.000 or above during the first week in December, as has been the case this year. The mean December 21-31 temperature in New York City was 40.2°. The median temperature was 41.5°. The coldest was 35.3° (1951) and the warmest was 44.0° (1979). In short, this historic experience would suggest that there will be no severe Arctic outbreaks in the East this month. It also suggests that New York City will likely have an average temperature of 40° or above this month.

Although the MJO moved into Phase 6 at a very high amplitude in recent days, the sample size of cases where the MJO moved into Phase 6 at an amplitude of 1.75 or above during December 1-15 is very small (n=5). Moreover, just a single case occurred during a predominantly EPO+/AO+ pattern and none occurred during a La Niña. Among those five cases, two had a cold or very cold December 21-31 period, one saw near normal conditions, and two had warm conditions. In short, the current high amplitude MJO does not provide a clear signal where things are headed.

Following very wet July-September periods, winter (December-February) precipitation has typically been near or below normal. The most recent exception was winter 2018-19.

The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -0.9°C for the week centered around December 1. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.87°C and the ENSO Region 3.4 anomaly has averaged -0.92°C. La Niña conditions will likely persist into at least late winter.

The SOI was +10.43 today.

The preliminary Arctic Oscillation (AO) figure was +2.262 today

On December 6 the MJO was in Phase 6 at an amplitude of 1.977 (RMM). The December 5-adjusted amplitude was 1.930 (RMM).

Based on sensitivity analysis applied to the latest guidance, there is an implied 83% probability that New York City will have a warmer than normal December (1991-2020 normal). December will likely finish with a mean temperature near 42.2° (3.1° above normal).

 

Always love your analysis, Don. It is possible we at least feel like Christmas by Christmas even if no major storms?

[donsutherland1]

19 minutes ago, mattinpa said:

Always love your analysis, Don. It is possible we at least feel like Christmas by Christmas even if no major storms?

It should feel more like it than during some recent winters. Severe cold will likely struggle to get out of NW Canada.

[brooklynwx99]

Overall, I remain very optimistic about the end of this month, even if the next week or so will be an unabated blowtorch. 

There are a couple of pattern drivers that lead me to believe that a pattern change is on the way, both of which have been discussed in this thread already!

1) The tropical forcing. We are currently in phase 6, and there is considerable agreement that we will enter phase 7 (and perhaps 8!) at high amplitude. This is shown by the RMM plots as well as standard OLR anomalies:

Phase 7 in December and January in -ENSO are correlated with very cold patterns for the E US as a whole:

Therefore, I do believe that the MJO will have a positive effect on the pattern. There is a chance that the La Nina could destructively interfere with the propagation of the MJO, but the overall weak status of the ENSO state as well as the very high confidence of propagation overall lead me to believe that this is unlikely.

2) The Scandinavian ridging that is going to develop in the medium range with very high confidence. Both major ensembles are in great agreement that a highly anomalous Scandinavian ridge is going to form. A 2 sigma ridge will certainly have an impact on our pattern. These cutoff ridges are known to retrograde towards the NAO domain and provide intense blocking (March 2018) as well as provide heat fluxes to disrupt the SPV, which is also being shown on modeling as well. This is also coupled with a strong MJO pulse into 6/7, which has been known to help disrupt the SPV as well. Both of these may work in tandem to significantly perturb the SPV and promote prolonged blocking (this has been shown in some extended model runs).

Based on the two significant pattern drivers noted here, I do expect a pretty quick change into a favorable (perhaps highly favorable) pattern for winter weather around Christmas week. There will likely be a period of time where the cold air dumps into the W US, but it should leak over as it usually does. The one wild card is if the MJO wave is interfered with. If this is the case, there could be some prolonged ridging over the E US as the western trough remains in place. However, I really don't buy it here.

Generally, based on the composites shown, the MJO will have more of a positive impact on the EPO domain (and some Greenland blocking influence), and the Scandinavian ridge will have much more of an impact on the NAO domain. It's certainly nice to see all of these pattern drivers move forward and become stronger in time, and it shows that the pieces will likely be in place to shake things up. Therefore, I do expect some insanely warm weather over the next week, but I have the impression that it'll snap the other way to close out the month.

[Dan76]

[EasternLI]

35 minutes ago, brooklynwx99 said:

Overall, I remain very optimistic about the end of this month, even if the next week or so will be an unabated blowtorch. 

There are a couple of pattern drivers that lead me to believe that a pattern change is on the way, both of which have been discussed in this thread already!

1) The tropical forcing. We are currently in phase 6, and there is considerable agreement that we will enter phase 7 (and perhaps 8!) at high amplitude. This is shown by the RMM plots as well as standard OLR anomalies:

Phase 7 in December and January in -ENSO are correlated with very cold patterns for the E US as a whole:

Therefore, I do believe that the MJO will have a positive effect on the pattern. There is a chance that the La Nina could destructively interfere with the propagation of the MJO, but the overall weak status of the ENSO state as well as the very high confidence of propagation overall lead me to believe that this is unlikely.

2) The Scandinavian ridging that is going to develop in the medium range with very high confidence. Both major ensembles are in great agreement that a highly anomalous Scandinavian ridge is going to form. A 2 sigma ridge will certainly have an impact on our pattern. These cutoff ridges are known to retrograde towards the NAO domain and provide intense blocking (March 2018) as well as provide heat fluxes to disrupt the SPV, which is also being shown on modeling as well. This is also coupled with a strong MJO pulse into 6/7, which has been known to help disrupt the SPV as well. Both of these may work in tandem to significantly perturb the SPV and promote prolonged blocking (this has been shown in some extended model runs).

Based on the two significant pattern drivers noted here, I do expect a pretty quick change into a favorable (perhaps highly favorable) pattern for winter weather around Christmas week. There will likely be a period of time where the cold air dumps into the W US, but it should leak over as it usually does. The one wild card is if the MJO wave is interfered with. If this is the case, there could be some prolonged ridging over the E US as the western trough remains in place. However, I really don't buy it here.

Generally, based on the composites shown, the MJO will have more of a positive impact on the EPO domain (and some Greenland blocking influence), and the Scandinavian ridge will have much more of an impact on the NAO domain. It's certainly nice to see all of these pattern drivers move forward and become stronger in time, and it shows that the pieces will likely be in place to shake things up. Therefore, I do expect some insanely warm weather over the next week, but I have the impression that it'll snap the other way to close out the month.

Great post. An interesting thing about the background state this year. Its actually really favorable for mjo wave propagation, it would seem. Solar correlation is suggested in research to have a lag ~3 years. East QBO. La Niña. 

https://journals.ametsoc.org/view/journals/clim/33/1/jcli-d-18-0811.1.xml?tab_body=fulltext-display

Specifically, under cool ENSO, easterly QBO, and SMIN conditions, evidence favors a strengthened wave train that propagates farther eastward and more strongly modulates SLP and SAT anomalies. The modulation is increased further when two or more of these conditions are simultaneously in effect. While internal intraseasonal variability is large and these influences may not be apparent during a given MJO cycle in a given winter, the length of currently available reanalysis datasets allows them to be detected via averaging and construction of mean MJO phase composites.

[wdrag]

A couple of days ago modeling offered a potential rain to snow event for the 12th. No longer. 

But a thread may still be needed soon for damaging wind Saturday evening.  Right now I'll go with modeling being a little over amped.  We have had a couple of small scale wind events the past week with CFP's.  This looks a little more potent but I think waiting a bit longer is useful.  12z/8 EPS has 64kt at 850MB on the WAA sw flow in the afternoon and 50KT+ on the CAA evening WNW flow.  18z GEFS is about 55-60KT on the sw flow and 45-50kt on westerly CAA. 

[Daniel Boone]

1 hour ago, EasternLI said:

Great post. An interesting thing about the background state this year. Its actually really favorable for mjo wave propagation, it would seem. Solar correlation is suggested in research to have a lag ~3 years. East QBO. La Niña. 

https://journals.ametsoc.org/view/journals/clim/33/1/jcli-d-18-0811.1.xml?tab_body=fulltext-display

Specifically, under cool ENSO, easterly QBO, and SMIN conditions, evidence favors a strengthened wave train that propagates farther eastward and more strongly modulates SLP and SAT anomalies. The modulation is increased further when two or more of these conditions are simultaneously in effect. While internal intraseasonal variability is large and these influences may not be apparent during a given MJO cycle in a given winter, the length of currently available reanalysis datasets allows them to be detected via averaging and construction of mean MJO phase composites.

Problem is, Invests continue to develop in west Pac that weaken or hamper the propagation n2 cold phases.

[TheManWithNoFace]

Hey everyone I need some help. Many months ago someone posted a chart of annual mean dewpoints at a local observation station over the last several years, if I recall correctly. I need to find that or something similar. Can anyone help?

[Rjay]

10 minutes ago, TheManWithNoFace said:

Hey everyone I need some help. Many months ago someone posted a chart of annual mean dewpoints at a local observation station over the last several years, if I recall correctly. I need to find that or something similar. Can anyone help?

I tried finding it but the search function is a disaster on here.  @bluewavehas this info.

[MJO812]

Gfs brings the cold after the 18th fwiw

[SnoSki14]

18 minutes ago, MJO812 said:

Gfs brings the cold after the 18th fwiw

Not as blow torchy either. We sort of get back fronted as the main heat surge focuses towards the Midwest. 

Certainly a possibility. 

[EasternLI]

8 hours ago, Daniel Boone said:

Problem is, Invests continue to develop in west Pac that weaken or hamper the propagation n2 cold phases.

Yeah, always a concern. I've definitely had that in mind. HM actually touched on this with an interesting post yesterday. 

 

[dmillz25]

5 minutes ago, EasternLI said:

Yeah, always a concern. I've definitely had that in mind. HM actually touched on this with an interesting post yesterday. 

 

Yep could help build that -EPO ridge stronger

[wdrag]

Likely starting a thread at 6PM for the 4P-midnight time frame Saturday DEC 11 for scattered wind gusts 40-55Knots and embedded potential severe thunderstorms. Here is SPC Day 3 with marginal risk up into NJ. Have a day.

[Rtd208]

6 minutes ago, 5HzECMWFFreq said:

WoW at 06z GFS.
 

Interesting times ahead.

If this upcoming pattern change is real I think you are going to start seeing some interesting model solutions as we move forward. But that is still pretty far out to get overly excited about but a timeframe to keep an eye on nevertheless.

[the_other_guy]

3 minutes ago, bluewave said:

Another very warm pattern next few weeks as the warm up approaching the solstice and Christmas is becoming an an annual event.

Wont be a warm up this year…gonna be warm right through

[the_other_guy]

28F

Too bad that little storm didnt pan out. Would have been a nice touch of winter

[bluewave]

4 minutes ago, jfklganyc said:

Wont be a warm up this year…gonna be warm right through

It will be a warm up for us compared to how warm it has been to our west this month. The mid portion of December will be higher for us than the +3 to +4 of the first week . So some impressive departures by the solstice.

 

[CIK62]

The next 8 days are averaging 45degs.(39/52), +8, +5 nowadays.

Month to date is  44.3[+2.1]       Should be  44.6[+3.6] by the 17th.

Reached 45{Midnite} and 44 during day.

Today: 39-41,  wind nw.  to s., variable clouds.     Now BN could start by the 20th.      Christmas no snow, but maybe stays under 32 all day, for first time this season.     GFS has Miami in the 50's all Christmas Day.      Meanwhile  today/tomorrow in Dallas, back to back 80's may set records.

32*(62%RH) here at 6am.     35* at 9am.      39* at Noon.       40* at 2pm.      39* at 3pm.

[qg_omega]

27 minutes ago, jfklganyc said:

28F

Too bad that little storm didnt pan out. Would have been a nice touch of winter

I’ll take the coating on cars and grass this morning

[Allsnow]

30 minutes ago, bluewave said:

It will be a warm up for us compared to how warm it has been to our west this month. The mid portion of December will be higher for us than the +3 to +4 of the first week . So some impressive departures by the solstice.

 

That sure looks like a p6 response in Niña during December. We just won’t be able to sustain it 

[lee59]

30 degrees this morning with car doors frozen shut.

[Allsnow]

42/34 in the park yesterday. Should be another below normal day today. Models did a good job forecasting this cold shot 

[bluewave]

4 minutes ago, Allsnow said:

That sure looks like a p6 response in Niña during December. We just won’t be able to sustain it 

While the warmth in the East and big -PNA is typical for a neutral ENSO phase 6, a La Niña is supposed to be colder here with a +PNA. So that is telling us that the MJO is not having the intended effect for a La Niña. May be some type of interference pattern which has been noted recently. Could be related to the recent wave breaks in the WPAC and AAM spike. So we will have to be cautious solely relying on the MJO composites going forward until we get more clarity.

 

 

 

[donsutherland1]

Morning thoughts…

Today will be partly cloudy and cool. High temperatures will likely reach the lower 40s in most of the region. Likely high temperatures around the region include:

New York City (Central Park): 40°

Newark: 43°

Philadelphia: 43°

Normals:

New York City: 30-Year: 46.1°; 15-Year: 46.7°

Newark: 30-Year: 46.6°; 15-Year: 47.3°

Philadelphia: 30-Year: 47.7°; 15-Year: 48.5°

Milder air will begin to return tomorrow. Near record or perhaps even record warmth is possible in parts of the region on Saturday.

Daily records for December 11:

Allentown: 61°, 1952 and 1979

Baltimore: 69°, 1979

New York City: 64°, 1879

Newark: 65°, 1966 and 1971

Philadelphia: 65°, 1899 and 1971

Washington, DC: 68°, 1897, 1971, and 1979

[ForestHillWx]

24 currently. Dusting of snow on the yard. Momentary, seasonal mood setter.

[Allsnow]

26 minutes ago, bluewave said:

While the warmth in the East and big -PNA is typical for a neutral ENSO phase 6, a La Niña is supposed to be colder here with a +PNA. So that is telling us that the MJO is not having the intended effect for a La Niña. May be some type of interference pattern which has been noted recently. Could be related to the recent wave breaks in the WPAC and AAM spike. So we will have to be cautious solely relying on the MJO composites going forward until we get more clarity.

 

 

 

We have had a +pna last week 

[LibertyBell]

19 hours ago, jfklganyc said:

The 90s get over shadowed by 94 and 96. A lot of garbage in between though

the 80s were MUCH worse

and so were the 70s outside of 77-78