December 2018 Pattern And Forecast Discussion

[AMZ8990]

 The month of December is almost upon us so we figured it was time to create a December winter thread.  Looks like it could be a cold month with possible time frames that may support good conditions for winter storms.  Let the breakdown begin!  BTW Go VOLS today, #beatmizzou

[Carvers Gap]

I took a look at the CPC teleconnections just a minute ago.  The AO is forecast to go severely negative and the PNA to go strongly positive.  I don't trust the NAO index...but it rising later this month likely signals an EC storm.  What I "think" is going to happen in early December is a likely +PNA/-AO.  I think we will see some blocking over Greenland, though some has appeared to be east based.  What does that mean?  Likely it means quick moving features that will have difficulty phasing, but northwest flow areas will see some action.  Still early December is pretty hostile territory when it comes to snow IMBY.  I have lived here off-and-on for 37 years, and early December is just not a great time for snow in valley locations.  The mountains and elevation are another story altogether.  We see skiffs, dustings, and flurries, but not big storms.  So, I think it important to note that even though the pattern looks pretty decent.  While there are many things working against snow at this time of year I admittedly note that northwest TN (the new snow Mecca of the forum area) just recently cashed-in.  What a great run for them during recent winters.  Reminds me of the late 70s when I always thought all of the snow kept going to areas around Memphis!  Right now the pattern for the early December time frame is not even close to being in focus...so I don't really have any changes.  I really like the potential pattern that is coming after the warm-up.  Like others, I get a bit skittish when it looks a little too good.  If it is too good to be true.....Anyway, I hope all have a great Thanksgiving.  What a great community!

[John1122]

I've seen the  63-64 winter analog used several times so far in various winter forecasts.

That year started quickly. 

Large snows of 2 inches to way more in several cases, fell on November 29th, December 2nd, December 18th, December 22nd, December 23rd, and December 31st.

Snow also fell from a trace to .5 inches on November 30th, December 1st, 8th, 9th, 10th, 13th, 14th, 24th, and 27th.

[Carvers Gap]

Here is an interesting comparison of graphics.  Take a look at the Euro seasonal from early November and maybe(?) the most recent JAMSTEC in the winter thread where most of NA is cold.  Now, take a look at the 12z GEFS later in its run and how the cold is configured along the EC.  Almost a perfect match to the Euro seasonal AND it has some cold across much of the country which is somewhat similar to the JAMSTEC(but not a perfect comparison by any means).  That is a good sign.  That means that the early winter pattern(on the 12z GEFS) being depicted below correlates will to season forecasts from other models, especially the Euro seasonal.  No idea if that correlation occurs for the entire winter(or even if it verifies on that map!), but it can't hurt that the predicted pattern is showing itself this early.  

[Carvers Gap]

45 minutes ago, John1122 said:

I've seen the  63-64 winter analog used several times so far in various winter forecasts.

That year started quickly. 

Large snows of 2 inches to way more in several cases, fell on November 29th, December 2nd, December 18th, December 22nd, December 23rd, and December 31st.

Snow also fell from a trace to .5 inches on November 30th, December 1st, 8th, 9th, 10th, 13th, 14th, 24th, and 27th.

John, how did that winter unfold for DJF?  Thaws, ending, big storms, etc?

[Daniel Boone]

3 hours ago, Carvers Gap said:

I took a look at the CPC teleconnections just a minute ago.  The AO is forecast to go severely negative and the PNA to go strongly positive.  I don't trust the NAO index...but it rising later this month likely signals an EC storm.  What I "think" is going to happen in early December is a likely +PNA/-AO.  I think we will see some blocking over Greenland, though some has appeared to be east based.  What does that mean?  Likely it means quick moving features that will have difficulty phasing, but northwest flow areas will see some action.  Still early December is pretty hostile territory when it comes to snow IMBY.  I have lived here off-and-on for 37 years, and early December is just not a great time for snow in valley locations.  The mountains and elevation are another story altogether.  We see skiffs, dustings, and flurries, but not big storms.  So, I think it important to note that even though the pattern looks pretty decent.  While here are many things working against snow at this time of year I admittedly note that northwest TN (the new snow Mecca of the forum area) just recently cashed-in.  What a great run for them during recent winters.  Reminds me of the late 70s when I always thought all of the snow kept going to areas around Memphis!  Right now the pattern for the early December time frame is not even close to being in focus...so I don't really have any changes.  I really like the potential pattern that is coming after the warm-up.  Like others, I get a bit skittish when it looks a little too good.  If it is too good to be true.....Anyway, I hope all have a great Thanksgiving.  What a great community!

Late 70's winters were extremely cold/snowy here in Lee County.  72" reported in Pennington gap area in 77-78.

[Carvers Gap]

1 hour ago, Daniel Boone said:

Late 70's winters were extremely cold/snowy here in Lee County.  72" reported in Pennington gap area in 77-78.

That is Montana weather right there.  Indeed, those were some great winters with incredible cold fronts. I should note that I lived in Knoxville then and was just a grade schooler.   And we received a lot of snow there when I was a kid compared to nowadays. Places that were always mentioned were Paducah, Memphis, Crossville.  I thought the Tri-Cities were always cold and snowy.  Unlike today, southwest Virginia was not even on my radar.  My only weather came from Margie Ison on WBIR and my weather radio.  Between those two, I thought I was the stuff.  I have liked weather for a long time!  But then, like today, I was not always right.  

[Daniel Boone]

21 hours ago, Carvers Gap said:

That is Montana weather right there.  Indeed, those were some great winters with incredible cold fronts. I should note that I lived in Knoxville then and was just a grade schooler.   And we received a lot of snow there when I was a kid compared to nowadays. Places that were always mentioned were Paducah, Memphis, Crossville.  I thought the Tri-Cities were always cold and snowy.  Unlike today, southwest Virginia was not even on my radar.  My only weather came from Margie Ison on WBIR and my weather radio.  Between those two, I thought I was the stuff.  I have liked weather for a long time!  But then, like today, I was not always right.  

Brother,  you are an inspiring poster !!  I too watched Margie, as a teenager. She was good . 95-96 was closest to 77-78 with just over 50 inches in Pennington gap un my years of observations.  Incidentally,  Wise seasonal state record of 123.5 was recorded that winter.

 

[John1122]

On 11/18/2018 at 2:57 PM, Carvers Gap said:

John, how did that winter unfold for DJF?  Thaws, ending, big storms, etc?

The December 31st event spilled into January with half a foot falling on Jan 1st. It was mostly cold til mid-month with 4 inches falling on the 12th. It never got as frigid in January though, it was sub zero in December, approaching -10. Jan 18th til Feb 5th was mostly a thaw. Upper 40s to upper 50s for highs. After that it was below normal for the most part for the rest of the month. Not frigid but cold.  It finished slightly BN for January even with the warm up, it snowed a few inches during the month. In February it was classic Nino temps,  it wasn't very cold for lows but the highs were very suppressed.  The month ended at about -6 with decent snows of 3-8 inches on the 6th,  19th-21st and the 28th which was the largest event. That one got BNA to Knoxville and points north with 4-8 inches. March warmed up fast after the 1st, but had a big cold shot the last of the month. It ended at -2 temp wise but without more than a few small trace snow events.

The Nov-March period was BN every month, and right at 42 inches of snow fell during that time. December was the prize winner with just over 20 inches falling, December was also the coldest of the months finishing at 10 degrees BN for the month.

[John1122]

Actually forgot to add November to that total. 45 inches fell that winter. 44.5 of it fell Nov 29th - Feb 28th. March, as I noted, only saw a few dustings here.

[nrgjeff]

ECMWF Euro weeklies remain cold most weeks. CFS is gradually succumbing. Resistance is futile. Let the power of the dark cold side flow through.

Happy for a Thanksgiving mild break, especially for Chattanooga's Holiday Cheer at the Pier Friday, much better and far more rewarding than shopping!

Otherwise looks cold through early December. Mid-December the Euro weeklies show a mild break, which lines up with the EPS MJO forecast (at Day 14) so FWIW.

Euro weeklies are cold again by week 6 (week 5 EIA Fri-Thu weeks) or about December 20. The mild mid-Dec and cold end matches that 1969 analog. Parts of the region had a white Christmas in 1969, but I don't want to get too carried away. Still fun enough that I've mentioned it in two threads now, lol!

November is starting to remind me of cold years where the blocking just kept on giving more cold. We'll see, but this is a statistically favorable pattern to be in early if one likes winter.

[Carvers Gap]

23 minutes ago, nrgjeff said:

ECMWF Euro weeklies remain cold most weeks. CFS is gradually succumbing. Resistance is futile. Let the power of the dark cold side flow through.

Happy for a Thanksgiving mild break, especially for Chattanooga's Holiday Cheer at the Pier Friday, much better and far more rewarding than shopping!

Otherwise looks cold through early December. Mid-December the Euro weeklies show a mild break, which lines up with the EPS MJO forecast (at Day 14) so FWIW.

Euro weeklies are cold again by week 6 (week 5 EIA Fri-Thu weeks) or about December 20. The mild mid-Dec and cold end matches that 1969 analog. Parts of the region had a white Christmas in 1969, but I don't want to get too carried away. Still fun enough that I've mentioned it in two threads now, lol!

November is starting to remind me of cold years where the blocking just kept on giving more cold. We'll see, but this is a statistically favorable pattern to be in early if one likes winter.

Bob Chill mentioned this as well and I thought it when I looked at the Euro Weeklies last night....I wonder if the Dec warm-up will be less than modeled(like the one around Thanksgiving)?  But yeah, the warm-up along w considering the MJO forecast would make sense.  And possibly a good thing, maybe we rotate through the best MJO phases around our coldest time of the year traditionally, early January.  

[Carvers Gap]

When I look at the d10-15 EPS frontal boundary draped west to east...the 240 18z GFS is what comes to mind.

[Carvers Gap]

The d10-15 EPS is about as cold as it can get given that it is an ensemble....I mean cold.  I don't mind seeing everything pushed back a few days.  But if that d10-15 pattern verifies, I think somebody in the forum area will likely have something to talk about.  Going to be tough for systems to cut later in that time frame.  If we can still keep some cold around by the second week of December, much better odds...

[Carvers Gap]

...I mean a straight discharge of cold into the eastern United States.  I will try not to hype....but the only worry with that is that it snows in New Orleans.

[Holston_River_Rambler]

Taking Carver's post in to account (posted while I was typing the below) the first part of this post is regarding the nearer term (pre day 10):

So, does the -NAO now work for us like putting your thumb over a water hose with the furious Pac jet others have been pointing out?  All that energy just gets funneled through, under the big block in eastern Canada and into the Atlantic without a cooperative Pac. block to funnel or split it in a favorable direction?

On the other had fast flows can be wild/ changeable flows? Last year around early December I think (if I remember correctly) we saw in a very different ENSO state how poorly models did and how quickly things could change.  

Now post day 10:  Masiello argues, if I read him correctly, that the cyclonic wave break brought on by the Pac could initiate a new (maybe refreshed is better) -NAO, (using Nov.-Dec. 1963 and 1977 as analogue years) and colder temps. 

[Holston_River_Rambler]

Also, let's see how this ages (not endorsing, just throwing it out there and let's see what happens): 

 

[Carvers Gap]

Looks like the EPS is going to try to sneak a warm-up into the pattern during days 8-10.  The GEFS is less than enthused.  That said, both look pretty cold after d10.  I wonder if that cold will get pushed back a few days given model tendencies to jump the gun w cold (or warm) at that range.  I am sort of pulling for that cold to get pushed into the second week(even the third).  Something to keep in mind, there is a ton of energy in this pattern.  Have you ever seen the plinko board analogy regarding prediction.  The further down the board the prediction goes, the more possibilities there are.  Well, this pattern is like dropping four or five pucks onto the board at the same time and trying to predict the outcome at the bottom.  Back to actual weather talk, I noticed one of the mets on the MA board discussed that the tight spacing across NA which is making it tough to allow for a storm to deepen.  I agree.  I think the Nino pattern being so active along with it still being November just makes it tough for storms to deepen along the EC.  So, no real surprises.  I mean really...it is still November.  I do think the cold for early December "may" get pushed back a few days.  It is pretty crazy to see the EPS banging the cold drum like it is for d10-15.  But we all know the drill...it needs to get inside of d10 before taking it seriously.  The warm spell that it adamantly displayed for d10-15 will not verify at near the strength nor the duration.  

Happy Thanksgiving to the forum.  Some great incredibly good football on both Friday and Saturday.  Some great basketball.  Some great food.  And I can run my wood stove instead of my AC!  

[tnweathernut]

Good post Carvers.

Speaking of storms being so close together they can’t amplify.......  I am probably in the minority, but I actually prefer those types of systems for our area.  Just have to get the temperature profile right and then it’s game on with little worry about WAA.  

Give me a blocking to the northeast, a cold high pressing in from the north, and overrunning precip or weak vort passes south of us and I’d take that every time.

Happy Thanksgiving everyone!

[Holston_River_Rambler]

I like the progression of the 12z EPS at 500 mb from hour 192 on. Eastern Canada blocking sliding south, upper low looking to try wobble west and south into Hudson's Bay, not only helping to position and hold the E. Canada blocking, but also helping to increase a Western Canada ridge: https://imgur.com/a/Z0lYJSz 

I almost feel like if I had another panel on Tropical Tidbits, the lowest heights and trough axis would move and consolidate to E. TX.   240 hours+ so I guess we'll see. I like that this is an evolution of a pattern (the model has started to see the new pattern and ingested it), vs a new pattern showing its hand for the first time. 

Established pattern + progression > first look from a distance when dealing with models?

TBH not sure it is established yet, but we're getting close. 

 

 

 

[jaxjagman]

Don't think we've seen the weeklies look like that in A FEW years.It's not bad but it still don't show no AK ridge or for that matter the HP still looks more west into the Aleutians..East Asia shows some change upcoming but still overall Dec looks to be still BN.I like the way the BSR maps looks like heading into Dec with the MJO seems like a warmup before Christmas.Really like after Christmas but overall it dont look bad.Maybe we can get a shot at severe before hand..meh,more deep south is my thinking

[Carvers Gap]

Last night’s Euro Weeklies look a bit conflicted among themselves.  The overall pattern through week three is cold...after that, it is warm through the end of the run into early Jan.  Jax notes of the AK BN heights.  Now, this is not a one time trend...it has been trending this way for a few runs.  Even a few runs of the GEFS do hint at BN heights over AK.  But as we have seen recently, warm-ups are not verifying well, though we get a sneaky one in about a week.  Overall, if you like winter...the Weeklies have something for you.  If you like warm, they have something for you.  Again, there are times that they do not teleconnect well.  That said, a common feature that shows up from week 4 to the end of the run are BN heights over AK and an NAO that is a bit east of where we need it.  Maybe a hint at a return to winter during January...but the next three weeks should be cold.  Again, this is a tough time of the year to get snow IMBY...but maybe we can steal a storm before the (maybe?) thaw in mid December.   The overall question...are they right?  We will know later I guess.

I still have my December at slightly above normal for temps.  I almost changed it, but have not yet.  To be sure, those week three temps(on the Weeklies....week two of Dec)may make it tough to get back to normal or AN. That call has been on very shaky ground...now it is just shaky ground. LOL.  

JB did share that the Canadian Weeklies are cold...so something to maybe balance out the run last night....

As an addendum, the Euro Weeklies also have times where they show almost no cold air (than normal) over the entire northern hemisphere.  That is often a flag that the run has a warm bias.

[Holston_River_Rambler]

Decided to go back and look at some Decembers to remember: 1963, (since some have it as an analogue for this Dec.), Dec 1969 (since Jeff mentioned it may have had a white Christmas), and 2009,(since it worked out well for some).

I went to 

http://meteocentre.com/reanalyses/get_reanalyses.php?lang=en&area=hnord&yyyy=1997&mm=11&dd=20&run=12&mod=ncep 

and made some gifs of the 500 mb patterns and MSLPs:

Edited to include 1953, after reading some raindancewx's and our ENSO discussion. Seems to be some worry about the loss of a Modoki today and Raindancewx liked 1953 as an analogue for this year's Dec. 1953 pattern looks somewhat familiar to what the models are now showing for the first week of Dec. Cutter, cutter....then another cutter. Then we get this for the 13 - 15th December 1953: https://imgur.com/jSwv05K 

1963: https://imgur.com/0rrQW6a  (the whole month since many have used it as an analogue; mostly 6z and 18z snapshots after Dec. 10, but I used 0z and 12z near anything that looked like a storm for the area. Storms around Christmas and New Year)

1969: https://i.imgur.com/c8npZub.gifv (Dec. 20-22)

2009: https://i.imgur.com/MD99suk.gifv (Dec. 17 -19)

 

All very different looks at 500mb.  All got the job done for at least parts of the forum.  I understand that analogues don't mean the same thing will happen again, but thought it couldn't hurt to look.  Mostly inspired by the desire to see how the overall patterns looked and to see if I could see any specific beneficial set up for December storms.  Willing to do more if anyone has dates they want to look at. I did this with the static maps last spring, but these gifs allow us to see the overall flow/ progression over time. 

 

 

 

[Holston_River_Rambler]

What the heck, might as well do some more weak El Nino Decembers:

Dec. 1968: cutters on top of more cutters, especially late month.  Nothing worth make a gif for. Maybe a slight chance that there was something Dec 7 -9 (weak low to our south that eventually cranked up to the NE; some nice blocking in the second half of the month, but not in the best arrangement for our area (example: https://imgur.com/a/8487tri)

Dec. 1976: looked cold overall. a couple of lows to our south and massive blocking (https://imgur.com/Xd1DJLt) at the end of the month initiated by a storm which took a favorable track for us: https://imgur.com/a/vEqRLBL 

Dec. 1978: cutter cold, cutter cold, until mid month when some big blocking began to develop: https://imgur.com/a/iyrZwDi  Sadly no lows to our south that I could see across the Gulf coast or in the Gulf, but it looked like the cold came late month and early Jan 1978. 

 

 

 

[jaxjagman]

Some differences in the AAM,the analogs tho using NDJ of the GEFS bias corrected sorta and kinda resemble what the Euro weeklies look like with heights above in the Western Aleutians and not near the AK region.The composite maps are when the AAM IS -1 and below

Credit:Snowy Hibbo for the AAM composite plots for NDJ

[jaxjagman]

Don't mind this look into late Nov.-Dec.Once again this is biased GEFS which does not like phase 2 until it figures it out later.Same with the Euro into phase 6,we discussed this last fall-winter

[Holston_River_Rambler]

I agree with the MJO. If I remember correctly, models change their tune as we rotate through the MJO phases. Maybe because of base state programming to take into account this type of forcing?  7 - 1 (maybe 2 depending on the situation) are the cold/ favorable phases for Dec. for us.  We'll see if long range solutions start to change as we get into those phases. I also think there is a delay between a favorable state and its result for us. 

I think we're looking at cutters, but maybe even a chance for some sneaky follow up energy until the 10th onward. Then a trough is cut out and we'll see what we get.  Wouldn't be surprised to see what we saw last year at this time: front over some part of the south or our area, but this time with a different ENSO state. I REALLY like that gulf lows seem to want to develop this fall, maybe that changes the result. 

Looking like maybe some quick but squally upslope after this Monday-Tuesday system as a second vort. trails the main one.  It will depend on how much it digs. 

[jaxjagman]

Prognostic Discussion for Week 3-4 Temperature and Experimental Precipitation Outlooks 
NWS Climate Prediction Center College Park MD 
300PM EST Fri Nov 23 2018 

Week 3-4 Forecast Discussion Valid Sat Dec 08 2018-Fri Dec 21 2018 

The Weeks 3-4 outlook is issued against the backdrop of an especially uncertain ENSO base state for this time of year. So far there has been little in the way of convective coupling with above-normal SSTs over the central Pacific, suggesting ENSO teleconnections might not be readily observed as we head into December. The MJO has remained active over the past few weeks with the enhanced phase now over the West Pacific. This broadly favors below-normal temperatures over much of the central and eastern CONUS during Weeks 2-4. The dynamical model guidance is in good agreement on continued eastward propagation of the MJO signal over the next two weeks, with the enhanced phase emerging over the Indian Ocean during early December. This would favor a change toward a milder pattern over east-central North America, but at the very end of this period and thereafter. 

The dynamical model forecasts from the CFS and ECMWF are in very good agreement overall. An anomalous 500-hPa ridge is forecast over the North Pacific near the Date Line, with a downstream trough-ridge pattern over Northeast Pacific and central North America. The forecast -NAO/AO pattern over the next one to two weeks is largely gone in the operational ensemble means for Weeks 3-4, replaced with the aforementioned pattern that would be milder than normal especially over the central CONUS. The ECMWF shows the NPO/WP pattern trending toward the positive phase for the period, which would tend to favor warmer-than-normal temperatures over much of the CONUS. The experimental SubX guidance is similar to the operational guidance, but maintains larger negative height anomalies over the Northeast and a colder solution over the eastern CONUS. The official temperature outlook relies heavily on an objective consolidation of statistical guidance (that includes trends, ENSO, and MJO) and the operational dynamical models, with some tilt toward the colder SubX pattern. Above-normal temperatures are favored over much of the northern and central CONUS, with below-normal temperatures favored over the Northeast and Mid-Atlantic. An expected buildup of snow over the next two weeks, along with the calibrated ECMWF forecast, lead to below-normal temperatures favored over parts of the central and southern Rockies. Models are in excellent agreement with respect to below-normal temperatures over northern Alaska. 

The precipitation outlook has broad coverage and low probabilities, emphasizing inferred patterns of vertical motion from the super-synoptic circulation pattern. Forecast troughing off the West Coast favors above-normal precipitation over the Northwest and parts of northern California. A large swath of the central and northern CONUS is favored to have below-normal precipitation near and downstream of the anomalous ridge axis. Above-normal precipitation over the Southeast is favored due to an expected frontal zone and is a prominent feature in nearly all the dynamical solutions. 

Given persistent above-normal SSTs in the vicinity of Hawaii, above-normal temperatures are also favored across the islands, though probabilities are more modest for the western islands. Dynamical models suggest enhanced rainfall especially over the eastern islands, but this is in part offset by the low-frequency state that would tend to favor drier conditions with time. 

[Daniel Boone]

14 hours ago, Holston_River_Rambler said:

What the heck, might as well do some more weak El Nino Decembers:

Dec. 1968: cutters on top of more cutters, especially late month.  Nothing worth make a gif for. Maybe a slight chance that there was something Dec 7 -9 (weak low to our south that eventually cranked up to the NE; some nice blocking in the second half of the month, but not in the best arrangement for our area (example: https://imgur.com/a/8487tri)

Dec. 1976: looked cold overall. a couple of lows to our south and massive blocking (https://imgur.com/Xd1DJLt) at the end of the month initiated by a storm which took a favorable track for us: https://imgur.com/a/vEqRLBL 

Dec. 1978: cutter cold, cutter cold, until mid month when some big blocking began to develop: https://imgur.com/a/iyrZwDi  Sadly no lows to our south that I could see across the Gulf coast or in the Gulf, but it looked like the cold came late month and early Jan 1978. 

 

 

 

77-78  was snowiest winter I've recorded here in Lee County. 72 inches. 4 inches fell Christmas day. However, it didn't start until early afternoon. There was already snowcover in shady areas since around the 10th. 

[Holston_River_Rambler]

2 hours ago, Daniel Boone said:

77-78  was snowiest winter I've recorded here in Lee County. 72 inches. 4 inches fell Christmas day. However, it didn't start until early afternoon. There was already snowcover in shady areas since around the 10th. 

Looking at December 77 at 500mb it looks like a wild month. Looked cold at the beginning, then a short flip to mild, then a flip back to cold just before Christmas.  Around the 10th there was a 1049mb High dropping down from the Dakotas.  Looks like there could have been a nice clipper that swung through on Christmas. I am am only able to see the map at 500mb with MSLP, so there is probably a lot of the specific details at the surface I'm missing.