Winter 2014-2015 Pattern Discussion Thread I

[GaWx]

That's the one!  Make that zr a huge, big rogue sleet, and I'm on board with the analog.  Getting two really good storms one right after the other, is on my bucket list.  I've seen 3, two ok, and one real good, but two or three real good will take some cold air and a split stream lasting a few weeks most likely.  Got an analog for that?  I'm ready....the sleds in the underground lair being hot rodded, the moles are doing the pre winter mole thrum, and I've found a new hill to try.  Meanwhile, I had a 26, and two 27's and it's 42 now, so some cold air for Nov is about.  Just waiting on a disturbance to ride down and do a flurry dance over N Ga.  T

 

 Over the last 138 winters, I counted 56 in Atlanta with at least one major winter storm (40%). I've found 10 winters with 2+ major winter storms or about one every 14 winters (7% of them). So, although infrequent, 2+ majors isn't as rare as some might think. 2 of those 10 winters actually had 3 majors (1.5% of all winters). 4 of those 10 winters were in similar ENSO territory (in or very near weak Nino) to how 2014-5 looks. 1 of those 4 winters actually had 3 majors (1935-6). 5 of the other 6 winters were either neutral negative or weak La Nina. So, weakish ENSO has clearly been more favorable for multiple major winters since that covers 9 of the 10 winters. 2 of my top analogs for 2014-5 are 1884-5 and 1939-40, both of which had 2 majors.

 

I count 3.5"+ of SN, 1.5"+ of IP, or enough ZR to cause widespread outages as majors.

 

 10 Winters with 2-3 majors in Atlanta (7% of them):

 

**1884-5: 2 (ZR/IP combo, SN) (J, F) very cold and very wet winter

   1894-5: 2 (SN, SN) (F, F) very cold but dry winter;

*  1904-5: 2 (ZR, ZR) (F, F) very cold but dry winter

    1917-8: 2 (IP, ZR) (D, J) very cold and near norm precip. winter

*  1935-6: 3 (ZR, ZR, SN) (D, J, J) very cold and very wet winter

** 1939-0: 2 (ZR, SN) (J, J) very cold and near norm precip. winter

    1959-0: 3 (ZR, ZR, SN) (M, M, M) near norm DJF but coldest M ever; wet DJF but near norm M

    1961-2: 2 (SN, ZR) (J, J) near norm temp.'s but cold Jan. and very wet winter

    1978-9: 2 (ZR, IP) (F, F) very cold and near norm precip. winter

    1999-0: 2 (ZR, ZR) (J, J) warm winter overall but J near norm; DF very dry but J near norm precip.

 

* similar ENSO to 2014-5

** 2 of my 4 top analogs for 2014-5

 

 As one can see and would expect, very cold (~3 F or more below normal) dominated, including March of 1960. Even Jan. of 1962 was cold (~2 F below normal). The only noncold exception of these 10 was a near normal Jan. of 2000.

 

 However, precip. was all over the board though having 3 of 10 very wet winters is quite notable. Whereas normal or wet has been better than dry in general, both Feb.'s of 1895 and 1905 produced two major storms with drier than normal total precip. However, they are also the two coldest Feb.'s on record!

 

 What am I thinking for KATL for 2014-5 major winter storm chances (if anyone cares)? Well, as mentioned, 1+ of them have occurred in 40% of winters. However, I'm expecting a very cold KATL winter (say, 3+ colder than normal) due to the expectations of a combo of weak to low end moderate El Nino, solid +PDO, solid -AO, and solid -NAO. Going back to 1950, all 7 Nino's with a DJF averaged -AO lower than -0.9 were 3+ colder than normal. Now, a whopping 69% of very cold winters (18 of 26) had at least one major winter storm. Just looking at the best four analogs (these had a warm October), three of the four (75%) of them had at least one. So, based on these strong odds, I'm now predicting a major winter storm at KATL this winter with a nontrivial chance for a 2nd one. Here's why. Although the chance for 2+ majors is only 7% based on all winters, an impressive 27% of the very cold ones (7 of 26...nice sample size) had 2+ majors...so, four times as high a chance for 2+ majors during a very cold winter. Now, looking at just my top four analog winters (all very cold), an impressive 2 of the 4 (50%) had 2 majors. So, if anything, the true underlying chance may very well be higher than 27% and closer to 50% but the top analog sample is small. The main point is that there appears to be a way above climo chance for two major winter storms this winter at KATL. However, this is still not high enough for me to outrightly predict 2 majors. So, I'm sticking to predicting one but with a decent chance for two. IF there are two majors, I'd expect one to be mainly ZR and the other to be mainly SN and/or IP. IF there is only one, I'm guessing it would be mainly SN. IF there are two majors, I'd expect at least one to be in Jan.

 

 As mentioned, KATL has gotten 2+ majors every 14 years on average. Not that it means much, but it has been 15 winters since the last double (1999-2000). For the fun of it, here are the intervals in years between multiple winter storm winters using the chart I made up above: 10, 10, 13, 18, 4, 20, 2, 17, and 21. So, adding a 15 to the end of that list would seemingly fit in pretty well fwiw.

 

 Even if there is only 1 major, I'm expecting at least two other measurable wintry precip. events at KATL based on analogs and general Nino climo. In other words, I'm expecting at least three measurable wintry precip. events in total.

 

 Even if the first half of Dec. is dominated by mildness, I'd still expect an overall very cold DJF (~3 or more colder than normal). One of the top analogs, 1939-40, reinforces that idea. Also, the cold November gives me even more confidence.

 

So, as superjames would put it, I'm all in for this winter and about as all in as I've ever been for any winter.

[franklin NCwx]

Great post Larry.

[Cold Rain]

yup ! strat warm looking good .

That could be the wild card that keeps December from being +, anomaly-wise. If we do get an early, favorable strat warming, the AO will tank.

[LithiaWx]

That could be the wild card that keeps December from being +, anomaly-wise. If we do get an early, favorable strat warming, the AO will tank.

The article seems to indicate that the warming won't start until at least he first week of December. If I'm correct I rememebr there being a lag between the warming and the splitting of the PV. It's a rather long lag I believe and the warming doesn't guarantee a split unless it's a very aggressive warming, That said we want this on our side and it appears everything regarding the stratosphere is lining up. That said we don't have to have a SSW event to have a great winter either,

[packbacker]

Great post Larry!   For reference on what happened during Nov-Feb of 1939-1940…

 

 

[Cold Rain]

The article seems to indicate that the warming won't start until at least he first week of December. If I'm correct I rememebr there being a lag between the warming and the splitting of the PV. It's a rather long lag I believe and the warming doesn't guarantee a split unless it's a very aggressive warming, That said we want this on our side and it appears everything regarding the starosphere is lining up. That said we don't have to have a SSW event to have a great winter either,

Strongly agree with your last sentence. The strat warming can split or disturb the vortex. Doesn't have to split to facilitate a -AO. I think you're right on the lag. The length of the lag can vary, right?

[packbacker]

6z GFS parallel says what warmup in the 11-15 day period, looks pretty good for winter weather actually, LOL. But, since models are always wrong I guess we toss. JB sounded defeated this morning he is in full backpedal mode, telling his commercial clients the first half of Dec will be warm.

[Cold Rain]

6z GFS parallel says what warmup in the 11-15 day period, looks pretty good for winter weather actually, LOL. But, since models are always wrong I guess we toss. JB sounded defeated this morning he is in full backpedal mode, telling his commercial clients the first half of Dec will be warm.

 

Why would he sound so defeated?  Was he expecting a wall to wall cold December?  Many have been positing that December would start off warm.

 

Forgetting meteorology for a second and just looking at LR model data, they're still shifting around in la la land.  I'm not sure there is a definitive answer on what to expect for the first half of December yet.  A transitional or variable pattern could average either warm or cold.  IMO, there is neither a solid reason to expect a warm first half of December or a cold first half of December other than that it might fit standard Nino climo.  Would you say this year fits standard Nino climo?

[CherokeeGA]

 Over the last 138 winters, I counted 56 in Atlanta with at least one major winter storm (40%).

 

This is a wonderful post, thank you so much for all the effort that went into it.

 

That first sentence alone, quoted above, should help explain to many people why Atlanta tends to do poorly during what seem like mild winter events to outsiders.  When you consider that most elected officials only hold office for 2-4 years, AND you consider that even in the DOT and elsewhere job turnover is not uncommon, AND you realize that we only see a multiple major about once every 14 years, and at most one or two minors per year... it should not surprise anyone that the folks "in charge" do not have the experience to handle winter weather events.  It also helps point out how unrealistic it is to purchase extensive amounts of plows and other equipment for something that might not even occur within the machine's lifetime.  Basically it isn't like Atlanta as a community gets a lot of practice at it.   The average Atlantan will only see 4-5 of these in a lifetime, as you define "major".

 

I'm so tempted to point anyone who cries "you people are so inept, why are you having problems with a few inches of snow?" to your post forevermore.

[Cold Rain]

For comparison, here are 3 different 0z model runs for 240:

 

GFS:

 

 

Parallel GFS:

 

 

Euro:

 

 

Do any of these images give anyone any reason to conclude that the first half of December will be warm?  Cold?  Variable?

 

The parallel GFS pretty much keeps the trough in the east and the ridge on the west through 240, with the exception of the cutter before Thanksgiving.  the Euro at 240 at 12z yesterday had a big SE ridge.  While this run has higher heights over the SE and east, it doesn't scream locked in blowtorch to me.

 

Based on these images, the expectation for December should probably be a variable start with a trend toward cool IF we give any weight at all to standard El Nino climo and a possible strat warming event.

[burgertime]

For comparison, here are 3 different 0z model runs for 240:

 

GFS:

 

GFS240.png

 

Parallel GFS:

 

ParallelGFS240.png

 

Euro:

 

Euro240.png

 

Do any of these images give anyone any reason to conclude that the first half of December will be warm?  Cold?  Variable?

 

The parallel GFS pretty much keeps the trough in the east and the ridge on the west through 240, with the exception of the cutter before Thanksgiving.  the Euro at 240 at 12z yesterday had a big SE ridge.  While this run has higher heights over the SE and east, it doesn't scream locked in blowtorch to me.

 

Based on these images, the expectation for December should probably be a variable start with a trend toward cool IF we give any weight at all to standard El Nino climo and a possible strat warming event.

 

 

I will say this. Looking at models I tend to look to see how much thickness is sagging down across Canada and how far east it is getting. It's usually a good indicator of the PV coming down or of just a general colder look in the east. On the last frame of the Euro you see this coming south from Ontario.  Again this pattern really reminds me of last year in the LR. You would have model madness in the LR with almost none of them agreeing. All would do wild flips to warm then to cold and back again. I'll reserve judgement for when we get to Thanksgiving...but I already get the feeling they are almost pointless to look at. 

[BullCityWx]

That euro run looks alot like what happened this week. Big upper midwest storm drags down huge arctic blast. 

[Cold Rain]

I will say this. Looking at models I tend to look to see how much thickness is sagging down across Canada and how far east it is getting. It's usually a good indicator of the PV coming down or of just a general colder look in the east. On the last frame of the Euro you see this coming south from Ontario.  Again this pattern really reminds me of last year in the LR. You would have model madness in the LR with almost none of them agreeing. All would do wild flips to warm then to cold and back again. I'll reserve judgement for when we get to Thanksgiving...but I already get the feeling they are almost pointless to look at. 

 

This is a really good post and I am glad you mentioned the cold in Canada.  That was one thing that stuck out to me too.  If you run the animation (and it's kind of coarse with the 24 hr Euro), you can kind of see the cold migrating south and east in Canada.  Again, like you said, I don't know if it's correct.  But it is encouraging to see Canada so cold.  Even in a variable pattern, it won't take much to tap it and bring it down.  Whether we get an early snow or not is pointless to debate right now, but frequent cool downs or cold shots would possibly be able to offset any warm-ups that take place.

 

Edit: You can also see another block forming in the EPO region (at least I think I'm looking at that correctly).  And heights are higher near the Pole.  I would still like to see a hint of blocking in Greenland, but we may be too early for that yet.

[packbacker]

Why would he sound so defeated? Was he expecting a wall to wall cold December? Many have been positing that December would start off warm.

Forgetting meteorology for a second and just looking at LR model data, they're still shifting around in la la land. I'm not sure there is a definitive answer on what to expect for the first half of December yet. A transitional or variable pattern could average either warm or cold. IMO, there is neither a solid reason to expect a warm first half of December or a cold first half of December other than that it might fit standard Nino climo. Would you say this year fits standard Nino climo?

Defeated may not be the best word, more of a darn we are not going to get a wall to wall cold. I think there has been plenty of nino's that have cold Dec and warm Dec. 2009/10 didnt flip till 2nd half of Dec. The good news is there is storm after storm being shown on the models, we need to keep that going into Jan.

Edit: personally I could care less if the first 3 weeks of Dec is warm. The stratosphere and continuing enso warming is more important. Would be nice if we could get stay as warm as possible, we do much better in mod nino's.

[Bob Chill]

I'm surprised JB is singing a warm tune for the first half of Dec. There is simply no way to be definitive about anything that far out. It's been exceptionally choppy lately on LR ensembles over the last few days. It's a very uncertain period down the line. The "big relaxation" keeps moving out in time every day. It brings back memories of last winter when the repetition seemed unstoppable. LR stable warm patterns on the models never materialized. Not one single time. And there were plenty.

My wag right now is an extended period of riding a see-saw but having our source region remain below normal means that any cold shot has the ability to be pretty cold. Even if it only lasts for a few days. Same with the warm ups in advance of fronts. Short lived. I think we can all live with that.

One of the mets in our subforum made a great post this morning:
 

Typical model bias and something worth noting. When I looked at the 6z Xbox GFS and the ENS, I thought I was looking at a 3 day old model run. Looks like a pretty -AO until the last few frames of the run. Greenland stays very torchy. However, the high heights over Alaska seem pretty locked in even on the EPS, which has an overall slight improvement in the LR versus the last 3 runs or so.

A true pattern reload is inevitable in the next 2.5 weeks IMO and one could argue you'd like to have it the first few days of December rather than having it punted to December 6-7th.

Right now the scandinavian ridge is modeled to push all the way into Greenland during the d11-15 range. This will help fight off a SE ridge even. The Aleutian ridge could very well extend N of AK as well and we go back to a -epo. Without a more classic block in place our wx patterns will be progressive but plenty of cold to be tapped.

I really don't know which way things will break going into Dec but JB calling for warm seems at risk IMO.

 

ETA: The GEFS has done awful in the 14 day range with the AO since the first big drop in Oct. It's completely missed all the big drops at long leads and has consistently been modeling the index to rise too fast and too much late in the cycle. Verification hasn't busted high with any significance in over 6 weeks. It's been AOB the mean for quite some time. 

 

[JoMo]

JB's call for warmer for a brief period is based on the MJO forecast (forecast to go through 3 & 4) and some of the 'pull back' analogs, I believe. Looking at the 00z Euro Ensemble vs control. They are like night and day. So I'd say there's probably a large amount of spread in the ensembles themselves.

[POWERSTROKE]

I'm surprised JB is singing a warm tune for the first half of Dec. There is simply no way to be definitive about anything that far out. It's been exceptionally choppy lately on LR ensembles over the last few days. It's a very uncertain period down the line. The "big relaxation" keeps moving out in time every day. It brings back memories of last winter when the repetition seemed unstoppable. LR stable warm patterns on the models never materialized. Not one single time. And there were plenty.

My wag right now is an extended period of riding a see-saw but having our source region remain below normal means that any cold shot has the ability to be pretty cold. Even if it only lasts for a few days. Same with the warm ups in advance of fronts. Short lived. I think we can all live with that.

One of the mets in our subforum made a great post this morning:

 

Right now the scandinavian ridge is modeled to push all the way into Greenland during the d11-15 range. This will help fight off a SE ridge even. The Aleutian ridge could very well extend N of AK as well and we go back to a -epo. Without a more classic block in place our wx patterns will be progressive but plenty of cold to be tapped.

I really don't know which way things will break going into Dec but JB calling for warm seems at risk IMO.

 

ETA: The GEFS has done awful in the 14 day range with the AO since the first big drop in Oct. It's completely missed all the big drops at long leads and has consistently been modeling the index to rise too fast and too much late in the cycle. Verification hasn't busted high with any significance in over 6 weeks. It's been AOB the mean for quite some time. 

 

AO14day.GIF

He isn't backing up.  He has said for a while that first part of December could be warm.  He did say no need to panic

[LithiaWx]

Who at this point is calling for a cold and stormy first half of December?  Nobody?

[Bob Chill]

He isn't backing up.  He has said for a while that first part of December could be warm.  He did say no need to panic

 

Ah, gotchya. I don't read JB's stuff. Just pick up bits and pieces from the forum. So he'll be backing up when the arctic hounds come screaming in a pack during the first week of the month then. 

[nflwxman]

Who at this point is calling for a cold and stormy first half of December?  Nobody?

I think the bigger key is when the relaxation of the pattern commences and how long it ends up being.  There certainly doesn't appear to be any significant signal to suggest a SJS throttle down or an overly dry period.  Temperatures are certainly up in the air at this point, but seasonal and transient seems like a good bet (which is not a snow heavy pattern in these parts).  Like Bob said above, the first 2 weeks of December would be "bonus" winter in these parts as climo is not quite there for snow.

 

While there is likely to be a solid period of + or neutral AO, if the ensembles keep punting a relaxation (which was a prevalent occurrence last year), then all bets may be off in a few short weeks, IMO.  A lot of mets, including JB, might have to reevaluate if that comes to pass.

[LithiaWx]

I think the bigger key is when the relaxation of the pattern commences and how long it ends up being.  There certainly doesn't appear to be any significant signal to suggest a SJS throttle down or an overly dry period.  Temperatures are certainly up in the air at this point, but seasonal and transient seems like a good bet (which is not a snow heavy pattern in these parts).  Like Bob said above, the first 2 weeks of December would be "bonus" winter in these parts as climo is not quite there for snow.

 

While there is likely to be a solid period of + or neutral AO, if the ensembles keep punting a relaxation (which was a prevalent occurrence last year), then all bets may be off in a few short weeks, IMO.  A lot of mets, including JB, might have to reevaluate if that comes to pass.

 

Agreed, seasonal and transient won't get it done in December in this part of the country either.  I'm looking forward to blocking and amplification hopefully coming about in the second part of December and onward.

[nflwxman]

Agreed, seasonal and transient won't get it done in December in this part of the country either.  I'm looking forward to blocking and amplification hopefully coming about in the second part of December and onward.

While this is the expectation, pattern persistence is powerful.  Don't be surprised if the first half of December turns out to have an even slightly negative departure or a messy event or two (more likely NC and north).  Even the unlucky catch a few breaks now and then.

[BullCityWx]

The control member of the euro ensemble drives down two formidable cold shots in the next 16 days. 

[BullCityWx]

While this is the expectation, pattern persistence is powerful.  Don't be surprised if the first half of December turns out to have an even slightly negative departure or a messy event or two (more likely NC and north).  Even the unlucky catch a few breaks now and then.

 

Yep. There's -35C air in central canada thats going to follow that cutter on the 0z euro too. Almost looks like what we just went through.

[tnweathernut]

Funny that DT was going warm the first of December, then he flipped to cold. At about the same time JB was going cold and flipped warmer till mid December. Peeing contest perhaps?

[GaWx]

Great post Larry!   For reference on what happened during Nov-Feb of 1939-1940…

 

1) Franklin and Packbacker, thanks!

2) Packbacker, thanks for posting the Nov-Feb. 1939-40 maps. So, to review what he posted, Nov. was cold in the SE but then Dec. was near normal in the SE (with the first half warmer than normal and last part colder than normal) and was quite warm in much of the rest of the U.S. Then the Jan-Feb. period was very cold, highlighted by the frigid Jan. I'll add one more, October. Oct. of 1939 was warm in the SE (and much of the E U.S.) as per this map (the warm Oct. of 1939 was one of four wintry (precipwise at least in/near ATL) ENSO analogs with a warm SE Oct., the reason I was pulling for a warm Oct.). Oct.-Nov. of 2014 are turning out to be fairly similar to Oct.-Nov. of 1939 in much of the E US:

 

 

Repost of packbacker's Nov. of 1939 map:

 

Repost of Dec. of 1939: (I'm not predicting it to be mild but in case it starts off that way)

 

Jan. of 1940: FRIGID!

[BullCityWx]

Funny that DT was going warm the first of December, then he flipped to cold. At about the same time JB was going cold and flipped warmer till mid December. Peeing contest perhaps?

 

I have never known DT to get into any sort of pissing contest. ever. 

[snowlover91]

12z Parallel GFS at hour 240 says what warmup?

[superjames1992]

Speaking of 1940, I believe it flurried in Raleigh on May 2, 1940.

[NCSNOW]

Imo December,like November, will have a negative temp departure compared to normal espeacilly in my neck of the woods Greensboro area. Maybe not as extreme espeacilly since our daily normals start to come down pretty significantly starting the last week of November. I'm betting the pattern we have been in now since November 1st until it breaks. The cold shots are transient but they will just keep on coming down and their the real deal, none of this bleeding in over the apps mess. Observe what's happening up near Alaska, it's wash rinse repeat. When things actually change, not long range model wise, but verify differently on a consistent basis up there, then and only then will I beleive a new pattern is emerging or shaking up differently.