Winter 2014-2015 Medium-Term Discussion

[coh]

Amazing amount of variability on the long range forecasts lately. Anyone who thinks they've got a handle on how the rest of the winter will play out is fooling themselves.

 

Don, thanks for your posts and explanations...very helpful to those of us who haven't kept up with the science of long range prediction, teleconnections, etc (and are trying to catch up).

 

Chris

[donsutherland1]

Another illustration of the uncertainty that exists in the medium-term.

 

 

With the model guidance lurching wildly from one idea to another, it makes sense to wait until the picture becomes a bit clearer. With respect to the above possible event, an accumulating snowfall in Philadelphia is probably as likely as an all rain event. The lack of run-to-run continuity suggests avoiding making a call on the precipitation type at this point in time.

[Whitelakeroy]

Merry Christmas Don.  Thanks for that lump of coal in my stocking ... 

 

Great write up.  I was in the UP @ MTU during that crappy winter of 91-92.  I believe we will end up with a better winter than 91-92.

 

Nothing more humbling than the weather can be to use weather geeks.

[donsutherland1]

Merry Christmas Don.  Thanks for that lump of coal in my stocking ... 

 

Great write up.  I was in the UP @ MTU during that crappy winter of 91-92.  I believe we will end up with a better winter than 91-92.

 

Nothing more humbling than the weather can be to use weather geeks.

Thanks and have a great Christmas (or Hanukkah, depending which one you celebrate). Technically, as I still hold to a cold January and February, I haven't delivered the coal just yet. Like you, I don't think this winter will be anything close to a 1991-92 horror.

[michsnowfreak]

Merry Christmas Don.  Thanks for that lump of coal in my stocking ... 

 

Great write up.  I was in the UP @ MTU during that crappy winter of 91-92.  I believe we will end up with a better winter than 91-92.

 

Nothing more humbling than the weather can be to use weather geeks.

1991-92 was actually not a bad winter here in SE MI like it was out east. It was mild, but with several good snowstorms, actually finishing the season with a normal (actually SLIGHTLY above normal) snowfall of 43.5" at DTW. It included a snowstorm (Jan 14th) that is about as good a storm as you can get here (tremendous snowfall rates, thunder & lightning). Actually, that winter is what several of our SE MI posters in some of our recent brutal winters have claimed that would be their dream winter. Several big snowstorms/periods of winter, but several nice periods in between, not sustained cold.

[jbcmh81]

So what happened to the October snow cover doing its thing? 

[Absolute Humidity]

Perhaps Nuri blew up winter before it had a chance to begin 75 76 style. The raging -QBO pretty much kills any chance of an average -NAO. As for Cohen, he's no more bullet proof than Madden-Julian and with two major AO back to back busts looking possible, SAI SCE become just another mediocre tool in the limited and somewhat dysfunctional toolbox of long range meteorology. We'll see.

[JBG]

As the calendar advanced toward spring, winter finally tried to awaken from its all too long slumber. Days were now growing longer and winter’s opportunities were dwindling fast. The East Coast witnessed cold anomalies and above normal March snowfall. But that late and regionally-limited rally could not salvage what had once appeared to have been a promising winter back in November. For those who are interested, that winter was 1991-92.

 

Are we in the early stages of a replay of this nightmare? Certainly, the latest AO forecasts are extremely frightening. For now, though, it’s still a little premature to make that call and I’m not yet ready to give up on the still young winter of 2014-15. But one can no longer deny the reality that a warm winter has now rudely barged into the realm of possibility. Still, the El Niño this time around is weaker than it was in 1991-92. Perhaps, that detail will prove crucial in the longer-run.

 

To all, enjoy the rest of Hanukkah, have a great Christmas and New Year.

Didn't 1971-2, 1972-3 and 2001-2, all with very different ENSO states behave similarly?

[InstantWeatherMaps]

Don't write off winter just yet...

 

[donsutherland1]

Didn't 1971-2, 1972-3 and 2001-2, all with very different ENSO states behave similarly?

Yes, but for a variety of reasons. I still do not think a 1991-92 style nightmare is likely.

[GaWx]

Yes, but for a variety of reasons. I still do not think a 1991-92 style nightmare is likely.

 

 I also don't expect a 1991-2 warmth repeat. However, that winter interestingly featured a 5" snowstorm at Atlanta 1/18-9, which gave them 250% of their total seasonal average. The warm winter of 2001-2 was similar in that there was one 4.6" snowstorm 1/2-3. Moral of the story: sometimes an otherwise lackluster winter (warm) has produced impressive snow down in the south due to just one snowstorm sneaking in at just the right time.

[cbmclean]

Don,

 

I am a semi-educated layman who usually keeps his mouth shut and lets the professionals discuss.  There is something which really has me curious, however.  I have been reading some of your posts about extreme volatility in the medium and long term forecast tools.  Do you have any idea as to the source of this volatility? 

 

From my understanding, the models are fundamentally giant calculators which take input data and solve a giant field of differential equations.  Why do the models sometimes give stable results some weeks out and othertimes not.  Is it because the input data itself is unstable?    

[stadiumwave]

I think all this cancel winter talk to wedded to the models & impatient winter lovers.MJO forecast seems to scaring everyone but I'm not sure why since verification of MJO forecast the last few months has been awful. Models are already now showing a very weak wave when everyone already sunk their teeth into the large wave.

2nd stratospheric signs look great...relax.

[Powerball]

1991-92 was actually not a bad winter here in SE MI like it was out east. It was mild, but with several good snowstorms, actually finishing the season with a normal (actually SLIGHTLY above normal) snowfall of 43.5" at DTW. It included a snowstorm (Jan 14th) that is about as good a storm as you can get here (tremendous snowfall rates, thunder & lightning). Actually, that winter is what several of our SE MI posters in some of our recent brutal winters have claimed that would be their dream winter. Several big snowstorms/periods of winter, but several nice periods in between, not sustained cold.

 

The one thing about the Jan. 14th, 1992 snowstorm, being that it ran the spine of the Apps. and tracked over Erie, PA, is that the NW suburbs probably were "screwed" by it. It was more so an eatside special...

[Harry]

The one thing about the Jan. 14th, 1992 snowstorm, being that it ran the spine of the Apps. and tracked over Erie, PA, is that the NW suburbs probably were "screwed" by it. It was more so an eatside special...

 

No.. KBTL got 7.8" from that storm. BTW.. It came up from the sw across Ohio ( near Columbus ) to Erie.

[JBG]

Yes, but for a variety of reasons. I still do not think a 1991-92 style nightmare is likely.

My point is that other setups than 1991-2 can create a rump of a winter in late February-March when the sun angle and other factors make a real winter unlikely. 1955-6 and 1992-3 was really the only ones I can think of where a blah winter effectually came to life at the end.

[Powerball]

No.. KBTL got 7.8" from that storm. BTW.. It came up from the sw across Ohio ( near Columbus ) to Erie.

 

That's interesting then. Wouldn't normally expect snows to get that far NW with a track so far east (I think you all typically need the low to track to Sandusky from around Memphis?).

[Harry]

That's interesting then. Wouldn't normally expect snows to get that far NW with a track so far east (I think you all typically need the low to track to Sandusky from around Memphis?).

 

Depends on the system but yeah that is normally the favored track and or in that area from Toledo to the west side of Cleveland.. Columbus is usually a good fail/safe line if coming from the wsw/sw/ssw/s..

[uncle W]

My point is that other setups than 1991-2 can create a rump of a winter in late February-March when the sun angle and other factors make a real winter unlikely. 1955-6 and 1992-3 was really the only ones I can think of where a blah winter effectually came to life at the end.

91-92 had two snowstorms between March 18th and 22nd...1972-73 and 1997-98 had a measurable snowfall on March 22nd...They had five measurable snowfalls between them for the entire two winters in KNYC...so far NYC has two this season...If this winter is going to have above normal snowfall it better have a good ending...February or bust...

[donsutherland1]

Several morning thoughts:

 

1. The ensemble members continue to diverge quite a bit when it comes to the AO forecast for the first 10 days of January. One cluster takes the AO to around +1.5 before forecasting a decline. A few members from that cluster ultimately take the AO to or below -2. However, a second cluster takes the AO to +2 to +4 before forecasting a decline. If those members of the first cluster that take the AO to or below -2 are correct, that could be a strong hint that January will be a predominantly blocky month. If, however, the second cluster is correct, blocking will likely be tough to come by.

 

Since 1950, there were 9 cases in which the AO stood between +1.5 and +2.5 in the 12/20-25 timeframe (as it did this year) and then fell to between -1 and 0 in the 12/26-30 timeframe (where it currently is). 6 cases saw the AO fall to -1.5 or below without having ever reached +2.0 during the 1/1-10 timeframe. Those cases had a median of 23.5 days where the AO was negative (mean was 23.8 days) and median of 15 days where it was -1.0 or below (mean was 15.8 days).

 

In contrast, there were 2 cases where the AO rose to +2 or above during the 1/1-10 timeframe from that set of 9 cases. The median and mean number of days in January during which the AO was negative was 4.5. The mean and median number of days on which it was -1 or below was 2.5.

 

Given the large ensemble spread and lack of sudden stratospheric warming events (weak events in which a narrow slice of the stratosphere warms don't qualify as SSWs and none are shown on the guidance at this time) that have little chance of displacing or splitting the polar vortex, a statistical analysis may provide insight. The caveat is that the sample size and subsets are small.

 

In short, the AO's evolution in coming days could provide a powerful clue as to what lies ahead.

 

2. Were the strongly positive AO to verify, and were the past cases to be representative, the probability of a predominantly positive winter (DJF) AO could increase markedly. If so, this could mark the second consecutive winter that both the OPI and SAI failed to provide good insight. If so, perhaps a variable that accounts for Eurasian snow tendency during the closing week or two of October)--snow cover had fallen by the end of the month from an earlier peak this year--might add value to the overall index. More worrisome, perhaps the earlier strong scores were more, in part, the result of sample size and that the actual relationship might be at least somewhat weaker.

 

3. On the positive side, the EPO is forecast to fall strongly negative in coming days and then remain predominantly negative through the next 15 days. Periodic runs of the operational GFS have brought some of the Arctic air into the U.S. That scenario would be more likely than a warmer one if the first cluster of ensemble AO forecasts noted in point #1 proves accurate.

[GaWx]

Several morning thoughts:

 

1. The ensemble members continue to diverge quite a bit when it comes to the AO forecast for the first 10 days of January. One cluster takes the AO to around +1.5 before forecasting a decline. A few members from that cluster ultimately take the AO to or below -2. However, a second cluster takes the AO to +2 to +4 before forecasting a decline. If those members of the first cluster that take the AO to or below -2 are correct, that could be a strong hint that January will be a predominantly blocky month. If, however, the second cluster is correct, blocking will likely be tough to come by.

 

Since 1950, there were 9 cases in which the AO stood between +1.5 and +2.5 in the 12/20-25 timeframe (as it did this year) and then fell to between -1 and 0 in the 12/26-30 timeframe (where it currently is). 6 cases saw the AO fall to -1.5 or below without having ever reached +2.0 during the 1/1-10 timeframe. Those cases had a median of 23.5 days where the AO was negative (mean was 23.8 days) and median of 15 days where it was -1.0 or below (mean was 15.8 days).

 

In contrast, there were 2 cases where the AO rose to +2 or above during the 1/1-10 timeframe from that set of 9 cases. The median and mean number of days in January during which the AO was negative was 4.5. The mean and median number of days on which it was -1 or below was 2.5.

 

Given the large ensemble spread and lack of sudden stratospheric warming events (weak events in which a narrow slice of the stratosphere warms don't qualify as SSWs and none are shown on the guidance at this time) that have little chance of displacing or splitting the polar vortex, a statistical analysis may provide insight. The caveat is that the sample size and subsets are small.

 

In short, the AO's evolution in coming days could provide a powerful clue as to what lies ahead.

 

2. Were the strongly positive AO to verify, and were the past cases to be representative, the probability of a predominantly positive winter (DJF) AO could increase markedly. If so, this could mark the second consecutive winter that both the OPI and SAI failed to provide good insight. If so, perhaps a variable that accounts for Eurasian snow tendency during the closing week or two of October)--snow cover had fallen by the end of the month from an earlier peak this year--might add value to the overall index. More worrisome, perhaps the earlier strong scores were more, in part, the result of sample size and that the actual relationship might be at least somewhat weaker.

 

3. On the positive side, the EPO is forecast to fall strongly negative in coming days and then remain predominantly negative through the next 15 days. Periodic runs of the operational GFS have brought some of the Arctic air into the U.S. That scenario would be more likely than a warmer one if the first cluster of ensemble AO forecasts noted in point #1 proves accurate.

Don,

1) Are you sure last year's SAI failed to provide much insight? I'll need to recheck my own analysis in case I'm not recalling correctly, but I kind of thought the SAI of last year didn't do bad.

2) I had voiced a disappointment and concern about the massive end of month melting in the snowcover thread, but that concern was shot down because the SAI is based on a regression formula rather than a simple increase.

[donsutherland1]

Don,

1) Are you sure last year's SAI failed to provide much insight? I'll need to recheck my own analysis in case I'm not recalling correctly, but I kind of thought the SAI of last year didn't do bad.

2) I had voiced a disappointment and concern about the massive end of month melting in the snowcover thread, but that concern was shot down because the SAI is based on a regression formula rather than a simple average.

GaWx,

 

Check your analysis, as perhaps I'm mistaken, but I believe the AO was not as positive as frequently as implied by the SAI. January had an AO average near -1 with 23 days < 0 and February was near 0 for the monthly average with 11 days < 0. OPI fared much worse.

 

IMO, your point takes on added importance, especially if this winter turns out to be predominantly AO+.

[Harry]

Several morning thoughts:

 

1. The ensemble members continue to diverge quite a bit when it comes to the AO forecast for the first 10 days of January. One cluster takes the AO to around +1.5 before forecasting a decline. A few members from that cluster ultimately take the AO to or below -2. However, a second cluster takes the AO to +2 to +4 before forecasting a decline. If those members of the first cluster that take the AO to or below -2 are correct, that could be a strong hint that January will be a predominantly blocky month. If, however, the second cluster is correct, blocking will likely be tough to come by.

 

Since 1950, there were 9 cases in which the AO stood between +1.5 and +2.5 in the 12/20-25 timeframe (as it did this year) and then fell to between -1 and 0 in the 12/26-30 timeframe (where it currently is). 6 cases saw the AO fall to -1.5 or below without having ever reached +2.0 during the 1/1-10 timeframe. Those cases had a median of 23.5 days where the AO was negative (mean was 23.8 days) and median of 15 days where it was -1.0 or below (mean was 15.8 days).

 

In contrast, there were 2 cases where the AO rose to +2 or above during the 1/1-10 timeframe from that set of 9 cases. The median and mean number of days in January during which the AO was negative was 4.5. The mean and median number of days on which it was -1 or below was 2.5.

 

Given the large ensemble spread and lack of sudden stratospheric warming events (weak events in which a narrow slice of the stratosphere warms don't qualify as SSWs and none are shown on the guidance at this time) that have little chance of displacing or splitting the polar vortex, a statistical analysis may provide insight. The caveat is that the sample size and subsets are small.

 

In short, the AO's evolution in coming days could provide a powerful clue as to what lies ahead.

 

2. Were the strongly positive AO to verify, and were the past cases to be representative, the probability of a predominantly positive winter (DJF) AO could increase markedly. If so, this could mark the second consecutive winter that both the OPI and SAI failed to provide good insight. If so, perhaps a variable that accounts for Eurasian snow tendency during the closing week or two of October)--snow cover had fallen by the end of the month from an earlier peak this year--might add value to the overall index. More worrisome, perhaps the earlier strong scores were more, in part, the result of sample size and that the actual relationship might be at least somewhat weaker.

 

3. On the positive side, the EPO is forecast to fall strongly negative in coming days and then remain predominantly negative through the next 15 days. Periodic runs of the operational GFS have brought some of the Arctic air into the U.S. That scenario would be more likely than a warmer one if the first cluster of ensemble AO forecasts noted in point #1 proves accurate.

 

 

I'll be okay with a -EPO/+AO.. Kinda what we had last winter.

 

I still suspect the EPO plays havoc with the SAI/AO/NAO..

[Ginx snewx]

Don't make the mistake many made last November 13 by overemphasizing the AO and diminishing the EPO #coldtimes

[Harry]

Don't make the mistake many made last November 13 by overemphasizing the AO and diminishing the EPO #coldtimes

 

 

Yep.. Personally i'll take a -EPO any day over a -AO..

[Polar Vortex 2014]

Since it's looking increasingly likely that December 2014 will rank among the top five warmest Decembers on record, I decided to take a look at temperatures in the ensuing January, February and March following top ten warm Decembers. Now, I'm not saying this has any predictive value whatsoever. I was just curious. The results are below.

 

 

 

 

It looks like warm Decembers are typically followed by mild Januaries, especially in the upper Midwest. The ensuing February sand March pattern tends to favor warmth in the west, with cooler anomalies in the east. Note that these maps mask some individual months that featured exceptional cold and/or snow, such as January 1940, February 1934 and March 1958.

[winterymix]

The EURO screams persistence through the first five days of January.

Canadian cold tries to spill south from Canada but the swift west to east

flow has a strong moderating influence.

Persistence seems to be skillful this early mild winter.

[AlaskaETC]

I'll be okay with a -EPO/+AO.. Kinda what we had last winter.

 

I still suspect the EPO plays havoc with the SAI/AO/NAO..

 

Doesn't a -EPO/-NAO go hand in hand though?

[donsutherland1]

I'll be okay with a -EPO/+AO.. Kinda what we had last winter.

 

I still suspect the EPO plays havoc with the SAI/AO/NAO..

It should be noted that during January and February, when the cold was most widespread, 34/59 (58%) days had an AO-.

[donsutherland1]

Don,

 

I am a semi-educated layman who usually keeps his mouth shut and lets the professionals discuss.  There is something which really has me curious, however.  I have been reading some of your posts about extreme volatility in the medium and long term forecast tools.  Do you have any idea as to the source of this volatility? 

 

From my understanding, the models are fundamentally giant calculators which take input data and solve a giant field of differential equations.  Why do the models sometimes give stable results some weeks out and othertimes not.  Is it because the input data itself is unstable?    

It's difficult to pin the uncertainty on any single factor. The magnitude of uncertainty is not dissimilar to what one witnesses during the vernal and autumnal transitions. It will be interesting to see where things wind up down the road.