How Important is December Snowfall?

[nzucker]

We don't need the jet to migrate farther south.. we just had a long period of suppression by a too dominant -NAO. But yeah.. if the -NAO sticks around we will cash in eventually

SNE will do fine eventually (average to slightly above) if we continue with a strong -NAO block despite the mediocre Pacific. It's really a problem down here, though, Andrew....70-71 had a very -NAO and we still saw very little snow in NYC metro despite the Atlantic appearing favorable for big events. It's just so hard for us to get significant snowstorms in a strong La Niña...there was an incredible gradient that year with 20" snowfall around here and 140" in Burlington, VT. Even 55-56, our most famous strong La Niña winter, only had 33" in Central Park despite an amazing stretch of snow and cold in March.

Dec '88 had a +NAO...and the rest of the winter had an obscene +NAO...I think that was the most +NAO/AO winter on record.

The NAO/AO tendency has me feeling a lot better about avoiding a repeat. I don't even think this month will be bad despite a frustrating start. We should cash in at some point.

Yes, it was the most +NAO/+AO on record and had widespread consequences for Arctic sea ice patterns like the disintegration of the Beaufort Gyre which was probably due to both the +AO and some global warming. I don't think we're going to do as badly as that year, I mean heck Boston only had like 17" of snow, but I'm not loving how this December seems so dry with the only precipitation coming in the form of cutting rainstorms. I like some of the longer-range threats but it's hard to trust the models which have been all over the place lately.

[skierinvermont]

SNE will do fine eventually (average to slightly above) if we continue with a strong -NAO block despite the mediocre Pacific. It's really a problem down here, though, Andrew....70-71 had a very -NAO and we still saw very little snow in NYC metro despite the Atlantic appearing favorable for big events. It's just so hard for us to get significant snowstorms in a strong La Niña...there was an incredible gradient that year with 20" snowfall around here and 140" in Burlington, VT. Even 55-56, our most famous strong La Niña winter, only had 33" in Central Park despite an amazing stretch of snow and cold in March.

There's such a small sample size of La Ninas with a -NAO I don't think you really can know what would occur in the Mid-Atlantic

[ORH_wxman]

There's such a small sample size of La Ninas with a -NAO I don't think you really can know what would occur in the Mid-Atlantic

Its hard for south of NYC to do well in any pattern that favors northern stream dominance. Even with a -NAO, it will be hard for the M.A. to do very well. There's obviously exceptions and maybe this year will be one of them. But even in a -NAO winter, you'll get a lot of northern stream systems that redevelop into Miller Bs or SWFEs that redevelop S of LI....screwing areas south of that.

If we can pop a couple +PNA patterns in tandem with the -NAO, then the M.A. will def have more of a chance to cash in on a KU...or KU-like storm.

[nzucker]

There's such a small sample size of La Ninas with a -NAO I don't think you really can know what would occur in the Mid-Atlantic

Yeah it's pretty rare to have a -NAO with a strong La Niña so it's hard to tell....both 1903-04 and 1916-17 were moderate/strong Niñas with a very -NAO index if we can trust the data from back then. Both were impressive winters in NYC metro, with 50" or so falling and very cold temperatures. We just haven't cashed in big with a strong Niña in so long I'm pretty doubtful....54-55 was a disaster, 55-56 was good but not a blockbuster, 73-74 was OK, 75-76 sucked, 88-89 sucked, 98-99 sucked, 99-00 sucked. None of these winters were good for DCA. Of course many of those winters sucked because of the lack of a -NAO block, which we definitely have this year. 88-89 had the most positive NAO on record.

I was pretty steadfast in my winter forecast that the NAO would average negative this year against HM and other mets, and I still am clinging to that idea. We're going to average such a -NAO in December that it will be hard to be positive for DJF, and I think it will carry on for a while before finally moderating in late January or early February. This is like the lamp that never burns out; the models try to break down the block and mets explain why it might weaken, but then it builds back into a 5SD blocking pattern. I never could have predicted such a -NAO in a strong La Niña, however. I am starting to think I should have gone a bit colder overall in the East in the winter forecast, but we'll see.

[skierinvermont]

Its hard for south of NYC to do well in any pattern that favors northern stream dominance. Even with a -NAO, it will be hard for the M.A. to do very well. There's obviously exceptions and maybe this year will be one of them. But even in a -NAO winter, you'll get a lot of northern stream systems that redevelop into Miller Bs or SWFEs that redevelop S of LI....screwing areas south of that.

If we can pop a couple +PNA patterns in tandem with the -NAO, then the M.A. will def have more of a chance to cash in on a KU...or KU-like storm.

OK yes it is harder w/o the STJ.. but it is hard to weight the two factors. Certainly a -NAO nina is better for them than a +NAO, and we don't really have the stats to know if it favors above or below average.

[nzucker]

OK yes it is harder.. but it is hard to weight the two factors. Certainly a -NAO nina is better for them than a +NAO, and we don't really have the stats to know if it favors above or below average.

I disagree with this...we had a very -NAO in 54-55, 55-56, and 70-71...none of these winters were kind to the DCA/BWI crew. The jet just isn't there to produce snow.

[ORH_wxman]

OK yes it is harder.. but it is hard to weight the two factors. Certainly a -NAO nina is better for them than a +NAO, and we don't really have the stats to know if it favors above or below average.

Yeah the sample size of a -NAO in moderate or stronger Ninas is so low as to kill any realistic confidence. But the pattern in Ninas regardless of the NAO is still northern stream dominated.

That favors a lot of clippers, Miller Bs, and SWFEs. None of which are very favorable for the M.A. You can still get a northern stream system to dig enough though and get the M.A. if the ridging out west is good.

For New England, we don't care about the PAC side ridging as much when the NAO is negative...we just want systems to come east be forced to redevelop or slide under LI.

[skierinvermont]

I disagree with this...we had a very -NAO in 54-55, 55-56, and 70-71...none of these winters were kind to the DCA/BWI crew. The jet just isn't there to produce snow.

I don't think 3 is big enough to say really.

In 2 of those 3 DC was not that far below average and the snow fell in the months that had a -NAO but not in the +NAO month. Only 1 of the years was a dud ('54-55).

Then there is 1903-04 and 1916-17 you brought up which were both above average in DC. -NAO/Nina.

Also 1995-1996 was a weak Nina which theoretically wouldn't have had much of a STJ and that was the previous record year in DC. Obviously it's not a mod/strong and that is a little different but it still favors Nina-like patterns more than a strong STJ. What was the STJ like that year?

I certainly wouldn't say a -NAO/Nina is great for the mid-atlantic but it could be enough to bring them to average or slightly above if we had a large enough sample size.

Also if we're talking about the northern NYC suburbs then you can still get Miller Bs, SWFE and clippers so the fact that it's a Nina is not as important if the NAO is negative.

[weathafella]

Yeah it's pretty rare to have a -NAO with a strong La Niña so it's hard to tell....both 1903-04 and 1916-17 were moderate/strong Niñas with a very -NAO index if we can trust the data from back then. Both were impressive winters in NYC metro, with 50" or so falling and very cold temperatures. We just haven't cashed in big with a strong Niña in so long I'm pretty doubtful....54-55 was a disaster, 55-56 was good but not a blockbuster, 73-74 was OK, 75-76 sucked, 88-89 sucked, 98-99 sucked, 99-00 sucked. None of these winters were good for DCA. Of course many of those winters sucked because of the lack of a -NAO block, which we definitely have this year. 88-89 had the most positive NAO on record.

I was pretty steadfast in my winter forecast that the NAO would average negative this year against HM and other mets, and I still am clinging to that idea. We're going to average such a -NAO in December that it will be hard to be positive for DJF, and I think it will carry on for a while before finally moderating in late January or early February. This is like the lamp that never burns out; the models try to break down the block and mets explain why it might weaken, but then it builds back into a 5SD blocking pattern. I never could have predicted such a -NAO in a strong La Niña, however. I am starting to think I should have gone a bit colder overall in the East in the winter forecast, but we'll see.

I think the sample size of Ninas with -NAO is bigger than any of us knows. The accurate monitoring has only been around for 60 years but if you had it going back hundreds you'd have real predictive ability. Unfortunately, everything from those days is a guess.

[Ginx snewx]

Maybe my view has swung more to the consistency and deep snow pack side of it now because I know I most likely will never top that storm in February. That was it for my lifetime! 46 inches in four days shall not be surpassed unless I move to the Tug Hill. LOL

Now I need to enjoy the finer nuances of winter wx, a several hour white out, thunder snow, deep snowpack, etc. I want more big storms obviously, but I have seen my biggest in all likelihood.

You sound like me Rick LOL

[Cold Miser]

As depressing as CT Rain's initial stats seem, as well as Will's for Worcester, what happens when you throw temperature into the mix? Just curious if December temps have any impact on what may or may not happen the rest of the winter as far as frozen precip goes?

[CoastalWx]

As depressing as CT Rain's initial stats seem, as well as Will's for Worcester, what happens when you throw temperature into the mix? Just curious if December temps have any impact on what may or may not happen the rest of the winter as far as frozen precip goes?

I would think that significantly above normal temps in December, may allude to a bad winter. I think the examples Ryan and Will likely had December's that were well above normal.

We're fortunate enough so that winter months that are above normal (not significantly) often still produce good snows. I think it applies more for ORH than say BDL, but the idea is there, especially away from southern coastal areas.

[nzucker]

I don't think 3 is big enough to say really.

In 2 of those 3 DC was not that far below average and the snow fell in the months that had a -NAO but not in the +NAO month. Only 1 of the years was a dud ('54-55).

Then there is 1903-04 and 1916-17 you brought up which were both above average in DC. -NAO/Nina.

Also 1995-1996 was a weak Nina which theoretically wouldn't have had much of a STJ and that was the previous record year in DC. Obviously it's not a mod/strong and that is a little different but it still favors Nina-like patterns more than a strong STJ. What was the STJ like that year?

I certainly wouldn't say a -NAO/Nina is great for the mid-atlantic but it could be enough to bring them to average or slightly above if we had a large enough sample size.

Also if we're talking about the northern NYC suburbs then you can still get Miller Bs, SWFE and clippers so the fact that it's a Nina is not as important if the NAO is negative.

We also have to take into account that the jet stream pattern has changed somewhat since winters like 1903-04 and 1916-17 due to global warming and thus higher 500mb heights everywhere; a colder climate may have made a strong La Niña more suitable for DC in the old days. We also don't know how strong those Niñas really were although we can guess than 1903-04 was moderate and 1916-17 probably strong.

There was a STJ later in the 95-96 season, for the February and March storms, as the Niña wasn't really around at that point. The January 1996 blizzard, however, was caused by a split polar jet. I don't think we can use weak Niñas as analogs since they have such a different pattern from the stronger events; most weak Niña and negative-neutral winters have been pretty good like 60-61, 66-67, 83-84, 95-96, 05-06 etc.

[Kbosch]

The bottom line to this still is if you lose a month during the period you're supposed to get snow you're likely to end up with less than normal. We didn't need stats to figure that out (I hope), though they back it up. It's an obvious concept. Here on the CT coast December-February, and occasionally the first week or two of March, are my snow times. If I blow December totally we're taking nearly 1/3 of the possible time away from me. The odds are weighted against above normal seasonal totals, even if the next two months did end up normal or slightly above. They have to overperform by whatever you've missed out with 33% less time just to get to average.

[CT Rain]

Thanks - I just skimmed it I didn't run the stats but it became pretty obvious that a bad December isn't just a predictor of a bad winter, it's also a predictor of a bad J-M. I think you were sort of suggesting that might be the case, I'm still somewhat surprised it's such a strong predictor. I didn't know Upton average 31".. GON only averages 22" or so, I might be more like 24 or 25" since I am 5 miles from the shore.

I'd say Groton is more like 25"... New Haven is in the low 30s too...just a hair more than Upton.

When I started crunching the numbers I was definitely surprised as you guys were about the signal a bad Dec carried over into the rest of the winter.

[Ginx snewx]

I'd say Groton is more like 25"... New Haven is in the low 30s too...just a hair more than Upton.

When I started crunching the numbers I was definitely surprised as you guys were about the signal a bad Dec carried over into the rest of the winter.

Good thread, best start one with big Dec snows after we rock from Monday on.

[tamarack]

The 12-yr avg Dec snowfall IMBY is 19.1". In 7 of those winters, Dec's departure from avg was the same as for the winter. Two poor Dec (12.6" and 7.8") led into good snow winters (04-05, with 60" 2/10 thru 3/12, and 06-07 with 37" in April.) Three went the other way, though two were barely above the avg, 19.8" in 01 and 21.5" last year. 2003 was the standout, as 38.4" in Dec was followed by only 34.3" for the rest of the snow season. That year is probably the best SNE candidate for big Dec storm torching to bare ground; AUG had 18-20" and was down to 1" a week later, up to 14" after the 12/15 storm then back to almost nothing by Christmas.

Two of my 13 winters in Gardiner became well above avg snow producers after horrible Dec. The avg Dec there had 13.3", though that's skewed by 43.2" in 12/95, nearly twice the next best Dec - median is 9". 12/86 had only 3.7" but 1/87 had 49.3". Then 12/92 brought 3.4" (least snowy Dec at that location) and Feb/Mar '93 totaled 80.6".

In Ft. Kent, the three big winters, 76-77, 81-82, 83-84, all had big Decembers. In fact, those three Decembers were the three snowiest months I measured there.

[skierinvermont]

I'd say Groton is more like 25"... New Haven is in the low 30s too...just a hair more than Upton.

When I started crunching the numbers I was definitely surprised as you guys were about the signal a bad Dec carried over into the rest of the winter.

I actually found some good data for Groton after a long time searching. The 1971-2000 average is 20.2", the 1971-2010 average was 22.1" and the 1948-present average was 24.5"

It seems Groton's average snowfall has declined moreso than some of the other stations have. They had a ton of snow in the 50s and 60s and the 2010s were only a partial recovery.

I think based on this I feel pretty comfortable using 22" as Groton's annual average snowfall as a compromise between the 1971-2000 terrible 20.2", and the longer term much higher 24.5". It's probably a combination of bad luck and long-term decline.

[CT Rain]

I actually found some good data for Groton after a long time searching. The 1971-2000 average is 20.2", the 1970-2010 average was 22.4" and the 1948-present average was 24.5"

It seems Groton's average snowfall has declined moreso than some of the other stations have. They had a ton of snow in the 50s and 60s and the 2010s were only a partial recovery.

I don't buy the 1971-2000 average to be honest. The COOP data is frequently spotty and unrepresentative of surrounding towns.

[skierinvermont]

I don't buy the 1971-2000 average to be honest. The COOP data is frequently spotty and unrepresentative of surrounding towns.

Well there was very little missing data .. there are a few months there where it says "NR" but I didn't include them in my averages so they wouldn't effect it (as opposed to using a zero when data is missing). You could be right though.. maybe poor measuring or there are days missing even though the month is reported.

On the other hand Groton is directly on the water and is the first to changeover. They also seem to miss out on some of the action CC gets.

[CT Rain]

Well there was very little missing data .. there are a few months there where it says "NR" but I didn't include them in my averages so they wouldn't effect it (as opposed to using a zero when data is missing). You could be right though.. maybe poor measuring or there are days missing even though the month is reported.

On the other hand Groton is directly on the water and is the first to changeover. They also seem to miss out on some of the action CC gets.

Sometimes you'll see measurements that are taken once a day at some of these coop sites which can really screw things up at a place like Groton.

Say you get 6" of snow during the day and flip to rain in the evening. Your 7 am snowfall measurement is 0.

Obviously a lot of stations don't do this but some certainly do.

[CT Rain]

Well there was very little missing data .. there are a few months there where it says "NR" but I didn't include them in my averages so they wouldn't effect it (as opposed to using a zero when data is missing). You could be right though.. maybe poor measuring or there are days missing even though the month is reported.

On the other hand Groton is directly on the water and is the first to changeover. They also seem to miss out on some of the action CC gets.

Yeah it's definitely a pit for good snow. HVN is like 32" or so... BDR is in the 20s and GON is probably the low spot in the state 23-25 or so?

[skierinvermont]

Yeah it's definitely a pit for good snow. HVN is like 32" or so... BDR is in the 20s and GON is probably the low spot in the state 23-25 or so?

Yeah if BDR is in the upper 20s on the water at the airport then I would guess GON is 23-25 too, slightly higher than the coop data maybe. I can think of quite a few storms where BDR got much more than GON, very few the other way around. Are those 1971-2000 or long term numbers?

[H2Otown_WX]

I know this is a small sample size, but here's my snowfall totals since December 2001 by 12/10. Obviously, as Ginx said in this thread, the 2000's were very good for snow in December so I guess it's all I have ever known.

2001: 3"

2002: 19.5"

2003: 9"

2004: 3"

2005: 19"

2006: 0

2007: 1" (The 12/13 storm upped that number a few days later)

2008: 0

2009: 7"

So, since 2001 I have averaged a little under 7" of snow by this date. Again, a small sample size that probably doesn't mean much. It is interesting to note that 2004 had only 3" by this time and ended up being a huge winter. It snowed on November 12th and then it didn't snow again until December 20th. I guess the gist of it is November and early December are sometimes very telling (2002, 2005) and other times you just have to wait it out (2004, 2008). I think Will mentioned it is more typical to play a legitimate game of catch up in El Ninos but it's less likely in La Ninas. Hopefully we can have another 2008-2009. One other factor that could be skewing these statistics is the fact that the day before today (12/9) has had a couple of fairly large events. 12" on 12/9/05 and 7" last year.

[ORH_wxman]

Sometimes you'll see measurements that are taken once a day at some of these coop sites which can really screw things up at a place like Groton.

Say you get 6" of snow during the day and flip to rain in the evening. Your 7 am snowfall measurement is 0.

Obviously a lot of stations don't do this but some certainly do.

Yeah I wouldn't buy 22" for Groton...its likely a few inches too low.

[Ginx snewx]

I know this is a small sample size, but here's my snowfall totals since December 2001 by 12/10. Obviously, as Ginx said in this thread, the 2000's were very good for snow in December so I guess it's all I have ever known.

2001: 3"

2002: 19.5"

2003: 9"

2004: 3"

2005: 19"

2006: 0

2007: 1" (The 12/13 storm upped that number a few days later)

2008: 0

2009: 7"

So, since 2001 I have averaged a little under 7" of snow by this date. Again, a small sample size that probably doesn't mean much. It is interesting to note that 2004 had only 3" by this time and ended up being a huge winter. It snowed on November 12th and then it didn't snow again until December 20th. I guess the gist of it is November and early December are sometimes very telling (2002, 2005) and other times you just have to wait it out (2004, 2008). I think Will mentioned it is more typical to play a legitimate game of catch up in El Ninos but it's less likely in La Ninas. Hopefully we can have another 2008-2009. One other factor that could be skewing these statistics is the fact that the day before today (12/9) has had a couple of fairly large events. 12" on 12/9/05 and 7" last year.

Good post, it is coming we need a thread about great Dec snows and the winter totals

[JoeD]

OK for those of us farther east, here are the stats for BOS when less than 5 inches fell during the month:

Year/Dec Total/Seasonal Total

1936 / 0.7 / 8.2

1937 / 4.6 / 35.8

1938 / 1.3 / 38.5

1940 / 4.5 / 39.7

1941 / 0.2 / 29.5

1943 / 0.3 / 27.2

1946 / 4.9 / 19.4

1949 / 2.4 / 32.0

1950 / 2.7 / 29.7

1952 / 2.4 / 29.8

1953 / 0.0 / 23.6

1955 / 1.8 / 60.9

1957 / 0.0 / 44.7

1958 / 4.6 / 34.1

1965 / 2.3 / 44.1

1972 / 3.3 / 10.3

1973 / 0.0 / 36.9

1974 / 3.6 / 27.6

1979 / 0.4 / 12.7

1983 / 2.6 / 43.0

1984 / 3.7 / 26.6

1985 / 1.3 / 18.1

1986 / 3.4 / 42.5

1988 / 3.7 / 15.5

1990 / 1.2 / 19.1

1995 / 1.5 / 14.9

1998 / 0.8 / 36.4

1999 / 0.0 / 22.4

2000 / 4.5 / 44.2

2006 / 0.8 / 17.1

Dec Avg 7.8

Seasonal Avg 42.3

[NorthShoreWx]

Sometimes you'll see measurements that are taken once a day at some of these coop sites which can really screw things up at a place like Groton.

Say you get 6" of snow during the day and flip to rain in the evening. Your 7 am snowfall measurement is 0.

Obviously a lot of stations don't do this but some certainly do.

This is very common with coops and happens at some higher order stations as well. I have a spreadsheet sorted with all days with snowfall reported at any LI coop going back as far as I could grab coop records and the discrepancies between stations for the same events (which I have to guess at what constitutes an event since they don't all report the same day) are massive. A few stand out as worse than the others. GON may be a similar example.

[Kbosch]

OK for those of us farther east, here are the stats for BOS when less than 5 inches fell during the month:

Year/Dec Total/Seasonal Total

1936 / 0.7 / 8.2

1937 / 4.6 / 35.8

1938 / 1.3 / 38.5

1940 / 4.5 / 39.7

1941 / 0.2 / 29.5

1943 / 0.3 / 27.2

1946 / 4.9 / 19.4

1949 / 2.4 / 32.0

1950 / 2.7 / 29.7

1952 / 2.4 / 29.8

1953 / 0.0 / 23.6

1955 / 1.8 / 60.9

1957 / 0.0 / 44.7

1958 / 4.6 / 34.1

1965 / 2.3 / 44.1

1972 / 3.3 / 10.3

1973 / 0.0 / 36.9

1974 / 3.6 / 27.6

1979 / 0.4 / 12.7

1983 / 2.6 / 43.0

1984 / 3.7 / 26.6

1985 / 1.3 / 18.1

1986 / 3.4 / 42.5

1988 / 3.7 / 15.5

1990 / 1.2 / 19.1

1995 / 1.5 / 14.9

1998 / 0.8 / 36.4

1999 / 0.0 / 22.4

2000 / 4.5 / 44.2

2006 / 0.8 / 17.1

Dec Avg 7.8

Seasonal Avg 42.3

And it looks like 6/30 were over the seasonal average. Ouch. The data keeps backing up common sense.

EDIT: and 4 of those 6 were barely at 44.2, 44.1, 44.7, and 42.5

[snowman21]

I actually found some good data for Groton after a long time searching. The 1971-2000 average is 20.2", the 1971-2010 average was 22.1" and the 1948-present average was 24.5"

It seems Groton's average snowfall has declined moreso than some of the other stations have. They had a ton of snow in the 50s and 60s and the 2010s were only a partial recovery.

I think based on this I feel pretty comfortable using 22" as Groton's annual average snowfall as a compromise between the 1971-2000 terrible 20.2", and the longer term much higher 24.5". It's probably a combination of bad luck and long-term decline.

Since the 2004-05 season, I've averaged 32.5 inches in Old Lyme (about 2 miles from the Sound), but of course that is skewed by the 59.4 inches in the great 2004-05 season.