AO Forecast to Plunge

[uncle W]

Morning thoughts:

1) After taking some time to examine the synoptic pattern and having a look at some of the KU snowstorms for more ideal patterns, I suspect that a good idea for the range of solutions is between the 12/24 0z and 12/24 6z runs of the GFS. There is still a possibility of a solution outside those two, but the opportunity for that outcome is waning.

2) Translated into real weather, parts of New England have the best chance at seeing a 4"-8" snowfall with locally higher amounts. The Jersey Shore, New York City, and southwestern Connecticut have a decent chance of picking up 1"-3" maybe 2"-4" locally (farther east) but there is still an uncomfortably high risk of even lighter amounts.

3) The severe shot of cold shown at the end of the 12/24 0z run of the GFS does not fit the emerging synoptic situation from the Ohio Valley eastward. A more modest shot of cold is still possible there. Stronger cold is possible north of the Canada-U.S. border.

Disclaimer: Those who are faint of heart should stop reading here.

Ugly snowfall Statistics: ENSO Region 3.4 Anomaly -1 or below in both December and January

Boston:

December snowfall < 10": 6/7 (86%) cases had < 40" seasonal snowfall; < 10" December snowfall and no measurable November snowfall: 5/5 (100%) cases had < 40" seasonal snowfall

New York City:

December snowfall < 2.5": 9/10 (90%) cases had < 20" seasonal snowfall

Washington, DC (DCA):

12/12 (100%) of those La Niña cases had < 20" seasonal snowfall; 5/12 (42%) of those La Niña cases had < 10" seasonal snowfall

only 1956-57 and 1971-72 got over 20" for the season when there was 3" or less in December during La Nina...The storm track has a wide turn this year along the coast...Storms are actually missing us to the south then grazing us from the northeast....

[ThatWxGuy16]

Im wondering if that extremely cold last week of Jan in 1951 also led to a very cold beginning to February.

that cold end to Jan certainly impacted the beginning of Feb...well below normal for the eastern half during the first days of the month...after that, however, pretty different for sure...

However, like brian said, it's only one year so don't take too much out of this....

First ten days...

next ten days...

last days...

[easternsnowman]

only 1956-57 and 1971-72 got over 20" for the season when there was 3" or less in December during La Nina...The storm track has a wide turn this year along the coast...Storms are actually missing us to the south then grazing us from the northeast....

Past statistics could'nt explain last year. I believe we are now in different patterns that may be hard to explain from analogs.

[uncle W]

that cold end to Jan certainly impacted the beginning of Feb...well below normal for the eastern half during the first days of the month...after that, however, pretty different for sure...

However, like brian said, it's only one year so don't take too much out of this....

First ten days...

next ten days...

last days...

in NYC it was cold from 1/22-2/11...On 1/22-23 the minimum temperature was 18 but a storm tracking to the west brought rain and quickly rising temperatures before it got colder again to stay for three weeks...12/27 and 3/8 were the peak dates of blocking that winter...I mentioned before NYC got its coldest temperature that winter on 12/27 and its biggest snowfall...On March 8th, 1951 the blocking reached December levels and NYC saw its coldest temp for that month on the 10th...there were a few storms that year that tracked to our west bringing rapidly rising temperatures with rain instead snow despite the strong blocking at times...the ao was negative also around 1/28 and 2/9...January 31st and February 9th saw their monthly minimums...The cold spells that winter coincided with the negative ao...The storms were to far south or to far west to give NYC much snow...Sounds fimilar...

[uncle W]

Past statistics could'nt explain last year. I believe we are now in different patterns that may be hard to explain from analogs.

no analog or storm is exactly the same...analogs like 1950-51 and 1954-55 look pretty good now...1962 is not far behind and it had the Maine blizzard that was blocked for days...

[donsutherland1]

Past statistics could'nt explain last year. I believe we are now in different patterns that may be hard to explain from analogs.

Not exactly correct. Synoptically, the idea of a strong subtropical jet coupled with extreme blocking suggested multiple KU storm opportunities. It's a shame that Eastern's threads weren't archived, as I had used a few of the analogs to note that the December 2009 KU storm likely wasn't the last and that I thought another 1-2 were a realistic prospect. 1957-58 (2) and 1986-87 (3) offered some hints of what could happen when the subtropical jet was active and cold was present. That 4 occurred was beyond anything in the analogs. But the insight from the analogs was that there was a lot of potential. That insight is the value of analogs. One shouldn't try to utilize them for exact details or solutions but to flesh out general ideas. It's the former use that causes many to misunderstand analogs. FWIW, analogs/case studies are widely used in many fields, and they are used because when used properly, they can add value.

[uncle W]

Not exactly correct. Synoptically, the idea of a strong subtropical jet coupled with extreme blocking suggested multiple KU storm opportunities. It's a shame that Eastern's threads weren't archived, as I had used a few of the analogs to note that the December 2009 KU storm likely wasn't the last and that I thought another 1-2 were a realistic prospect. 1957-58 (2) and 1986-87 (3) offered some hints of what could happen when the subtropical jet was active and cold was present. That 4 occurred was beyond anything in the analogs. But the insight from the analogs was that there was a lot of potential. That insight is the value of analogs. One shouldn't try to utilize them for exact details or solutions but to flesh out general ideas. It's the former use that causes many to misunderstand analogs. FWIW, analogs/case studies are widely used in many fields, and they are used because when used properly, they can add value.

I agree and I lost some posts on eastern also that showed analogs that called for a snowy February...this year most of the analogs arn't snowy unfortunately and so far it has worked out...

[okie333]

Past statistics could'nt explain last year. I believe we are now in different patterns that may be hard to explain from analogs.

According to solar theory you would need ~800 years of daily data (two full 400-year cycles) to have sufficient sample sizes. We barely have two full 60-year oceanic cycles, and those get thrown out if the solar changes to a Maunder-style. IMO the currently used zero point of the AO would be a +1 or so on the 800-year scale, and the real average is near -1 on today's scale... pure speculation, but the old NASA papers (one from 2000 especially comes to mind) seem to suggest a drastically different AO during long solar minima... which is the case during approximately 1/4 of each (roughly 400-year) cycle.

[wxdudemike]

I actually put this in one of our reports today illustrating the neat similarities of this Dec MTD to the 1950 Dec. The spatial temperature pattern correlation over the CONUS was r=0.88 according to our calculations.

1950

2010

One of the other nice similarities (and not totally unrelated obviously) was the ridge/trough pattern across the NH during Dec 1950 and this Dec (same days as maps above)...

Dec 2010

1950

Does this make 1950 all of a sudden a front-runner for the upcoming January? No, not necessarily, but Dec 1950 did feature a cold ENSO (-0.93) with a -AO (-1.93) and -NAO (-1.02).

The following January had a clear breakdown in the blocking as measured by the monthly AO and NAO values (-0.085 and 0.08, respectively).

While the debate is certainly open on whether this January will see a similar breakdown in the blocking the ensemble guidance is hinting at it...at least on average.

Note the 12z GFS and ECMWF ensembles means show positive values for the AO as we get into Jan (might be hard to see but they are the thicker lines the plots below). I mention the debate in the sentence above because look how many d@mn members are still dropping the hammer and return to low index values!

Nice post, and thanks for the information! 2 quick questions....Where can I can get that AO forecast with the ECM members included? Also, I noticed that 1950 had a very cool looking November, but that doesn't match 2010 at all. Is November less important when matching up for the winter or was it just not a good match last month? Thanks!

[donsutherland1]

Morning thoughts...

It has been a wonderful night for the models (trending in the right direction in a fairly big way). If the storm proves as large as the GFS is suggesting, the GFS will have scored an epic coup with its sudden recognition of the event yesterday. As I'll be heading out to visit family and will likely miss multiple model runs ( ), I'll post my preliminary estimates for select cities:

Allentown: 3"-6"

Baltimore: 4"-8"

Boston: 12"-18"

Harrisburg: 3"-6"

Hartford: 6"-12"

Islip: 7"-14"

New York City: 6"-12"

Norfolk: 4"-8"

Philadelphia: 5"-10"

Providence: 8"-16"

Richmond: 4"-8"

Washington, DC: 4"-8"

[JBG]

New York City: 6"-12"

Nothing for north or west of NYC like ABE or HPN?

[VAwxman]

Maybe not the right thread, but since Don tossed out amounts, I will make a rough guess.. very rough since I'm away on vacation and haven't looked in as much detail as normal, but maybe that actually helps since the models have been all over the place the last few days lol.

Only going to do the major cities though.

RIC: 4-6"

DCA: 1-3"

BWI: 3-5"

PHL: 6-10"

NYC: 12-18"

BDL: too much to bother with (18-24")

BOS: 12-18"

[donsutherland1]

My final estimates:

Albany: 6"-12"

Allentown: 4"-8"

Baltimore: 3"-6"

Boston: 12"-18"

Concord: 8"-16"

Harrisburg: 2"-4"

Hartford: 8"-16"

Islip: 12"-18"

New York City: 12"-18"

Newark: 8"-16"

Norfolk: 4"-8"

Philadelphia: 6"-12"

Providence: 8"-16"

Richmond: 3"-6"

Washington, DC: 2"-4"

[winterymix]

Don: just for fun, where would you select ground zero with the most prolific snows and ground blizzard conditions?

[donsutherland1]

Don: just for fun, where would you select ground zero with the most prolific snows and ground blizzard conditions?

My guess is that the heaviest snows will probably fall somewhere in an area bounded by BDR and ISP out to ORH and BOS. Blizzard conditions could occur along the south shore of the Long Island Sound, across portions of Long Island and the greater Boston area. I'm not sure if NYC will see blizzard conditions, though JFK has a better chance.

[donsutherland1]

Nothing for north or west of NYC like ABE or HPN?

ABE will probably see 4"-8" and HPN could pick up 8"-16".

[A-L-E-X]

My guess is that the heaviest snows will probably fall somewhere in an area bounded by BDR and ISP out to ORH and BOS. Blizzard conditions could occur along the south shore of the Long Island Sound, across portions of Long Island and the greater Boston area. I'm not sure if NYC will see blizzard conditions, though JFK has a better chance.

Im 5 miles southeast of JFK, Don! Also, looks like there might be some mixed precip out by Westhampton and further east on the Island. The last track I looked at had the Low hitting Montauk Point as a 965 mb low.

[donsutherland1]

Earlier in this thread, I posted dismal snowfall statistics for moderate/strong La Niña winters when December had little or no snowfall. A snowy December improves the odds of a generally snowy winter, with significant snows (10" or more) usually returning either in February or March. April often had at least some accumulation of snow.

Some quick stats:

Boston: Moderate/Strong La Niña cases (1871-2009): 9" or more December snowfall:

- 4/5 (80%) cases had 50" or more seasonal snowfall

New York City: Moderate/Strong La Niña cases (1871-2009): 3" or more December snowfall:

- 8/9 (89%) cases had 20" or more seasonal snowfall

- 5/9 (56%) cases had 30" or more seasonal snowfall

-2/2 (100%) cases with 10" or more December snowfall had 30" or more seasonal snowfall

[Amped]

-NAO still pitching a shutout.

[Mike Calloway]

The 3 reference years 1950, 1995, and 2000 had very cold Decembers in the deep south. For B'ham for instance, Dec. '50 is the 7th coldest Dec. on record. Dec 2000, is the 3rd coldest December, and this December so far will easily make the top five list for coldest Decembers. Feb'51 and Feb.'96 started out with severe cold and winter storms. Dec '95 had some very cold outbreaks but averaged slightly above normal.

[uofmiami]

Earlier in this thread, I posted dismal snowfall statistics for moderate/strong La Niña winters when December had little or no snowfall. A snowy December improves the odds of a generally snowy winter, with significant snows (10" or more) usually returning either in February or March. April often had at least some accumulation of snow.

Some quick stats:

Boston: Moderate/Strong La Niña cases (1871-2009): 9" or more December snowfall:

- 4/5 (80%) cases had 50" or more seasonal snowfall

New York City: Moderate/Strong La Niña cases (1871-2009): 3" or more December snowfall:

- 8/9 (89%) cases had 20" or more seasonal snowfall

- 5/9 (56%) cases had 30" or more seasonal snowfall

-2/2 (100%) cases with 10" or more December snowfall had 30" or more seasonal snowfall

Don,

What winter years were the 2/2 in NYC where we had 10" or more in NYC and ended up with 30" or more for the season? Thanks. Great info BTW, keep it up!

[donsutherland1]

Don,

What winter years were the 2/2 in NYC where we had 10" or more in NYC and ended up with 30" or more for the season? Thanks. Great info BTW, keep it up!

1886-87 and 1916-17.

[A-L-E-X]

Thanks, Don! The 1916-17 analog still lives! First of back to back 50 inch plus snowfall seasons for NYC-- and ONLY. I didnt know about that one from the ninteenth century though-- what was NYC seasonal snowfall that year, Don?

[RIC Airport]

Thanks, Don! The 1916-17 analog still lives! First of back to back 50 inch plus snowfall seasons for NYC-- and ONLY. I didnt know about that one from the ninteenth century though-- what was NYC seasonal snowfall that year, Don?

December 1916 also was a top 10 month at RIC for snowfall with 9.1" And December 2010 has now exceeded that total coming in at 10.3" so far officially. And similar to this month, December 1886 also brought a huge snowstorm early in the month for central and southeastern VA.

Is 1892-93 a good analog?

[donsutherland1]

Thanks, Don! The 1916-17 analog still lives! First of back to back 50 inch plus snowfall seasons for NYC-- and ONLY. I didnt know about that one from the ninteenth century though-- what was NYC seasonal snowfall that year, Don?

32.9"

[radarman]

Don,

In the New York Times on Sat. in the op/ed section there is an article by a scientist and forecaster named Judah Cohen from AER inc., which describes a climate change link to the negative phase of the AO.

http://www.nytimes.com/2010/12/26/opinion/26cohen.html?src=twrhp

Mr. Cohen's work is fairly well known and has been discussed back on eastern. He has published several papers, often with Gong and Entekhabi, describing a relationship between autumnal Siberian snowfall and the wintertime phase of the AO. I interned with Mr. Cohen back in the early 2000s, though at that time we were still examining the mechanism and hadn't looked at any climate connection. The article in the times suggests (indirectly perhaps) that the massive negative sd's we've seen the past few years may become more common going forward. I am not entirely convinced that the sample size is sufficient to suggest that Siberian snowfall has increased recently, but if it has, I do believe we would see blocking episodes more regularly. I respect your knowledge very much, and I am curious if you are aware of the Times article and the science behind the claims, if you think the link to the AO is legitimate, and finally, if you believe, as Mr. Cohen does, that these major blocking episodes may become more common going forward.

Thanks in advance.

(mods, feel free to move this to the climate change forum if necessary)

[Ender]

D0 10hPa:

D3 10hPa:

D7 10hPa:

D10 10hPa:

D0 50hPa:

D3 50hPa:

D7 50hPa:

D10 50hPa:

[Amped]

Looks like a warming first 10 days of January

[Carvers Gap]

Looks like a warming first 10 days of January

Mad Cheese, do mind explaining those charts by Ender? Or Ender, you can give an explanation(since your are a met, I don't want to waste your time). I don't need a long explanation...Just what the significance is from day 0-10.

[Ender]

Mad Cheese, do mind explaining those charts by Ender? Or Ender, you can give an explanation(since your are a met, I don't want to waste your time). I don't need a long explanation...Just what the significance is from day 0-10.

My time has no real value, though I appreciate your consideration nonetheless.

I've only been watching the stratosphere for a year, but it sure looks similar the beginnings of the last few warming events. Keep in mind that those warmings were shown in the models somewhat earlier than they actually took place...and their impact to sensible weather (i.e. Colder here) was typically weeks after the warming event actually commenced.

Edit: I should be able to at least spell it correctly.