February 1-15: A Snowy Pattern Unfolds

[donsutherland1]

After a torturously long journey through a mainly warm January, winter is ready to return to the eastern United States. While the cold at the beginning of February won’t be anything close to extreme, it will be much more significant and noticeable than most of what was present in January.

At the same time, it will begin to snow again in parts of the Mid-Atlantic and the I-95 Corridor that seems to have forgotten what it is like to enjoy a snowstorm. All said, February looks to be snowier than normal from at least Washington, DC to Boston. There is some potential that it could be special in terms of snowfall, but I'll err on the side of conservatism. The strengthening of the La Niña to levels comparable to 1995-96 levels should not significantly impede the snowfall potential.

Both the NCEP ensemble 500 mb mean anomalies and the experimental CDC ensembles depict above normal height anomalies stretching across North America during the approximately 216 hour-360 hour timeframe. Such a situation has, in the past, sometimes suggested the possibility for severe cold (days with subfreezing highs and nights with lows < 20°) down the road. At this time, I believe the best potential for such cold will lie after the first week in February and perhaps after February 10.

Given the situation with the EPO, one might well need a situation whereby an open trof amplifies into a vertically-stacked closed system, which transitions into a new vortex. While such a storm would not assured to be a major East Coast snowstorm, some Kocin-Uccellini storms have been of that variety i.e., March 1960 and March 1993. If moderate to strong blocking is present then the cold could lock in. Otherwise, a strengthening MJO could lead to a milder period after mid-February.

Before then, a cooler but not yet very cold pattern should be evolving. Accumulations of snow from Washington, D.C. to Boston are likely in the first week of February. Given the snowfall discussion below, I have high confidence in such accumulations for the first week in February.

Elsewhere, the Pacific Northwest looks to run warmer than normal through at least the first week of February. During the February 8-15 period, given the potential for at least one outbreak of more serious cold, the Southeast and Florida will need to watch for a possible cold period with frost.

Conclusion:

I expect at least the following:

∙ February 1-7: Temperatures from Washington, DC to Boston should average near normal to somewhat above normal. As previously discussed, the cooldown is likely to be gradual.
∙ February 8-15: Overall readings in the Richmond to Boston areas should be somewhat below normal.. There is a chance of at least one or more days lows < 20° from Richmond to Boston.
∙ Washington, DC, Philadelphia, New York City, and Boston should all see some accumulations snow in the first week in February. More significant accumulations are possible during the second week.

Monthly snowfall:
Right now, based on a combination of historic climatology, ENSO analogs, and hints in the modeling, I believe February 2006 will see the following monthly snowfall amounts:

Boston: 12” or more
New York City: 10” or more
Philadelphia: 10” or more
Washington, DC (DCA): 8” or more

The Case for a Snowy February:
Four factors tie together quite well:

1) Historic Climatology: There are some very strong signals that Winter 2005-06 could be snowier than normal. The November-December snowfall provides perhaps the strongest indication. Winters in which patterns produce abundant snowfall across the Mid-Atlantic and southern New England often have the tendency to produce additional abundant snowfall later in the season--often in January and/or February--after perhaps a break.

In December, New York City received 9.7” snowfall. Since 1869, the following has held true: November: Trace or more/December: 9” or more: 19/22 (86%) seasons received 30” or more snowfall; Median snowfall: 42.0”; Mean snowfall: 42.3”

In Washington, DC, 7/8 (88%) years in which the November temperature came to 50.2° +/- 1° and December saw 3.0" or greater snowfall, seasonal snowfall reached or exceeded 20" and 5/8 (63%) reached or exceeded 30". Median seasonal snowfall came to 31.2” and mean seasonal snowfall amounted to 28.5”

2) ENSO Analogs:

∙ All cases with similar ENSO Region Anomalies:

Boston:
Mean snowfall: 12.3”
Median snowfall: 11.4”
15” or more snowfall: 38%
10” or more snowfall: 69%
Most: 23.5”, February 1967

New York City:
Mean snowfall: 9.4”
Median snowfall: 9.9”
15” or more snowfall: 23%
10” or more snowfall: 46%
Most: 23.6”, February 1967

Washington, DC (DCA):
Mean snowfall: 7.0”
Median snowfall: 4.1”
15” or more snowfall: 23%
10” or more snowfall: 31%
Most: 19.0”, February 1967

∙ ENSO Region anomalies and NAO < 0:

Boston:
Mean snowfall: 13.7”
Median snowfall: 13.2”
15” or more snowfall: 33%
10” or more snowfall: 83%

New York City:
Mean snowfall: 11.1”
Median snowfall: 10.3”
15” or more snowfall: 33%
10” or more snowfall: 50%

Washington, DC (DCA):
Mean snowfall: 10.0”
Median snowfall: 9.4”
15” or more snowfall: 33%
10” or more snowfall: 50%

∙ ENSO Region anomalies and Historic Climatology:

Boston:
Mean snowfall: 13.8”
Median snowfall: 15.5”
15” or more snowfall: 67%
10” or more snowfall: 67%

New York City:
Mean snowfall: 15.6”
Median snowfall: 21.2”
15” or more snowfall: 67%
10” or more snowfall: 67%

Washington, DC (DCA):
Mean snowfall: 13.8”
Median snowfall: 15.2”
15” or more snowfall: 67%
10” or more snowfall: 67%

3) CPC Objective Analogs: In recent days, among the following dates has come up for the medium-term:

February 9, 1953, February 10, 1953, February 4, 1954, January 19, 1956,January 20, 1956, January 21, 1956, February 17, 1957, January 25, 1958, January 26, 1964, February 3, 1961, February 4, 1961, February 7, 1968, February 8, 1968, February 5, 1978, February 6, 1978, February 17, 1978, February 18, 1978, February 20, 1978, January 20, 1980, February 4, 1980, February 5, 1980, February 6, 1980, February 8, 1980

If one takes each of those dates +/- 3 days, one finds that at least 0.1” snow accumulated as follows:

Boston: 22/23 (96%) cases
New York City: 13/23 (57%) cases
Washington, DC 16/23 (70%) cases

If one refines that list and only includes the dates for seasons with similar ENSO anomalies, one finds that at least 0.1” snow accumulated as follows:

Boston: 5/5 (100%) cases
New York City: 3/5 (60%) cases
Washington, DC: 5/5 (100%) cases

In addition, two periods from among the above dates had major East Coast snowstorms (February 3-4, 1961 and February 5-6, 1978). Two years (1956 and 1958) saw such snowstorms later in the season.

4) Model Guidance: For several runs, the GFS and ECMWF have been showing some potential (but not with a great deal of consistency) for on or more snowfalls in the extended range (February 1 and later).

Given points 3 and 4, I believe one can reasonably conclude that some snowfall potential lies ahead for the opening week of February. If one then ties together both the ENSO Region anomalies and historic climatology, a strong case can be made for a snowy February.

Teleconnection Hints: New York City Cases

Frequency of Snowfall:

In general, the following combinations typically highlight patterns with above normal occurrences (40% or more above the historic norm) of accumulating snow:

February 1-15:
NAO: -1.00 to -1.99 and PNA+
NAO: -2.00 and below and PNA –
NAO: -4.00 or below and PNA +
NAO: -4.00 or below and PNA -

Most frequent (60% or more above historic norm):
NAO: -1.00 to -1.99 and PNA+
NAO: -2.00 to -2.99 and PNA-
NAO: -4.00 or below and PNA-

February 16-29:
NAO: -2.00 to -3.99 and PNA-
NAO: -4.00 or below and PNA+

Most frequent (60% or more above historic norm):
NAO: -2.00 to -3.99 and PNA-
NAO: -4.00 or below and PNA+

Significant Snowfall (4” or more):

February 1-15:
NAO- and PNA- 28%
NAO- and PNA+ 33% (4 “Kocin-Uccellini” snowstorms)
NAO+ and PNA- 22% (1 “Kocin-Uccellini” snowstorm)
NAO+ and PNA+ 17% (1 “Kocin-Uccellini” snowstorm)

NAO+ 39% (2 “Kocin-Uccellini” snowstorms)
NAO- 61% (4 “Kocin-Uccellini” snowstorms)
PNA- 44% (1 “Kocin-Uccellini” snowstorm)
PNA+ 56% (5 “Kocin-Uccellini snowstorms)

February 16-29:
NAO- and PNA- 31% (1 “Kocin-Uccellini” snowstorm)
NAO- and PNA+ 31% (1 “Kocin-Uccellini” snowstorm)
NAO+ and PNA- 38% (3 “Kocin-Uccellini” snowstorms)
NAO+ and PNA+ None

NAO+ 39% (3 “Kocin-Uccellini” snowstorms)
NAO- 61% (2 “Kocin-Uccellini” snowstorms)
PNA- 69% (4 “Kocin-Uccellini” snowstorm)
PNA+ 31% (1 “Kocin-Uccellini snowstorm)

[boca]

Don thanks for the heads up here in Florida. My mother in law lives in New Jersey and she forgotten how to drive in snow so maybe she'll get her shot in the 1st week of February.

[Jim Hughes]

Good outlook Don. I think you are correct about the colder air coming and your snowfall time frame is almost right on target. I think mid month may be the best time. I was ready to send out a DC snowfall forecast last night to some news contacts but I balked because I can not settle on the exact three day period. (I have always only given a 3 day slot. )

I am thinking either the 13th-15th or 14th-16th. These time frames would be somewhat of a repeatable January pattern. OF course the steering currents must change a little as well as the the warmth.

The very sharp warming in the stratosphere during the past 48 hours points toward it getting really cold around the 16th. This usually implies a storm pulling down some colder air so I am really starting to feel very confident about accumulating snow around the Washington DC area. And many other areas for that matter.

I need to look over a couple of things a little better. Maybe a post later tonight.


Jim

[Stephanie]

It almost always seems like we get our best snows aroung President's Day weekend.

Last night that front blew threw - THUNDERSNOW, lightning, wind, the whole nine yards. It was wild!!!

[donsutherland1]

Jim,

The recent stratospheric warming is an encouraging development. Perhaps the ongoing decline in the Arctic Oscillation is, in part, on account of that high-level warming.

FWIW, for the past several days, AccuWeather's Elliot Abrams has been discussing this phenomenon. Briefly, he explained that "some research has suggested that when the polar vortex in that area weakens or reverses to leave a high pressure area in place, it signals subsequent high latitude blocking in the troposphere..." Such blocking can lead to colder outcomes in the eastern United States.

[donsutherland1]

Stephanie,

It was an incredible evening for many. I saw multiple reports of hail up to 1" in diameter in Philadelphia:


NWUS51 KPHI 250356
LSRPHI

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1056 PM EST TUE JAN 24 2006

..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..

0929 PM TSTM WND GST READING 40.34N 75.93W
01/24/2006 48 MPH BERKS PA OFFICIAL NWS OBS

A WIND GUST TO 48 MPH WAS REPORTED AT THE READING
AIRPORT.

1038 PM HAIL PHILADELPHIA 40.01N 75.13W
01/24/2006 1.00 INCH PHILADELPHIA PA OFFICIAL NWS OBS

1.00-INCH HAIL WAS REPORTED AT THE PHILADELPHIA
INTERNATIONAL AIRPORT.

1045 PM HAIL PHILADELPHIA 40.01N 75.13W
01/24/2006 1.00 INCH PHILADELPHIA PA TRAINED SPOTTER

1.00-INCH HAIL REPORTED ON THE WALT WHITMAN BRIDGE.

1052 PM HAIL MAPLE SHADE 39.95N 75.00W
01/24/2006 0.25 INCH BURLINGTON NJ NWS EMPLOYEE

PEA SIZED HAIL COVERING THE GROUND IN MAPLE SHADE.

[jasons2k]

I'll be in NYC from Feb 8th-12th. I hope to see some snow when I'm up there, that would be awesome. I just hope it's not so bad we can't do anything but stay in the Hotel room.

[terstorm1012]

It almost always seems like we get our best snows aroung President's Day weekend.

Last night that front blew threw - THUNDERSNOW, lightning, wind, the whole nine yards. It was wild!!!

We TOTALLY had Thundersnow last night around 830, it was INSANE!

[Jim Hughes]

Jim,

The recent stratospheric warming is an encouraging development. Perhaps the ongoing decline in the Arctic Oscillation is, in part, on account of that high-level warming.

FWIW, for the past several days, AccuWeather's Elliot Abrams has been discussing this phenomenon. Briefly, he explained that "some research has suggested that when the polar vortex in that area weakens or reverses to leave a high pressure area in place, it signals subsequent high latitude blocking in the troposphere..." Such blocking can lead to colder outcomes in the eastern United States.

Yes the warming in the stratopshere at the poles occurs when the westerlies reverse themselves and we see easterlies. This then usually effects the teleconnections in the troposphere up north. The key is finding the triggering mechanism.

This current warming is very extreme. Especially for this time of year. It's only reached this level a couple of times and fairly extreme weather events followed. Mid February could be one for the record books.


Jim

[tomboudreau]

It almost always seems like we get our best snows aroung President's Day weekend.

Last night that front blew threw - THUNDERSNOW, lightning, wind, the whole nine yards. It was wild!!!

We TOTALLY had Thundersnow last night around 830, it was INSANE!

We had 2 period of thundersnow yesterday and this morning. The first happened last night between 5:45 and 6:00. The second one occured around 3:15 this morning. We were getting ready to leave the house at 5:45 when the first one took place. The second one woke me up from a dead sleep. It was a couple of good rumbles of thunder and the lightning was incredibly vivid. We got a total of 2 inches today from the persistant lake effect band that setup shop off of Lake Erie. I have a feeling, work got more then we did at the house. They usually get between 1 and 2 inches more then what we do here.

[Brent]

I'll be in NYC from Feb 8th-12th. I hope to see some snow when I'm up there, that would be awesome. I just hope it's not so bad we can't do anything but stay in the Hotel room.

You'll be in New York... it'd have to be an extreme blizzard to shut them down... not 3 flakes like down here.

[Coredesat]

Great discussion, Don.

What are your thoughts on snowfall in Richmond during this period?

[donsutherland1]

Team Ragnarok,

It's still a little soon to highlight possible specific threats for the Richmond area. I'd suggest that the risk will probably be growing only after the first week of the month (probably 2/10-20 is the best bet, as it's when I think the month's cold might reach its peak). For the month as a whole, Richmond will probably reach its normal snowfall and possibly exceed it.

The strong signal for a rising PNA+ is helpful. One will need to see a more strongly negative NAO than is currently progged. There's still time for that to happen.

[Portastorm]

Don,

Do you see the brunt of the cold affecting the NE part of the U.S. first and then backing southwestward as some are suggesting?

[Hybridstorm_November2001]

We shall see. I'm not looking for a lasting cool down across the East myself, maybe a week tops. With more possible Pacific origin systems coming into the area from the West in the long term. I just do not see it in the cards. Anything can happen though.

[bob rulz]

What about the west? Will it cool down at all or will it stay about where it is now?

[senorpepr]

After a torturously long journey through a mainly warm January...

Who says it's been torturously long?

I do realize the rest of the nation and their concerns, but locally... this has been a VERY pleasant January. The bills are low (too warm for too much heat/too cool for AC), hardly any snow, a few decent rains to keep us near normal precip-wise... it's be wonderful.

[Hybridstorm_November2001]

I agree. This is the first end of January in at least ten years that I can still see my front lawn. I was able to take down my Christmas decorations yesterday. Which I usually can't do because the ones on the ground are buried in snow and ice up to the middle of March, or sometimes later. I'm with you on this one, I'm not complaining.

[donsutherland1]

Some quick thoughts...

- Model consensus on the overall evolution of things toward a colder, snowier regime is looking good even as details remain somewhat uncertain.

- Per the NCEP ensemble 500 mb mean anomalies, the development and expansion of a trough in the East around or after 2/4 with its being consolidated after the first week in February looks good. It would be after the first week or first 10 days of February that the threat of significant cold could increase.

- Per the NCEP ensemble 500 mb mean anomalies and various runs of the guidance, opportunities for snowfall could be on the increase, especially from near the end of the first week in February onward.

All said, I have little reason to change my thinking from the initial post in this thread.

[donsutherland1]

Portastorm,

Sorry about the delayed reply. I was on vacation. I believe the trough will expand westward from the East Coast (strong signal on the latest GFS ensemble means) but perhaps in a discontinuous fashion.