November 2012 Observations and Discussions

[MJO812]

1995,2010,1977 and 2008 keeps on showing up as analogs for this winter. All those winters were good for the area.

[MJO812]

Big cold outbreak in the 1st week of December on the GFS

[nzucker]

Big cold outbreak in the 1st week of December on the GFS

That's a monster -NAO...almost all of Greenland is above 0C at 850mb. We also have a nice Aleutian ridge showing up on the later panels of the GFS as it amplifies towards the pole. The fantasy range shows highs in the 20s for NYC during the first days of December when average highs are around 48F. Looks like some -20 departures if anything close to this verifies.

I continue to be impressed by how cold November has been as well. High was only 46.9F today, and this has been a relatively mild part of the month compared to the first week. Average high is still 55F in Westchester, and most days recently have been in the low to mid 40s. Not a bad month if you like a wintry feel.

[MJO812]

0z GGEM still has the Thanksgiving storm. 977 low.

http://collaboration.cmc.ec.gc.ca/cmc/cmdn/pcpn_type/pcpn_type_gem_reg.html

[nzucker]

The cold signal for after Thanksgiving is improving as well....0z GFS brings in a nice shot of -10 850s, serious departures for late November:

[MJO812]

Jamsec model is cold for this winter

[MJO812]

Major -NAO on the 0z GFS

[Weathergun]

The 0z GEFS has substanial -NAO developing by beginning of December. Hopefully the trend keeps up:

[okie333]

Major -NAO on the 0z GFS

No kidding.

[Weathergun]

Don't worry about the 6z OP GFS. The 6z GEFS is even stronger than 0z run, with the -NAO between 11-15days:

[TWCCraig]

GFS shows warm up towards the end of November/ early December, despite the -NAO.

[bluewave]

The Euro is showing a typical blocking ridge amplification process that we have seen

before. First we get a major 300M+ to 400M ridge maxing out on the Pacific side followed

by a ridge building near Greenland.

This was how the November 2010 blocking pattern evolved with the major amplification first

on the Pacific side followed by Greenland several days later.

[MJO812]

^^^

That's why 2010 keeps on coming up as an analog

[SACRUS]

thru the 16th. All sites remain below avg precip a continuing trend.

tem departures:

EWR: -4.2

TTN: - 4.3

NYC: - 5.0

LGA: -4.4

JFK: -5.0

[Isotherm]

The JAMSTEC idea of a colder/drier than normal winter may not be far-fetched given the dry regime we've seen this autumn. But keep in mind that for our area, we've seen plenty of snowy winters w/ a drier than avg precip pattern. It's not a requirement for us like it is for C/N NNE as they have a much higher percentage of their winter precip as snow. For us, only about 25% of the winter precip falls as snow anyway, hence our relatively low averages compared to the 60s+ in north/central New England.

I will say my wall of skepticism is beginning to break down, but I'd like to have another several more days to see if this starts showing up in the < D 10 time frame. As Chris (bluewave) correctly noted, the Aleutian high anomaly amplification nwd is often the onset of a high latitude blocking pattern. So we'll have to keep an eye on that to see if it does in fact extend across the pole. If so, blocking on both sides of the North American continent will change the whole tune of December big time.

[uncle W]

The JAMSTEC idea of a colder/drier than normal winter may not be far-fetched given the dry regime we've seen this autumn. But keep in mind that for our area, we've seen plenty of snowy winters w/ a drier than avg precip pattern. It's not a requirement for us like it is for C/N NNE as they have a much higher percentage of their winter precip as snow. For us, only about 25% of the winter precip falls as snow anyway, hence our relatively low averages compared to the 60s+ in north/central New England.

I will say my wall of skepticism is beginning to break down, but I'd like to have another several more days to see if this starts showing up in the < D 10 time frame. As Chris (bluewave) correctly noted, the Aleutian high anomaly amplification nwd is often the onset of a high latitude blocking pattern. So we'll have to keep an eye on that to see if it does in fact extend across the pole. If so, blocking on both sides of the North American continent will change the whole tune of December big time.

the late 50's and 1960's were dry but had plenty of coastal storms...So it can snow in a dry pattern...

[bluewave]

the late 50's and 1960's were dry but had plenty of coastal storms...So it can snow in a dry pattern...

Yeah, as long as you get a big jackpot storm like during February 78 and 06 a dry pattern can produce snow for you.

[Weathergun]

The GEFS continues to be most bullish with MJO in phases month at the end of this month. The 500mb composite shows a -NAO and +PNA with a Aleutian low. The 12z GEFS today shows -NAO and Aleutian Ridge regressing, in beginning of December:

[earthlight]

Dec 2010 is beginning to appear on analogs more often -- but I can't remember if we had a big Aleutian ridge during that period prior to the development of a -NAO. It should be noted that, although its presence isn't a bad thing, losing the huge tremendous Aleutian ridge and adding a west based NAO isn't a bad thing either. The 12z GEFS hint at an encouraging pattern heading into December, although admittedly not a perfect one, this would more than likely suffice to bring wintry threats in by the first week of meteorological winter.

[CooL]

Not much day 8-10 agreement between the ops. Euro has a much better look with the nao going negative. More in line with the gefs

[earthlight]

The Euro is showing a typical blocking ridge amplification process that we have seen

before. First we get a major 300M+ to 400M ridge maxing out on the Pacific side followed

by a ridge building near Greenland.

This was how the November 2010 blocking pattern evolved with the major amplification first

on the Pacific side followed by Greenland several days later.

Was doing some research on this exact thing and just saw your post. Terrific stuff man.

After perusing through some stuff earlier this afternoon it seems that some (not all, but some) of the "big patterns" can feature the return of blocking through the development of a big positive anomaly over the Aleutians which then ends up over Greenland sometimes with a lower stratospheric vortex split.

Without getting too worked up, I will say that if the GEFS were to be rolled forward we would be looking at a very wintry pattern by Dec 1 without a doubt. But we have to carefully watch the MJO as well over the next week or two -- the GEFS are really bullish there as well as Weathergun noted.

This is a huge pattern for us and most of the Northeast US especially by Dec 1:

http://www.meteo.psu.edu/~fxg1/ENSHGTAVGNH_6z/f288.gif

[Isotherm]

Here's a composite of H5 patterns for years in the last -PDO decadal phase(and the new one) that featured a -PNA, -AO, and -NAO overall for DJF. The resultant years that fit were: 1958-59, 1961-62, 1967-68, and 2008-09, all neutral ENSO winter seasons as well. Those four winters were quite cold, but again, going along with the dry theme, rather hit and miss on the snowfall events. Not saying that'll happen this year. However, the pattern depicted on D 10+ guidance looks fairly similar to these 4 years regarding the Aleutian ridge/-EPO connection across the top to west based -NAO. Underneath you've got a belt of below normal heights from the PAC NW east to the NE US. These are the type of patterns that can yield bitter cold from coast to coast given the -PNA/-NAO and AK ridging. However, without the Western US ridging, you also tend to lack bigger snowfalls on the east coast. Food for thought.

DJF H5 composite of years w/ -PNA/-AO/-NAO/-EPO:

Breaking them down by year.

1958-59

1961-62

1967-68

2008-09

[earthlight]

Here's a composite of H5 patterns for years in the last -PDO decadal phase(and the new one) that featured a -PNA, -AO, and -NAO overall for DJF. The resultant years that fit were: 1958-59, 1961-62, 1967-68, and 2008-09, all neutral ENSO winter seasons as well. Those four winters were quite cold, but again, going along with the dry theme, rather hit and miss on the snowfall events. Not saying that'll happen this year. However, the pattern depicted on D 10+ guidance looks fairly similar to these 4 years regarding the Aleutian ridge/-EPO connection across the top to west based -NAO. Underneath you've got a belt of below normal heights from the PAC NW east to the NE US. These are the type of patterns that can yield bitter cold from coast to coast given the -PNA/-NAO and AK ridging. However, without the Western US ridging, you also tend to lack bigger snowfalls on the east coast. Food for thought.

DJF H5 composite of years w/ -PNA/-AO/-NAO/-EPO:

I think we have to watch the amplitude of the -NAO for that down the road as well as the EPO/Aleutian ridge. The Aleutian ridge should help dislodge cold air into Canada and if we get the -NAO to develop it will keep it there. But many people don't remember, in a similar pattern in Dec 2010 -- we had a huge block anomaly that eventually retrograded to Central Canada (Still one of the best Davis Straight blocks i've ever seen). Anyway -- it essentially suppressed the pattern ... we missed two or more storm chances that just had no chance of coming up the coast.

A less anomalous version of that could give us a whole bunch of moderate events that aren't big huge blockbusters but aren't flattened and over Bermuda.

[MJO812]

^^

Except the Boxing day storm

[earthlight]

^^

Except the Boxing day storm

Boxing Day, not coincidentally, developed later in the month when the humungous Central/Southeast Canada block finally became a bit less anomalous and moved into a more favorable position. Here is the pattern on Dec 15 2010. You can see the huge PV anomaly over the Northeast. And it is forced to stay there because of the huge ridge over Central Canada, which you can see on the very top of the screen with 552+dm heights.

http://www.meteo.psu.edu/~fxg1/NARR/2010/121521.png

[Isotherm]

I think we have to watch the amplitude of the -NAO for that down the road as well as the EPO/Aleutian ridge. The Aleutian ridge should help dislodge cold air into Canada and if we get the -NAO to develop it will keep it there. But many people don't remember, in a similar pattern in Dec 2010 -- we had a huge block anomaly that eventually retrograded to Central Canada (Still one of the best Davis Straight blocks i've ever seen). Anyway -- it essentially suppressed the pattern ... we missed two or more storm chances that just had no chance of coming up the coast.

A less anomalous version of that could give us a whole bunch of moderate events that aren't big huge blockbusters but aren't flattened and over Bermuda.

Yeah the magnitude of the -NAO is certainly important - agreed. With that being said, of those 4 years I mentioned, most of them were not strongly negative -NAO winters, in fact they all had a +NAO for at least 1 month of the meteorological winter. So I do believe the -PNA/Western troughing does act as a detriment in terms of big eastern snows, for obvious reasons. If you don't have big amplification immediately upstream in the West it's tough to carve out a deep, meridional trough on the east coast and thus have a SW-NE moving Miller A type moisture laden bomb. The Western and Eastern trough together seems to favor a stream of light/moderate events as you noted, more like 08-09 and those other years mentioned above. Of course nothing is a guarantee, and as we saw with Dec 2010, you can occasionally get big snowstorms with a -PNA. Plus, after last winter, I'm sure most would be more than happy with any kind of lght or mdt event potential. All speculation now anyway.

[MJO812]

Storm potential at the end of this month. It is showing up on the op and ensemble runs.

[Animal]

missed sandy and the snow storm,

when can I expect snow?

where r the storms?

[MJO812]

0z GFS has a glc for the end of the month storm. After that, the cold air rushes in for a short time.

[rcad1]

You say cold air rushes in for a short time does that mean it gets cold for 3 days and then gets warm again if so that's useless we need cold air to come and stay not to cold though cause we also don't want the storm track to be suppressed...