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Snow And Arctic Cold Potential To Start February


bluewave

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Both the ECMWF and GFS ensemble means are indicating that heights will rise

enough near Greenland to at least temporarily displace the polar vortex 

south as February begins. The polar vortex dropping south in this -AO

pattern will allow Arctic high pressure to remain in place over SE Canada.

Most of the time since the beginning of December the polar vortex has remained

anchored in place near Greenland in a strong +AO pattern. Any pieces of energy

cutting underneath in association the subtropical jet would encounter a fresh

source of Arctic air to the north. While it's too early for any individual storm

details, there should be a window of opportunity for snow in early February along

with Arctic cold.

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Looks like the Pacific pattern is also much improved (sustained -EPO) so we may still have opportunities even if the Atlantic pattern is less favorable. 

 

We'll see if the window of opportunity can produce some snow potential in early February with the forecast

rebound in heights near Greenland. Maybe in about 3-5 days or so some individual storm threats may come 

into better focus as the models handle them best from around 120 hrs and under.

 

Good to see you posting again, Bluewave!! :thumbsup:

 

El Nino winters are usually back-loaded, and hopefully the Northeast can cash in on a snowy end to the winter. 

 

Good to hear from you again also, JM. All the best of luck with your new job opportunity in Austin.

 

Eh this isn't technically a Nino right? I still hope it's back-loaded.

 

It was weak El Nino conditions with the strongest impact on the STJ in December when

California picked up the much needed rainfall. January saw the weakening of the STJ

which was a bit more active at times working in a split flow capacity with the northern

branch. We'll see if the recent sharp SOI drop will be associated with a more 

energetic STJ around the beginning of February.

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Below is a table showing the AO/PNA tendencies for NYC's 6" or greater snowstorms in February (1950-2014):

 

AO01232015.jpg
 

 

A PNA+ is relatively less important than it is for January. It is still important for the biggest snowstorms, with 60% of 10" or greater snowstorms commencing with a PNA+ vs. 50% for those in the 6"-9.9" range.

 

The overall sample size for the table is 27.

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Below is a table showing the AO/PNA tendencies for NYC's 6" or greater snowstorms in February (1950-2014):

 

AO01232015.jpg

 

 

A PNA+ is relatively less important than it is for January. It is still important for the biggest snowstorms, with 60% of 10" or greater snowstorms commencing with a PNA+ vs. 50% for those in the 6"-9.9" range.

 

The overall sample size for the table is 27.

 

We are just starting to see the GEFS AO index drop around the beginning of February in response

to the height rises and higher pressures closer to Greenland. It will be interesting to see how low a level we can reach

as we get closer to that time.

 

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We are just starting to see the GEFS AO index drop around the beginning of February in response

to the height rises and higher pressures closer to Greenland. It will be interesting to see how low a level we can reach

as we get closer to that time.

 

attachicon.gifao.sprd2.jpg

I agree. The most recent dip sent the AO down to a little above -1.6 (earlier forecasts were in the -3 to -2 range). If the forecast drop takes place, the 1/29-2/5 period might offer a real window of opportunity for a possible significant storm, especially as the subtropical jet is likely to be fairly active. Perhaps some earlier but not consistent runs showing a large coastal storm during that timeframe are some hints of the potential.

 

If the AO falls to -2 or below, that could be a strong hint that the climatologically-preferred negative state could predominate in February. There's nothing really magical about -2, but the development of strong blocking in late January or early February has typically been a precursor of a predominantly negative AO for February. I remain cautiously optimistic that we can salvage February. A meaningful negative AO winter average appears unlikely, as the AO would need to average  -2.302 from tomorrow through the end of February to achieve a winter average of -0.5. Just to reach 0, it would need to average -1.062 during that same timeframe. Both figures will very likely rise given the near-term forecast of a possibly brief period of a strongly positive AO.

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Me, Isotherm, Doug, and others have been talking about these changes for awhile. The MJO it will strengthen in phase 8 during the first of week February. 500mb composite for the MJO ifor February a supports -AO/-NAO:

 

2iaspok.jpg

 

FebruaryPhase8all500mb.gif

 

 

 

Agree weathergun. I've found the roundy plots to be fairly accurate this season in terms of ascertaining the progression of tropical forcing in the Pacific, generally more representative than the MJO plots. We should maintain conducive forcing over the next couple weeks to continue to tilt the AO negative, after a transient positive surge, and possibly initiate a -NAO episode the first week of February. I'm not confident on a longer-term / persistent -NAO just yet, but I do think the AO will be predominately negative going forward. Stratospheric trends support that as well. We have seen a fairly sharp decrease in solar parameters which could help increase heights near Greenland in the medium term.

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Always believed February would deliver and the signs are very encouraging. Such a nice cold look with the displaced PV and things don't look very dry as subtropical jet remains active.

Your lips to G-d's ears. Though nothing, including today's "storm" seems to be working out this winter.
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Always believed February would deliver and the signs are very encouraging. Such a nice cold look with the displaced PV and things don't look very dry as subtropical jet remains active.

You what ? You have canceled winter 100 x . Dude you posted predicting the long range is a joke and how everyone is going to bust. So many of us wrote that El Niño winters were back loaded winters. You were not in our camp.

If you thought we would see some meager snowfalls that's about it.

There are a lot of cxl winter posts missing I believe NEG NAO saw that too.

So please do not say you saw what's coming or that Feb would produce. What's coming may rival some of the best periods you've seen if it holds.

Your coldest 5 day period is in front of you. KNYC should beat its 4 from early Jan and if things break right we do very well in the snow dept. Feb cold could have some real staying power.

Now I've written about cold all winter , that has not erased.

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so far January 2015 is averaging 30.5 including yesterday...It could drop a degree or two with a very cold last week of the month...Last years coldest 30 days averaged 28.5...We have a good chance for a colder 30 day period than last year...snowfall has a long way to go to catch up with last year...I still think NYC will end up with 30-35"...TWT...

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