The Winter 2010-11 NYC/PHL Medium Range Thread

[Rainshadow]

Thanks for that, shadow.

IIRC, last winter we saw the -NAO progged to erode in the 90-120 frames virtually all season long. That may be a weenie wish this year given the PAC. Still, it is worth noting.

I wouldn't sell the -nao short until Dr. McCoy says "The -NAO is dead, Jim." Its like forecasting the end of a persistent weather pattern, you could be wrong every day trying to guess when it will end, or be wrong the day it finally breaks. Either way I'd be wrong.

[Nikolai]

The MJO emerging in the warm phases maybe part of reason the -nao is relaxing or heading east late this week, not entirely sure if that can occur that quickly. As far as the epo being the driver of change, I usually give it 5 to 7 days to be an instrument of "change", which would still be mid December about the same the -nao looks like its going to flex its muscle again. We'll see who wins.

I dunno about that. I don't think the MJO will play a significant role in changing the pattern; it looks to drift close or back to nowhere land, and by the middle of the month I think we could be by phase 7/8.

[A-L-E-X]

The NAO isn't forecasted to go very negative. The AO is.

Also, the retrogading storm on the Euro looks like February 25-26.

Arent the two linked?  Like last year, when one goes south so does the other.....

[Rainshadow]

I dunno about that. I don't think the MJO will play a significant role in changing the pattern; it looks to drift close or back to nowhere land, and by the middle of the month I think we could be by phase 7/8.

MJO thoughts were more about late this week, there is a correlation between the MJO and EPO and probably because the GFS has a weak MJO evolving as you posted the EPO starts going back toward neutrality late. Other model MJO projections unfortunately have not updated since 12/2 on the CPC web site.

[am19psu]

I dunno about that. I don't think the MJO will play a significant role in changing the pattern; it looks to drift close or back to nowhere land, and by the middle of the month I think we could be by phase 7/8.

That might be too fast, but the Hovmoller charts from Paul Roundy's site are showing a quick progression for this pulse.

[MJO812]

Arent the two linked? Like last year, when one goes south so does the other.....

Not 100 percent sure but I think they are.

[am19psu]

Not 100 percent sure but I think they are.

They're very strongly correlated.

AO loading pattern:

NAO loading pattern:

[A-L-E-X]

How high is the correlation?  I remember hearing it was better than 80% but I dont have an exact number.

[MJO812]

After the storm next week, blocking looks to come back stronger than what we have now.

[am19psu]

How high is the correlation? I remember hearing it was better than 80% but I dont have an exact number.

Thompson et al. (2003) reports 0.95 over the North Atlantic. Try googling Northern Annular Mode for some more papers about it.

[jrodd321]

After the storm next week, blocking looks to come back stronger than what we have now.

Just in time to supresss the next storm and then relax when one begins to cut.

[A-L-E-X]

Just in time to supresss the next storm and then relax when one begins to cut.

80s redux lol

[MJO812]

Accuweather's 1st map

http://www.accuweather.com/blogs/news/story/42618/major-snowstorm-could-hit-the.asp

[MJO812]

:stun:

Do we live in Alaska or in the northeast?

[jrodd321]

:stun:

Do we live in Alaska or in the northeast?

That is pretty epic!

[nzucker]

Accuweather's 1st map

http://www.accuweath...uld-hit-the.asp

Looks OK but I imagine the storm might be a bit warmer than that. Considering the antecedent airmass has moderated a lot over the Mid-Atlantic, it would be a stretch for NYC to see too much of a mix with this track. Definitely seems smart to lean towards the warmer solutions given the lack of blocking before the storm and the strength of the shortwave over the Plains.

[A-L-E-X]

Maybe we will get in on the action that western Europe got.  Delayed but not denied

[A-L-E-X]

Looks OK but I imagine the storm might be a bit warmer than that. Considering the antecedent airmass has moderated a lot over the Mid-Atlantic, it would be a stretch for NYC to see too much of a mix with this track. Definitely seems smart to lean towards the warmer solutions given the lack of blocking before the storm and the strength of the shortwave over the Plains.

Is your take that the storm after that will be the big one for us (once the cold air settles back in)?

[MJO812]

12z GGEM ensembles aren't bad. Some have this storm going inland and some show this storm as a coastal.

[tombo82685]

12z GGEM ensembles aren't bad. Some have this storm going inland and some show this storm as a coastal.

euro ens have primary to cle secondary over abe

[nzucker]

Maybe we will get in on the action that western Europe got. Delayed but not denied

The problem is that the Pacific is not really behaving with first having a Central Pacific trough and then a GoA low. All Europe needs is the -NAO to block the westerlies off the Atlantic whereas we need more cooperation from both basins. Europe is also at a higher latitude than the Mid-Atlantic so when an arctic airmass is present, they tend to get snow. It's just rare, at least in the last 20 years, for them to see cold continental airmasses as they've had last winter and this one.

Is your take that the storm after that will be the big one for us (once the cold air settles back in)?

It's really way too early to tell. The only thing you can say is that the pattern looks favorable with a 570dm+ block over Greenland and more of a +PNA in the Pacific. We still have the GoA low to deal with which is trying to flatten heights in the west so it's not perfect. Way too far out to focus on individual threats at this point, in my opinion.

[A-L-E-X]

The problem is that the Pacific is not really behaving with first having a Central Pacific trough and then a GoA low. All Europe needs is the -NAO to block the westerlies off the Atlantic whereas we need more cooperation from both basins. Europe is also at a higher latitude than the Mid-Atlantic so when an arctic airmass is present, they tend to get snow. It's just rare, at least in the last 20 years, for them to see cold continental airmasses as they've had last winter and this one.

It's really way too early to tell. The only thing you can say is that the pattern looks favorable with a 570dm+ block over Greenland and more of a +PNA in the Pacific. We still have the GoA low to deal with which is trying to flatten heights in the west so it's not perfect. Way too far out to focus on individual threats at this point, in my opinion.

This makes you wonder why London was in a big snow drought for so long.  Their latitude is like 51 N and yet they average less snow than NYC which is 10 degrees latitude south of them.

[jm1220]

12z GGEM ensembles aren't bad. Some have this storm going inland and some show this storm as a coastal.

Just take a look at the overall pattern, and the setup of the northern/southern streams. In a pattern where there's no or transient blocking over Greenland and no 50-50 feature, it's hard right off the bat to have an all or mostly snowstorm in the coastal plain this time of year due just to water temperatures, and the tendency of storms to cut north once they get to our longitude. Storms tend to strengthen once they arrive east of the Miss. River and gain access to heat/H20 from the Gulf and Atlantic, and then try to cut north as they strengthen. You usually need some kind of blocking mechanism north of us to keep a storm southeast of us anyway. Secondly, during a Nina, the northern stream is dominant, meaning there are many more clippers than usual and storms that cut north than usual due to a pattern that favors a trough over the west/Midwest and ridging over the Southeast. The northern stream is also more energetic, making it even easier for storms to sharpen in the flow and cut north. That makes it even more essential that the cold air around here is locked into place to possibly force the storm to transfer to the coast, or force a southerly path. During strong Ninas like this, without a favorable pattern northeast of us to block up the fast northern stream-dominated storminess, it's very unlikely that we get a snow event near the coast. That's why it looks very likely to be rain or almost all rain near the coast this time. The only way I see that changing is if the clipper that comes before it strengthens and cuts off, forcing the next storm to move around to its south, or the Greenland blocking somehow stays in place. The good thing is, this storm for Sunday/Mon looks like it might be strong enough to force another block to develop, setting up a chance down the road. But without that in place this winter, it's likely rain for us right off the bat. Ninas favor the Lake effect snowbelts and the Midwest for a reason.

[Ger]

This makes you wonder why London was in a big snow drought for so long. Their latitude is like 51 N and yet they average less snow than NYC which is 10 degrees latitude south of them.

Answer to this is easy: the Gulf Stream keeps London in a Seattle-type state of ocean-influenced temps (with the warm waters of the stream having a profound effect), overcast skies, and moderate precipitation.

[MJO812]

Here is our next storm.

[mattinpa]

Here is our next storm.

I know - we have a decent high in a better position, but it's way out yet again.

[MJO812]

0z GFS ensemble mean

http://raleighwx.americanwx.com/models/gfsensemble/00zgfsensemblep12144.gif

http://raleighwx.americanwx.com/models/gfsensemble/00zgfsensemblep12156.gif

East of the op run.

[MJO812]

0z GGEM is still way west.

[JBG]

AO is forecasted to plunge to -6

which, if comes to fruition, would actually give us a shot at a fully occluded storm retrograding WWD into the NYC metro area... lol... sound familiar?

NAO. It is forecasted to go very negative. When something like that happens, you can have bizarre retrograding storm scenarios such as the one the 0z Euro showed last night.

Are you analogizing this to the February 25-26, 2010 snowicane?

[whiteoutwx1796]

I know - we have a decent high in a better position, but it's way out yet again.

I'd say our next shot is 264/276. Theres some decent blocking w a 50/50 in place