The Winter 2010-11 NYC/PHL Medium Range Thread

[am19psu]

This thread is for NYC/PHL Metro medium and long range forecasts. Wes, rainshadow, HM, etc. all know way more about this type of forecasting than me, but it's the area of meteorology that is most scientifically interesting to me at the moment. I figured it would be better to keep a separate thread from the obs thread to keep it on topic. Hopefully, it goes well.

[am19psu]

It's a tough call whether next weekend is cool or outright cold. The Euro has really been backing off on the chill, while the GFS has been hanging on. The MJO should be be in the P8-P1 area, which would indicate less cold. The GWO should be in G1-G2, also indicating temperate weather. On the other hand, there will be a strong Arctic airmass bleeding down the Rockies next week. My guess is that we'll end up slightly below normal, but not well below like model runs a few days ago were showing.

[earthlight]

It's a tough call whether next weekend is cool or outright cold. The Euro has really been backing off on the chill, while the GFS has been hanging on. The MJO should be be in the P8-P1 area, which would indicate less cold. The GWO should be in G1-G2, also indicating temperate weather. On the other hand, there will be a strong Arctic airmass bleeding down the Rockies next week. My guess is that we'll end up slightly below normal, but not well below like model runs a few days ago were showing.

This winter will probably feature several cold events where it feels like the "trough that never could get here". These type of patterns tend to repeat themselves in the current ENSO state as well. I like where we're sitting for early to mid December, though, to at least get some moderately cold air in here.

[am19psu]

This winter will probably feature several cold events where it feels like the "trough that never could get here". These type of patterns tend to repeat themselves in the current ENSO state as well. I like where we're sitting for early to mid December, though, to at least get some moderately cold air in here.

I agree that we'll get some really cold air this year. It's really all dependent on whether the NAO is set up properly as the Arctic airmasses come into the Plains.

If you buy into Paul Roundy's tropical convection forecasts, the MJO will be in P3 to start December, which could start the month out really warm across the East. Nina climo, obviously, favors cold for the month as a whole, though.

[earthlight]

I agree that we'll get some really cold air this year. It's really all dependent on whether the NAO is set up properly as the Arctic airmasses come into the Plains.

Yeah, the east/west based NAO proved to be a big play maker last year. I think this season, especially, the PNA will become a major player on the field. The pattern developing on global ensembles could be favorable for a huge east coast trough with the blocking in place, a +PNA ridge and a -NAO, but the -PNA that's forecast to develop by most ensembles leads to a big ridge in the Central Pacific Ocean and a big trough on the west coast, leading to a general zonal gradient pattern over the Central and Eastern US.

[am19psu]

Yeah, the east/west based NAO proved to be a big play maker last year. I think this season, especially, the PNA will become a major player on the field. The pattern developing on global ensembles could be favorable for a huge east coast trough with the blocking in place, a +PNA ridge and a -NAO, but the -PNA that's forecast to develop by most ensembles leads to a big ridge in the Central Pacific Ocean and a big trough on the west coast, leading to a general zonal gradient pattern over the Central and Eastern US.

Yup, the Pacific is going to be a big driver. In Jan/Feb, when the +EPO/-PNA pattern sets up, it's not going to matter what the NAO does. Hopefully, for the cold lovers, it's not set up that way the whole month.

I'm curious: what makes you bullish on the cold for the first half of December? The tropical stuff seems to favor the latter half.

[earthlight]

Yup, the Pacific is going to be a big driver. In Jan/Feb, when the +EPO/-PNA pattern sets up, it's not going to matter what the NAO does. Hopefully, for the cold lovers, it's not set up that way the whole month.

I'm curious: what makes you bullish on the cold for the first half of December? The tropical stuff seems to favor the latter half.

I think there's a ton of cold air right now that's entering western Canada..which could very easily make it's way to the Central and Eastern US by the end of the month or beginning of December. With the favorable blocking in place and the global ensembles forecasting -NAO values for the next few weeks...the potential definitely exists for some of that cold air to make it's way east. I'm more bullish on the early December potential for snow than I am for cold to be honest, it's going to be really hard to get well established below normal departures in this area this winter.

[earthlight]

Here's this afternoon's 12z global ensemble heights in the long range. I'm not complaining, but the Pacific could certainly be better. Lots of potential here extrapolated.

[am19psu]

Here's this afternoon's 12z global ensemble heights in the long range. I'm not complaining, but the Pacific could certainly be better. Lots of potential here extrapolated.

Yeah, that ridge over the Aleutians could be a major fly in the ointment, or it could be a godsend if if dumps Arctic air into the Plains that can get eastward.

[earthlight]

Yeah, that ridge over the Aleutians could be a major fly in the ointment.

Certainly. It screws with the entire longwave pattern all the way down to the CONUS..developing the gradient pattern. Those historically, especially in early December, favor only our area (sometimes) and north into Southern New England for snowfall events. The -NAO could come into play, and potentially help us in that department, though. We will see.

[Dsnowx53]

Not really a fan of the Aleutian Highs. Even with a -EPO, if your heights are too high over the Aleutians, that will lead the surge of cold air to be dumped too far west, and we'll get some modified cold, but not great cold...plus since we'll be well on the east-side of the surge, that will mean we'll have SE ridging to deal with. The -NAO will be huge! We really, really need one, IMO.

[Nikolai]

Certainly. It screws with the entire longwave pattern all the way down to the CONUS..developing the gradient pattern. Those historically, especially in early December, favor only our area (sometimes) and north into Southern New England for snowfall events. The -NAO could come into play, and potentially help us in that department, though. We will see.

The 12z EURO is really great... it really gets a -NAO going by 240, although far off. I think it's doing something funky with the W. Canada ridge closing off and drifting away... if anyone remembers, that was a common theme in the long range during 08-09 and it didn't verify very well.

I still think the next week is relatively normal with a shift to cold by the 18th, and very legitimate snow threats begin after the 21st continuing into December. Front-loaded winter FTW.

[earthlight]

The 12z EURO is really great... it really gets a -NAO going by 240, although far off. I think it's doing something funky with the W. Canada ridge closing off and drifting away... if anyone remembers, that was a common theme in the long range during 08-09 and it didn't verify very well.

I still think the next week is relatively normal with a shift to cold by the 18th, and very legitimate snow threats begin after the 21st continuing into December. Front-loaded winter FTW.

The W Canada ridge closing off is a function of the large ridge in the Aleutians and central Pacific and the -PNA development...so it's not all that far fetched although I can't say I completely trust the solution. The evidence for the medium/long range right now definitely suggests more of a gradient pattern than a +PNA/-NAO trough in the east-type setup, I will say that much. Nice post by the way.

[earthlight]

Not really a fan of the Aleutian Highs. Even with a -EPO, if your heights are too high over the Aleutians, that will lead the surge of cold air to be dumped too far west, and we'll get some modified cold, but not great cold...plus since we'll be well on the east-side of the surge, that will mean we'll have SE ridging to deal with. The -NAO will be huge! We really, really need one, IMO.

Strongly agree, at least early on. The -NAO and it's positioning (west/east based) are huge players on the field when you have a potential gradient-type (although not textbook) pattern potentially setting up.

[Analog96]

This winter will probably feature several cold events where it feels like the "trough that never could get here". These type of patterns tend to repeat themselves in the current ENSO state as well. I like where we're sitting for early to mid December, though, to at least get some moderately cold air in here.

I'm just sayin', but from about late December until early February, if the trough "just barely gets here" that could put us in a good spot for frequent snows, or at least mixed, events.

[Nikolai]

I'm just sayin', but from about late December until early February, if the trough "just barely gets here" that could put us in a good spot for frequent snows, or at least mixed, events.

I think the late Nov/Dec/early Jan period will perform very well, but after 1/20, we're dead... the Nina finally rages after that. I think the decadel cycles are a major booster for the cold December idea, given we've finally emerged from the horrible Decembers of the 70s/80s/90s and Decembers now (for the past decade) have actually averaged more snow (I believe the numbers are close to 8.0" vs 7.5") than January. I think the trend holds strong (through the next several decades at least), and we see a new trend begin to emerge in the 2010s--cold/snowy D/Js, and relatively warmer/less snowy Februarys. I think we're entering a predominantly Nina cycle, and the Februarys of the 2010s, although very impressive, were a blip--January WILL regain its traditional role as the month with the most snow after 2013-14.

In the meantime, buckle down. I've been gunning for a cold late Nov/Dec for a long time, and I'll eat my words if I'm wrong--but I think the models are coming around to support me wrt my statement. Watch out for a SW flow event pre-Thanksgiving (whether we can hold on to the cold or not is debatable,) but I think by Thanksgiving we will be seeing threats a-plenty. The NAO is finally coming around to what will be the "normal" state through mid-January, with the ridging over Greenland increasingly prominent in recent model runs. What matters most will be Pacific cooperation--we saw in 08-09 a cold pattern without a great Pacific, I think we'll see the same here.

Write me down for 10"+ for NYC this December--just enjoy the snow now, because February/March are going to be horrid!

[Nikolai]

"speaking of the devil"...

the 00z GFS gives us our first mixed-ish event of the season around D6-7.

clearly very far-off, but the first time it's shown us with decent precip after sub-freezing 850s have moved in.

[CoastalWx]

Strongly agree, at least early on. The -NAO and it's positioning (west/east based) are huge players on the field when you have a potential gradient-type (although not textbook) pattern potentially setting up.

I think the Aleutian ridge and -NAO can be a good combo to have..even down by NYC. When that occurs, you get both ridges sort of poking at the North Pole and shoving the cold down into southern Canada, as it spreads out from e-w. If they NAO is half decent. NYC could cash in. What you have to watch out for in these setups, is the RNA type pattern with a big sw-ne tilted trough over the west coast. That will pump up the se ridge, and we know what happens. Personally, I wish this were 2-3 weeks from now, but beggars can't be choosers.

[earthlight]

I think the Aleutian ridge and -NAO can be a good combo to have..even down by NYC. When that occurs, you get both ridges sort of poking at the North Pole and shoving the cold down into southern Canada, as it spreads out from e-w. If they NAO is half decent. NYC could cash in. What you have to watch out for in these setups, is the RNA type pattern with a big sw-ne tilted trough over the west coast. That will pump up the se ridge, and we know what happens. Personally, I wish this were 2-3 weeks from now, but beggars can't be choosers.

Yeah, I agree. I was discussing it last night with a friend, it's almost like a good block or a well placed NAO with the Aleutian ridge could be like a gradient-type pattern, but a bit further south or with a less-sharp gradient. That all ties in to the SE ridge which you mentioned..and obviously it's strength will also be a make or break type deal as to where the sharp gradient sets up. I think we're in a good spot. 2-3 weeks from now the cold air will probably unload or have just been unloading, and we could be set up well especially given the global ensemble NAO forecasts.

[Dsnowx53]

The Aleutian High pattern can be GREAT with a -NAO...while the brunt of the cold is still to the west, you certainly get more of the cold than you normally would, and the -NAO would help to squash the SE ridge...that would lead to a GREAT gradient pattern, and we'd be off to the races!!

The only problem is that if you don't get the -NAO, it could be an ugly pattern.

[Guest Noreaster]

The Aleutian High pattern can be GREAT with a -NAO...while the brunt of the cold is still to the west, you certainly get more of the cold than you normally would, and the -NAO would help to squash the SE ridge...that would lead to a GREAT gradient pattern, and we'd be off to the races!!

The only problem is that if you don't get the -NAO, it could be an ugly pattern.

strong signals of a robust west based NAO shaping up and that combined with a -EPO and active northern jet will do wonders for the Northeast. If the -PNA holds, could be seeing a few strong to severe Miller B storms that get trapped under a large block. If the PNA goes +, its Miller A time. Either way, its a win win.

[jm1220]

The Aleutian High pattern can be GREAT with a -NAO...while the brunt of the cold is still to the west, you certainly get more of the cold than you normally would, and the -NAO would help to squash the SE ridge...that would lead to a GREAT gradient pattern, and we'd be off to the races!!

The only problem is that if you don't get the -NAO, it could be an ugly pattern.

The snowcover so far in eastern Canada is very encouraging for supporting a good quality cold snap or two later on this month and Dec. The cold air will definitely be available, so it's a question of where it goes and how far South. The pattern you described is also great because it encourages a southerly flow off the Gulf, and a locked in place cold air mass here, so it creates many opportunities for overrunning events.

The SST profile in the Atlantic is great for locking a -NAO in, so I definitely think some opportunities will present themselves particularly early in the winter. Later on, I'm not sure the riproaring PAC jet will allow for much blocking, and the SE ridge will win out regardless. Without the -NAO, there's nothing to stop the SE ridge given the prevailing Nina pattern of troughiness in the West/Midwest and cutter after cutter.

[tombo82685]

12z euro backed off and postponed the cold. 0z run basically had it cold straight through starting from next thursday.

[Guest Noreaster]

12z euro backed off and postponed the cold. 0z run basically had it cold straight through starting from next thursday.

burp run perhaps?

[Alpha5]

12z euro backed off and postponed the cold. 0z run basically had it cold straight through starting from next thursday.

GFS was cold at 12z...complete flip in the two models from yesterday

[tombo82685]

burp run perhaps?

very possible, won't know till tonights 0z run. The 0z run from last night actually had frozen precip for pa and ny state in the interior. The 12z does look like it has a nice -nao, although it looks east based with the big hgt anomalies over greenland and a little back towards the bering straights.

[Guest Noreaster]

very possible, won't know till tonights 0z run. The 0z run from last night actually had frozen precip for pa and ny state in the interior. The 12z does look like it has a nice -nao, although it looks east based with the big hgt anomalies over greenland and a little back towards the bering straights.

I don't know a lot, but perhaps its the megga block being shown? does that mess up the model equations?

[tombo82685]

I don't know a lot, but perhaps its the megga block being shown? does that mess up the model equations?

it could play havoc, but like you said maybe this is a blurp. For about 5-6 runs in a row the euro had the cold blast.

[Alpha5]

Clipper potential around the 18-20th time frame

[tombo82685]

Clipper potential around the 18-20th time frame

as of now, looks like thats only for new england areas.