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Pattern Change thread

ORH_wxman

By ORH_wxman,
in New England

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mahk_webstah

mahk_webstah

Posted
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That is also a ridiculous -NAO signal for that far out on a smoothed ensemble mean...you can clearly see how much it wants to raise heights over Greenland.

I would think that with a srong -nao that even if an op model is showing a storm cutting up to our west that it would trend south and/or redevelop on the coast. If the block is in place by tday then perhaps we trend south with that storm

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CoastalWx

CoastalWx

Posted
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00z EURO is east based and the 00z GFS is west based with the -NAO block. Coastalwx, since the La Nina forces cooling over the eastern Pacific tropical regions, this means that the +PNA ridging pattern cannot be sustained right? So does this mean that in La Ninas, the western Atlantic Ocean warms and builds up the SE Ridge?

Well the se ridge isn't all the Atlantic, but certainly warmer waters in the Atlantic could help sustain it. We have lost some of the big anomalies in the Gulf and se coast however.

The se ridge is formed from everything teleconnecting. Latent heat release from convection in the Indonesia area helps form a downstream ridge over the central Pacific. The central Pacific ridge teleconnects to a big -PNA trough over the west coast. This in turn pumps up and forms a se ridge across the Gulf of Mexico and deep south. This is a very general overview. Obviously intensity and the location of the coldest anomalies in the tropical Pacific ocean help determine where these physical features set up shop.

What would be ideal, is to have a -nao constantly battling the se ridge, This would end up causing a huge battle ground with an active jetstream and multiple storm chances. The -nao would throw some cold air into the picture as well to increase snow chances. The argument is that during a mdt/strong La Nina, the blocking does not want to hang around for a while, due to an active jetstream. There is some evidence that -nao's like to hang around when we have a very strong -pdo and also, mdt/strong nina's have had a -nao during the 50-70's. This occured during the last -nao decadal cycle, while the recent mdt/strong nina's have had +nao's during the +nao decadal cycle. We'll see how this plays out.

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skierinvermont

skierinvermont

Posted
Posted

The Zucker Model has an obvious warm bias.

Naw.. just 5 or 6 days ago he was telling me how great the 11-15 day pattern would be. I kept telling him that given the -PNA it's all dependent on the NAO block becoming west based enough to direct the cold into the east which is far from a lock on a 11-15 day model forecast. We all know how that one turned out..

Obviously the old run was better, but you are sticking a deterministic model run in front of me at 240 hours and using it to prove a point when in reality theres a good chance it will show us with -15C 850 temps tomorrow at 12z. That's pretty poor reasoning.

I want to hear actual physical reasons why the pattern wont be favorable for a snow event in the 10 days past Thanksgiving here.

Agreed... 1 run of the Op Euro extrapolated from the D10 means absolutely nothing. The GFS and Euro Ensemble means clearly want to take the NAO negative and there's plenty of cold air in Canada. It's all a question of exactly where the block sets up.

To be fair to Zucker I think he was just saying that the Op Euro doesn't look good extrapolated from D10 which is true.. but I don't know why one would pay much attention to that at all given the ensemble means of the past several runs from the GFS and Euro.

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40/70 Benchmark

40/70 Benchmark

Posted
Posted

The cold wont come south without a big +PNA...that was never the idea. NAO will push it east though and should hit New England and the Great Lakes.

I know you are trying to not make it snow here....but the weather will do what it wants. We'll see who is right and who is wrong by Dec 10th. My bet is we end up with a below avg regime after T-day and there will be threats. No guarantee the snow threats work out...but they will be there and the temps should avg below normal.

He is a classic case of intelligence outrunning experience and common sense; he'll be a great forecaster in about 3 years time.

Boo hoo...no snow for Tday....welcome to climo.

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ORH_wxman

ORH_wxman

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SW flow events actually somewhat negate the disadvantage of being in close proximity to Dec ssts; its coastals which exploit that moreso.

Correct...its one of the reasons Boston saw so much snow in December in 1970, 1975, and 2007....a lot of SW flow events in there where sfc winds are northerly.

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dryslot

dryslot

Posted
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Correct...its one of the reasons Boston saw so much snow in December in 1970, 1975, and 2007....a lot of SW flow events in there where sfc winds are northerly.

SWFE, They are great here as well as i am approx 25 miles from the water and don't have any ocean effect ala 07-08 good example, SE winds are a killer def with the warmer sst's at this time of year.

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CoastalWx

CoastalWx

Posted
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The better high placement is over quebec........... :thumbsup:

Yeah the big polar highs ridging in from the Great lakes are my favorite. Very little marine contamination. My point was that the whole Boston can't snow in December argument can be flawed...especially during a La Nina. Sure climo says it is more difficult, but a relatively cold antecedent airmass, with a high to the north is really all you need.

Plus Ray wants highs that are northeast of Maine, for is CF fetish.

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dryslot

dryslot

Posted
Posted

Yeah the big polar highs ridging in from the Great lakes are my favorite. Very little marine contamination. My point was that the whole Boston can't snow in December argument can be flawed...especially during a La Nina. Sure climo says it is more difficult, but a relatively cold antecedent airmass, with a high to the north is really all you need.

Plus Ray wants highs that are northeast of Maine, for is CF fetish.

They are mine as well as they typically move the polar air SE, To strong a high can hurt me here but still benifit you guys down there as it will block LP from reaching the GOM...

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CCPSUSuperstorm2010

CCPSUSuperstorm2010

Posted
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Well the se ridge isn't all the Atlantic, but certainly warmer waters in the Atlantic could help sustain it. We have lost some of the big anomalies in the Gulf and se coast however.

The se ridge is formed from everything teleconnecting. Latent heat release from convection in the Indonesia area helps form a downstream ridge over the central Pacific. The central Pacific ridge teleconnects to a big -PNA trough over the west coast. This in turn pumps up and forms a se ridge across the Gulf of Mexico and deep south. This is a very general overview. Obviously intensity and the location of the coldest anomalies in the tropical Pacific ocean help determine where these physical features set up shop.

What would be ideal, is to have a -nao constantly battling the se ridge, This would end up causing a huge battle ground with an active jetstream and multiple storm chances. The -nao would throw some cold air into the picture as well to increase snow chances. The argument is that during a mdt/strong La Nina, the blocking does not want to hang around for a while, due to an active jetstream. There is some evidence that -nao's like to hang around when we have a very strong -pdo and also, mdt/strong nina's have had a -nao during the 50-70's. This occured during the last -nao decadal cycle, while the recent mdt/strong nina's have had +nao's during the +nao decadal cycle. We'll see how this plays out.

Thanks for the explanation Coastal. Very well thought out explanation into the simplistic view of the overall pattern.

Don't we like to see +PNAs regardless of what ENSO phase we are in?

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CoastalWx

CoastalWx

Posted
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Thanks for the explanation Coastal. Very well thought out explanation into the simplistic view of the overall pattern.

Don't we like to see +PNAs regardless of what ENSO phase we are in?

Yeah a +PNA is good because when this occurs, by definition we have a ridge out west. If you have a ridge out west, more than likely you have a trough in the east, and hence the cold. These are more likely during El Nino's because it goes back to the argument for where the tropical forcing is. El Nino's usually have forcing much farther east...like near the dateline. This is in turn develops ridging out in the west.

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40/70 Benchmark

40/70 Benchmark

Posted
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Yeah the big polar highs ridging in from the Great lakes are my favorite. Very little marine contamination. My point was that the whole Boston can't snow in December argument can be flawed...especially during a La Nina. Sure climo says it is more difficult, but a relatively cold antecedent airmass, with a high to the north is really all you need.

Plus Ray wants highs that are northeast of Maine, for is CF fetish.

Bingo....the 12* pure sugar slammers, with max CSI over Brockton don't really do it for me...I want it to rain on CC.

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