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The Winter 2010-11 NYC/PHL Medium Range Thread


am19psu

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Pretty much stating that the demise of the -nao has been greatly exaggerated.

post-623-0-30927900-1291307422.gif

Once the block gets this strong it has a tendency to be pretty tenacious and usually tries to come back even after it weakens as each big vortex that develops to its southwest pumps warm air back into the ridge. That said, for us. the block location has been little too far south to allow the 50 50 low to get going, The current vortex/trough is part of the reason the clipper looks to be such a dud. There's no room for amplification.

This will be a good test of the mjo as it suggests that the pattern will flip warm in mid dec. We'll see what happens and which wins. NAO or mjo climo.

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Pretty much stating that the demise of the -nao has been greatly exaggerated.

post-623-0-30927900-1291307422.gif

Welcome to the -PDO phase. I'll go out on a limb and predict that the NAO will remain negative(on average) during December, January, February and neutral during March. There will be some brief positive periods, obviously. I expect the numerous northern stream systems and miller B's to continuously rebuild the Greenland ridge. Most of the snow for 40S will arrive with overrunning events and WAA.

This type of pattern definitely won't result in your typical strong/mod la nina winter.

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Welcome to the -PDO phase. I'll go out on a limb and predict that the NAO will remain negative(on average) during December, January, February and neutral during March. There will be some brief positive periods, obviously. I expect the numerous northern stream systems and miller B's to continuously rebuild the Greenland ridge. Most of the snow for 40S will arrive with overrunning events and WAA.

This type of pattern definitely won't result in your typical strong/mod la nina winter.

You'll deserve a huge :thumbsup: if that verifies, everything that I have read points to either a neutral or positive nao for this winter, which is obviously in trouble for this month.

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Once the block gets this strong it has a tendency to be pretty tenacious and usually tries to come back even after it weakens as each big vortex that develops to its southwest pumps warm air back into the ridge. That said, for us. the block location has been little too far south to allow the 50 50 low to get going, The current vortex/trough is part of the reason the clipper looks to be such a dud. There's no room for amplification.

This will be a good test of the mjo as it suggests that the pattern will flip warm in mid dec. We'll see what happens and which wins. NAO or mjo climo.

Wes,

Yeah I was just looking at the various agency outlooks and the ukmet has it warm also which I thought Matt said was one of the better MJO projectors. At anyrate it might be a battle royale this mid December. As per this clipper, there were a couple of northern stream crushed lows this fall so I guess this probable outcome is not that surprising.

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Yea can't complain about the nao just continuing to be negative with a few flexes here and there. Storm chaces when it flexes?

Yeah perhaps. It's just very interesting how persistent this block has been. Back in the 50's and 60's, we did have at least several mdt-stg Nina's that had a -nao, so clearly this has happened before. I think many of us are just used to the blowtorch ninas of the 80's and 90's, but these also occurred during the +nao decadal phase. Clearly back even during the -nao decadal phase, the MJO forcing didn't necessarily trump the nao signal. I have no clue where this is going and certainly am not a long range expert, but obviously there are other things going on to help keep this block going. Who knows though...maybe we go raging +nao during Jan and Feb, or perhaps we only recover to a near neutral-negative phase. Certainly will be fun to watch unfold. There is also some research as to the correlation of the -PDO and -NAO. It seems that the rise and fall of both are almost hand in hand, but like with many other meteorological variables...it's the chicken or the egg argument.

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Wes,

Yeah I was just looking at the various agency outlooks and the ukmet has it warm also which I thought Matt said was one of the better MJO projectors. At anyrate it might be a battle royale this mid December. As per this clipper, there were a couple of northern stream crushed lows this fall so I guess this probable outcome is not that surprising.

No, I think that is also one of the problems with moderate to strong ninas. I keep going back to 1975-1976. The first two months had a neutral to negative nao and then we torch but despite having a really cold Jan, dca didn't get squat. I'm not a big single season anlogs guy so I doubt we'll do as bad this year and also doubt that the winter month temps will have the same sign as that year.

I just hope there are enough storm threats to allow me to write some blogs.

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Ok, so I think we can say with a good deal of certainty that colder than normal temperatures are a lock from today until at least mid December. The issue now becomes - do we get significant snow to coincide with the brutal chill? Well as I mentioned the other day, often times in strong ninas we get these cold/dry patterns that don't produce much more than a light < 3" event. But our best window of opportunity looks to be mid December, the 12th-15th.

The clipper for this weekend will be suppressed well south, in fact folks in southern Virginia may pick up an inch or two out of it. Then for next week, the polar vortex remains in an unfavorable position for any stormiess reaching the Northeast. With the trough axis essentially sitting on the East Coast, all your baroclinicity and cyclogenesis potential is far out to sea. Terrible looking map for a big snowstorm but great for cold/dry pattern. We need that PV to retrograde back NW to near Hudson's Bay so some semblance of ridging can return to the SE ridge. Remember, a little SE ridging is a good thing as is allows lows to turn the corner NE towards the VA capes.

What you see in the following GFS projection for the middle of next week indicates Bermuda is the best spot for storminess.

gfs_500_138s.gif

Beyond that time frame, the -NAO will weaken, but NOT collapse entirely, and that's the key for us. We'll have a neg nao/ao continuing into mid december, but the trough axis will be shifting significantly further west, retrograding into the Mid-west. Thus we're in a much more conducive location for snow in the December 12th-16th period w/ a large scale trough from PAC NW to NE US, -PNA/-NAO regime.

gfs_500_228s.gif

At least w/ that set-up, we can see some gradient driven events. The next 6-8 days look like bone dry NW flow and the occasional flurry if we're lucky.

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gfs looks good at 18z, 200 hrs out about. I knew there was gonna be a storm off the coast when i saw the deeper trough and ridging out west. Atleast the gfs and euro are agreeing on a storm right now. 1 thing i really like, is that the cold air will def be there...

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