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January 2016 Pattern Disco


Damage In Tolland

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The stratosphere part of his AO theory doesn't make sense to me. Why would SAI on the ground make a difference 30 miles up?

 

The wave flux helps disturb the PV and break it up, leading to a SSW. Right now, the big Icelandic low really helped build this -AO. The strat is getting disturbed, but no SSW yet.  This -AO is occurring with record cold in the strat. 

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While individual storm details are a roll of the dice past 120 hrs, this is going to be

the most impressive positive to negative AO shift on record from November-December

to January. The storm details will get worked out later.

 

attachicon.gifao.sprd2.gif

 

 

In addition to that it probably it's probably the coldest flip from Dec to Jan in over 100 years.

More importantly there's more than 1 snowstorm in this pattern over the next 15 days in the MA/NE.

An active jet is taking shape and with all those high heights it's just a matter of time before 1 or 2 make a run.

It's not a 1 and done type of pattern.

The tale of two seasons is being written as we speak, now for the blizzard part.

We wait.

We verify.

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Regarding Cohen's hypothesis, I think as long as a SSW is achieved this winter, the physics of the hypothesis will verify. If we take a year like 2009-10 for example, which I believe featured very high snow cover advance, the official SSW actually didn't occur until February 9th, 2010. But the stratosphere was perturbed well prior to that, and obviously we had the -AO in place from December onward. I think 2009-10 would be considered a verification of the hypothesis. As I've posted before, the AO is almost always negative prior to the SSW.

 

One of the primary differences between this year and last year, IMO, is that the troposphere is much more conducive for the development of high latitude blocking. Secondly, I would argue the QBO state/direction and solar is more favorable than last year.

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2009-2010 had everything going for a SSW though. My question is how can you say SAI is responsible? Waiting until Feb seems too late for verification. Even this year, I would say that if we did get a SSW, would that happen without that 930 Iceland beast? I think these are fair questions to ask. The -AO started from that really. 

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2009-2010 had everything going for a SSW though. My question is how can you say SAI is responsible? Waiting until Feb seems too late for verification. Even this year, I would say that if we did get a SSW, would that happen without that 930 Iceland beast? I think these are fair questions to ask. The -AO started from that really. 

Last time I'll ask you this year, promise!

Are the new Euro monthlies out and how do they look?

Since this was more for seasonal purposes, I thought it belonged in this thread vs. the model thread. Thanks.

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Last time I'll ask you this year, promise!

Are the new Euro monthlies out and how do they look?

Since this was more for seasonal purposes, I thought it belonged in this thread vs. the model thread. Thanks.

 

 

I posted on the 46 day ensembles in NY ( Will become the new weeklies ) 

 

Jan 15- 25 VG

Jan 25- Feb 5 - well pull back but never lose the higher heights in Canada or STJ , trough in the SE 

FEB 5 - 20 VG

 

The break is not warm - N to AN but it`s been pushed back 5 days since last week .

 

Pretty good look IMO . 

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2009-2010 had everything going for a SSW though. My question is how can you say SAI is responsible? Waiting until Feb seems too late for verification. Even this year, I would say that if we did get a SSW, would that happen without that 930 Iceland beast? I think these are fair questions to ask. The -AO started from that really. 

 

 

My thoughts are similar. Like many of our LR forecasting tools, some of them might be correlation / strong correlation without a proven causative link. When there are numerous conducive variables, how do we effectively isolate one of them? In 2009-10, we not only had the +SAI, but also conducive tropospheric indicators, a descending / easterly QBO, and the weakest solar activity seen in decades. So the question becomes: was the tropospheric -AO initiated due to one or all of the aforementioned factors? My guess is that the perfect storm of favorable ingredients led to the result, and they worked cooperatively. The SAI hypothesis seems to be based upon solid dynamics, but as you said, it's difficult to isolate that variable and prove causation. It may very well be that high snow cover years occur concurrently with another variable which is actually more responsible for inducing the tropospheric -AO. Certainly many unanswered questions.

 

Going forward, in terms of this year, it looks like we continue to maintain a very elongated vortex over the next couple weeks w/ warmth pressing via the Aleutian ridge and on European side. Mostly wave-1 forced so far. This winter is a very interesting test case as we're in uncharted territory in a number of ways.

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With the Arctic Oscillation's beginning its descent toward forecast values of -4.000 or below over the next 4-7 days, opportunities for measurable snowfall should increase over parts of North America, particularly the Middle Atlantic region. Since 1950, there have been 10 cases during which the AO first fell to -4.000 or below during the period from January 15 +/- 10 days. With two exceptions, Boston, Detroit, New York City, Philadelphia, and Washington, DC all saw at least some measurable snowfall from the date the AO first fell to -4.000 through the following 30 days.

 

Below is the latest AO forecast and statistics for those cases:

 

AO01082016c.jpg

 

 

Small changes in the Teleconnection Forecasts...

 

- There is larger agreement among the GFS ensemble members that the AO will fall to -5.000 to -4.000 toward mid-month, with somewhat fewer taking it below -5.000. The overall idea of the development of severe blocking remains unchanged. Today's AO figure was -2.758, which is the lowest it has been this winter.

 

- The NAO was slightly negative. It has been positive for 37 of the first 39 days of meteorological winter or 95% of the time. In contrast, the AO has been positive 72% of the time so far. The NAO is forecast to go strongly negative.

 

- The PNA remains positive. Consistent with a PDO+, the PNA+ has been the general rule this winter so far. The PNA has been positive for 82% of days and at or above +1.000 on 38% of the days. It is forecast to remain positive through the extended range, though one cluster of ensembles takes it to strongly positive levels and another cluster toward near neutral levels by the end of the ensemble forecast.

 

All said, given climatology, the forecast sustained AO-/PNA+ pattern should lead to an increase in snowfall opportunities in the eastern U.S., with the largest increase over the baseline being focused on the Middle Atlantic region.

Glad that Donny and I are one the same page.

The show is in the mid atlantic this season, just how many tickets are made available to be distributed up the coast remains to be seen.

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