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Snow in the first week of November


Typhoon Tip

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Good call, only off by a week or so.

Actually ...not really off by a week... The title says the first week of November, but only the title - you have to read the thing and you'll see that it was pretty liberally applied for after the 20th of October... That, AND, heh, if you believe some of the guidance, Saturday may not be the end of it -

That said, the real reason for the bump is not as self-promoting as it may seem; it's educational, because I believe the application of teleconnector science was pretty spot on actually.

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Actually ...not really off by a week... The title says the first week of November, but only the title - you have to read the thing and you'll see that it was pretty liberally applied for after the 20th of October... That, AND, heh, if you believe some of the guidance, Saturday may not be the end of it -

That said, the real reason for the bump is not as self-promoting as it may seem; it's educational, because I believe the application of teleconnector science was pretty spot on actually.

Dude you nailed the teleconnections from way way out when it was still 90 degrees and I was hanging out at the beach enjoying record warmth. Kudos for the early posts and signal recognition. Funny to read some of the people accidentally predicting the actual outcome with things like "not like i mean 12 inches for all" and stuff like that. Great thread Tip.

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:clap: :clap:

I'm going to have to go through and re-read your posts so I can really get a handle on your train of thought and understand it for myself, seems like you might be on to something.

Glancing through though great job!:mapsnow:

What does your notation of the P at the end of +PNAP stand for?

Also, where are you finding the actual std. dev. numbers from for each teleconnection?

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These are not overwhelming singular teleconnector signals, but they are more impressive when they occur in tandem that way. I call that “teleconnector convergence” and have for years… Anyway, it’s when you get multiple signals from disparate source regions; in my own evaluation/reanalysis I have found that to be more reliable than using just one or the other teleconnectors alone – and that is kind of a duh moment anyway.

Could you explain your teleconnector convergence theory a little more?:thumbsup:

You were mentioning a -PNA combining with a -NAO for a good cold pattern...and you called the result correctly, but do you have any thoughts on how we acheived this with a slightly positive NAO over the last few days and a nearly neutral PNA. Could you offer any insight to this and how it played out with your prediction?

Thanks! Just trying to grasp your ideas for use myself!

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Ensembles paint a cool look in the extended..but there's nothing overwhelming that supports a major cold outbreak or chances for snow other than uplsope snows in NNE and lake effect.

It's too early to be counting on the indices as far as PNA and NAO to determine how wintry the pattern looks. need to hold off untl November for that

lol

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Could you explain your teleconnector convergence theory a little more?:thumbsup:

You were mentioning a -PNA combining with a -NAO for a good cold pattern...and you called the result correctly, but do you have any thoughts on how we acheived this with a slightly positive NAO over the last few days and a nearly neutral PNA. Could you offer any insight to this and how it played out with your prediction?

Thanks! Just trying to grasp your ideas for use myself!

Thanks all -

Hey QVector',

Firstly, this is a primer for anyone so it is written this way for a purpose (thanks for asking though..)

What sources for SD? CPC mentions in their headers for the indexes:

"The daily AO indices are shown for the previous 120 days, and the ensemble forecasts of the daily AO index at selected lead times are appended onto the time series. The indices are standardized by standard deviation of the observed monthly AO index from 1979-2000. A 3-day running mean is applied to the forecast time series. "

PNAP = Perennial North American Pattern. I feel it is important to delineate that from PNA, because PNA and PNAP are not always on the same page. The Perennial North American Pattern is the mean longer term pattern over the course of the average year, which features a flat western ridge and a shallow eastern trough. Knowing this is useful when in discourse, because one can refer to an amplified PNAP pattern as being an enhanced version of a western ridge, eastern trough couplet; most importantly, that can take place in a -PNA, or a +PNA. Hence, the need to set them apart. PNA, Pacific North - American oscillation has an immense domain space. The western 2/3rds of it may compute negative, while the area that encompasses the U.S may be negative - the PNA would overall thus compute as negative despite the flow over North America not agreeing. +PNAP vs -PNAP is the better use during those times. I used PNAP in the original because the PNA's influence was hidden by the fact that it wasn't hugely positive during the time of the cold incursion and subsequent snow threats - it was the differential that was the key (more below).

It all probably sounds more handsome than it is.. The short and skinny is that I have found Teleconnector Convergence (I should probably try and write a formal paper) to be more reliable than just looking at the PNA, NAO, or EPO in quadrature. Many of us, I included, can focus too readily upon just one of those 3, and it works much of the time, granted. But the idea here is to try and consider the global circulation more as a whole entity rather than just what the left or right arm are doing. Thus, it is an expression that means: 2 disparate teleconnectors that have a common statistical signal pointed toward a given place and time.

The conceptual model for 2 disparate sources, for example, the PNA and NAO don't really share domain space (not according to CDC's coordinates); within that understanding, there can be opposing signals depending on location to location affected by either.

-PNA/-NAO can imply large scale deconstructive R-wave interference. ...More likely to be observed during unstable global wave numbers.

+PNA/-NAO can imply large scale constructive R-wave interference. ...More likely to be observed during stable global wave numbers.

Of the two above +PNA/-NAO could be construed as Convergent in the simplest sense, however the situation gets complicated in a hurry when we then have to consider that these individual teleconnetors et al, are constantly differentiating in time, with respect to them selves, and to one another (with less speed than the vagaries of any given operational run for ~ D5 and beyond). There is also a seasonal "effectiveness" - in summer this really should not be used with much confidence. Best when served between October 1 and June 1 :)

But I digress...

I didn't go into this as deep in the original write-up because I was at work, on lunch break - oy vay. However, the Arctic Oscillation fell across 2.5 weeks, from +2SD (Standard Deviations), to -1SD. Therein is an example of needing to consider the differential, not just the mode. That amounted to dropping some 3 SDs; considering the scale only goes to +5 or -5, that's 3 units of the statistical mass out of 10, i.e., a lot of weight! Owing to the fact that -AO is a cold signal for 45N latitude(s), correcting the characteristics of the overall AO downward some 3 SD in just 2.5 weeks was likely going to deliver some cold into the 45-60 N band around the hemisphere (probably picking the the most favored conveyor regions to do so - sometimes that favors the Eurasia side, granted). There was also a cryosphere idea in there where leading that negative differentiating was a 1.5 month long positive bias in the AO - that somewhat complicates this in that cold air was being generated during that time, yet bottled up at high latitudes. When said downward index trend signaled at least some release was assumed.

A PNA rise was a cool teleconnector aimed at West Va. An NAO fall is a cool teleconnector aimed at OH. A well behaved negative -AO differential (reasonable gamble) is a cool signal from Washington state to Maine, the overlap in those 3 has most mass over PA- New England.

It doesn't always work - I'll be the first to tell you - but it has allowed me to pick up on some intriguing signals, sometimes long before the operational runs have even painted them, in the past. The NAO was neutral as you say, however, it was +1SD on the 10th of October, so the 10 day differential is negative.

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  • 3 weeks later...

Tip thank you so much for the indepth write up to my questions. I apologize for the delay since I was out of the country for the past 3 weeks. It makes a lot of sense and I'm going to see if I can impliment it myself. BTW I realize the SD stuff right after I wrote that :wacko:

Where can I find the Perennial North American Pattern numbers at?

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