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December 2022


dmillz25
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We're in about as good of shape as was humanly possible for this December currently IMO. As per ensembles (EPS+GEFS). Steady as she goes. Tropical convection layout starting to look more favorable again towards the end of these runs too now.

I'm on the hunt for heavy polar vortex damage too. Resulting in a protracted period of -AO. That's not off the table yet either. Not sure what else one would like to see at the end of any November.

This year is interesting and it'll be fun to see what happens. 

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9 minutes ago, EasternLI said:

We're in about as good of shape as was humanly possible for this December currently IMO. As per ensembles (EPS+GEFS). Steady as she goes. Tropical convection layout starting to look more favorable again towards the end of these runs too now.

I'm on the hunt for heavy polar vortex damage too. Resulting in a protracted period of -AO. That's not off the table yet either. Not sure what else one would like to see at the end of any November.

This year is interesting and it'll be fun to see what happens. 

This is a classic early season bottom up blocking event with a forecast for a record weak vortex at 100 mb. 
 

 

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There are a few ways to get a -NAO pattern. One way is for MJO 8 forcing near South America to pump - NAO block over Greenland. The bottom up process in the forecast is faster. A SSW higher up in the stratosphere can take up to 3 weeks to work down to the troposphere. This is what happened in February 2018 so we hit 80° before the blocking  emerged in March. While there is  La Niña forcing initially maintaining the -PNA trough in the West, a retrogression west of the -NAO block can turn the -PNA more neutral and even positive. This is what happened in December 2010. 

 

 

 

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1 hour ago, bluewave said:

There are a few ways to get a -NAO pattern. One way is for MJO 8 forcing near South America to pump - NAO block over Greenland. The bottom up process in the forecast is faster. A SSW higher up in the stratosphere can take up to 3 weeks to work down to the troposphere. This is what happened in February 2018 so we hit 80° before the blocking  emerged in March. While there is some weak La Niña forcing initially maintaining the -PNA trough in the West, a retrogression west of the -NAO block can turn the -PNA more neutral and even positive. This is what happened in December 2010. So the stronger the -NAO is in early December, the better a chance there is for the Pacific to improve by as early as the 2nd week of December. But it will probably take a few cutters during the first week of December to help pull the trough east.

 

 

 

Which blocking set up lasts longer? Or are there too many variables to determine?

Forky mentioned this is similar to 2010, which lasted approx 6 weeks.

2018 lasted about the same.

Both resulted in massive snowfall totals of course.

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54 minutes ago, EastonSN+ said:

Which blocking set up lasts longer? Or are there too many variables to determine?

Forky mentioned this is similar to 2010, which lasted approx 6 weeks.

2018 lasted about the same.

Both resulted in massive snowfall totals of course.

The timing here is a lot better than it was in 2018.

Once past February it's extremely difficult for urban areas to get extreme snowfall totals.

 

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3 hours ago, EasternLI said:

We're in about as good of shape as was humanly possible for this December currently IMO. As per ensembles (EPS+GEFS). Steady as she goes. Tropical convection layout starting to look more favorable again towards the end of these runs too now.

I'm on the hunt for heavy polar vortex damage too. Resulting in a protracted period of -AO. That's not off the table yet either. Not sure what else one would like to see at the end of any November.

This year is interesting and it'll be fun to see what happens. 

I can't help but think that a mild November was good to set this up.

 

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32 minutes ago, bluewave said:

Both types of blocking set ups can last a long time provided there is at least one day when the -AO drops below -3. Most Decembers with at least one daily -3 or lower AO reading can feature an -AO lasting through most of the month. The blocking in the troposphere can become so strong that it propagates into the stratosphere and causes a SSW in January or February. That has happened following several strong December blocking episodes. A number of those winters featured blocking for 2 or 3 months of the DJF period.

How many times did this happen where we didn't get a large amount of snow and how much did luck factor into 2010-11?

I remember MANY very cold blocky December-Januarys in the 80s when we did not have much snow (it was usually suppressed.)

ALSO WE MUST REMEMBER THAT 2010-11 WAS A LA NINA AFTER AN EL NINO, THIS POINT CANNOT BE EMPHASIZED ENOUGH.  THOSE TEND TO BE VERY SNOWY HERE.

 

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1 hour ago, LibertyBell said:

I can't help but think that a mild November was good to set this up.

 

From what I've read, you really want to see a cold shot in the 2nd half of November. That's seems to be an important piece of the puzzle. What's interesting about that is, we've done that as well this year with the record -EPO episode. 

 

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5 minutes ago, EasternLI said:

From what I've read, you really want to see a cold shot in the 2nd half of November. That's seems to be an important piece of the puzzle. What's interesting about that is, we've done that as well this year with the record -EPO episode. 

 

Yes the snowy composite had a mild first half of November (up to the 15th ish) and then cold in the second half.  1993-94 was a prime example of that.

 

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6 minutes ago, bluewave said:

2010 was a unique case since it was a continuation of the historic blocking that began in June 2009. We have not seen a pattern like that since then. When 2010 was mentioned in these threads recently, it was in regard to having a PNA improvement later in the month. The 12z guidance continues with a parade of cutters into early December. So the hope is that the -AO can retrograde enough by mid-month to improve the Pacific side which is very hostile. December 2012 was a recent example of multiple - 3 -AO days but no improvement on the Pacific side. But we did eventually get the SSW in January 2013. So we are hoping that improvement on the Pacific doesn’t  end up getting pushed further out in time. A daily -3 AO in December usually means there will be chances for snow. I believe the only case when this didn’t happen was 2001-2002.  

 

https://csl.noaa.gov/groups/csl8/sswcompendium/majorevents.html

JAN 2013 7-Jan-13


 

https://ftp.cpc.ncep.noaa.gov/cwlinks/norm.daily.ao.index.b500101.current.ascii

Regardless of 1997-98 being considered the least snowiest winter of all time for us (going by DJF) or even 1972-73 if you consider the whole snow season, I'll always consider 2001-02 as the most extreme winter we've ever had (for both warmth and snowlessness.)  2001-02 was the polar opposite of 1995-96.

 

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8 minutes ago, Allsnow said:

Don’t like all those deep blues off the west coast on the ensembles 

Whenever we see a retrograding nao block like this it's hard not to get exciting about the prospects for something significant to happen once the block eases up a bit.  It's just such a favorable setup for winter wx in the northeast.  

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