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December Forecast Discussion


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Punt December, but that has no bearing on the rest of winter. For the life of me I can't find the paper that discusses the three types of 500 mph flow for arctic outbreaks. However I know they are north, northwest and southwest. Yes, you read that right - southwest. Of course west won't work per the blowtorch. Believe the southwest version is coming, but not to the Southeast.

Southwest 500 mph flow includes the main jet stream migrating south over the western US and allowing very cold air over Canada to dive south through the Plains. Depending on the position of the trough it may affect the inter-Mountain West. That cold air can only slowly ooze east of the storm track and in very shallow form. That storm track is Ohio Valley even in late December. While the Mid South may get glancing shots of cold, it won't last. And the Deep South can punt.

Let your heart not be troubled though. We had several weeks of below normal temps from late October through November. Assuming this winter returns to some sort of normalcy, one can expect weather patterns to last from 4-6 weeks. We are in the warm phase of the cycle right now. Sometime in January it should flip cold. If -AO accompanies like in Novie, January could be interesting. If we get a +AO then chalk it up to living in the South. One might have to travel, but not too far.

Either way in January as troughs return east of the Mississippi River, look for at least some upslope in the NC Highcountry. :ski:

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Punt December, but that has no bearing on the rest of winter. For the life of me I can't find the paper that discusses the three types of 500 mph flow for arctic outbreaks. However I know they are north, northwest and southwest. Yes, you read that right - southwest. Of course west won't work per the blowtorch. Believe the southwest version is coming, but not to the Southeast.

Southwest 500 mph flow includes the main jet stream migrating south over the western US and allowing very cold air over Canada to dive south through the Plains. Depending on the position of the trough it may affect the inter-Mountain West. That cold air can only slowly ooze east of the storm track and in very shallow form. That storm track is Ohio Valley even in late December. While the Mid South may get glancing shots of cold, it won't last. And the Deep South can punt.

Let your heart not be troubled though. We had several weeks of below normal temps from late October through November. Assuming this winter returns to some sort of normalcy, one can expect weather patterns to last from 4-6 weeks. We are in the warm phase of the cycle right now. Sometime in January it should flip cold. If -AO accompanies like in Novie, January could be interesting. If we get a +AO then chalk it up to living in the South. One might have to travel, but not too far.

Either way in January as troughs return east of the Mississippi River, look for at least some upslope in the NC Highcountry. :ski:

Best post of the day!

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Euro at hr240 - wow, it doesn't get much uglier than this in the high latitudes. Strong negative anomalies in the areas where you want to see strong positive anomalies.

Here's a 500mb composite of the Top 10 Coldest January's for Charlotte (since 1948). You can see this is almost exactly opposite of today's hr240 Euro across the high latitudes.

s500mbanom.png

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Here's a 500mb composite of the Top 10 Coldest January's for Charlotte (since 1948). You can see this is almost exactly opposite of today's hr240 Euro across the high latitudes.

Have you done the reanalysis for the preceding December?

I don't take the Euro as bad news...I sincerely doubt that this is the pattern for the entire winter and that only goes through Dec 14...So, if it lets go around Christmas or New Years, there is still plenty of time for some winter. Lets save the cliff diving until then. I feel as though I am being backed into a cold forecast corner by the negative wave of lemmings on here (and I am on the slightly above side tho nothing like last year). It would be nice for some to do their own analysis and learn rather than just repeat stuff...that is what is truly annoying. We are here for weather forecast discussion (in this thread). So the "I heards" and "Everyone says" added with statements of doom are frustrating to the point of not wanting to post anymore.

Having said all that and getting back on track, I still believe that this winter is likely to have some serious swings...we have been seeing those for quite a few months...Anyone remember all time record highs in late June....yet the summer was only near normal on the whole.

Suprised no one has said anything about an in situ CAD event on the Day 10 Euro... :whistle:

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Have you done the reanalysis for the preceding December?

I don't take the Euro as bad news...I sincerely doubt that this is the pattern for the entire winter and that only goes through Dec 14...So, if it lets go around Christmas or New Years, there is still plenty of time for some winter. Lets save the cliff diving until then. I feel as though I am being backed into a cold forecast corner by the negative wave of lemmings on here (and I am on the slightly above side tho nothing like last year). It would be nice for some to do their own analysis and learn rather than just repeat stuff...that is what is truly annoying. We are here for weather forecast discussion (in this thread). So the "I heards" and "Everyone says" added with statements of doom are frustrating to the point of not wanting to post anymore.

Having said all that and getting back on track, I still believe that this winter is likely to have some serious swings...we have been seeing those for quite a few months...Anyone remember all time record highs in late June....yet the summer was only near normal on the whole.

Suprised no one has said anything about an in situ CAD event on the Day 10 Euro... :whistle:

You know, I was thinking that little critter at the end of the Euro run looked interesting. It's at least worth watching.

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I think we will have more CAD events to worry about than normal. IMO its going to be the year of the wedge.

For those wanting to learn about CAD events check out this PDF. Lots of good stuff here.

http://www.erh.noaa.gov/er/hq/ssd/erps/tem/tem4.pdf

As for insitu CAD it says this

"Hybrid" events possess features which are typically weaker than those of "classical"

CAD, and diabatic processes such as evaporative cooling from precipitation or reduced solar

radiation from clouds can tip the scales toward a damming event. During "in situ" damming

cases, evaporative cooling due to precipitation leads to low-level cold air advection from a

parent high not in a favorable damming location.

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Have you done the reanalysis for the preceding December?

I don't take the Euro as bad news...I sincerely doubt that this is the pattern for the entire winter and that only goes through Dec 14...So, if it lets go around Christmas or New Years, there is still plenty of time for some winter. Lets save the cliff diving until then. I feel as though I am being backed into a cold forecast corner by the negative wave of lemmings on here (and I am on the slightly above side tho nothing like last year). It would be nice for some to do their own analysis and learn rather than just repeat stuff...that is what is truly annoying. We are here for weather forecast discussion (in this thread). So the "I heards" and "Everyone says" added with statements of doom are frustrating to the point of not wanting to post anymore.

Oh I wasn't trying to draw any conclusions about what the day 10 Euro meant for later in Dec or Jan. I had recently pulled that top 10 cold composite for Jan, and it struck me that the day 10 Euro was showing opposite anomalies in the key areas. Who knows if the day 10 Euro will verify for day 10 or any other period...but I know this much, it's NOT a look you want to see if you want a good wintry pattern in the southeast.

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Oh I wasn't trying to draw any conclusions about what the day 10 Euro meant for later in Dec or Jan. I had recently pulled that top 10 cold composite for Jan, and it struck me that the day 10 Euro was showing opposite anomalies in the key areas. Who knows if the day 10 Euro will verify for day 10 or any other period...but I know this much, it's NOT a look you want to see if you want a good wintry pattern in the southeast.

Of course...I was just curious if you had looked at the individual Dec's preceding...would be interesting to see if there were significant flips...

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Have you done the reanalysis for the preceding December?

I don't take the Euro as bad news...I sincerely doubt that this is the pattern for the entire winter and that only goes through Dec 14...So, if it lets go around Christmas or New Years, there is still plenty of time for some winter. Lets save the cliff diving until then. I feel as though I am being backed into a cold forecast corner by the negative wave of lemmings on here (and I am on the slightly above side tho nothing like last year). It would be nice for some to do their own analysis and learn rather than just repeat stuff...that is what is truly annoying. We are here for weather forecast discussion (in this thread). So the "I heards" and "Everyone says" added with statements of doom are frustrating to the point of not wanting to post anymore.

Having said all that and getting back on track, I still believe that this winter is likely to have some serious swings...we have been seeing those for quite a few months...Anyone remember all time record highs in late June....yet the summer was only near normal on the whole.

Suprised no one has said anything about an in situ CAD event on the Day 10 Euro... :whistle:

.

For what it's worth I've posted a couple of times about how I felt 12/13 - 12/17 would yield potential for cad areas to see mix/ice event. Not gonna rehash the reasons why, but point is on two separate occasions gfs spit out overrunning cad event affecting us in nc around this time frame. With all the cold along us border it should be easier than most think to get hp in place in ne to wedge sneaky shallow cold down the east side of apps and get some overrunning from some split flow. I'd keep an eye on this time frame. I think we will see several of these events the first half of winter. Way more so than snow events/potential with the pattern we are evolving into.

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'Pattern change' is really all about perspective for some folks. The upper air pattern over the North Hemisphere is going to undoubtedly change over the next 10 days. Just take Alaska for instance. There will be a change from a huge, persistent vortex to a substantial ridge. I have been talking about this change, as have a lot of other mets and forecasters, for a while.

This change will flood the northern US with arctic air with time and set up a baroclinic zone with waves of precip moving along it...as well as a significant system or two. A period active with storm systems for the central and eastern US will be a big change as well.

However, at least for a while, the Southeast will be on the warm side of this zone.

But make no mistake about it, the pattern change is indeed occurring as scheduled...the ramifications for the Southeast might not be what snow fans want, at least over the next 10+ days.

And another thing....the way people are talking, you would think we have been in this massive, blowtorch pattern for weeks and weeks on end. We just finished a very cool month of November. So it's not like we are stuck in endless warmth.

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'Pattern change' is really all about perspective for some folks. The upper air pattern over the North Hemisphere is going to undoubtedly change over the next 10 days. Just take Alaska for instance. There will be a change from a huge, persistent vortex to a substantial ridge. I have been talking about this change, as have a lot of other mets and forecasters, for a while.

This change will flood the northern US with arctic air with time and set up a baroclinic zone with waves of precip moving along it...as well as a significant system or two. A period active with storm systems for the central and eastern US will be a big change as well.

However, at least for a while, the Southeast will be on the warm side of this zone.

But make no mistake about it, the pattern change is indeed occurring as scheduled...the ramifications for the Southeast might not be what snow fans want, at least over the next 10+ days.

And another thing....the way people are talking, you would think we have been in this massive, blowtorch pattern for weeks and weeks on end. We just finished a very cool month of November. So it's not like we are stuck in endless warmth.

Excellent post. I've been saying the same thing in the northeastern subforums. This is a pattern change and will be completed by this weekend.

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Of course...I was just curious if you had looked at the individual Dec's preceding...would be interesting to see if there were significant flips...

Gotcha

For the preceeding Dec's...

Dec 1984 temps were very warm

Dec 1987 temps were warm

Dec 1947, 1965, 1977, 1978, 1980 temps were near avg

Dec 1969, 1976, 1981 temps were cold

Here's the Jan composite from the original post - Top 10 coldest Jan in Charlotte (since 1948)

s500mbanom.png

The biggest pattern flips from Dec to Jan occurred in 65-66 and 84-85

dec65.png

jan66.png

dec84jm.png

jan85.png

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