December Forecast Discussion

[LithiaWx]

At least for most of December. For all we know, we may get a 2 to 3 week period of some real cold and experience a big snow. I don't think people should swing to the extremes on the prospects of the

This is true but it sure seems if everyone is punting December then unless early January starts off in a cold direction the prospect of a great winter goes down in flames. If things don't look promising in the LR come early January I'm going to hope for a single storm at just the right time followed by a quick warmup.

We will start to run out of days if prospects of a great pattern keeps getting pushed back. This winter mirrors last winter in a few ways. We kept pushing back the pattern change and we never got whhat we needed. I'm still looking for a damn threat at this point. It feels like the last real storm I tracked was Jan '11 nearly two years ago....

[FoothillsNC]

It feels like the last real storm I tracked was Jan '11 nearly two years ago....

Same here...I saw a couple of flakes last February just as the storm was ending, which was literally the least amount of snow I've ever seen in this county in my lifetime. I sort of wish I didn't see those so it was a complete non Winter. Even so, I think enough obs around the Carolinas pointed out the fact it was a snowless Winter for the first time in NC/SC for the first time ever in records.

But , here's a little bit of hope for northern GA, and the Carolinas especially. Without running the risk of sound in my backyard -centric, ( I already laid out my thoughts for above normal snow in TN Valley), I think this area just in northern GA to the western Carolinas has a shot at above normal snows still based on what happened in similar indices. Here's a look at the unique look of some neutral years with a cold -PDO, a -PNA and a -AO pattern, which is basically what we have here. Winter didn't start until later on in the season. As you can see, 1969 and 1960 both stand out with a similar look of the indices (the +PNA was on 1960, but -PNA 1969), but overwhelmingly, the -AO and -NAO stand out, with a PNA that is 50/50. Now I'm not calling for a mid Feb- mid Mar 1960 pattern as that was the mother of all Winter Weather patterns in Tn, north Al, north GA and the western Carolinas, but the idea is that things changed later on, even following some record warm temps in December and folks were shocked what happened later on. But in general, I'd still prefer a +PNA pattern ( like what happened in 09/10, 10/11) but in some cases , a very strong neg. -AO/-NAO pattern led to such a supressed pattern, that it had to deliver Winter storms, even without a good +PNA, but its a rarity. So over the coming weeks/months, I would keep my eyes in eastern Canada and Southern Greenland for blocking. It almost always holds the key to signage of a supressed storm track in general.

PNA

AO

NAO

PDO

[griteater]

Here's a 2011/2012 comparison of the 500mb pattern for Nov 15 - Dec 5.

2011 had the ridge south, with trough north configuration in the E Pacific and W Atlantic, promoting fast flow across southern Canada, really precluding any chance of -NAO development.

2012 has more meridonal flow with better setup for high latitude blocking, but the big trough in the E Pacific is a death sentence for developing a wintry pattern into early Dec across the country.

Both of these are terrible tho I would take the 2012 look over 2011 because of the better high latitude setup (in the context of rolling this forward)...but I wouldn't want to live off the difference.

[packbacker]

This post may get deleted as it doesn't relate to Dec forecast specifically, but I plotted the 10 year average snowfall for RDU over the past 120+ years and ever since 1990 we have been in quite the funk. I believe weather comes in cycles and either we have 2 things going on, we are about to embark on a 20+ year run of above average snowfall or our climate is changing (global warming?). My personal opinion is we are just in down cycle since 1990, yeah we have had a good year here or there but our 10 year average has been down for the past 20+ years and if weather is cyclical we are about to embark on a 20+ year above average for snow. So it might not start this year, but it's got to turn around soon. Hopefully Eyewall doesn't move to the NE, things will change soon, I hope.

[LithiaWx]

Same here...I saw a couple of flakes last February just as the storm was ending, which was literally the least amount of snow I've ever seen in this county in my lifetime. I sort of wish I didn't see those so it was a complete non Winter. Even so, I think enough obs around the Carolinas pointed out the fact it was a snowless Winter for the first time in NC/SC for the first time ever in records.

But , here's a little bit of hope for northern GA, and the Carolinas especially. Without running the risk of sound in my backyard -centric, ( I already laid out my thoughts for above normal snow in TN Valley), I think this area just in northern GA to the western Carolinas has a shot at above normal snows still based on what happened in similar indices. Here's a look at the unique look of some neutral years with a cold -PDO, a -PNA and a -AO pattern, which is basically what we have here. Winter didn't start until later on in the season. As you can see, 1969 and 1960 both stand out with a similar look of the indices (the +PNA was on 1960, but -PNA 1969), but overwhelmingly, the -AO and -NAO stand out, with a PNA that is 50/50. Now I'm not calling for a mid Feb- mid Mar 1960 pattern as that was the mother of all Winter Weather patterns in Tn, north Al, north GA and the western Carolinas, but the idea is that things changed later on, even following some record warm temps in December and folks were shocked what happened later on. But in general, I'd still prefer a +PNA pattern ( like what happened in 09/10, 10/11) but in some cases , a very strong neg. -AO/-NAO pattern led to such a supressed pattern, that it had to deliver Winter storms, even without a good +PNA, but its a rarity. So over the coming weeks/months, I would keep my eyes in eastern Canada and Southern Greenland for blocking. It almost always holds the key to signage of a supressed storm track in general.

PNA

AO

NAO

PDO

Even the fantastic winter of '10-'11 started cold but ended warm. I hope that this winter can do the ame thing just a 180 version of it. Who knows what is coming down later this winter but I can't say I'm pleased with our start but I'm not on the cliff edge yet either.

BTW great post as allways -

[FoothillsNC]

Even the fantastic winter of '10-'11 started cold but ended warm. I hope that this winter can do the ame thing just a 180 version of it. Who knows what is coming down later this winter but I can't say I'm pleased with our start but I'm not on the cliff edge yet either.

BTW great post as allways -

True, you never know with Winter forecasts...I've seen the best go down in flames and then a good pattern suddenly come from nowhere at the last minute. For the region as a whole, I'd certainly prefer a good +PNA pattern and warm Gulf of Alaska, in tandem with warm Greenland waters, like 2002. 2009/10 fit that to a good degree too, as do a lot of Winters that brought widespread Winter weather. Some years are very localized, and this may be one of those, who knows yet. I don't really want snow or cold, just enjoy watching others get what they want, like 2009-11 years, as it's a hassle for me. The irony is that *usually* my area is an anomaly, like the previous 2 good Winters in the Southeast, here it was still only about average, with much greater snow relative to normals,all around here. Look at the snow accumulation maps of upstate SC and CLT southern piedmont if you don't believe me. Normally a big snow here means cold rain many other areas and the absolute perfect track, which doesn't happen often. I wouldn't head to the cliff until mid February yet, but sustained cold is unlikely anytime this month atleast.

[Cold Rain]

Good posts, guys. Thanks for the research and analysis. I haven't researched analogues to our current set-up, but just looking at the models, a bad Pacific (that's unlikely to change anytime soon at all), an Atlantic/blocking that is neither going to be optimally placed nor strong enough, and the fact that the coldest air is likely to relocate to the other side of the globe all adds up to the idea that it's essentially going to be the second week of Jan. at the earliest for a cold and wintry pattern to have the possibility of getting established in this part of the country.

These things look to be against us for at least the next 15 days. That puts us near Christmas. Then, assuming everything starts to come together immediately, it will take another week or two to get cold and stormy. And that's IF things turn immediately. They likely won't. It will probably take a while for the pattern to start reconfiguring. And who knows if at that time it'll reconfigure optimally. But assuming it does, that probably takes till mid-Jan. That's fine. But it's starting become very clear that we're in trouble again this year.

[griteater]

ever since 1990 we have been in quite the funk

If you want to live through a bad winter decade, go back to the 1990's. For Charlotte, only 1 of the 10 years had temps below the long term average (1996)...and 0 years had snowfall above the long term average. Of course, there were a couple of big ticket items tucked in there for some - Mar '93 and Jan '96

[eyewall]

How many completely zeroed out last year in terms of seasonal snow amounts? Anyway it seems an big snow in the east in October is a kiss of death. I need to see if there are any notable correlations in that regard aside from this year and last.

[burgertime]

How many completely zeroed out last year in terms of seasonal snow amounts? Anyway it seems an big snow in the east in October is a kiss of death. I need to see if there are any notable correlations in that regard aside from this year and last.

I had a big fat zero here in Charlotte. You know there is nothing going on when more conversation is going on about facebook than the GFS. Which speaking of the 00z isn't anything to write home about....it does show a little back side snow at around hour 200 but it's the typical cold chasing rain.

[burgertime]

As usual the GFS redeems it's self in the last few panels. On Christmas Eve it brings freezing temps down to almost Florida and has a raging snow storm in NY.

[GaffneyPeach]

How many completely zeroed out last year in terms of seasonal snow amounts? Anyway it seems an big snow in the east in October is a kiss of death. I need to see if there are any notable correlations in that regard aside from this year and last.

Not one single flake or pellet last Winter...or decent threat of any. Worst Winter ever...

[Thunderhead Hawkins]

How many completely zeroed out last year in terms of seasonal snow amounts? Anyway it seems an big snow in the east in October is a kiss of death. I need to see if there are any notable correlations in that regard aside from this year and last.

This was the only noteable snow here last season and it was very isolate. I just got lucky that day. Instability snow showers can be fun, especially if they hang around for a few minutes.

[HKY_WX]

Man, the AO is going to be really negative this month. Most likely in the -2 to -3 range on average for December. If take that into account, it's astounding we're having a warm pattern. Something tells me there will be a violent system at some point to change this pattern in the next few weeks.

Below is a 500mb blend of the only other winters w/ oct-nov-dec averges below zero for each month on the PDO and AO. Notice how cold they are, despite the Aleutian ridge which we have this winter so far.

[griteater]

Ouch at the GFS dropping wave after wave just off the West Coast. The whole -PDO deal though - we can make this work, but 1) Got to have strong west based -NAO block, and 2) If PNA is negative, just need the ridge axis in the E Pacific to not be too far off the west coast (as long as the positive ridge anomalies on the east side of the ridge in the eastern Pacific are just touching the west coast, it can work - i.e. storm track can stay suppressed enough if a good -NAO block is in place)

[HKY_WX]

Just for the record, here was the following Jan and Feb for those years, so there's still plenty of time left for a good winter:

[griteater]

What's interesting HKY is that the positive AO anomalies have been located on the other side of the pole...so, the AO is registering negative, but we don't have those anomalies where we need them to get the cold air in here...i.e. the NAO has been around neutral the past 2 weeks. Still a good sign though to have the blocking up there.

[HKY_WX]

What's interesting HKY is that the positive AO anomalies have been located on the other side of the pole...so, the AO is registering negative, but we don't have those anomalies where we need them to get the cold air in here...i.e. the NAO has been around neutral the past 2 weeks. Still a good sign though to have the blocking up there.

True, the possible retrogression of those anomalies into Greenland could be important. If we can get to a traditional -AO pattern, that could set us up for the rest of winter if these analogs are correct.

Let's hope this GFS run below is right:

http://www.meteo.psu...nsloopwide.html

You can see by hour 240 the pattern is pretty identical to the above analog year maps.

[MichaelJ]

Yes it does Hky but isn't that because the model searches for the closest comparable record in it's database and just copies it verbatim? Correct me if I am wrong that the general patterns would likely be similar but so many things go into matching it up that just one going awry will screw the whole run up

[buckeyefan1]

Man, the AO is going to be really negative this month. Most likely in the -2 to -3 range on average for December. If take that into account, it's astounding we're having a warm pattern. Something tells me there will be a violent system at some point to change this pattern in the next few weeks.

Below is a 500mb blend of the only other winters w/ oct-nov-dec averges below zero for each month on the PDO and AO. Notice how cold they are, despite the Aleutian ridge which we have this winter so far.

I agree with this

[WilkesboroDude]

I agree with this

Sort of how like SuperStorm Sandy changed our pattern from wet/cool to drought/warm? Just the polar opposite?

[burgertime]

Sort of how like SuperStorm Sandy changed our pattern from wet/cool to drought/warm? Just the polar opposite?

It's kind of like the rubber band analogy that is often used. You pull the band back far enough it eventually snaps and goes the other direction, it's during that snap you often get the craziest weather.

[NC_hailstorm]

The strat PV is still forecasted to move to Siberia from Greenland.Also a feature I've been watching lately has been the GFS putting a huge strat block in the Alaska/Yukon/NW Canada area but that's still in la la land.

I believe this is has been classified as a minor warming or a Canadian warming.Fascinating to watch and observe but the weather will do what it will do.

[buckeyefan1]

Sort of how like SuperStorm Sandy changed our pattern from wet/cool to drought/warm? Just the polar opposite?

It's kind of like the rubber band analogy that is often used. You pull the band back far enough it eventually snaps and goes the other direction, it's during that snap you often get the craziest weather.

Exactly

[Southern Track]

The Pacific hate us, is the Atlantic breaking up with us as well?

[Marion_NC_WX]

All of a sudden Wednesday has become a lot more interesting for the High Country...GFS has quick secondary development shortly after our front passes through. Some much needed rain east of the Apps and maybe a close call for Mitchell, Avery and Watauga.

Robert was hinting at this a few days ago and the GFS did its typical "losing the storm" at days 5-7 and the 12z brings it back...also some support from Euro.

[HKY_WX]

Yes it does Hky but isn't that because the model searches for the closest comparable record in it's database and just copies it verbatim? Correct me if I am wrong that the general patterns would likely be similar but so many things go into matching it up that just one going awry will screw the whole run up

I actually manually input those years. They were based on Oct-Nov-Dec all individually averaging negative on the PDO and AO monthly statistical output found here and here going back to 1950. Granted, the outcome on the 500mb map was somewhat predictable, but nonetheless it's interesting to see how much the last 9 days have stood out. But it could also be good news for the rest of winter.

[Wow]

Small note: Robert (FoothillsNC) has created a blog here. Anyone interested go to:

[WilkesboroDude]

NWS Greenville Forecast

We might be able to eke out cape on the order of a few hundred...but

without the deep layer forcing that usually accompanies the better

high shear Low Cape events...we may be limited in terms of how much

severe weather we get with this frontal passage. We certainly will

not be able to turn our back on it. With that in mind...we should

begin Monday with the leading edge of shower activity moving into

the western zones and that should gradually translate east through the day.

The mountains and foothills stand the best chance...and a likely to

categorical pop was kept there per the mosguide and sref. Pop was

limited to slight/chance until late afternoon over the Piedmont per the

timing of the model consensus.

[Disc]

That was the previous outlook, by the way.