Winter 2014-2015 Pattern Discussion Thread I

[Southern Track]

WRAL's Greg Fishel says things start to look interesting next week. Just don't count on him to discuss any long range modeling.

 

I certainly know enough not to go out on any silly limbs with regard to winter forecasts, but suffice it to say the overall large scale pattern is one that catches my eye starting in about a week. As weather enthusiasts know, our best shot for significant winter events in central North Carolina result from cold high pressure to the north and moisture laden low pressure areas traveling across the southern U.S. After a dry period from this coming Wednesday through the following Monday, there are indications of an active southern storm track developing. Will there be enough cold air in place for any of those systems to make use of? Way too early to tell. And if one long range computer model forecast comes out in the coming days and has something interesting over North Carolina, you can count on me NOT to show it. I'm looking at a large scale pattern, not a random out of control computer model forecast. Yes I know, if I show it, and it turns out to be right, I could be a hero. Sorry, not interested. Let someone else have the glory.

 

That's about the best approach a Met can take.  That active southern track showing up does look very interesting.  Not a lot of cold air to work with as it looks right now though.

[mackerel_sky]

Maybe the not so cold look now, will be a colder look as we get closer!? Kind of like this current torch we are in that is about normal at best!

[Southern Track]

Agree Mack. We don't need extreme cold. As you and I can recall, the best storms in the upstate have been marginally cold. Jan '87.

[FallsLake]

Maybe the not so cold look now, will be a colder look as we get closer!? Kind of like this current torch we are in that is about normal at best!

Also if your looking for wintery precip we don't want all the cold barreling past us (..cold and dry). We want it just cold enough with system running below (east of) us.    

[FallsLake]

Not sure what I think of the indices:

 

PNA looks to stay positive

NAO looks to peak at +2 then drop towards neutral 

AO wildly averages neutral

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/teleconnections.shtml

[mackerel_sky]

6z GFS looks cold from 19-25th, hopefully some precip can show up.

[Webberweather53]

I think it's pretty obvious by now that the recent & ongoing amplification/acceleration of the subtropical jet is being primarily enforced by increased upper level divergence from an upward MJO pulse that is encroaching on the central Pacific (MJO phase 7-8)...

 

200hpa Vector Wind Anomalies

 

200hpa Velocity Potential (blue/purple=upper level divergence, green/yellow=upper level convergence)

[Met1985]

HM posting some good analysis in what is coming down the road in the Mid Atlantic forum this morning.

[Ollie Williams]

A series of southern lows starts next week and will begin our threats for snowfall, despite the lack of a true -NAO/Arctic Air. Marginal but sufficient air and a juicy southern low can deliver with a proper track. There are clearly 2 threats in the next 2 weeks, one of which is pretty close to xmas.

The other good news is that it is looking increasingly likely that a SSW will get going late Dec into early Jan. In some analogs, it took until second week of January for the AO to flip...then there are some that took even longer. The toughest part is trying to figure out when the AO flips. Either way, it's definitely the beginning of the eventual flip that you're seeing at the end of the computer models.

 

 

Good discussion from HM in the MA forum.  Even though he's referring to MA, I think this applies to some parts of SE area as well.  I also agree with his thoughts on the NAO. Reminds me of the Feb 12-13, 2014 snowstorm last winter when the NAO was around +1.

[NCSNOW]

Remember back in the winter of 2009/2010 there where multiple storms to track, non stop action. It started with the storm about a week before Christmas and didn't let up till lateFeb/ earlyMarch. Thing is everyone of them had temp issues. By that I mean it was always nip and tuck either with 850s or surface temps. Most of the time alot of us scored big and a few times some.of us got cold rained ( espeacilly urs truly with the 1st one). But What made that winter unique was the daily model watching of threats and i.mean short to medium, not this 220- 364 fantasy stuff. I beleive this year will produce close to as many storms to chase mainly because of an active stj/ nino just like 09/10. Doubt well have super cold constantly, but you don't necessarily need it in order to score. Put it this way I'd rather try hit the bullseye from 10 feet away with 12 darts/ oppurtunities, then 5 feet away with only 2 darts

[Snowless in Carrollton]

James Spann says there is no sign of an AO or NAO flip through Christmas and temps on Christmas day look normal in the southeast.

[LithiaWx]

James Spann says there is no sign of an AO or NAO flip through Christmas and temps on Christmas day look normal in the southeast.

 

CHRISTMAS? Long time readers know there is very little skill in a specific weather forecast beyond seven days, but we can often gather ideas about trends in the 7 to 15 day period. Still no sign of the Arctic Oscillation (AO) or the North Atlantic Oscillation (NAO) flipping negative for now, and it looks like temperatures will be close to average values. Doesn’t bode well for those dreaming of a White Christmas. See the Weather Xtreme video for maps, graphics, and more details.

 

^ what he actually said

[Snowless in Carrollton]

CHRISTMAS? Long time readers know there is very little skill in a specific weather forecast beyond seven days, but we can often gather ideas about trends in the 7 to 15 day period. Still no sign of the Arctic Oscillation (AO) or the North Atlantic Oscillation (NAO) flipping negative for now, and it looks like temperatures will be close to average values. Doesn’t bode well for those dreaming of a White Christmas. See the Weather Xtreme video for maps, graphics, and more details.

^ what he actually said

and what he said is exactly what I said that he said. Temps close to average values, which doesn't bode well for a white Christmas.

[Southern Track]

James Spann says there is no sign of an AO or NAO flip through Christmas and temps on Christmas day look normal in the southeast.

 

Forecasting temps to be about average two weeks out.  Now that's a bold forecast...

[LithiaWx]

Forecasting temps to be about average two weeks out.  Now that's a bold forecast...

 

Spann has proven himself to be a great forecaster.  I'm not sure what you're trying to convey here.

[GaWx]

and what he said is exactly what I said that he said. Temps close to average values, which doesn't bode well for a white Christmas.

 

 Living in the Atlanta area and most of the nonmountainous SE doesn't bode well for a white Christmas, cold or not. Atlanta has had what..two white Christmases in 100+ years? So, ~2% chance per climo? I'll take the under at this point. .

 

 Now, mainly nonsticking flurries? That is a different ballgame. Better chance than 2% for that.

[DaculaWeather]

The same thing I conveyed on another forum, no TV met is going to go out on a limb and start talking about long range. Ain't gonna happen.

[metwannabe]

Spann has proven himself to be a great forecaster. I'm not sure what you're trying to convey here.

Spann has proven he is horrible during winter just go back over the last four years. I lived in Birmingham for a while. He is a great severe weather guy not so much during the winter months. Maybe this belongs in banter

[Southern Track]

Spann has proven himself to be a great forecaster.  I'm not sure what you're trying to convey here.

I know nothing of Spann or his forecasting abilities.  Stating that temps would be about average two weeks out is an no brainer.

 

 You have a historical average temp on a specific date for a reason.

[LithiaWx]

The thing about what Spann said is he is probably right if you look at the guidance.  Temps should remain seasonal + or - a degree or two and the AO and NAO aren't flipping in the 7-15 day timeframe.  There are mets who post on this board who have basically said the same thing. I don't care if people bash a met but go ahead and bash the forecast and say why he is wrong while you're at it for better effect. 

[Snowless in Carrollton]

Living in the Atlanta area and most of the nonmountainous SE doesn't bode well for a white Christmas, cold or not. Atlanta has had what..two white Christmases in 100+ years? So, ~2% chance per climo? I'll take the under at this point. .

Now, mainly nonsticking flurries? That is a different ballgame. Better chance than 2% for that.

I only recall 2 white Christmases in the last 25 years. 1989 and 2010.Oh and there was some snow left over on the ground in 2000 from snow a few days before so that's 3 in the last 25 years. I could be wrong about 1989, but I know there was one year in the late 80s or early 90s when there was snow on the ground on Christmas morning and it melted by noon.

[metwannabe]

The thing about what Spann said is he is probably right if you look at the guidance. Temps should remain seasonal + or - a degree or two and the AO and NAO aren't flipping in the 7-15 day timeframe. There are mets who post on this board who have basically said the same thing. I don't care if people bash a met but go ahead and bash the forecast and say why he is wrong while you're at it for better effect.

The point was clear he said there is no sign of the AO going negative. That's not a true statement. But his job is to provide a 5-7 day forecast not a three week forecast . so I can't blame him for not taking the time to dive deep into the data

[LithiaWx]

The point was clear he said there is no sign of the AO going negative. That's not a true statement. But his job is to provide a 5-7 day forecast not a three week forecast . so I can't blame him for not taking the time to dive deep into the data

 

I read from HM and usedtobe this AM in the mid-atlantic thread that the AO and NAO aren't flipping that soon.  What Spann said is supported by others.

 

 

Right now I'd still place the probability of getting snow xmas week pretty much at climo. I had been leaning a little above so I could still change my tune by Thursday's outlook but right now am not ready to pull the above normal for xmas lever.  The southern storm track is a big plus but the NAO and AO  are still likely to be positive or for the latter maybe neutral at best while the former is still gonna be positive.  We have to hope there is enough ridging over the west to sneak enough cold air into the area while also having the pressure stay high over the great lakes so any high pressure are doesn't get pushed off the coast.  That's always a worry with a positive nao.  Like you, I still think we have a good January and think the pattern looks to be improving some towards xmas but.....I tend to be conservative with pattern changes. 

 

 

Sounds good. Basically, the background PDO-ENSO state favors a climo progression, for a change. We've had a negative state for so long that usually there is no sign of a southern stream at this point or PNA. This background state allows each passing week to do what it is supposed to do in the Mid Atlantic and slowly increase probability of snow. That's really all you can ask for at this stage.

As far as anything significant, until the NAO/AO comes around that will obviously be low chances. But a parade of southern stream lows is definitely a welcomed sight!

[Webberweather53]

Andrew-Andrej is a weather enthusiast & an expert on modeling, especially for the stratosphere, he made this nice 3-D animation of the recent 6z GFS run showing the area of -75C temp as a function of height associated with the polar vortex... Notice how the vortex appears vertically stacked/annular initially, however, as time progresses, notice the region of -75C temps shrinks & it starts to tilt, a clear indication of what the model @ least assumes to be a stratospheric warming event...

https://dl.dropboxusercontent.com/u/16376055/dss.mov

[GaWx]

Interestingly, while Atlanta has apparently had only had two white Christmases over the last 100+ years, they have had three major ZR's that day since the 1940's!

[packbacker]

Andrew-Andrej is a weather enthusiast & an expert on modeling, especially for the stratosphere, he made this nice 3-D animation of the recent 6z GFS run showing the area of -75C temp as a function of height associated with the polar vortex... Notice how the vortex appears vertically stacked/annular initially, however, as time progresses, notice the region of -75C temps shrinks & it starts to tilt, a clear indication of what the model @ least assumes to be a stratospheric warming event...

https://dl.dropboxusercontent.com/u/16376055/dss.mov

 

Wow, that's very cool!  Let's hope the models keep on improving with the warming. 

[Snowless in Carrollton]

Interestingly, while Atlanta has apparently had only had two white Christmases over the last 100+ years, they have had three major ZR's that day since the 1940's!

can't we just count ZR as a white Christmas ? Its close enough, right ?

Do you know how many times Atlanta has recorded a trace of snow on Christmas ?

[LithiaWx]

I only recall 2 white Christmases in the last 25 years. 1989 and 2010.Oh and there was some snow left over on the ground in 2000 from snow a few days before so that's 3 in the last 25 years. I could be wrong about 1989, but I know there was one year in the late 80s or early 90s when there was snow on the ground on Christmas morning and it melted by noon.

 

Not sure of the year but I do remember waking up on a Christmas morning when I was a youngster and there was a dusting to a half inch on the ground.  Could have been 1989.

[Snowless in Carrollton]

Not sure of the year but I do remember waking up on a Christmas morning when I was a youngster and there was a dusting to a half inch on the ground. Could have been 1989.

I remember that too. I was very young but I remember it melted by noon. Maybe Larry can help us out on the year. I know parts of the south had snow around Christmas 1989, but not sure that was the year that we had snow .

[Webberweather53]

Remember back in the winter of 2009/2010 there where multiple storms to track, non stop action. It started with the storm about a week before Christmas and didn't let up till lateFeb/ earlyMarch. Thing is everyone of them had temp issues. By that I mean it was always nip and tuck either with 850s or surface temps. Most of the time alot of us scored big and a few times some.of us got cold rained ( espeacilly urs truly with the 1st one). But What made that winter unique was the daily model watching of threats and i.mean short to medium, not this 220- 364 fantasy stuff. I beleive this year will produce close to as many storms to chase mainly because of an active stj/ nino just like 09/10. Doubt well have super cold constantly, but you don't necessarily need it in order to score. Put it this way I'd rather try hit the bullseye from 10 feet away with 12 darts/ oppurtunities, then 5 feet away with only 2 darts

 

 

This isn't true at all... Yes 2009-10 was a good winter, but it did clearly let up for a few weeks in the heart of January (i.e. a January Thaw), in which I vividly recall many mets & weather weenies alike proclaiming winter was over, but we all know what happened a few weeks later...