Winter 2014-2015 Pattern Discussion Thread I

[packbacker]

Also, the CMC-ENS is similar to the GEFS.  Curious to see if the EPS starts ticking towards the GEFS/CMC-EPS. 

[packbacker]

The GEFS-BC is very cold in the 11-15 day...the Euro has the 2m temp anomolies.  

 

 

[franklin NCwx]

Also, the CMC-ENS is similar to the GEFS. Curious to see if the EPS starts ticking towards the GEFS/CMC-EPS.

eps did have a trough east of Hawaii. So it can't bury a trough in the southwest too.

[Jon]

PNA looks to go negative? Pretty sure I just saw that. Not good.

Yeah as I stated in my post...

 

We know the +PNA is set to break down and dive negative, how deep that dive goes is up in the air...Euro takes it down far by the 26th, but the GFS isn't the same, notice the 12z PARA run (and the regular GFS is similar ) rebuilds it back early.

 

Individual GFS 06z ensemble members you can see the PNA evolving back to positive after the 29th or so, most of you don't want to wait but unfortunately it will take a negative to neutral DIP in the LR and go back positive for the new year.

 

 

We've known the PNA was nose diving for a while now around the 23rd or so, it's not a surprise. It will rebound, though, especially with a extremely -EPO (see my last post) 

 

12z GFS ens members, huge trend in the LR for a +PNA...only a few members near neutral only 2 members negative.

 

Couldn't post these on my last post when I mentioned the -EPO diving because I was limited with images and had to post two separate times.

 

POSITIVE EPO

 

 

NEGATIVE EPO

[Webberweather53]

That's interesting...this is what the EPS shows, sucks for us (SE) the next 2 weeks but if builds up the snowpack/cold over northern/central US/CN then it might be what is best for us come mid-Jan.  But that means it could be 4 weeks before we get into a favorable situation, assuming the EPS is correct.  If the GEFS is correct the snowpack could still build up with clippers I guess, as that is a better pattern for us in the 10-15 day period.  I don't know which one will be correct.

 

 

Even w/ a favorable storm track w/ the southern edge of the snowpack struggling to even make it across the Canadian border out of Ontario & Quebec this pattern we have at the moment isn't one that will sustain cold & snow, we have to recharge the snowpack to our north & west before we get amped up about wintry weather...

Compare our current snowpack extent to some of the more significant CAD events of recent memory, we're not even in the same area code...  A general rule of thumb regarding the location of the southern edge of the snowpack in the eastern US is we need to at least get it down to the I-80/I-70 corridor or anywhere near or south of a line from about Pittsburgh thru Columbus, Fort Wayne, Chicago & points south to give ourselves a legitimate chance at seeing a nice CAD event here. We certainly have our work cut out for us...

 

 

[burgertime]

Looks like the EPS is going to start pushing colder air in the east around hour 300. You can see arctic air starting penetrate central Canada at around hour 264. Looks better oriented compared to last nights run. Where it actually ends up is another question. 

[BullCityWx]

Looks like the EPS is going to start pushing colder air in the east around hour 300. You can see arctic air starting penetrate central Canada at around hour 264. Looks better oriented compared to last nights run. Where it actually ends up is another question. 

 

I could live with a day or two of 65 if we get cold. 

[BullCityWx]

So, departures through the 15th: 

Atlanta: +4.8
Asheville: +3

Charleston: +0.8
Charlotte: +2.5

Columbia: +2.3
GSP: +3.3

Greensboro: +1.5

Raleigh: 0.0

 

Of those, I would assume CHS and RDU have the best shot at a normal month. Otherwise, we all could end up significantly above normal for the month, probably somewhere around +3, especially if we end up with a post christmas warm shot. 
 

[franklin NCwx]

what a deep trough and some nice blocking on the euro ensembles around Christmas.

[burgertime]

EPS goes back to it's cold west look out in the LR. 

[deltadog03]

Its interesting how the long range is trying to unfold.  Part of me is like, well hell, we are going to see the pattern change, its showing on the models.  However, the other part of me is well.....They showed a pattern change, now they are going back and forth.  Such a tough pattern to nail down.

[Cold Rain]

EPS goes back to it's cold west look out in the LR.

Did it ever abandon it? Seems like it's been stuck on that now for a while.

[franklin NCwx]

EPS goes back to it's cold west look out in the LR.

core of the cold is being dumped into the northern plains. It does have below normal heights in the sw. If it is right with leaving a piece of the trough in the sw (a known error in the model) it will get kicked east with the ensembles showing a trough east of Hawaii.

[SnowNiner]

Also, the CMC-ENS is similar to the GEFS.  Curious to see if the EPS starts ticking towards the GEFS/CMC-EPS. 

 

Something has to give here.  GEFS is still money for next week (probably a nice storm signal too...).  Somebody needs to start folding to somebody.  After the shot below, there's nothing but +PNA/-AO/-NAO through the rest of the run.  Who's right? 

 

[RONALD B]

core of the cold is being dumped into the northern plains. It does have below normal heights in the sw. If it is right with leaving a piece of the trough in the sw (a known error in the model) it will get kicked east with the ensembles showing a trough east of Hawaii.

i agree with this !

[Cold Rain]

^^ (SnowNiner image) Trough east of HI. That's how it's done, Euro!

[franklin NCwx]

Something has to give here. GEFS is still money for next week (probably a nice storm signal too...). Somebody needs to start folding to somebody. After the shot below, there's nothing but +PNA/-AO/-NAO through the rest of the run. Who's right?

it's probably somewhere in the middle. The gfs has a bias of being too fast. The models mostly agree with the pattern in the higher latitudes.

[deltadog03]

and with a trof east of hawaii in the su-tropics....That energy will NOT get buried into the SW.  I think there is HUGE potential for a big storm around Christmas. We shall see.  

[packbacker]

Did it ever abandon it? Seems like it's been stuck on that now for a while.

 

No, it's been consistent with trying to put the trough in the west.  But, I think it's ticking the trough east...compare the latest 12z EPS v/s the 0z EPS 36 hours ago.  You can see the ridge was oriented NE over the Aleutians on the 0z run 36 hours ago and now it's almost to the GOA and more NNE which forces the trough more east.  I think eventually it will be blend of the GEFS/EPS which will be pretty good for us.  Of course this is 10+ days away, but it's not day 15.

[burgertime]

Did it ever abandon it? Seems like it's been stuck on that now for a while.

 

Sorry should have been more clear. I had stated earlier that I thought the EPS would have a more cold centered east at hour 300 just extrapolating from hour 264 or so. The cold coming in through Canada looked better oriented and I thought it would translate to a more eastern solution with the trough. It didn't so it was "back" to a cold west. 

[SN_Lover]

Not understanding the huge emphasis on snow-pack. If anything increased snow-cover to the NE will reduce CAD. Diabatic effects are important, but not that important. 

[deltadog03]

There should be a nice build up of LOW LEVEL cold though as well.  That will push SE for sure.

[Webberweather53]

Not understanding the huge emphasis on snow-pack. If anything increased snow-cover to the NE will reduce CAD. Diabatic effects are important, but not that important. 

 

??? Lol. In that case, the massive snow cover last winter preceding the massive CAD event in the 2nd week of February going all the way down through central Virginia obviously didn't have anything to do w/ the snow & ice that fell well south of I-20 including Macon, GA, Charleston, SC, etc. nor the Civil Emergency that the entire state of SC was put under during the storm...

[burgertime]

18z trying hard to give us snow showers on the 24th.....surface temps are a wash but might be something left over as that low lifts..there's enough energy there to give someone some snow on the backside in NC. 

[burgertime]

18z PARA with that insane phased super storm for around Christmas. By the way 18z GFS in the LR says pattern change begins at 240. Major cold in the west moving east. By 288 winter is arriving in the SE. 

[SN_Lover]

??? Lol. In that case, the massive snow cover last winter preceding the massive CAD event in the 2nd week of February going all the way down through central Virginia obviously didn't have anything to do w/ the snow & ice that fell well south of I-20 including Macon, GA, Charleston, SC, etc. nor the Civil Emergency that the entire state of SC was put under during the storm...

Snow and cloud cover to the NE causes diabatic heating, which causes parcels to rise, lowering pressure in the NE. We need a high pressure in the NE to transport the cold air southward. 

[LithiaWx]

??? Lol. In that case, the massive snow cover last winter preceding the massive CAD event in the 2nd week of February going all the way down through central Virginia obviously didn't have anything to do w/ the snow & ice that fell well south of I-20 including Macon, GA, Charleston, SC, etc. nor the Civil Emergency that the entire state of SC was put under during the storm...

 

There are obviously lots of other factors that come together to produce a storm of the magnitude you are talking about.  Based on his latest response I think he is correct.  What he is saying appears to have merit.

[Webberweather53]

Snow and cloud cover to the NE causes diabatic heating, which causes parcels to rise, lowering pressure in the NE. We need a high pressure in the NE to transport the cold air southward. 

 

 

 

There are obviously lots of other factors that come together to produce a storm of the magnitude you are talking about.  Based on his latest response I think he is correct.  What he is saying appears to have merit.

 

I really thought some of this was common sense, to some degree, since when does snow cause diabatic heating? I think you have the processes of melting, freezing, & sublimation mixed up, among other things... You do realize if there's a region of high pressure over the northeast & southeastern Canada, there will likely be little-if any clouds in place right, and given other conditions are equal the ambient temperature over a region of snowpack vs w/o will be cooler to begin w/ before the clouds even move in? Snow because of it's color & due to kirchoff's law (poor absorber of a particular radiation band is also a poor emitter) reflects up to 90-95% of incoming solar radiation, cools the surrounding air because less shortwave radiation is absorbed into earth's surface, & more is reflected back out into space. The colder surrounding air due to the snowpack, causes the air to become less buoyant & sink, which leads to a piling up of air in the boundary layer forcing heights to rise, thus enhancing not negating a region of near surface high pressure. Not to mention, despite the fact that the air is a poor conductor of heat, some turbulent mixing is bound to occur between the surface & the lower levels, and this interaction with the underlying snowpack will lead to some cooling of the near surface air. Additionally, any appreciable sunshine that breaks out in the residence period between the formation/laying down of the snow & its application in a cold air damming event, will lead to sublimation of some snow (solid->gas) which further cools the air... His point doesn't have any merit...

[burgertime]

I agree with Webber..I think where a good snow pack helps during a CAD event to push more of a snow p-type as there is colder air to work with to push down to the surface. Robert would often talk about this as well when you have a CAD event it's much colder when there is good snow cover to our north. Obviously a snow storm can still happen, just like a -PNA can still produce a snow storm for the south but wouldn't you rather have a +PNA on your side? 

[Webberweather53]

There are obviously lots of other factors that come together to produce a storm of the magnitude you are talking about.  Based on his latest response I think he is correct.  What he is saying appears to have merit.

 

I already acknowledged in my original post there are clearly other factors in play...

"The faltering snowpack, especially over the eastern US, is a huge reason why this system next week will be primarily liquid instead of a robust winter storm, fresh snow like that w/ high albedo raises surface pressures in the PBL & increases the intensity of cold air advection & CAD here in the Carolinas when all other ambient conditions are approximately equal..."

 

Miller A is somewhat of a different story regarding wintry precipitation in general, but w/o a healthy snowpack to the north to increase the intensity, depth, & longevity of the cold air against an onslaught of warmer air aloft attempting to overrun it, in a Miller B, the snowpack in the northeastern US matters a lot... It's not a huge surprise when you look at how intrusive the snowpack was last year, extending down below I-70, w/ even more fresh snow laid down the day before just north of I-20 in upstate SC & into lower NC, that there were problems with ice down to I-16 in Georgia...