December 2011 General Disc/Obs

[Bob Chill]

6z GFS Op and ensemble mean and 0z Euro Op and ensemble mean all show a pretty decent pattern developing with a +PNA and the PV displaced south toward Hudson Bay. Still looks like transient cold shots since upstream blocking is weak, but certainly more of them and colder air associated with them.

Just got finished looking at the euro and 6z gfs and I agree that the pattern is better. Too bad it's just a different look of the current pattern and not a true change. Not bad though. We stand a much better chance at getting some ridging around greenland with the pv further south. I like that. And the ridge out west looks a heck of alot better.

Correct me if I'm taking out of my ass but one of the problems I've seen with the pattern is no ridging anywhere around AK. Energy keeps sliding under the ridge and closing off in the desert sw. With no block in place, every time this happens pumps up the ridge a bit and we get rain before the trailing cold front.

It wouldn't take much to fix this though.The last 2 panels of the NHEM 500 map on the euro hint at a more favorable setup in the pac. If the pv were to retrograde w just a little the heights could potentially build near greenland.

Considering how long the crappy pac and nao has been holding up I would have to hedge towards a continuance of crap but if things keep looking like this in the next couple days then I'm going to put my weenie glasses back on.

[mitchnick]

12Z NAM

now that's more like it

http://mag.ncep.noaa.gov/NCOMAGWEB/appcontroller?prevPage=Param&MainPage=indexℑ=&page=Param&cycle=12%2F13%2F2011+12UTC&rname=PRECIP+PARMS&pname=precip_ptot&pdesc=&model=NAM&area=NAMER&cat=MODEL+GUIDANCE&fcast=084&areaDesc=North+America+-+US+Canada+and+northern+Mexico&prevArea=NAMER&currKey=model&returnToModel=&imageSize=M

[mitchnick]

Just got finished looking at the euro and 6z gfs and I agree that the pattern is better. Too bad it's just a different look of the current pattern and not a true change. Not bad though. We stand a much better chance at getting some ridging around greenland with the pv further south. I like that. And the ridge out west looks a heck of alot better.

Correct me if I'm taking out of my ass but one of the problems I've seen with the pattern is no ridging anywhere around AK. Energy keeps sliding under the ridge and closing off in the desert sw. With no block in place, every time this happens pumps up the ridge a bit and we get rain before the trailing cold front.

It wouldn't take much to fix this though.The last 2 panels of the NHEM 500 map on the euro hint at a more favorable setup in the pac. If the pv were to retrograde w just a little the heights could potentially build near greenland.

Considering how long the crappy pac and nao has been holding up I would have to hedge towards a continuance of crap but if things keep looking like this in the next couple days then I'm going to put my weenie glasses back on.

this is all you need to know Bob....patience

[Bob Chill]

Can you explain for those of us who don't know all the details of PNA what that means? TIA

I think I can help with a simplistic explanation. It's a teleconnection and can be our friend when + and our enemy when -.

Quick and easy read: http://www.cpc.ncep.noaa.gov/data/teledoc/pna.shtml

Simpleton terms:

+PNA = ridge west and trough east and -PNA = opposite

When we have no blocking to our north near greenland (like right now), a +PNA is going the prominent driver of cold air and favorable track in the east. Long story short, we really need a ridge out west and a trough in the east if we even want to consider snow chances right now. If we have a -nao, we can have a trough out west and survive because the track is supressed. A -pna and -nao (aligned correctly) can pretty much put the entire country in a trough and we all get snow and cold. Without the block to the north, a -PNA almost always = seasonable to above average temps in the eastern third of the US.

Interestingly enough, the 6z gfs suggests a potential +pna and -nao. I doubt it's right but MA weenies love that combo.

[WxUSAF]

Can you explain for those of us who don't know all the details of PNA what that means? TIA

PNA = Pacific-North American

Basically just another index like the NAO or AO, but referring to whether there's ridging or troughing near the West Coast of North America. +PNA means ridging, -PNA means troughing. To get cold weather, we want a +PNA since an upstream (west) ridge means a trough over us, all things being equal.

Just got finished looking at the euro and 6z gfs and I agree that the pattern is better. Too bad it's just a different look of the current pattern and not a true change. Not bad though. We stand a much better chance at getting some ridging around greenland with the pv further south. I like that. And the ridge out west looks a heck of alot better.

Correct me if I'm taking out of my ass but one of the problems I've seen with the pattern is no ridging anywhere around AK. Energy keeps sliding under the ridge and closing off in the desert sw. With no block in place, every time this happens pumps up the ridge a bit and we get rain before the trailing cold front.

It wouldn't take much to fix this though.The last 2 panels of the NHEM 500 map on the euro hint at a more favorable setup in the pac. If the pv were to retrograde w just a little the heights could potentially build near greenland.

Considering how long the crappy pac and nao has been holding up I would have to hedge towards a continuance of crap but if things keep looking like this in the next couple days then I'm going to put my weenie glasses back on.

No, it's not a true pattern change, but it's a better look. On the downside, the models have teased us with this improving look a couple times in the last few weeks and the can keeps getting kicked down the road or the better look turns into a 2-3 day cool/cold shot and then it's back in the crapper.

From a snow perspective, energy sliding under a western ridge can be a very good thing. But, typically closed lows in the southwest don't work out well since they teleconnect to a strengthening SE ridge. We want s/w's to slip under the ridge but keep moving eastward.

6z GFS ensemble mean actually did build heights into Greenland around Day 10 but then loses it afterwards. Euro didn't show this.

I like the setup for this weekend if anything can actually happen, not for a big snow, but for something. Given we can't lock in a cold pattern, what we need is a transitory shot of cold air and then have a wave develop along the stationary front in the SE and give us some overrunning. Given the apparent lack of a potent s/w, that could never really produce a big storm, but could produce a 1-3" type event. That seems to be what a few runs were showing, but they now have anything even weaker and more surpressed.

[Bob Chill]

this is all you need to know Bob....patience

Patience?!? It's nearing mid Dec after a month+ long craptastic pattern with no tangible relief in sight. AND, I live in the MA where our winter window is the size of a cabin on a ship.

I'm probably one of the more relaxed around here but if I need more patience I should probably order some on amazon and stock up.

Eh, just kiddin. I'm not really worked up at all. We shall see what our lovely stratoshpere can whip us and send our way.

[Kmlwx]

12Z NAM

now that's more like it

http://mag.ncep.noaa...el=&imageSize=M

My reaction -

[usedtobe]

PNA = Pacific-North American

Basically just another index like the NAO or AO, but referring to whether there's ridging or troughing near the West Coast of North America. +PNA means ridging, -PNA means troughing. To get cold weather, we want a +PNA since an upstream (west) ridge means a trough over us, all things being equal.

No, it's not a true pattern change, but it's a better look. On the downside, the models have teased us with this improving look a couple times in the last few weeks and the can keeps getting kicked down the road or the better look turns into a 2-3 day cool/cold shot and then it's back in the crapper.

From a snow perspective, energy sliding under a western ridge can be a very good thing. But, typically closed lows in the southwest don't work out well since they teleconnect to a strengthening SE ridge. We want s/w's to slip under the ridge but keep moving eastward.

6z GFS ensemble mean actually did build heights into Greenland around Day 10 but then loses it afterwards. Euro didn't show this.

I like the setup for this weekend if anything can actually happen, not for a big snow, but for something. Given we can't lock in a cold pattern, what we need is a transitory shot of cold air and then have a wave develop along the stationary front in the SE and give us some overrunning. Given the apparent lack of a potent s/w, that could never really produce a big storm, but could produce a 1-3" type event. That seems to be what a few runs were showing, but they now have anything even weaker and more surpressed.

I was just about to post that when I read your post. I also don't think it a real pattern changer though ridging in AK and western Canada would certainly be an improvement.

[mitchnick]

Patience?!? It's nearing mid Dec after a month+ long craptastic pattern with no tangible relief in sight. AND, I live in the MA where our winter window is the size of a cabin on a ship.

I'm probably one of the more relaxed around here but if I need more patience I should probably order some on amazon and stock up.

Eh, just kiddin. I'm not really worked up at all. We shall see what our lovely stratoshpere can whip us and send our way.

by the way, here's the website where you can get those maps in case anyone wanted to know

http://www.geo.fu-be...tics/index.html

you generally want to look at the 30mb map, but you can often see a change beginning higher up, 1mb-10mb first since they work down, at least so I recall reading somewhere but someone can correct if wrong

anyway, when you compare the 240 hr map I posted with the 12hr map, you can see a huge difference

any change has got to give us an improvement

also, I posted a study paper in the NY sub forum that found high solar activity during an E QBO leads to colder stratosphere (as does low solar activity with a W QBO)

I recently said that the sun was screwing us so far and that paper confirms it; the sun has backed off and that may explain why we are now seeing a "forecasted" change in the polar vortex

as for the winter in general, we have had late start winters around here that have ended up not so bad snow-wise; I'm keeping the faith Bob since little or no snow before Christmas is not that unusual

[mappy]

I think I can help with a simplistic explanation. It's a teleconnection and can be our friend when + and our enemy when -.

Quick and easy read: http://www.cpc.ncep....ledoc/pna.shtml

Simpleton terms:

+PNA = ridge west and trough east and -PNA = opposite

When we have no blocking to our north near greenland (like right now), a +PNA is going the prominent driver of cold air and favorable track in the east. Long story short, we really need a ridge out west and a trough in the east if we even want to consider snow chances right now. If we have a -nao, we can have a trough out west and survive because the track is supressed. A -pna and -nao (aligned correctly) can pretty much put the entire country in a trough and we all get snow and cold. Without the block to the north, a -PNA almost always = seasonable to above average temps in the eastern third of the US.

Interestingly enough, the 6z gfs suggests a potential +pna and -nao. I doubt it's right but MA weenies love that combo.

PNA = Pacific-North American

Basically just another index like the NAO or AO, but referring to whether there's ridging or troughing near the West Coast of North America. +PNA means ridging, -PNA means troughing. To get cold weather, we want a +PNA since an upstream (west) ridge means a trough over us, all things being equal.

No, it's not a true pattern change, but it's a better look. On the downside, the models have teased us with this improving look a couple times in the last few weeks and the can keeps getting kicked down the road or the better look turns into a 2-3 day cool/cold shot and then it's back in the crapper.

From a snow perspective, energy sliding under a western ridge can be a very good thing. But, typically closed lows in the southwest don't work out well since they teleconnect to a strengthening SE ridge. We want s/w's to slip under the ridge but keep moving eastward.

6z GFS ensemble mean actually did build heights into Greenland around Day 10 but then loses it afterwards. Euro didn't show this.

I like the setup for this weekend if anything can actually happen, not for a big snow, but for something. Given we can't lock in a cold pattern, what we need is a transitory shot of cold air and then have a wave develop along the stationary front in the SE and give us some overrunning. Given the apparent lack of a potent s/w, that could never really produce a big storm, but could produce a 1-3" type event. That seems to be what a few runs were showing, but they now have anything even weaker and more surpressed.

Thank you guys, I understand now.

[WxUSAF]

Thank you guys, I understand now.

P.S. Sometimes people refer to a -PNA as a RNA. IMO, I don't like that terminology since it can be a bit confusing and the +/- is more conventional.

[mappy]

P.S. Sometimes people refer to a -PNA as a RNA. IMO, I don't like that terminology since it can be a bit confusing and the +/- is more conventional.

Thanks for letting me know before I asked what RNA was and felt dumb

[mattie g]

by the way, here's the website where you can get those maps in case anyone wanted to know

http://www.geo.fu-be...tics/index.html

you generally want to look at the 30mb map, but you can often see a change beginning higher up, 1mb-10mb first since they work down, at least so I recall reading somewhere but someone can correct if wrong

anyway, when you compare the 240 hr map I posted with the 12hr map, you can see a huge difference

any change has got to give us an improvement

also, I posted a study paper in the NY sub forum that found high solar activity during an E QBO leads to colder stratosphere (as does low solar activity with a W QBO)

I recently said that the sun was screwing us so far and that paper confirms it; the sun has backed off and that may explain why we are now seeing a "forecasted" change in the polar vortex

as for the winter in general, we have had late start winters around here that have ended up not so bad snow-wise; I'm keeping the faith Bob since little or no snow before Christmas is not that unusual

It's certainly not out of the realm of possibility that we have a predominant torch through the rest of the winter, but a two- or three-week stretch gets us to at least normal snowfall. In fact, I'd personally love that.

[WxUSAF]

12z GFS still has our potential little weekend surprise, but stubbornly keeps the precip out of the cold air. Figures we finally get cold air and a storm, but there's too much confluence over the northeast and southern Canada and the storm gets squashed...in the north trend we trust?

[Herb@MAWS]

Monday 12/12/11 was another day of local daytime high temp disparities.

BWI came in at 46 degrees while IMBY, only a 20-min drive NW of BWI, max temp was 37 degrees. However, morning lows matched up well with BWI at 22 and 21 IMBY.

[WxUSAF]

Herb...interesting. I use this station as a proxy for MBY, since it's less than 1 mile away. This station was a bit warmer than you each time.

http://spret.net/weather/index.html

Back to the 12z GFS...it is freaking COLD for Christmas. Highs near freezing?

Do you believe in Christmas miracles (wrap-around)?

[mappy]

I'll believe in Christmas wrap around when it is falling

[nw baltimore wx]

12z GFS still has our potential little weekend surprise, but stubbornly keeps the precip out of the cold air. Figures we finally get cold air and a storm, but there's too much confluence over the northeast and southern Canada and the storm gets squashed...in the north trend we trust?

I was wondering about that. But if we get the precip, will the cold retreat with it?

[WxUSAF]

I'll believe in Christmas wrap around when it is falling

Yes I'm dreaming here, but that would be a perfect Christmas eve. Cold, breezy and light snow falling.

[WxUSAF]

I was wondering about that. But if we get the precip, will the cold retreat with it?

Yes, it's a trade off (as it always is around here). There's probably a sweet-spot that keeps things sufficiently cold but allows the storm to move a bit farther north.

Perhaps a more exciting possibility (but a much longer shot) is the s/w that is coming down the Plains at the same time. The s/w catches up with the surface low north of Bermuda and finally gives it a boost. If that could happen closer to the coast that would maybe let it hug the coast a bit more and get it a bit stronger. This is spit-balling here, BTW...

[RickinBaltimore]

Yes I'm dreaming here, but that would be a perfect Christmas eve.  Cold, breezy and light snow falling.

Perfect football weather to see the Ravens & Browns

[WxUSAF]

Great football weather for a big dish of Rice.

Great pattern for snow for us. Sweet +PNA, troughing over Newfoundland, ridging into Greenland, confluence over NE.

[mappy]

^^^ yay?

[Ellinwood]

Great football weather for a big dish of Rice.

Great pattern for snow for us. Sweet +PNA, troughing over Newfoundland, ridging into Greenland, confluence over NE.

Not only that, but the AO/NAO forecasts in the medium range have been trending in the negative direction for a couple of days now (but still neutral/positive for most of it outside of the quick dip into -AO territory this weekend).

[mitchnick]

Canadian GGEM a little more positive on possible event over the weekend

has some measurable qpf into DCA/BWI, but I'm not certain about temps; probably too warm in light of light qpf

here are links to 84 and 96 hrs

http://www.weatherof...ast/233_100.gif

http://www.weatherof...ast/234_100.gif

[nw baltimore wx]

Yes, it's a trade off (as it always is around here). There's probably a sweet-spot that keeps things sufficiently cold but allows the storm to move a bit farther north.

Perhaps a more exciting possibility (but a much longer shot) is the s/w that is coming down the Plains at the same time. The s/w catches up with the surface low north of Bermuda and finally gives it a boost. If that could happen closer to the coast that would maybe let it hug the coast a bit more and get it a bit stronger. This is spit-balling here, BTW...

Yeah, but it's enjoyable to see a met being a weenie too.

[Bob Chill]

12Z NAM

now that's more like it

http://mag.ncep.noaa...el=&imageSize=M

Nah, that's nothing to worry about. The nam is always too wet.

by the way, here's the website where you can get those maps in case anyone wanted to know

http://www.geo.fu-be...tics/index.html

as for the winter in general, we have had late start winters around here that have ended up not so bad snow-wise; I'm keeping the faith Bob since little or no snow before Christmas is not that unusual

Thanks for the link. I just added to my arsenal of bookmarks for things that I'll look at regularly but only know enough about to be dangerous with.

Agree about snow. The only thing that I've changed my mind on is the possibility of an overall cold winter. I actually have a pretty good outlook on snow. I would have no problem hitting climo with a bunch of 1-3"s or 2-4"s. Big ones are great and all but it can be like chasing ghosts this far south.

I've posted alot of stats and stuff so far this year but I want fellow weenies to know that I'm only good at looking at past statistics and trends to better predict future outcomes. I'm a numbers guy. I'm not good at all with the "whys" and "hows" of past patterns. If I post crap I encourage anyone to step in and correct my thoughts. My entire weather knowledge is armchair based. Never took classes on it but I've been a snow (and weather) enthusiest since I was a kid so I pay attention to alot of stuff. I'm super thankful for finding eastern and it's continuation on amwx. I've learned an incredible amount of stuff here and the mets and knowledgeable posters willing to share their knowledge is awesome.

What I do for a career helps me analyze weather data. I've been in the financial portfolio risk analysis field and have designed several financial underwriting models. I spend my days reviewing past performance data to help predict and improve future perfomance expectations. This correlates well with weather data to some extent. The only reason I'm blabbing on about this stuff is because since I do post stats and stuff I don't want people thinking I'm a good weenie for weather forecasting beyond the #'s because I'm not.

[stormtracker]

Things finally starting to look up? Sun is starting to rise on us?

Wes will be in shortly to use my bowl of cheerios as a urinal.

[Ellinwood]

Things finally starting to look up? Sun is starting to rise on us?

Wes will be in shortly to use my bowl of cheerios as a urinal.

That's at least been the trend on the models recently... though we all know how fast that can change. Models skills are still on the low end compared to what we're used to seeing, so everything needs to be heavily scrutinized.

[WxUSAF]

^^^ yay?

Well, even if we don't get snow, it's nice to see the pattern very supportive of snow finally. Baby steps here.

Canadian GGEM a little more positive on possible event over the weekend

has some measurable qpf into DCA/BWI, but I'm not certain about temps; probably too warm in light of light qpf

here are links to 84 and 96 hrs

http://www.weatherof...ast/233_100.gif

http://www.weatherof...ast/234_100.gif

I have a hard time believing folks in DC/NVA/WV/MD would be too warm given how classic that pattern looks for snow for us. But, there's always a New And Different Screwing in the Mid-Atlantic.

Yeah, but it's enjoyable to see a met being a weenie too.

That's what I'm here for. I don't forecast anymore for pay, so this is all just fun.

Wes will be in shortly to use my bowl of cheerios as a urinal.

In the spirit of Christmas, maybe you could make a Scrooge emoticon for some of Wes's posts.