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December Forecast Discussion


Wow

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The 12Z looks to continue advertise a wetter pattern. We definitely need the rain. Don't see any real winter threats showing up just yet, though.

Well, climo doesn't allow anything of consequence until after Xmas, down here anyway, lol. It's why I thought you were crazy with the Christmas storm, It's usually only a little sleet, or some flurries, with the rare, occasional miracle storm, if we get anything at all, until the week after Christmas. But when I see the flow putting storms in the gulf, then I know the pattern will likely repeat when it can do some good. Seeing those storms out there in GoofyLand makes me think good thoughts for later, when it might cool off. To me, it the hardest leg of the tripod to get in winter. Get the rain pattern, then the cold has a chance to come down and meet it, with the timing. Get the rain every 3 to 5 days, and we have chances. Shot after shot of cold air into a drought gives cold air, lol. Which does beat the heck out of summer. But what I want is a split flow, and I'm happy to wait for the cold to phase in. T

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They must not have been that good... :o

I got caught up, i'll do it soon. The euro ensembles are flipping a lot more than the GFS. The GFS has been pretty consistent on a huge Greenland/Davis Strait block setting up around Dec 15, but euro is showing it more of a east based greenland block that doesn't advance far enough into western Greenland/Canada to flip the pattern permanently. Will be interested to see if it will flip back again. If the GFS is right, the last 2 weeks of December will be rockin.

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Systems every couple of days would be great,as we desperately need the rain.like someone already posted,get the wetter pattern first,then worry about the cold eventually getting involved.

Matthew East talked about the pattern changing and heading into a period where we'll have a storm system every few days. It might not lock in sustained cold, but I don't mind that. Just need it to be cold enough at the right time.

http://mattheweast.blogspot.com/2012/12/cooler-today-mild-weekend-ahead-changes.html

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00z GFS last night was full of potential....possible CAD events...cold air arriving first for one system that could be big...of course all of this past 240 but still we need to hope for that look.....Euro was just kind of "meh" in the LR.

The 6z run had a little coastal storm develop that could be interesting, but like you said it's in fantasy land. I does, though, follow a larger storm that's more of an Apps runner, which would make any developing storm following it to proceed more to the south.

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Okay, I got a few minutes so here we go GFS Ensemble mean.

240 hours next one block over Greenland the other in the Gulf of Alaska. (no more vortex)

http://raleighwx.americanwx.com/models/gfsensemble/00zgfsensembles500mbHeightAnomalyNH240.gif

Roll forward to 300 hours Greenland block retrograding west connection almost there.

http://raleighwx.americanwx.com/models/gfsensemble/00zgfsensembles500mbHeightAnomalyNH300.gif

Now out to 384 hours The Greenland block is over eastern Canada (west based -NAO and it's starting to hook up with the block over Alaska. Just in time for the Holidays so Santa can bring us some snow!!!

http://raleighwx.americanwx.com/models/gfsensemble/00zgfsensembles500mbHeightAnomalyNH384.gif

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It looks like a wetter pattern is still on tap, but it's a slow process. So far, I still think the Tennessee Valley side to Gulf States will end up with the best totals in the upcoming southwest flow, as there's always a tendency for rain there and less further east, but I do think further east like GA and Carolinas will finally start to get in on it. The Monday/Tuesday front will be the first decent shot, but it's still a quick mover and will drop less and less as it moves east, but then another one is on it's heels in southwest flow, and by then the pattern change is really in full gear and many systems will be topping the weak ridge in Gulf of Alaska, cruising through the Intermountain West and into Texas.

post-38-0-39066600-1354803709_thumb.gif

I think the GFS is too sharp, but the idea is that several good s/w will round the bend and attach to a stationary front draped across the Mid Atlantic stretching to Texas Coast. Those could have snow or ice on the north side in the Plains like Ok, Ks and increasing rains ahead of the system.

Behind that storm, yet another quick hit of cold , but I'd venture to guess with the Scandinavian block so far away, the next front too will stall out quickly and more precip would develop in the Deep South (rain). It's going to be very, very stormy overall , maximimizing coverage as much as possible in this flow, with much of the west Coast, esp NW much of the Rockies and at times the Plains, getting in on very stormy weather, with some snow where it's cold enough, so the snow pack is building in southern Canada and the northern US.

Next up...when does the Big Scanadinavian ridge re-locate? Who knows. But on the animations of eCMWF and GFS you can see it's slowly moving and trying to work toward eastern Canada, as split flow opens a gap there, and I've seen a block fill that gap a couple times this Fall so, "probably" that's where it will end up, but don't know when. I don't think it will be anytime too soon, so enjoy the southwest flow and rains, we need it. The models thought this would be the area (Greenland or so) for the first round of blocking but it didn't work out that way, and instead it's more east, but I don't see this as last year since we have some other anomalies at work that weren't around last season.

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Well that can't be good.

No hope until after 12/17/12 it looks like from what I am seeing. Which is not that long, but not sure how we are going to survive until then.

Just horrible! We are already 30 inches behind in snowfall with no hope for the next ten days. Not sure how we will survive either.

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Well that can't be good.

No hope until after 12/17/12 it looks like from what I am seeing. Which is not that long, but not sure how we are going to survive until then.

LOL...the pacific can't go all winter this bad...can it...the PNA has been negative it seems like forever, it's got to flip sometime...doesn't it!

I know the PNA has been positive it small blips but I am fairly sure it's averaged negative for atleast 6 months now.

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If the middle of the month comes to pass, it makes my ice storm prediction/wild guess for early mid. Jan. look pretty good still :) Get that nice repeat action, with cads and gulf lows over running. I like my chances for some sleet come Jan. and Feb. Of course, I'm still in that happy state where hope is springing eternal. We'll, see how the crystal ball looks come New Years..... but right now, at least, I'm feeling fine about some rains. It's just that I know breaking a drought ain't easy, and counting on GoofyLand to deliver is a fools game, but some wetter times do seem possible. Whether or not they find my area is always the key, but gulf storms seem to like folks who live nearer the gulf, whereas dragging fronts can break apart as they hit the Ala line, as we've seen lately :) T

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LOL...the pacific can't go all winter this bad...can it...the PNA has been negative it seems like forever, it's got to flip sometime...doesn't it!

I know the PNA has been positive it small blips but I am fairly sure it's averaged negative for atleast 6 months now.

Agreed pack - And even though it may have averaged negative for that long, we have been at or below normal temps overall which is somewhat hopeful. I continue to see a slow progression to seasonal, but progress none the less.

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I think it's important to remember when looking at maps and searching for patterns that might deliver cold, one should look for high pressure systems to the north as well as areas of confluence. Don't just pay attention to the height lines and the PNA and the NAO, but look for features like the ones mentioned above that can often deliver low level cold air in less than perfect H5 and H850 solutions.

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I think it's important to remember when looking at maps and searching for patterns that might deliver cold, one should look for high pressure systems to the north as well as areas of confluence. Don't just pay attention to the height lines and the PNA and the NAO, but look for features like the ones mentioned above that can often deliver low level cold air in less than perfect H5 and H850 solutions.

Which is why the last two runs of the GFS looked pretty good. A few favorable CAD events in those runs.

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He was just referring to the EURO. When I look at the GFS, any possible events look fairly long term from what I can tell. Does my 12/17/12 comment look off to you?

I'm not trying to be mean or anything but I just felt like your comment was useless and lacked any substance. Looking at the last few runs of the GFS I would say the NE is probably in play just before the 17th.

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One thing seems consistent on the models is Europe is staying cold. Is that because of the location of the block over Greenland; it's too far east? Does that make it a east based -NAO?

12zgfs500mbHeightAnomalyNH216.gif

Yes it's an east based NAO/Scandinavian block. The good news is that the ensembles continue to retrograde the NAO to more west based. Over Greenland and eastern Canada.

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The NAO retrograde west on the ensembles making it west based. Fun times ahead for the upper south with a -NAO -AO and active southern stream.

With the -PNA where do you think the boundary will set up for the storm track? Southern NC or further north?

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One thing seems consistent on the models is Europe is staying cold. Is that because of the location of the block over Greenland; it's too far east? Does that make it a east based -NAO?

Just to add on from FranklinWx...in a nutshell, an east based -NAO is when the max positive anomalies are centered east of Greenland. A west-based -NAO is when the max positive anomalies are centered around Greenland, or west/southwest of there. No 2 setups are alike, and there are obviously many other varibles, but going on past analogs, the best placement for SE wintry weather is when the max positive anomalies are located in the vicinity of southern Greenland and west/southwest of there to Hudson Bay. And yes, the placement and strength of the block is key in the resulting upstream and downstream troughs that form, and the cold air associated with those troughs. Dig around on Allan's site - he has a link to a doc from Rutgers that lays out the geographic domain of the NAO.

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