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December Mid-Long Range Discussion


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2/86 was such a fun month...stormy, frequent small to moderate snowstorms (6 separate snows), a couple of over-performers, and persistent cold from 2/7 through the end of the month. I can't think of a better month of snow in a year without any 6" snowstorms since I've been alive.

I liked feb 2007 as well

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No more naming storms allowed here. Bannable or banishable to SNE offense.

I'm grandfathered in.

But on a serious note, I like the idea of a colder pattern around Christmas time. I still think we have to wait until 2nd week of Jan for anything good. I hope I'm wrong, but Dec looks like a shut out. I'm fine with that.

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I liked feb 2007 as well

Yup, definitely. That was a great 4-event February. The last 2 overperformed (30 minute snow burst and 2/25), and as has been discussed multiple times, 2/13-14 was the most crippling winter storm since 2/03.

What IAD recorded during 2/86 is pretty astonishing for a winter without the big storm- six separate events: 1", 4", 1", 4", 4", 3"

The last three storms came within a week!

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Yup, definitely. That was a great 4-event February. The last 2 overperformed (30 minute snow burst and 2/25), and as has been discussed multiple times, 2/13-14 was the most crippling winter storm since 2/03.

What IAD recorded during 2/86 is pretty astonishing for a winter without the big storm- six separate events: 1", 4", 1", 4", 4", 3"

The last three storms came within a week!

it was a great week...That wasn't even a great PAC pattern....we had just enough ridging in the west to make it work....we had a greenland block of course....the mediocre PAC probably kept us from getting a KU....I think a couple of those were suppressed events...

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it was a great week...That wasn't even a great PAC pattern....we had just enough ridging in the west to make it work....we had a greenland block of course....the mediocre PAC probably kept us from getting a KU....I think a couple of those were suppressed events...

4.4" overall for the month with 3.5" falling at RIC on the 14th. Close call on the 10-11th....0.60" precip, but temps look cold enough both days... probably had precip type issues. Must've been a volatile pattern.... quite a few days with temps in the 60s sandwhiched in between the cold shots.

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4.4" overall for the month with 3.5" falling at RIC on the 14th. Close call on the 10-11th....0.60" precip, but temps look cold enough both days... probably had precip type issues. Must've been a volatile pattern.... quite a few days with temps in the 60s sandwhiched in between the cold shots.

That 2/14 snowfall was 0.8" at IAD so, yeah, that's the suppressed snow. And from 2/07-2/28, IAD only had one day with a high over 44 degrees and six days with a high over 40 degrees. That one day spiked to 54 for a high before the 3 moderate snowstorms in a week.

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I liked feb 2007 as well

Yup, I've got to agree! I've said this several times, but that winter is kind of underrated and forgotten in my opinion. Yeah, it sucks we missed out on the best part of the Valentine's Day storm (especially when it looked like we'd get hit) and got 3" sleet instead. But still, Feb. 2007 was highly interesting with the extremely cold temperatures, the sleet storm, a clipper thrown in there near the beginning of the month, and the "surprise" 5-inch snow on the 25th.

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That 2/14 snowfall was 0.8" at IAD so, yeah, that's the suppressed snow. And from 2/07-2/28, IAD only had one day with a high over 44 degrees and six days with a high over 40 degrees. That one day spiked to 54 for a high before the 3 moderate snowstorms in a week.

I believe DCA had a departure of approx. -7 degrees for Feb. 2007 if I recall correctly offhand. It was really cold! I'm sure BWI and IAD were very similar. In fact, much of the eastern third or so of the U.S. was quite frigid that month.

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Block is staying put for a while according to the models. Good news for sure. I am liking the thoughts on an end of month snow chance. The setup in the Atlantic is great in the long range. And the 0Z GFS is saying the cold will be there. Now we just have to get a SW to track across the SW. And the GFS is hinting at that. I know its in fantasy land 348HR. But love the look of this LONG RANGE 500 map.

00zgfs500mbHGHTNA348.gif

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00Z Euro has an interesting solution for days 7-8. It runs a primary into the lakes with a strong secondary forming off the coast. The question is, where does it originally form it between the 24 hours of the 2 panels?

Consider me skeptical of that scenario producing snow here. Never know I suppose.

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After reading a couple of rosey posts about the pattern, thought I'd look at the actual CPC ens member forecasts of the NAO and PNA. I've held off on the AO though it looks somewhat similar to the NAO forecasts though maybe with slightly more members showing a negative AO than what is being shown on the graph below. note that the graph shows quite a few members with the nao going very positive after around 10 days and also some staying negative. Also if you look at the correlations between the forecasts and what is observed in the long range, they are super low, not high enough to use with any confidence.

post-70-0-85298500-1355497262_thumb.gif

The PNA forecast is more consistent and pretty much stays negative through the run. It's forecasts have a much higher correlation with the observed values though by day 14 the correlation suggest the forecasts are also not very useful though the consistency of the negative AO during the past few months probably would give it a little more credence than the NAO forecasts.

post-70-0-34332600-1355497580_thumb.gif

Optimists can look at the forecasts and say at least half of ens members are forecasting a negative Nao and forecasts of the PNA aren't that good so there is a chance of a storm. \

Pessimists will look at the very positive NAO members and believe them and will then look at the negative PNA and say gosh, Dec is lost.

A realist will probably say snow looks unlikely through at least Christmas but we need the PNA to go positive to really keep storms from initially tracking to the OH Valley before reforming off the coast probably to our north.

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Consider me skeptical of that scenario producing snow here. Never know I suppose.

A general rule of thumb for Miller B's is you want the coastal to form south of your latitude. I'd guess the Euro and Euro ensembles form it just north of us, probably leaving us generally dry, cold and windy. Still a lot of ducks on the pond for the next couple weeks. Model's obviously are having trouble with so many s/w's interacting. This Miller B scenario for next Friday/Saturday just sort of popped up out of nowhere on all the overnight runs.

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Wes, from an index reading standpoint the NAO looks bad but when you look at the features being modeled it's not a kiss of death. The area of higher heights associated with the west based -nao moves towards hudson bay allowing for lower height behind to establish over GL. So a +nao on paper may look bad but when you look at the overall setup it's not really as bad. Not saying it's good but "ok" isn't a bad term. PNA sucks but that's a different discussion.

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I do have a question. If the NAO goes positive as modeled wouldn't it be easy to have the block re-establish itself? If the NAO went positive and the lower heights were spread south and west through Canada then we have big problems because we ridge out down here. But as shown I would think that a +nao isn't a kiss of death nor would it be difficult to get a more favorable look going forward.

I'll take me weenie glasses off now and concede that we're doomed.

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Consider me skeptical of that scenario producing snow here. Never know I suppose.

I agree. We very rarely do well in these type of setups where we have a primary in the GL and we have to wait for the coastal to take over and become the predominate low. With the limited maps available to me I would think this setup would be good enough for some mood flakes in the air back into the DC and Baltimore at the least though. Philly and north looks like they would be the ones to cash in. Of course the way the models have been going it is kind of a moot point because we will have a whole new solution come the 12Z suite. :whistle:

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Well, the good news about the GFS run is that the cold shot next weekend is now inside truncation and appears to be showing up no matter what convoluted mess the GFS throws out there for early next week. Jonjon and our lake-effect/upslope friends are going to CASH in a week from now. Phin might want to head out to Deep Creek.

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Well, the good news about the GFS run is that the cold shot next weekend is now inside truncation and appears to be showing up no matter what convoluted mess the GFS throws out there for early next week. Jonjon and our lake-effect/upslope friends are going to CASH in a week from now. Phin might want to head out to Deep Creek.

GFS is much stronger with the d7-8 system. Big time les / upslope signal. Ridge really pops in between the 2 ull's off of each coast. Overall a much more amplified solution than any previous runs. Impossible to say if it's a trend or a blip.

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Cold definitely comes in quicker on this run. Doesn't look like surface temps get out of the 30's for a good stretch. Most importantly, christmas eve and day look cold. Dry but cold. I think we're up to 7 gfs runs in a row showing that.

Last week of the month still showing some chilly temps and storms coming into socal and precip to our sw. But without a good block the track reverts to our nw. heh.

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The MJO going into phase 1/2 would have to have some effect on things as they historically have been cooler patterns for the eastern half of the US, right?

Earlier forecasts had it stronger. Now ens are showing "barely" out of the cod moving from phase 1-2. Trend is not friendly. But then again, mjo forecasts are notoriously tough and inaccurate as the lead time increases.

It looks like the -pna is going to continue to crush our dreams. We'll see I guess.

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The MJO going into phase 1/2 would have to have some effect on things as they historically have been cooler patterns for the eastern half of the US, right?

Earlier forecasts had it stronger. Now ens are showing "barely" out of the cod moving from phase 1-2. Trend is not friendly. But then again, mjo forecasts are notoriously tough and inaccurate as the lead time increases.

It looks like the -pna is going to continue to crush our dreams. We'll see I guess.

I speculated last week that it was possibly models mistaking a kelvin wave for the MJO and now I think that's right. The CHI fields are weak but divergent for a large longitude bound with various entities causing forcing / response in the EOFs. The 3 components are overlapping for MJO amplitude in phase 1 but it seems to be just a kelvin wave. Don't forget we also have Evan in the Central Pacific and westward waves initiating convection in between Evan and the Kelvin Wave. Overall, things are unorganized and not MJO like. I think the signal is bogus.

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