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Dec 24-28 winter weather period


Ji

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because models alone != forecasting

there have been a couple of reasons other than the models to think the pattern would suck, la nina and the monsterously strong ao and nao, the latter two signals usually gives up easily without a fight. I pretty much wrote off Dec at the beginning of the month. The current model look in the extended range pretty much fits preconceived notions of what the pattern should look like.

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Wes! conjure up some snow, *please*. :)

I was speaking more to his question about why we won't place faith in backyard solutions of model runs 5 days out versus accepting and recognizing broad weather patterns based on a variety of inputs.

I wish I could, maybe the 10% chance that we get snow based on the euro is correct. Otherwise, it looks grim into January. For you, the probabilities probably are higher being further west. The only flakes I've seen this year were in October, pretty sad.

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I consider our WV winter to be off to a decent start: cold and we've seen flakes a few times this month. we'll be in CT for Christmas so will miss whatever may fall out our way.

The 18Z GFS has trended pretty strongly towards the euro except quite a bit warmer. I think that may be the winner but it's still far enough away to say, ????? Though I'd bet for dc no snow.

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84 hr 18z NAM (yeah, I know) looks EUROish... 850 0c line is in C VA with the -3c line from BWI to Leesburg and then to the SE of Charleston WV in a NE to SW fashion... the 0c 2m line is west of the Apps... 1033 H is north/northeast of NY state in Canada but is moving east.

There is a s/w in NW MI and another one, albeit closed, in the TX panhandle. This is way different (well duh, of course it is Yoda!) than the 12z 78 hr h5 chart when you compare the 2

the SE Ridge is a breathing, living creature on the NAM

http://mag.ncep.noaa.gov/NCOMAGWEB/appcontroller?prevPage=Model&MainPage=indexℑ=&page=Param&cycle=12%2F20%2F2011+18UTC&rname=UPPER+AIR+PARMS&pname=500_vort_ht&pdesc=&model=NAM&area=NAMER&cat=MODEL+GUIDANCE&fcast=Loop+All&areaDesc=North+America+-+US+Canada+and+northern+Mexico&prevArea=NAMER&currKey=model&returnToModel=&imageSize=M

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I think some may have misinterpreted my post. I am not saying we should put faith in storms modeled 5 days out. I'm only saying that I don't see how we put faith in modeled solutions and patterns 10+ days out. It would seem to me that it would be more difficult to model the pattern than a storm, one being global, the other being at least partially regionalized. Not trying to say that this is true, only trying to get someone to turn my "uninformed" notions into informed notions. Wes mentioned using the AO as a forecast tool for the longer range. Heck, the AO index was adjusted upward, not went upward, the index just somehow changed by nearly 2 SD since yesterday. How can that be a reliable tool to use? Again, just asking questions here.

Obviously I would like the pattern to change. Although, as someone earlier mentioned, I'm just as worried that if it does, it will change to dry/cold. That's even worse in my view. Either way, if it were cold now, snowy now, and the pattern was forecast to be stable for the next month, continuing the very pattern that I want, I would still be highly skeptical of that. It's just hard for me to put confidence in solutions dealing with the 10+ day period when the most sophisticated, complex computer programs we have can't be very accurate even 5 days out.

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I think some may have misinterpreted my post. I am not saying we should put faith in storms modeled 5 days out. I'm only saying that I don't see how we put faith in modeled solutions and patterns 10+ days out. It would seem to me that it would be more difficult to model the pattern than a storm, one being global, the other being at least partially regionalized. Not trying to say that this is true, only trying to get someone to turn my "uninformed" notions into informed notions. Wes mentioned using the AO as a forecast tool for the longer range. Heck, the AO index was adjusted upward, not went upward, the index just somehow changed by nearly 2 SD since yesterday. How can that be a reliable tool to use? Again, just asking questions here.

Obviously I would like the pattern to change. Although, as someone earlier mentioned, I'm just as worried that if it does, it will change to dry/cold. That's even worse in my view. Either way, if it were cold now, snowy now, and the pattern was forecast to be stable for the next month, continuing the very pattern that I want, I would still be highly skeptical of that. It's just hard for me to put confidence in solutions dealing with the 10+ day period when the most sophisticated, complex computer programs we have can't be very accurate even 5 days out.

gymengineer had a good explain i thought. i dont think you can put absolute faith in a pattern 10 days out but large scale features are more stable generally or longer lasting usually at the least. it takes more to get it moving/changing/turning. models are pretty good these days at "catching" a storm days out but there are so many ingredients in winter or severe season where it's usually impossible to pinpoint details with much accuracy. generally i think as you get into the smaller scale it's harder to know much from X amount of time out. take a severe storm--you can generalize where one might pop but usually you have to wait till it does to know for sure. or a tornado.. you have to get even luckier.

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gymengineer had a good explain i thought. i dont think you can put absolute faith in a pattern 10 days out but large scale features are more stable generally or longer lasting usually at the least. it takes more to get it moving/changing/turning. models are pretty good these days at "catching" a storm days out but there are so many ingredients in winter or severe season where it's usually impossible to pinpoint details with much accuracy. generally i think as you get into the smaller scale it's harder to know much from X amount of time out. take a severe storm--you can generalize where one might pop but usually you have to wait till it does to know for sure. or a tornado.. you have to get even luckier.

Kind of like it's much easier to move small pebbles in a stream than it is a large boulder?

Question: Can surface events have large scale impacts on the upper level patterns, or are those changed by larger events like the SSW I've been reading about? Is it top down or do surface events play just as big of a role?

Also, thread related, the GFS sure changed big time. Is that a sign that this Christmas storm is a very sensitive event?

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Kind of like it's much easier to move small pebbles in a stream than it is a large boulder?

Question: Can surface events have large scale impacts on the upper level patterns, or are those changed by larger events like the SSW I've been reading about? Is it top down or do surface events play just as big of a role?

Also, thread related, the GFS sure changed big time. Is that a sign that this Christmas storm is a very sensitive event?

I'm not sure what you mean by surface events. Low pressure areas are related to what is happening aloft. Tropospheric waves can impact the pattern and produce blocking. Sudden stratsopheric warming events also can have an impact but they are pretty rare and many here seem to be overplaying them. However, when the stratospheric vortex and tropospheric vortex are both stronger than normal, it's tougher to get a blocking going.

Yes, as I mentioned to Zwytts, the pattern is not only a crappy one without much cold air but it is also one that is very hard for the models to handle very well because the various features are moving so quickly.

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I'm not sure what you mean by surface events. Low pressure areas are related to what is happening aloft. Tropospheric waves can impact the pattern and produce blocking. Sudden stratsopheric warming events also can have an impact but they are pretty rare and many here seem to be overplaying them. However, when the stratospheric vortex and tropospheric vortex are both stronger than normal, it's tougher to get a blocking going.

Yes, as I mentioned to Zwytts, the pattern is not only a crappy one without much cold air but it is also one that is very hard for the models to handle very well because the various features are moving so quickly.

I guess what I don't understand is which is the horse and which is the wagon. I'll try to give an example, and, at the same time, not appear too stupid.

I've seen times in winter storms when convection in the south ends up robbing some of the moisture that areas further north were depending on for their snow. At least that's what I've heard mets like on TWC say. I've seen thunderstorms blow up near storms headed for me that seem to kill the storm that I wanted to come my way. My question is, can storms at the surface end up different from how they are modeled, stronger say, and that in turn end up having an effect on the upper level pattern, thereby effecting the modeled forecast for the upper levels.

What are the biggest drivers of the upper level pattern? If you had to list 3, what would they be?

I know this probably is the wrong thread for this. Sorry, everyone. Last question, promise.

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Maybe I'm just not smart enough to figure this out, but it seems that we view storms on the models with skepticism, but we view 10 day (and longer) forecasts that tell us it is going to get warm as likely. Oh well.

WinterWxLuvr,

Right now, the "warm" idea fits the kind of pattern that is seemingly locked into place. That's why the "warm" idea is a higher confidence proposition than a possible medium-term snowstorm. In contrast, last December, one could have higher confidence in a "cold" idea given the extreme blocking that was in place.

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WinterWxLuvr,

Right now, the "warm" idea fits the kind of pattern that is seemingly locked into place. That's why the "warm" idea is a higher confidence proposition than a possible medium-term snowstorm. In contrast, last December, one could have higher confidence in a "cold" idea given the extreme blocking that was in place.

I guess that's my hang up. What is it that makes the pattern "locked". Are there forces at work that help to keep it that way, or is it a case of needing some type of "large" force to cause it to break loose?

BTW, thanks for the reply, and to all others who have answered. Lots of very smart people here in our thread, and it's a great opportunity to learn. I guess as a math guy, I love to look for cause and connection in everything.

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I guess that's my hang up. What is it that makes the pattern "locked". Are there forces at work that help to keep it that way, or is it a case of needing some type of "large" force to cause it to break loose?

The strength of the polar vortex is key to determining whether or not there is blocking (AO). Sometimes the polar vortex can be strong for extended periods of time (AO+). Sometimes it can be weak for extended periods of time (AO-). Sometimes it can fluctuate leading to changeable AO situations.

Sudden Stratospheric Warming (SSW) events can lead to the Polar Vortex's being displaced or splitting (sustaining or leading to an AO-). Other factors can also impact the strength of the polar vortex e.g., there has been some correlation between the buildup of snowcover in Siberia and the predominant AO state during the winter. IMO, much research remains to be conducted for better forecasts as to whether or not blocking will be frequent and/or persistent during a given winter.

Currently, despite the brief dip in the AO, the overall situation is one in which an AO+ is tlikely to remain the predominant state. Although some guidance suggests some warming of the stratosphere down the road, the guidance is not yet pointing to an SSW.

Not too surprisingly, the ensembles (GFS, CMC, and ECMWF) all continue to indicate that the AO will return to positive levels shortly and that the AO+ situation will prevail for some time to come.

Hence, there is little sign at present that the generally warm pattern will change dramatically. Cold shots will be transient and short-lived (IMO, the 12/20 18z GFS is probably too cold for the first week of January in the East given the pattern; some analog patterns and also the NAEFS hint at widespread mild readings in the Eastern 1/2 to 2/3 of the CONUS and southern Canada). Snowfall opportunities will also remain scarce and a KU-type snowstorm remains highly unlikely for the foreseeable future.

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balto sunpapers has cold rain for xmas day. How do you know that what is represented on the gfs is not just that, a cold rain?? No high to the north, where is your justification for snow??? Looks nice but are you just using wishful thinking???

I'm calling for snow? News to me

I think our chances for snow are very unlikely. i have not been on the snow train for this at all. My earlier post calling the GFS right was before looking at the 6z run. I don't buy the 6z at all.

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I'm calling for snow? News to me

I think our chances for snow are very unlikely. i have not been on the snow train for this at all. My earlier post calling the GFS right was before looking at the 6z run. I don't buy the 6z at all.

no I did not mean to say you were calling for snow, I picked you quote by accident. I meant Ji. I was just responding to Ji remark that it was back again. My apologies.

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