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Winter Pattern Discussion 2014-2015 (December/January)


Carvers Gap

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I agree, but the strong blocking signature around Hudson Bay and the active southern stream has my attention.

 

Good point.  I think that is what DT, Cosgrove, WxSouth, and Alan are seeing in some form or fashion.  Those four have definitetly been giving cautiously optimistic comments for the upcoming(and not so distant) forecast range.  I probably watch that signal less than I should.  But synoptics are a great tool.  The NAO taking a dip is a nice signal.  Looks like the hammer is getting ready to drop.

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EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1054 AM EST SUN DEC 14 2014

VALID 12Z WED DEC 17 2014 - 12Z SUN DEC 21 2014

...CHANCE OF WINTRY PRECIPITATION FROM THE MIDWEST TO THE CENTRAL
APPALACHIANS...

THE SUBTLE RESHUFFLING OF THE FLOW ACROSS CENTRAL NORTH AMERICA AT
THE MEDIUM RANGE IS EXPECTED TO SHIFT THE FOCUS OF HEAVY
PRECIPITATION FROM CALIFORNIA TO THE COASTAL PACIFIC NORTHWEST, AS
WELL AS INTRODUCE ENOUGH COLD AIR INTO EASTERN PORTIONS OF THE
UNITED STATES TO ALL FOR SNOW OR A WINTRY MIX ON THE NORTHERN EDGE
OF THE COMPLEX STORM SYSTEM EXPECTED TO TRACK THROUGH THE GULF
STATES. RELIED ON THE THE SOLID MIDDLE GROUND OF THE ECENS MEAN AS
A SYNOPTIC GUIDE THIS FORECAST PACKAGE, WHICH FOR THE EAST MEANS A
WAVE TRACK MORE SUPPRESSED THAN SOME OF THE GFS/GEFS GUIDANCE BUT
NOT AS SQUASHED AS THE CANADIAN MODELS.

CISCO

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In the back of my

mind I am growing a little concerned with the Euro's depiction of cold centering itself further west..... It would be a big bummer to be on the fence with the storm this weekend and then rain, wind, and 50's on Christmas.....

 

Just looked at the CPC ensembles.  All of them are beginning to show blocking that would center the cold east of the Mississippi.  Wouldn't surprise me at all if the cold started west and moved east.  Seems like the trough wants to center on this side of the country though.  Time will tell... Nino winters can be fickle.  But I think winter is on its way. 

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Good signature on the models for a storm of some sort next weekend.  My heart says this isn't the one but the Euro keeps sucking me back in.

 

Going to have to see a few more runs of the Euro before I buy anything.  Really need a cold source to draw from before getting widespread snows.  But I think the models "sense" the pattern change and are just trying to weed-out what the actual pattern will be.  Would really like to see you all end the snow drought.

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Just looked at the CPC ensembles. All of them are beginning to show blocking that would center the cold east of the Mississippi. Wouldn't surprise me at all if the cold started west and moved east. Seems like the trough wants to center on this side of the country though. Time will tell... Nino winters can be fickle. But I think winter is on its way.

Oh, I do too.........just speaking about the Christmas period since I have really liked that timeframe for about 10 days now.

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Just looked at the CPC ensembles.  All of them are beginning to show blocking that would center the cold east of the Mississippi.  Wouldn't surprise me at all if the cold started west and moved east.  Seems like the trough wants to center on this side of the country though.  Time will tell... Nino winters can be fickle.  But I think winter is on its way. 

 

Like you, it wouldn't surprise me to see the initial shot of arctic air settle in the west then come east.  Once the blocking gets established (hopefully) we should be on the receiving end.  Wouldn't be the first time that's happened.

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Oh, I do too.........just speaking about the Christmas period since I have really liked that timeframe for about 10 days now.

 

The old rule of thumb that big pattern changes are often preceded by winter storms would probably apply here.  In 09', that pretty much snuck-up on everyone involved.  The pattern was there, but the amounts over-performed.  Once that cold drops into the Lakes, we better hold on to our hats.  Ski slopes ought to be loving this weather.

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Like you, it wouldn't surprise me to see the initial shot of arctic air settle in the west then come east.  Once the blocking gets established (hopefully) we should be on the receiving end.  Wouldn't be the first time that's happened.

 

I will be very interested to see where the pattern eventually sets-up shop.  The NAO probably holds the keys to car w/ this pattern.  If it goes negative(and the CPC ensembles hint that it may in the medium range), then I think we see a lot of moisture cut from the GOM to a cone reaching from the Coastal plain to the eastern Valley.  I would suspect some over-running and ice potential will be in the cards once the cold settles in.  Juicy southern jet.

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It really seems that we are now seeing the transition from a fall Nino pattern to a winter Nino pattern - tnweathernut mentioned this a few weeks ago.  I think we are at the transition now.  Figuring out how this unfolds is part of what makes this a great hobby.  Nonetheless, looks like we are about to see winter make its initial presence known.

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Here is the snowfall from the 1st wave on the 12z Euro:

post-6441-141858974853.jpg

Here is the combined snowfall from both waves:

post-6441-141858985133.jpg

It is going to be a classic battle between the GFS and the Euro. I think the key to this system is how the models are handling the ejection of the trough over the western states. The Euro is stronger and deeper while the GFS is weaker and more strung out. I think these are biases of the models coming into play. The Euro seems to over amplify energy a lot of the time while the GFS likes to fade or weaken (string out) energy a lot of the time.

Normally we see a general compromise between the GFS/Euro or the GFS falls to the Euro.

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I don't know if the earthsat snowfall maps carry the same flawed algorithm........ I think they do.

I still wanted to provide a larger scale view of what the European model was saying there would be as far as snowfall output.attachicon.gifImageUploadedByTapatalk1418587753.742870.jpg

 

tnwxnut,

 Earthsat Euro snow maps are definitely flawed (count all precip. with temp.'s 32 or under as accum. SN), but it isn't Earthsat's fault. It is ECMWF's fault:

 

http://www.americanwx.com/bb/index.php/topic/44960-wxbells-snowfall-euro-maps-dont-make-much-sense/?p=3160669

 

That being said, if there's no CAD involved, this shouldn't be a big problem.

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I have maintained the storm around Christmas would be the one to watch, but seeing the euro ensemble mean east of the op, knowing the euro likes to wrap storms up a little too much, and knowing it has a slight warm bias.........next week might have some potential, especially for west and middle TN. Will be interesting to watch it play out.

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I have maintained the storm around Christmas would be the one to watch, but seeing the euro ensemble mean east of the op, knowing the euro likes to wrap storms up a little too much, and knowing it has a slight warm bias.........next week might have some potential, especially for west and middle TN. Will be interesting to watch it play out.

How about day 10-15 on the euro ensembles

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How about day 10-15 on the euro ensembles

I haven't looked at maps for that time frame on the 12z Euro Ensembles/EPS but the teleconnections look really good in the 10-15 day timeframe.

On the control run the AO/NAO look to go strongly negative toward the end of the run with mean in the negative territory on both the AO/NAO.

NAO:

post-6441-141859388666.jpg

AO:

post-6441-141859390925.jpg

I really like the way we are headed and it seems the pattern change is coming toward us instead of getting pushed back in time. This matches well with Nino analogs and the Cohen animations posted last week.

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I haven't looked at maps for that time frame on the 12z Euro Ensembles/EPS but the teleconnections look really good in the 10-15 day timeframe.

On the control run the AO/NAO look to go strongly negative toward the end of the run with mean in the negative territory on both the AO/NAO.

NAO:

ImageUploadedByTapatalk1418593884.648259.jpg

AO:

ImageUploadedByTapatalk1418593907.679941.jpg

I really like the way we are headed and it seems the pattern change is coming toward us instead of getting pushed back in time. This matches well with Nino analogs and the Cohen animations posted last week.

Great thanks so much!

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December 18th started the wide spread winter events in 2009. Hopefully this storm kicks it off again as that has been an analog I've seen multiple times. It is interesting to see if anything happens with the first system. I just never trust those snowfall total maps. The gem is showing a mix during that time and I suspect that snow map is just saying all precipitation is frozen.

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