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Medium/Long Range Discussion


tombo82685

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Just watch JBs morning video - he says relax and "stop this NAO focus" "Too many folks are focusing on indices that mean different things during transitional periods. He says to watch that tremendous cold air in NW Canada "has not been there at this time in near 10 years" He says a little hint as to what is coming is on the Euro day 10.

I agree with Tom - this will NOT be a warm winter. I think the warmth will not be as great in December and will balance off with a cold Christmas holiday period and we end near normal in December with above normal snowfall. This has been a very cool run here in the last 6 months with 4 of those 6 months averaging below normal here in NW Chesco.

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question, during neutral enso years is it common for the mjo to hang around the COD majority of the time?

Great question. I don't know the answer. My guess would have been it's more likely to make full orbits rather than be biased in certain octents, but I haven't been doing this long enough to know.

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^^^^ ewwww

that december wasnt actually bad. It was a normal december for philly. They had just shy of 3 inches of snow and monthly temp avg of +.2... Dt actually thinks differently on the 12z gefs. "'12Z gefs day 10 ...180 points differnt... RIDGE in east Pacific NAO moving to negative... MUCH colder over all pattern even shows HINTS of a possible l east coast winter storm DEC 15-17"

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How can there be such a difference of opinion

All mets have different opinions of what different signals and indices to use when making a medium/long range forecast in addition to weighting each of them. As it is, there are many conflicting signals battling for dominance of the North American weather pattern. Any one of these can take over at some point during the winter (like how we are seeing the Gulf of Alaska trough causing a torch in the US in early December). It's all a matter of whether or not your forecast is influenced by the signals that show more cold or those that show more warmth.

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All mets have different opinions of what different signals and indices to use when making a medium/long range forecast in addition to weighting each of them. As it is, there are many conflicting signals battling for dominance of the North American weather pattern. Any one of these can take over at some point during the winter (like how we are seeing the Gulf of Alaska trough causing a torch in the US in early December). It's all a matter of whether or not your forecast is influenced by the signals that show more cold or those that show more warmth.

and with basically a stalemate of an MJO and negative mtn torque it enhances the conflicting signals

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and with basically a stalemate of an MJO and negative mtn torque it enhances the conflicting signals

And mos tof the good ones are following these things. Imo, the MJO, AAM, and the stratosphere are usually the best indicators for the winter season pattern. Most everything else is noise (except for probably solar stuff, which I still don't have a handle on).

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Does a ridge centered that far off the west coast count as a pna?

PNA equation also takes into consideration how much ridging or lack thereof there is over the southeastern conus (sometimes that tips the index number scale).

But to answer this question, in this example, no. Also the EPO on this map is positive, so you could have instances where there is an index number positive PNA, but with also a positive EPO the conus is basically getting flooded with Pacific air.

Time sensitive:

http://raleighwx.americanwx.com/models/12zecmwfindices.html

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And mos tof the good ones are following these things. Imo, the MJO, AAM, and the stratosphere are usually the best indicators for the winter season pattern. Most everything else is noise (except for probably solar stuff, which I still don't have a handle on).

This.

Don't see any forcing mechanisms to drive a change, basically looks like we're going to be wafting colder one week, warmer one week.

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Joe D'Aleo with Weatherbell's headline this morning "December looking better every day" - guess that depends on your perspective - in this case a cold forecast!

"The GFS is beginning to take that cold air building in western North America further south and east. See the double warm surge week 1 but the beginnings of cold air intrusions, brief at first then more long lasting. By the end of the run the cold has vanquished the warmth. A few days later, see the northern tier has cold with a nice boundary for fun stuff to begin to happen. You can see late in the run a massive outbreak.It looks a lot like the 500mb anomaly from our analogs for December, with high latitude blocking draped over cut off lows. It suggests Alaska has donated their cold air to the lower 48 states. Last year it gave it up but to aras to the east in northern Canada as the NAO stayed + as we discussed yesterday.The AO and NAo are already behaving more like 2009/10, 2010/11 than 2011/12. Again this is happening in the polar troposphere without any stratospheric help. I believe that will come perhaps starting before mid December. If it does, that would cement the idea of a cold January in the analog set with the cold dominating"

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Maybe its me, but i dont see how you get all this meridonal flow when some of the pattern drivers don't support ridges like that. The -nao though i can see, The rocky mtn torque is on a good positive climb. The issue im having is how do you go from the flow we have now to a monsterous -epo/+pna ridge when the mjo absolutely has no fire to it at all with weak -OLR and+OLR until at the earliesT around christmas, as it looks now. Though, the mjo is pretty hard to predict on a weekly basis. Also, the east asian mtn torque doesn't support that wild meridonal flow as shown by the gfs. So my question is what else is driving the pattern to support this?

gltaum.90day.gif2012.png

gfs-500mb-hgt-mslp-nhem_300.png?1354379849

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Still on...Monday night into Tuesday AM. Pretty good for east of 99 and west of NJ Turnpike (0 850 line is about 15 miles east of the NJ Turnpike).

still way out in time but what the euro shows at h5 does not support an east coast storm...no -nao or pna ridge...that to me would look more like an inland runner. their is no feature to lock in a high for coastal sections.

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