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2015-16 Winter Pattern Discussion


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Not really , at least not for parts of my state . Would really only need a 5-6 inch storm to verify which we have received the last two winters

 Yes this is easily doable in The SE. The mtns, espeacilly northern NC mtns getting off to a late start would be the only tough ones since their seasonal average is so high anyway. Doubling up everyone elses could be done in one storm or it has before. So no biggie in that regards.

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Agree. Whole different world up there. wind comes out of the NW and its guranteed snow. With the lakes having zero ice we should see some big LES at some point and upslopes for our mtns if we ever can get a NW flow.

That's what we need really is some good upslope snow. That's what we get mist of our seasons snow from.
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For those who haven't seen the Euro weeklies, they updated today and show considerable improvement. The pattern begins changing around December 20th with occasional but transient ridges out west with a trough in the east. They only last a few days but it's a much better signal than the current pattern of trough west vs ridge east. At the end of the run there is a classic setup for a nice snow.. A nice cutoff in the Baja region with a building ridge over CA and weak trough in the east. Great pattern for the snow lovers like myself and January looks like it will turn colder as many have been predicting all season.

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I looked at the 500mb patterns for all strong to moderate El Ninos and wanted to find out what went wrong as far as the pattern goes with the El Ninos that produced below average snowfall for Raleigh, NC. Now before I get into it I want to say Ian (@ianlivingston on twitter, also Admin here at AmWx) helped me do this much easier by showing me a snowfall database I wasn't aware of. I was gathering snowfall data by hand and had been working on composites for days before he helped, so shout out to him. He also did some El Nino composite work today as well for DC, so check that out.

 

For Raleigh, here's what I found:

Average snowfalls for the differing intensities of Nino

Strong El Nino: 10.4" (N=6)

Moderate El Nino: 12.2" (N=5)

 

Averages were skewed due to two big years, both in differing data sets:

1965-66: 26" (strong)

1986-87: 23.4" (moderate)

 

On to the composites...these are 500mb anomalies for the included El Nino years. Sorry for the document, couldn't include all the images in one post due to an image limit.

 

As for the interpretation -- it's pretty clear:

 

First, the Strong El Ninos that produce above average snow for the winter have one thing in common....a giant ridge over the eastern seaboard w/ a pacific trough extending all the way into Texas. The opposite is true for El Ninos that produce below average snowfall in Raleigh. For those years, we see a +PNA for Dec with a trough in the southern US up the eastern seaboard.

 

Second, El Nino years that produce above average snowfall in Raleigh, regardless of strength of El Nino (moderate vs strong or super strong), have a pretty decent faux greenland block  or a west based -NAO or baffin block.

 

What does this all mean? The ridge over the east in December is a good thing.

 

Ninos.pdf

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What does this all mean? The ridge over the east in December is a good thing.

I for one am good with where we are right now and with how the nino pattern should evolve as we go into Jan>Feb>Mar, but the one red flag right now is the cold stratosphere.  If that hangs tough and we can't shake the solid +AO, it won't be pretty.

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I looked at the 500mb patterns for all strong to moderate El Ninos and wanted to find out what went wrong as far as the pattern goes with the El Ninos that produced below average snowfall for Raleigh, NC. Now before I get into it I want to say Ian (@ianlivingston on twitter, also Admin here at AmWx) helped me do this much easier by showing me a snowfall database I wasn't aware of. I was gathering snowfall data by hand and had been working on composites for days before he helped, so shout out to him. He also did some El Nino composite work today as well for DC, so check that out.

 

Can you share this database by any chance? I've been looking for archived RDU snow totals (seasonal/monthly/daily) for research but haven't found anything.

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I for one am good with where we are right now and with how the nino pattern should evolve as we go into Jan>Feb>Mar, but the one red flag right now is the cold stratosphere.  If that hangs tough and we can't shake the solid +AO, it won't be pretty.

Great research by Jon, thanks for sharing! It basically confirms what I've found in research and in my winter forecast as well; the warm December and current pattern is a good sign and expected. If we were below average or cold I would actually be concerned. The warm December is often a precursor to a cold January-February. Already you can see LR models starting to hint at the pattern change. The Canadian and Euro both show a much colder pattern taking hold after December 20th.

Also of note the long range euro is showing a weakening of the PV by December 20th. I expected it to weaken significantly between the end of December and early January so things look good there as well if this does occur.

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Nice Jon! Here are the snowy strong nino's, one thing that also sticks out is the Barents/Kara high. So far through the first week we have that but GEFS/EPS have low heights there the next couple of weeks. Someone on Twitter pointed that out a couple of weeks back, HM or maybe EWebb, with the analogs they were looking at. Would like to see ens change that as that is probably important.

0b315c930421d9a35476ac4a9782b987.jpg

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I for one am good with where we are right now and with how the nino pattern should evolve as we go into Jan>Feb>Mar, but the one red flag right now is the cold stratosphere.  If that hangs tough and we can't shake the solid +AO, it won't be pretty.

I'm with you; looking for a spike upwards real soon.

 

http://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/

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I looked at the 500mb patterns for all strong to moderate El Ninos and wanted to find out what went wrong as far as the pattern goes with the El Ninos that produced below average snowfall for Raleigh, NC. Now before I get into it I want to say Ian (@ianlivingston on twitter, also Admin here at AmWx) helped me do this much easier by showing me a snowfall database I wasn't aware of. I was gathering snowfall data by hand and had been working on composites for days before he helped, so shout out to him. He also did some El Nino composite work today as well for DC, so check that out.

For Raleigh, here's what I found:

Average snowfalls for the differing intensities of Nino

Strong El Nino: 10.4" (N=6)

Moderate El Nino: 12.2" (N=5)

Averages were skewed due to two big years, both in differing data sets:

1965-66: 26" (strong)

1986-87: 23.4" (moderate)

On to the composites...these are 500mb anomalies for the included El Nino years. Sorry for the document, couldn't include all the images in one post due to an image limit.

As for the interpretation -- it's pretty clear:

First, the Strong El Ninos that produce above average snow for the winter have one thing in common....a giant ridge over the eastern seaboard w/ a pacific trough extending all the way into Texas. The opposite is true for El Ninos that produce below average snowfall in Raleigh. For those years, we see a +PNA for Dec with a trough in the southern US up the eastern seaboard.

Second, El Nino years that produce above average snowfall in Raleigh, regardless of strength of El Nino (moderate vs strong or super strong), have a pretty decent faux greenland block or a west based -NAO or baffin block.

What does this all mean? The ridge over the east in December is a good thing.

Great writeup! The sample size is small, but that's inevitable. The good thing is that it looks pretty consistent with what's happening now and the pattern change that's expected to happen come January.

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Euro ensembles continue hinting at a cooler overall pattern after December 18-19th. They're now hinting at a PNA ridge building over AK and sliding east with the control showing a MASSIVE outbreak of cold air dropping down around Christmas Eve/Day.

Also FWIW, the new high res parallel Euro 45 day meteograms for RDU shows several snow chances in January. A few members show a nice snow around January 6-8th (more than 4") and then several other members show a nice snow around the 16-18th. Almost all of them show some type of light or accumulating snow for the area after the 6th of January but none until then. This lines up well with the expected pattern change not fully taking hold until the first week of January.

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Euro ensembles continue hinting at a cooler overall pattern after December 18-19th. They're now hinting at a PNA ridge building over AK and sliding east with the control showing a MASSIVE outbreak of cold air dropping down around Christmas Eve/Day.

Really?  I saw the one for 240hrs and it looked like business as usual.  how massive?  I only see what others post but it sounds like a positive

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I decided to look at the GFS 00z and 06z, and see what "went wrong" with the new model run.

 

The reason the 00z looked so good at the end of its run was because a large LP system was able to push a ridge up into NE Alaska/NW Canada and even the Arctic Sea about 5 days out:gfs_z500_mslp_namer_21.png

 

From there, a surface high pressure (which you can already see on the map above) began strengthening, and a piece of the ridge ended up being cut off:

gfs_z500_mslp_namer_29.png

 

From there, the HP continues to strengthen until:

gfs_z500_mslp_namer_45.png

 

 

The weird thing is, the 06z still has this LP system and ridge at the same frame, but the ridge never gets cut off and so the HP is never able to break up the PV in Canada:

gfs_z500_mslp_namer_28.png

At this point, my knowledge of weather is extremely limited, so I have no idea why the 06z is so different. I think it's best, however, to wait and see what the 12z says will happen.

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Indices looks a little better than yesterday. Nothing great but better: 

 

PNA - Falls to near neutral and basically averages that in the LR. Good clustering of member runs.

NAO - Falls to near neutral and averages that in the LR. Widespread differences in member runs.

AO    - Falls below neutral and then averages slightly below in the LR. Widespread differences in member runs. 

 

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/teleconnections.shtml

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