Sunday, December 9, 2012

December 17-20 Potential Major Winter Storm

There is now increasing potential for a major winter storm to occur over the East US. Let's jump right in.

Many of you know how I follow the Lezak Recurring Cycle (LRC), and track it every year to nail down who could get the best out of this winter. Well, thanks to the research of some fine folks at the AccuWeather Forums, it appears that this year's cycle will be 53 days. I tried to apply that timeframe to this potential storm system, and here's what I found.

This is the 500mb geopotential height anomaly for December 18th over North America. As the legend indicates, cool colors depict below normal heights, while warmer colors describe above normal heights. The forecast shows a deep low pressure system in the South Plains and near the Gulf Coast. In response to this deep disturbance, a positive PNA is trying to form. As we know, a positive PNA favors a storm track through the Ohio Valley/Midwest. Notice the presence of an east-based negative NAO as well. While a negative NAO is favorable for cold and snow in the Northeast, an east-based negative NAO (the ridge is east of Greenland) can favor the Plains and Midwest for cold and storms.

Using the 53 day LRC timetable, I traced back December 18th to October 28th, and here is the 500mb pattern observed that day.

Look at that! We see a strong system in the Ohio Valley on this day, as well as a weak high pressure system in the Southwest indicating a possible positive PNA. There is a negative NAO in place, though we can't tell whether it is west or east based. Does this look familiar to the first image shown? You bet. It looks like our 53 day cycle is working. **For future reference, ignore Hurricane Sandy in these observation images.**

This is the sea level pressure (SLP) forecast for December 18th, and we can see a strong storm system emerging from the Plains at this time. This system is likely to move northeast in response to the previously-mentioned negative NAO, but not towards the coast, as a positive PNA interjects and may try to send this system into the Ohio Valley.

The models are having some trouble, so let's go a day ahead to October 29th and see what happened.

(Again, IGNORE SANDY.) Our storm system has now moved to the east, wobbling a bit as it did so, and combined with Sandy. Notice we still had our positive PNA showing itself with high pressure in the West US. If we were to follow this system and discount Sandy, I still believe an eastward movement would have prevailed, likely not as fast if Sandy were not present. The lack of Sandy in this potential storm system, combined with a positive PNA and east-based negative NAO leads me to believe that this forecast system should go a little more to the north and east than it did in October.

Now, we are on December 19th with the ECMWF forecast, and we see our storm system has indeed moved to the northeast in response to the PNA and NAO, and the LRC. The system's strength is now holding at a very nice 987 millibars, with tight isobars indicating strong winds are ongoing across New England and parts of the Ohio Valley and Midwest. Despite this, 850mb temperatures tell me rain would be the big story, but with a positive PNA, negative NAO and possible negative AO, that could very well change.

It does look like the ECMWF has a pretty darn good handle on this system, especially with such a good match-up with the LRC. I believe that this storm system will happen, the question is, who will get hit the worst?

Andrew

24 comments:

Anonymous said...

Wait Andrew i'm somewhat confused? You say that this storm will affect the northeast or the midwest? I live in northern NJ, so do you think it could affect my area? Also doesn't a positive PNA mean a favorable pattern for the east coast? Thanks!

Anonymous said...

Hi Andrew i live just east of knoxville tn and was wondering if u could give any insight as to when we will get our first snow event and what does it take to get a snowevent here such as -nao positive pna ext. thanks

WX BRIAN said...

anonymous 1: It could affect both, (go through mid west,then to the northeast),... At least, i Think that is what he was showing.

Anonymous said...

Thanks Andrew!


Crossing my fingers that we grt a snow event sometime in december here in DC

keep us updated!

Anonymous said...

Very interesting. Hope to see the GFS come around soon.

mike paulocsak said...

If this would happen it would probably go through the Midwest,Ohio Valley,then to the Northeast.Here is the thing though.The main low pressure system would die out and a second stronger low would develop off the east coast.The East Coast would get plenty of snow.Just a thought.

john smith said...

being obsessed with the weather, I thought id like this. So far has been nothing but a let down. I cant help but believe it, but i have learned not to. get my hopes up, to be shot down. Hope you enjoy that. You are wasting your time, as well as others'. Stop saying there will be harsh winters as well as storms. You cannot get tomorrow right. Do not believe this fictitious storm prediction. December was supposed to be cold. So much for that. Great job.

Aran Jacobs said...

Could you please do an update on the 14-16 storm.

Aran Jacobs said...

In Valparaiso, IN almost 6 inches are supposed to fall on the 18-19.Do you think this is associated?

Aran Jacobs said...

(THIS FOLLOWS THE LAST COMMENT)It is odd because no model I have looked at so far shows it coming through the midwest.Not even a snow band here yet they still say it is going to happen.The ECMWF is supporting this snowstorm go through the south and come up the coast extremely strong in a circular kind of hurricane type shape.

Andrew said...

Anonymous #1: It could affect both areas. The positive PNA is most favorable for the Midwest/Ohio Valley, but also does help the East Coast.

Anonymous #2: There are a few decent chances coming up the rest of the month.

John: You went out of your way to write a comment like that? Who's the one wasting their time now?

Aran: I will later on today. I have not looked closely at Indiana's forecast yet.

SKNOW said...

Alright everyone. Now, first off, the weather is just like all of us, it can be unpredictable! Andrew and all the other experts are doing their best to predict what could or what might happen. Any forecast more than 3 days out is an educated guess at best. These weather blogs are supposed to be FUN!!!!! I want snow too as much as the next person!!!! PATIENCE!

Anonymous said...

Lake-effect snow here in Porter county today, but only 1-2" for the northeast part of the county and an inch or less for other portions of it. Mid next week looks like the most favorable set-up, Tue-Thu, 18-20.

Anonymous said...

Looking good, Andrew, keep us posted. I think the most favorable track will be from Arkansas into southeast Michigan. Still quite early to stick with that, but you know that all these model trends would average on that track. So it that were to play out you folks wanting snow in Chicago area will definately get your share of it. We'll see what happens.

Ray T. said...

Good job guy, you're right on with NWS! We see that Greenland Block setting back up and you bet that will aide in the formation. Models always have difficulty this far out, but looking at the last 5 runs, they have not changed a great deal. The period to watch is probably more like the 18-21, I don't think we'll begin to see this storm's affects until the Wednesday the 18. I've been working with Romeoville, IL NWS Office for 18 years and I've only seen a handful of storms which we're as large as what models are depicting with little change from run-to-run. This system is like to be at least twice as potent as the one that hit the Twin Cities area with near, and in some areas, over a foot of snow. But it IS still early and abrupt changes can come along, however; where there is smoke, there is fire, and eventually the big one will come. Keep up the good work, you are very intelligent my friend!

Anonymous said...

John... It is NOT ficticious storm, it's showing up on all of the models, so if you don't like it, then why don't you simply stay off this blog? Keep your own day job and go fuck yourself, asshole.

Anonymous said...

Andrew, I like the long-term forecast you have for this storm. Better than most "meteorologists" at our local news stations. What do you look for in the northwest ohio/southeast michigan area? Accuweather has the forecast of snow with varying intensity for Hillsdale, MI with amounts near the 6-7" range. What do you see?

Anonymous said...

In Danville, VA will it be a rain or snow event? The temps are scaring me accumulation wise, and I would like to know the possible accumulations.

mike paulocsak said...

I SAID IT BEFORE AND I'LL SAY IT AGAIIN!IF YOU DO NOT LIKE ANDREW'S WEATHER SITE LEAVE!!!!!!!!!!!!!!!!!!!!HE DID NOT FORCE YOU TO COME HERE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!I WANT SNOW JUST AS BAD AS THE OTHERS,BUT I'M NOT GOING TO WINE AND CRY ABOUT IT LIKE A BABY!!!!!!!DON'T BLAME ANDREW,HE IS JUST THE MESSENGER!

Anonymous said...

I dont know what is more depressing the winter so far or some of these comments. mid to long range forecasting is long shots but anything is possible yet at this point.

Anonymous said...

Andrew, any idea yet if central Iowa will much precipitation? Good work keep it up

Anonymous said...

Wait, I see something that should be there, but isn't...with height anomalies like that over the PNW as well as over the southern Plains, wouldn't that have also previously brought a strong storm system through the eastern half of Wyoming, Colorado and New Mexico, bringing a brief round of heavy snow for the Front Range, then sag southeast into the panhandle of Texas, and continued to strengthen as it did? In other words, wouldn't that have started out as a Blue Norther type of event before ejecting eastward?

Anonymous said...

Would Raleigh,nc get in on this?

Anonymous said...

I am the one who asked the Colorado question, I have to say, no matter what anyone does to criticize you, I am always and will always be supportive of the hard work and dedication that you painstakingly put into each and every detail regarding long range outlooks, and yes, granted that many times the weather changes like lightning, and sometimes those changes can not be foreseen in time to be able to make any difference, as we are only human, if we knew exactly what the weather was going to do, we wouldn't be called forecasters, we would be called psychics, right? lol
Anyways, I always enjoy reading about what is possible for the future of the weather world.
I did notice that lately the models have been leaving the entire western half of the US out of the maps, which makes me sad, but still, I will always come here to enjoy reading the long range updates, and getting excited or depressed about what to expect, so no matter what happens, I will always be a supporter of Andrew and all his crew here on The Weather Centre.