Monday, December 17, 2012

December 19-22 High-Impact Blizzard Event

I have once again upgraded the title of this event from 'Potential Blizzard' to 'High Impact Blizzard'. The following represents my truest thoughts and NO hype. All posting from now on is directly related to what you should know to prepare yourself for this high impact blizzard event.

**This post is dedicated to Daniel Barden, age 7, a victim of the Connecticut shootings.**

"This is truly a battle of the models."

What you see above is storm tracks for the future from several models of the 12z suite. The pink lines are from the Canadian model, the brown lines from the United Kingdonm's UKMET model, the asparagus-colored line signifies the NOGAPS model, the neon green shows the NAM model, and the red belongs to the American GFS model. We are looking at the lines that go from Oklahoma to Illinois and Wisconsin- that is our storm.

Recently, the models have been converging on this solution of taking the system northeast into Chicago, possibly just north, giving the biggest snow to north Wisconsin and similar areas. In a bizarre twist, the NAM was the one that started this new north trend, and the storm isn't even inside it's domain!! If the storm isn't inside the domain, it means the model is essentially shooting in the dark- models have no idea what's going on until the system is within the forecast domain. That said, we can (temporarily) render the NAM model (and its ensembles, the SREF) out. Regardless, all of the models mentioned above are in the 'North Camp', where the storm goes into Chicago or nearby areas.

Here's where things get interesting, and this is why this truly is a battle of the models.

ECMWF Hour 72 forecast
ECMWF Ensembles Hour 72 forecast
The ECMWF and ECMWF Ensembles are taking the South Camp at this time. The South Camp involves the system going through southern Illinois, and that is just what the ECMWF/ECMWF Ensembles are going. Now, you may be thinking that I should disregard it just because it's the outlier. However, the ECMWF and ECMWF Ensembles have been incredibly consistent thus far with this system, whereas the GFS has moved north or south by at least 50 miles every run thus far. One must also remember that the ECMWF Ensembles are composed of 51 separate forecasts compared to the meager 16 or so ensemble members in the GFS Ensembles.

This is an image of anomaly correlations at the 500mb level from several global models. In the upper image we have the North Hemisphere, and the South Hemisphere is on the bottom image. On the bottom left we have the correlation statistics, and if we look closely, we see the numbers. The ECMWF beats out the GFS easily with 0.926 correlation on the ECMWF to 0.901 correlation on the GFS. The UKMET ties with the GFS. That said, there is reason to believe the ECMWF- something many are not doing at the moment. The ECMWF has historically done well with winter storms and is known for Catching onto solutions other models have not, so such a situation playing out here is not out of the question.

Analogs of situations similar to this one can also be helpful. This is a 72-hour snowfall accumulation of the top-ranked analog for this storm system. It was in 1996, and heavy snow fell in the Upper Midwest, something that would suggest a North Camp solution. Analogs can be deceiving, but it is worth mentioning a negative PNA and negative NAO were present for this storm system. I can't say I don't believe this analog could repeat itself this time around.

Frankly, it comes down to which is more significant at the moment- the consensus or the outlier. On one hand, we have several semi-reliable global models going for one solution, with one model and one ensemble set (both extremely reliable) going for another solution.

I'm not willing to pick a forecast preference, because this is an epic battle I feel will need to be settled in the day or two away from the system's impacts. However, no matter the track, there will be heavy snow and very high winds- such a combination would indeed produce blizzard conditions. I will fill you in more tomorrow morning and through the evening as more information becomes available.

Here's my new call for a forecast graphic:

Forecast Preference: Indifferent To All
Confidence: N/A



Aran Jacobs said...

I must say I think it will go through Chicago.That is because the EUROPEAN models took it there and those are extremely reliable.What do you mean by Wisconsin and similar places?

Armando said...

Hey Andrew just want to say you're a great meteorologist who knows his stuff! Anyway i'm over here in NJ, and it's good to see their snow drought could end. Now i want to know is when will our chance arrive? Joe Bastardi has been talking about this storm after Christmas that could be a possible nor'easter(hoping), and once we know what this storm is going to deliver , can you keep updating the 26-28 storm? Thanks

Storm-Chaser Wx said...

I would agree very much so with this "battle of the systems" event, and of course these are subject to change, the thing I dont understand is that the HPC is going off the GFS and the ECMWF models. On the 3-7 day outlook, it takes the LP system through southern illinois and into the northeast, but the snowfall probabilities show otherwise. I am a little confused with what people are saying, but I am definitely going for a more northern track because of how the other models are showing a same northern track. I am still calling for a good 8-12 inches of snow throughout the Upper Mississippi Valley. This could be the big winter storm that the upper midwest has been waiting for. it's just crazy that the models are non-agreeable considering that we are only a few days away, hoping for the best though!

Andrew said...

Aran: The ECMWF and its ensembles did not go through Chicago; as I said, they went through S. IL. Wisconsin and similar places was for the North Camp.

Armando: I made a post on the chance for a storm in this timeframe just now:

Storm-Chaser WX: The NWS offices are nearly disregarding the ECMWF, so I have a feeling they're getting that info from the GFS.

Aaron Evans said...

What about West Virginia?

eddie said...

What about Detroit will we get snow here and how much

Rod Houston said...

Yet again it looks like rain for Chicago. When will it it be favorable for a heavy snow event for Chicago?This doesn't look good.It's very frustrating that when we have the potential for snowfall,it ends up raining instead.