Blizzard 2016: The art of sniffing out a long-range snowstorm


I’m going to start this post with a mea culpa. My seasonal snowfall forecast was terrible. I ran toward the snowless end of a super El Nino for various reasons, but chief among them was a faulty version of ‘playing the odds.’ I’ll call it not enough information.

Since making that guesscast, I’ve spent much of the winter deep-diving into strong Ninos (my knowledge prior was more cursory), examining more features of long-range forecasting, and of course fine-tuning my general prediction of the future. ūüėČ

Related: D.C.’s double-digit snowstorms: A history and guide to the patterns that produced them

Long story short, and as I’ve said many times, I¬†claim no major skill outside a month. Someday I hope to change that, but as a forecaster I’ve worked my way up from the bottom. Nowcasting is my true love, day 1-3 is my bread and butter, and I’m starting to feel good out to a month.

Despite the low-snowcast back in November, and thoroughly enjoying our warmest December on record, by the turn of the year the signs were starting to show themselves.

A quality pattern is like a fine meal, it can take a while to fully cook. As research I did a few months ago on strong El Nino winters in D.C. showed, and general consensus of big storms for the D.C. area also reveals, blocking is often the key.

Blocking? Surface high pressure over the polar regions, and mid-level high pressure anomalies over the Greenland region. Often the surface high pressure and mid-level high pressure are more or less co-located as well, but those are your “in a nutshell” definitions for negative Arctic Oscillation (-AO) in the former case¬†and negative North Atlantic Oscillation (-NAO) in the latter.

Configuration of the blocking matters too, and what we saw showing up in early January certainly started to line up with snowy strong El Nino periods in the past.

The 1941 strong El Nino period shown above was mid-February onward. It was a turning point time frame. About two weeks later, a snowy period was underway following a colder pattern. A large event occurred in early March. The 1966 period needs no explanation to a snow lover. Neither was a forecast, but a look.

Basically what we know at this point — around the start of January 2016 — is that blocking patterns favorable for snow in the past were showing up on models. In any year that’s a good sign if you’re a snow lover. In a year with an El Nino enhanced southern jet stream it’s a reason to get at least a¬†little tingly.

Why? There are so many theoretical opportunities to be had.

The signal for snowier times continued on the most reliable long-range model guidance. As the first week of the month finished, we were looking at a day 11-15 period full of snowy situations.

The¬†model ensemble means — Euro¬†analogs shown above —¬†in this range were quite suggestive of snow. This run highlighted above had December 19, 2009 as one example. Just D.C.’s biggest December snowstorm on record! Other events came several days after or before the period shown. Most of the analogs had snow in D.C., some quite a bit.

Big storms like the Greenland block configuration.

In a lot of cases, the snowstorm comes after the block flexes. Via the European ensemble loop above, that process is shown. Interestingly enough, from January 7, the period in which the block broke down was already evident as the January 22 zone. Right when the storm happened.

Pumped. And getting pumpeder.

From this sort of range, really anything outside 7 days in particular, you’re looking at a pattern that’s favorable. Choosing the storm is another matter.

What we know we had: High-latitude blocking in favorable locations. The -AO was helping deliver colder air to the United States. The -NAO was helping lay the tracks. An active split-stream southern jet. If anything, it’s been hard to keep track of all the storms. Classic Nino.¬†Loads of high pressure.¬†One thing we haven’t lacked¬†of late¬†is¬†surface high pressure across the northern tier of the United States. Cold air source!

About 10 days prior to the event, pattern recognition continued to scream potential. The setup was quite similar to a composite for D.C.’s largest snowstorms in El Nino, and overall.

Model runs started to react.

The long-range operationals usually just spit out random nonsense toward the ends of their runs at day 10 or to day 16. But when you start seeing runs showing big storms after a period of little such activity at any range, you often know something’s up.

The pattern was ripe, but full of questions. In some cases it was hard to count all the waves.

Choosing the storm ended up being a little tricky. Before the blizzard of January 21-24, the East Coast had a close call. I mean, it never truly looked like it was going to really go to town outside a run or two, but it had some quality potential, if it had dreamed the impossible dream.

Digging briefly deeper into the maps above and littered throughout, D.C.’s biggest snow storms are so heavily tied to 500mb ridging in the southern half of Greenland area to Hudson Bay region it’s hard to ignore it when you see it setting up.

By my research, roughly 75 percent of D.C.’s¬†eight inch or greater snowstorms have had¬†high pressure anomalies at 500mb in this region either day of, or in the week or so lead-up to a storm.

Again, the first real shot was always something of a long shot, but it still fit what we’ve seen produce before. It required a perfect alignment among the split streams to phase or partially phase with a big northern-split low.

Alas, the phase didn’t occur and the storm slid off to¬†the south of the D.C. region. But it brought more snow than most were expecting, including a dusting or so to the D.C. area, and a few inches toward the coast.

The block was still present, and actually nearing peak around then. As noted above, and despite storms like those which happened in February 2010 as the block was peaking, we often need to wait till it relaxes or gives in entirely to get our storm.

Remember the look below. That’s a 2010 Snowmageddon look.

And… it was ready to break down.

Researcher Heather Archambault, among others, has found that there is a relationship between these types of phase changes in the North Atlantic Oscillation and northeast winter storms. Add another pro snowstorm bullet point to the growing list.

About a week out, nearing the limit on signals for an event, models started dialing in.

The first hints of this storm were even around a few days earlier, but I don’t think we are quite at the point where day 10 modeling is to be taken super seriously. I know I didn’t take it too seriously at first, even given the pattern’s potential. I mean, it’s day 10!

Once inside a week it started getting a little nuts. High precipitation, plenty of high-end potential, and reasonable clustering of ideas.

As the weather story goes, the big ones lock in early.

This one certainly did and in some ways perhaps more strongly than many of its predecessors. Even since the amazing 2009-10 winter there have been so many advances in numerical weather prediction that it’s hard to compare such recent times to this go.

The snowy looks continued, and got better. Then snow lover celebration got underway.

The rest, as they say, is history. A category 4 NESIS struck a large part of the northeast. It was the biggest snowstorm from D.C. to Southern New England since the Presidents Day weekend storm of 2003. It’ll be long remembered among the all-time greats.


p.s., I put this together partly to be able to reference it myself again in the future. I’m still sort of a newbie when it comes to long-range forecasting. A semi-success is one worth trying to remember how to recreate. There are a number of other long-range forecasters who observed pattern potential in the leadup to this historic event. I of course did not expect an event of such magnitude the entire time watching things come together either! I am in awe of the fact that I have now seen three 20 inch or greater snowstorms in D.C. over the course of a decade in the city. It is truly the age of the northeast snowstorm.

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