January 17 Alabama Snow… A Look Back

A quick hitting winter storm impacted Alabama on Thursday, January 17, thanks to a deep 500 mb upper low moving right overhead.

Here is the forecast graphic we used going into the event…

The broad placement and general idea for the event was right on the money, but the devil is in the details, and clearly there were problems.

You know the saying… “cold core upper low, weatherman’s woe”. This is from the discussion on the blog Wednesday evening…

“As I have stated here in recent days, we have a limited skill set in dealing with snow output from cold core upper lows like this. No two systems act the same, and I can almost guarantee you there will be surprises. Some of you will get more snow than you expect, and others will see nothing more than a flake or two. There is very little skill in identifying the exact placement of the heaviest band of snow.”

While most folks did indeed get two inches or less… as forecast, there were also surprises, also as forecast.

Let’s look at the surprises…

*The heaviest snow was west of where our forecast indicated. I figured the highest snow amounts would be over the northeast counties. It was to the west… over Walker, Cullman, Northeast Jefferson, and Blount Counties. Amounts over these three counties were generally three inches… with locally higher amounts. (note… the map below is only for the Birmingham NWS CWA; it does not include the Huntsville NWS counties)

The snow shut off over Northeast Alabama seemingly as the result of some kind of occlusion process which shut down the dynamic forcing for a while. A large scale version of the same process that can choke off a tornado for a while in a severe storm.

*The biggest surprise was the degree of travel issues related to the snow. I expected very little issues, with black top roads only being wet in most places except for higher terrain. I was wrong.

An analog event in December 1997, which produced 3-5 inch snows over West Alabama with a similar cold core, resulted in no traffic issues, and only wet roads. This time, the snow came down so fast that roads were snow covered, and we had a number of wrecks and traffic snarls through the midday and afternoon hours. I-65 north of Cullman was a huge mess.

I have said many times humility is missing in our science; there simply is much to learn. The guys at the NWS in Washington, D.C. are taking some real heat for a big time snow bust with this system.

Many were furious at school system administrators for their decisions on school openings, closings, and transportation schedules yesterday. Don’t get mad at them, get mad at me. They can only use the guidance provided by professional meteorologists, and I honestly didn’t think road conditions would be so impacted by the snow. They are in a no-win situation during winter weather events, much like those of us in my profession. You will make people mad pretty much by any decision in their case, or forecast in our case. But this time the main issue was bad guidance on road conditions. And, that is our fault, not theirs.

Pretty confident cold core snow output across the Deep South will remain a mystery for at least one more generation. We will do some digging through the charts in coming weeks to look back at this from a science perspective and see how we can do better next time. And, also, review the impact on travel. Honestly, we are in the weather forecasting business, and not the travel forecasting business, and maybe we should not dabble as much into forecast road conditions. Some great advice given to me long ago… “tell them what you know, and don’t tell them what you don’t know”.

Let’s go enjoy the sunny weekend….

Tags: forecast

Category: Hodgepodge