Living in a Soup Bowl: Forecasting During an Inversion


Usually the Wasatch Front is one of the most beautiful places in the world. We have ski resorts just minutes from downtown Salt Lake. The Wasatch Range and the Oquirrh Mountains surround the valley. It’s a breathtaking view from almost every home in Salt Lake County. That’s not the case in late-January. Sure enough, without fail, high pressure traps in all the pollution from every single speeding SUV, every idling school bus, the refineries and coal burning stoves and leaves us in a mucky, mess.

The atmospheric set up is simple. The high pressure and stagnant air leave us trapped like a soup bowl between those amazing mountain ranges and remind us why it’s so expensive to live in Park City, and why a day up the canyon can do amazing things for the spirit.

Inversion is defined as when temperatures rise with height. When forecasting, there are a few simple ways to determine whether we’re under an inversion. The easiest way is usually just by looking out the window. When it gets really bad you can’t see the mountains. You can also drive up to the benches of Salt Lake. At the mouth of Parley’s Canyon (which leads you straight to Park City), you can look down and get a disturbing view of what you’re breathing. Or, if you still aren’t sure, you can check the temperatures. At my CBS station we have weather stations at several of the major resorts here that have pictures associated with them. Many times, when it’s really ugly here in the valley, canyon areas like Park City, Snowbird and Brighton are crystal clear and warm. In fact, the temperatures at the ski areas are always higher than here in the valley during an inversion which is pretty amazing considering altitude. The altitude of Salt Lake City is 4670 feet. In the canyons, you quickly get to 7200 feet in Park City and even higher at Snowbird (8000 feet) and Brighton (8700 feet). During really deep inversion days, we’ll have temperatures in the 40’s at the resorts while we’ll struggle to hit high 20’s and low 30’s in Salt Lake.

We see all kinds of consequences from inversion. When pollution levels get high enough, the EPA here in town will issue burn restrictions. However, this will be changing. Years ago it actually WAS the coal burning stoves that were big contributors to the pollution. Now, the main offenders are drivers. There is even a group here in Salt Lake that just gave a presentation to our governor of ways to reduce pollution during the inversion. They call themselves “Utah Physicians for a Cleaner Environment”. They believe the bad air is slowly killing us all, especially young kids and the elderly. They say more people, statistically, die on those bad days in January and early February. They propose a few things. One, they want the speed limit on Interstate 15 reduced to 55 miles per hour. They believe public transportation should be funded by taxpayers and be free to those willing to use it. They want buses to stop idling in parking lots. They say the refineries here should be forced to adhere to higher standards that would keep the air cleaner. (A couple of the refineries have already spent millions doing so, according to the EPA.)

I think one of the problems we have as a society is we’ve gotten used to someone else taking care of our problems. For example, when gas prices go up, we want the government to step-in to fix it. When we have trash, we put it out on the curb and someone picks it up and gets rid of it. We’ve gotten out of the mindset of thinking that WE need to be responsible for what we do to the environment. When interviewing the doctor who is spearheading the movement, it’s evident that he is taking responsibility for what he does and does not contribute to the environment. Should we be driving SUV’s if we don’t need the space? He says no. Should we be taking public transportation when we can? He says yes.

His ideas are good. Actually implementing them would be great, especially on a broader scale.

Determining when we’ll have an inversion is pretty simple. Anytime we start getting into a pattern without storms, wind or mixing. Or in other words, we get a strong ridge of high pressure for any extended period of time we are going to get inversion. Trying to get the temperatures is tough. FOUS data tends to really overestimate the highs and lows. The 500 mb heights will rise on the charts but in actuality the temperatures don’t end up reflecting it. So, what do we do? We make educated guesses. And, as one of our meteorologists says, we use consistence. “What it is, is what it’s gonna be”. Those are his words and they’re pretty accurate during inversion. Then, we hope for a storm! Is there expert opinion out there? Yes. Once we hit March 1st, give the models a little more of a chance. Why? The sun angle will, by that point has a tendency to heat things up and “burn through” that inversion.

Another thing I like to do is look at past years on our climate data. It’s not too hard to figure out, or remember when we were inverted in years past. It can give a good idea of what we’ll look at. I don’t think you can give the “climo” numbers enough credit.

I also believe it’s really important to look at the trends. What did the GFSX say about yesterday and what does it say about 7 days out. If it was significantly off yesterday, chances are it’s not reading the temperature and taking that inversion into account. Then, study the models. And I really mean study them. Figure out which one is doing the best job reading the temperatures day to day. Lean on those for the most guidance.

Finally, look to the senior meteorologists at your station or even in your market. What do those “old timers” who have been in the market for decades have to say? You have to respect the “gut feelings” of those who have been forecasting one place for our entire lives.

To sum it up, no one likes the inversion. It seems to serve no purpose except maybe to remind us, a few times a year, to think about what we’re doing to help, or hurt the atmosphere. Maybe it’s worth spending the extra money on a hybrid car. Or, if we have a long commute, at least use a car that is fuel-efficient. At the very least, we can go the speed limit and get the most for our money and help the environment at the same time. If enough people took action it would not only help our forecasting efforts, it would help the environment too.