We talk about the jet stream all the time when we’re telling you about the upcoming forecast. It’s one of the most important things in our sky that affects whether you see snow or sun at your home. Here’s how it works and how we use it to forecast.
I always like to say our jet stream is our storm conveyor belt. It transports storm energy, and if near us, we get storms. The jet stream is a fast-moving current of air at about the same height that planes fly in our sky. There are two of them in each hemisphere:
- Sub-Tropical jet stream (located typically around 30 degrees of latitude)
- Polar jet stream (located typically around 60 degrees of latitude)
The jet stream exists because of temperature contrasts. It’s warmer at the equator than at the poles. The atmosphere loves to be in balance, so the hot air rises and moves north toward the cold air. It smashes into this cold air, and the clash creates wind… a lot of it. As for why there are two of them… that’s a story for another time.
Because the jet stream separates warm and cold air, we can use it to figure out our temperatures. When the jet is north of us, temperatures (tend to be) above average. You could say the warm air is winning. When it’s south of us, the cool side is winning, and temperatures tend to be below average.
So let’s talk storms. When the jet stream travels in a straight line, storms move fast and are weak. This is called zonal flow in meteorology. But sometimes, we get a big dip in the jet stream, which we call meridional flow. This does two things. It slows down storms, and it lets a lot of warm air mix with a lot of cold air. This creates strong areas of low pressure that can dump tons of snow over Colorado in winter and can lead to severe weather in summer. Small changes in the track of the jet stream often mean the difference between a foot of snow and a cloudy day for us.
We have a stronger jet stream and stronger storms in winter. That’s because it’s colder at the North Pole in winter than it is in summer… but the tropics are hot all the time. A bigger temperature contrast creates more wind (and stronger storms).
With our jet stream taking on a straighter line shape this week and generally remaining close to us or slightly south, temperatures will be close to average, and passing systems will be quick-moving. The next big dip will be at the end of this weekend. When we talk about a “pattern change,” this is typically what we’re referring to.
____
Have a question or story idea you would like the First Alert 5 Weather team to consider? Email: weather@koaa.com
Watch KOAA News5 on your time, anytime with our free streaming app available for your Roku, FireTV, AppleTV and Android TV. Just search KOAA News5, download and start watching.
