This interview has been edited for brevity and clarity.
Bill Burton: It's time for us to take a look at the Science Behind the Forecast as I'm joined by WAVE 3 meteorologist Tawana Andrew. Good morning, Tawana.
Tawana Andrew: Good morning. Today, we're going with the flow with our topic.
BB: This is what I love most about Science Behind the Forecast. I'm always learning something new. Today, it's something I had never even heard of before that we're going to be talking about that is so incredibly important to weather. It's called Rossby waves. Explain, please.
TA: Rossby waves are planetary waves. We have some in the ocean, but we also have some in our atmosphere, and they play a big part in our weather and climate. So they're named after a really cool dude. His name is Carl Rossby. He discovered them in the 1930s, and what he figured out is that the Earth's geography plays a role in the formation of Rossby waves in two particular ways.
First, the sun is heating land masses unevenly, so that is leading to temperature differences and atmospheric pressure differences. Secondly, as the air is rising over elevated areas, so think mountains and hills. That leads to inequalities in temperature distribution, both vertically and horizontally throughout our atmosphere.
And the wind is always going to try to return things to a balanced state. The wind is very Zen. It wants everything to be exactly the way it's supposed to be, right? So as it's trying to return to a balanced state, it's changing direction and speed in an attempt to do so, and while the wind is trying to restore balance, you have the earth rotating so you have the Coriolis Effect coming into play. Plus, the sun is still continuing to heat our planet unevenly, leading to even more changes in the wind. And eventually you end up with these wave-like patterns that develop across the globe.
The waves in the ocean are itty bitty in comparison to Rossby waves. Rossby waves can be anywhere from 3,000 to 5,000 miles long.
BB: They can be longer than the country?
TA: They can be longer than the country. So that is why we can see weather moving very slowly across the country. And I mean, they move from west to east. They creep. They can move at about 11 miles per hour.
BB: Well, nobody wants to get a speeding ticket, and apparently neither do Rossby waves.
TA: But apparently they're just creeping. They're just creeping along. And they do so, and they circle around the globe at about five to 10 miles in altitude. They also helped locate jet streams. So most of the time, but not all the time, but most of the time, right along the boundary of a Rossby wave, you will find a jet stream. And while the Rossby wave itself is moving at 11 miles per hour, the wind within the jet stream can be moving at 115 miles per hour. So some wacky things happening above our heads all the time.
The Rossby waves also serve as pathways for low pressure systems across the entire planet. There's usually around four to five of them moving around the planet at a time, but there could be as little as three or as many as seven happening. And here's why they're super important, because they help to transfer colder air from near the poles down towards the equator, and of course, that heat from the tropics up into the polar regions. Once again, trying to get everything back into that balanced state.
And underneath the valleys or troughs of a Rossby wave, this is where you typically find areas of low pressure. This is why you get the stormy, active, unsettled weather in those spots and in the waves, ridges and highs, there's usually some calm weather. So as the wave is traveling across the globe, it will take that type of weather along with it. So that is why you'll see one half of the country dealing with incredibly active weather, storms, a lot of rain, a lot of snow, while the other half of the country is quiet and dry and sunny. The majority of the time, that's because of a Rossby wave.
