This weekend produced two record highs: one in temperature at a steamy 82 degrees and the other in sheer volume of charred Oregonians, most of whose fair skin hadn’t seen the sun in months and who, in a fit of spring fever, wore far too little clothing. After watering the garden to keep my cold crops from wilting in the heat, I retreated to the shade of the porch to drink lemonade, pick my banjo, and ponder what is going on with this crazy weather?
Funny you should ask: like the Midwestern heat wave of March 2012, this anomalous (but welcome) warmth owed its existence to a wiggle in the jet stream. You’ve probably heard forecasters talk about the jet, and motion to some horizontal lines on a weather map. But the jet stream merits a little more attention; it is a fundamentally important part of life at mid-latitude.
A jet stream is literally a river of air that circumnavigates the globe high above the surface at break-neck speeds in excess of 100 miles per hour! They exist because air heated at the equator moves poleward to balance the Earth’s temperature gradient but doesn’t arrive at its destination because of the Earth’s rotation. Instead, it is hijacked into a kind of high-velocity orbit.
A simple way to think about it is that a bird at rest at the equator is actually moving at the speed the earth rotates. When that bird flies north, it also keeps moving to the east at its original speed. However, since the circumference of the earth is smaller at higher latitudes, the surface moves slower here than at the equator (because less distance is covered over the same time interval—in this case, a day). This means that a bird flying from the south moves eastward faster than an observer in Oregon, leading to the illusion that its path has been deflected to the east. In fact, from the bird’s perspective, it is flying in a straight line! This effect, known as the Coriolis force, muscles pole-bound air into eastward moving jet streams in both hemispheres.
Physics aside, these jets hurtle along about 8 miles above the earth in the neighborhoods of 30 and 55 degrees of latitude. They help determine where the boundary between wet and dry climates sits by channeling transient weather systems—storms cannot cross these fronts. They also account for some of the mysterious differences in average temperature between cities at similar latitudes: a persistent kink in the polar jet caused by the Rocky Mountains jutting up into the atmosphere pushes the current into Canada, where it cools and brings frigid air into New England during the winter. This helps explain why it is bitterly cold there, but mild and temperate in comparable locations in Europe.
The whys of heat waves
The average position of these jets varies regularly with the seasons, and with El Nino events (and there is evidence that it is shifting now due to climate change). But they also develop kinks and wiggles, often because of abnormal surface temperature patterns causing air to rise in different places. If these kinks become entrenched because of reinforcing mechanisms (i.e. the position of the jet causes a location to warm, which further stabilizes the jet, which causes more warming…you get the idea), this sets the stage for some very interesting weather.
This is exactly what happened during the extended heat-wave in March, when cities across the country logged a record number of record highs, often by margins wider than 20 degrees! (see this blog for a fascinating run-down of superlatives!). The same kind of situation led to devastating heat waves in Europe in 2003 and Russia in 2010, and also, most likely, to the Dust Bowl! So you see, the jet stream is pretty important indeed!
What happened this week was the waggle to March’s wiggle. Instead of bringing cold air into Oregon from the North Pacific (and warm air from the Gulf of Mexico into the Midwest), we got a breath of summer from Baja and the eastern half of the country got some Canadian chill! Unfortunately, this wiggle wriggled away, and now we are back to April showers.
One final scientific note:
You might be wondering if this extreme weather is due to climate change. The best answer is that the probability of having a heat wave has increased due to climate change, but no single weather event can be directly and solely attributed to climate change. It boils down to the fundamental difference between weather and climate: weather is what you experience every day and climate is the average weather over a long period (usually at least 30 years). Both theory and climate models predict that there will be more extreme weather events as the Earth warms, but there is a certain amount of inherent variability in weather, even during periods of unchanging climates. You can read some expert opinions on this topic in this New York Times blog.
Hungry with heat stroke
Still, for most Oregonians, 82 degrees is about as hot as we like it. It makes us feel like we live in some other part of the world, a place where you might eat a good down-home meal on the porch in the late evening after the heat abates. So that’s exactly what we did. Here’s an Oregonian version of Southern food, perfect for the next round of jet stream acrobatics (or summer, if you’re patient).
Baked cauliflower and cheese is a new twist on my mom’s mac and cheese recipe (still one of my favorite meals on the planet). She always served it with potato chips on top, and I just can’t see any reason to fix what ain’t broke. A birthday present from my brother—smoked paprika—inspired me to try the baked beans. It worked splendidly, giving this vegetarian version the perfect amount of smoky flavor. And the slaw is just about as healthy and refreshing as it gets, not to mention, purple!
2 c. béchamel sauce:
4 tbsp. butter
4 tbsp. flour
2 c. milk
¼ tsp. nutmeg
¼ tsp. worcestershire sauce (the veggie kind, if you care)
½ tsp. lemon juice
½ tsp. paprika
salt and pepper
½ onion, chopped
1 c. cheese, shredded
1 head cauliflower, chopped
2 c. kale, chopped
1 c. cheese, shredded
2 c. kettle chips, crushed (about one 9 oz. bag, I recommend Kettle Brand Salt and Cracked Pepper)
Preheat oven to 375°F.
Melt the butter over medium heat in a large saucepan then add the flour, whisking constantly.
Lower the heat, add the milk, and cook for 10-15 minutes, stirring frequently, until the sauce thickens considerably.
In the meantime, grease a large baking dish. Toss the cauliflower and kale inside.
When the sauce is opaque and thick enough to ooze off the spoon, add the spices and onion, adjusting to taste. Cook 10 minutes more.
Remove from heat, stir in 1 c. of cheese, and pour over vegetables.
Top with the remaining cup of cheese and sprinkle with crushed potato chips.
Bake for 30 minutes, or until the cheese starts to brown.
2 c. dried navy beans, soaked overnight
½ onion, thinly sliced
3 c. water
1 tbsp. olive oil
1½ tbsp tomato paste
¼ c. molasses
1” ginger, grated
½ tsp. mustard seed
½-1 tsp. smoked paprika
salt and pepper
a few tbsp. sugar, if you like them sweet
a splash of hot sauce, if you like them with a kick
Preheat oven to 300°F.
Combine all ingredients in a heat-proof skillet (again, I use cast iron).
Bring to a boil, then cover and bake for 2 hours, or until beans are soft. Add more water if necessary.
This can also be done in a crockpot, but it requires 8-12 hours.
½ red cabbage, sliced
1 beet, raw, shredded
1 c. dried cranberries
2 scallions, sliced
⅓ c. canola oil
2 tbsp. cider vinegar
1 tbsp. sugar
dash of salt
Combine cabbage, beet, cranberries and scallion in a large bowl.
In a separate bowl, whisk together oil, vinegar, and sugar.
Toss with slaw, and add salt to taste.