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Two Steps Forward

Climate change and the new language of weather

The weather outside is frightful. What, exactly, do we call it?

The United States was tied up in winter weather over the Thanksgiving weekend, from torrential rain in the West to ice and snow in the Midwest to cold winds in the East. Traffic, airports and family travel plans all seemed to be snarled, or worse.

Nothing new there — weather messes things up all year long, especially as the calendar hits December, wherever you are in the Northern Hemisphere. What’s new is the kind of weather we’re experiencing, along with the growing list of weather terms being used by meteorologists to describe it.

It’s not simply a matter of coining new words. No doubt, weather experts must tire of the relatively limited vocabulary of quotidian forecasts: wind; rain; snow; sleet; hail; clouds; sunshine; fog; and all the rest. What’s driving the new verbiage are actual shifts in the weather itself — exacerbated, if not caused, by a changing climate.

I’ve been collecting these terms, as befits a self-described "word guy" who revels in new coinages and usage cases. (Most of them, at least. I’m still grappling with such linguistic manglings as "gendering," "efforting," "glamping," "listicle" and "worstest," among others. But I digress.)

Here in California, we’ve had a series of heavy downpours over the past week — up to half a foot in some areas. It is a much-needed drenching to quell, finally, another season of hellacious wildfires — not to mention blanket the Sierra mountains to the east in several feet of snow, helping ensure our drinking water supply for the coming year (and a happy ski season for some). The rain and snow will continue well into the coming week, say forecasters, a blessing in this parched state (if you don't count the resulting mudslides).

These days, it’s no longer just garden variety precipitation.
But these days, it’s no longer just garden-variety precipitation. Over the weekend, an atmospheric river led to flooding in some parts of California, while a bomb cyclone, the result of something called bombogenesis, wreaked havoc on the plans of some holiday travelers.

Say what?

Welcome to the new language of weather. Most of these terms aren’t exactly new, but most are just entering popular usage as they are deployed to describe weather phenomena once considered rare or exotic.

And yes: weather and climate are different things. But there’s little question that changes in the former are being driven by changes in the latter.

Indeed, extreme weather’s connection to climate change is a subject of eternal debate — the weaponization of weather, as the New York Times described it earlier this year. Climate advocates and their detractors each seem to use the latest weather patterns as proof points about the state and fate of our global climate, homing in on warmer summers, on the part of those advocating for climate action, or colder winters, on the part of skeptics and deniers. Never mind that climate change is said to exacerbate both, making hots hotter, colds colder, dries drier and wets wetter.

As the U.S. government’s National Oceanic and Atmospheric Administration explains in no uncertain terms:

Incidents of extreme weather are projected to increase as a result of climate change. Many locations will see a substantial increase in the number of heat waves they experience per year and a likely decrease in episodes of severe cold. Precipitation events are expected to become less frequent but more intense in many areas, and droughts will be more frequent and severe in areas where average precipitation is projected to decrease.

Forget everything you know about seasonal patterns. It’s a whole new era, in both weather and climate.
In other words, forget everything you know about seasonal patterns: What the weather should be at any given point, what should be blooming when, what animals should be migrating where, etc. It’s a whole new era, in both weather and climate.

In that spirit, here are seven newfangled weather terms to know:

  • Atmospheric river — a column of water vapor that develops over the ocean and is wrung out when it makes landfall. These columns move with the weather, carrying an amount of water vapor roughly equivalent to the average water flow at the mouth of the Mississippi River. When an atmospheric river makes landfall, it typically unleashes its cache of water in the form of rain or snow.
  • Bomb cyclone (also referred to as a weather bomb or meteorological bomb) — is the result of bombogenesis (see below), so-called because it can develop quickly and explosively. Bomb cyclones result from a severe drop in atmospheric pressure over a short period of time and typically take the form of intense wind gusts or massive snowfall. Major impacts can include beach erosion and coastal flooding, especially at high tide.
  • Bombogenesis (also called cyclogenesis) — is the process that leads to bomb cyclones, resulting when a storm's barometric pressure drops by 24 millibars (a measure of atmospheric pressure) in 24 hours, creating a sudden low-pressure system. Low pressure makes for intense storms, so a bomb cyclone is a system that builds up a significant amount of strength in a short period of time. As winds converge in the area, they can rotate and form a cyclone at the center. The swirling air moves higher into the atmosphere where moisture condenses and forms precipitation.
  • Derecho — a large, fast-moving complex of thunderstorms with powerful and destructive straight-line winds. (Derecho is Spanish for "straight.") A mostly warm-weather phenomenon, derechos occur mostly in summer in the Northern Hemisphere within areas of moderately strong instability and moderately strong vertical wind shear. However, a derecho may occur at any time of the year, day or night.
  • Flash drought — the rapid onset of drought, in contrast with conventional drought, which is mainly driven by a persistent lack of precipitation over time. A flash drought usually includes abnormally high temperatures, winds or strong sunlight that leads to abnormally high evapotranspiration rates. Flash droughts are often accompanied by erratic and intense downpours over sharply defined geographic areas.
  • Polar vortex — a seasonal atmospheric phenomenon in which a system of strong, high-level winds — better known as the jet stream — surrounds an extremely cold pocket of Arctic air. In winter, for example, the polar vortex at the North Pole expands, sending cold air southward, often leading to outbreaks of frigid temperatures in the northern and eastern United States. A polar vortex was also a factor in the bomb cyclone that battered the U.S. East Coast in 2018.
  • Thundersnow — as the name implies, is a thunderstorm with snow falling instead of rain. It was once considered a rare phenomenon, but it is becoming more common, say meteorologists. One challenge: Because snow acts as a sound suppressor, it muffles thunder and limits the sound’s ability to bounce and spread. Unless the lightning is directly overhead, one might see only a bright flash without hearing the thunder. Thus, ironically, "thundersnow" can be as quiet as — well, snow.

Did I miss any? If so, please let me know. After all, I’ll be holed up inside for the next several days: There’s an atmospheric river passing through.

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