2 days ago
Where flooding's concerned, here's one weather term you may hear a lot more about in the coming years
This doesn't mean that major flooding events haven't occurred before now. They certainly have. There are lots of examples of freshwater flooding from heavy rain in the global database over the past century and a half. But in our warmer world, these types of events are becoming more likely, and the gap between when they occur is shrinking.
Think of precipitable water as a column of air above your head. This column contains all of the available moisture that can come down in the form of precipitation. When this column of air is full of moisture, the precipitable water goes up.
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A day that has the potential for lots of flooding might see precipitable water at 2 or 3 inches or even more. That's a lot of water that can come down in a short amount of time, overwhelming sewer systems, streams, and even larger rivers if the rain lasts long enough. We saw just such an event
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Here's an example from the Texas flooding event back around the Fourth of July, you can see the plume of moisture pushing north through the Plains.
Huge amounts of moisture pushed through Texas over the Fourth of July weekend.
Pivotal
Notice in the chart below that precipitable water has been increasing over the past several decades. There's no reason to believe this trend is not going to continue and become more prevalent.
Precipitable water in the Northeast US continues to rise due to our warming climate.
University of Maine Climate Change Institute
Another reason for more moisture in the air is because warmer temperatures mean more evaporation. As you evaporate more water vapor into the atmosphere, it becomes laden, and if that saturated air starts to cool, all of that moisture condenses in the form of big raindrops. If it's cold enough, precipitable water can also bring very heavy snow events.
Although the climate is warming, it's still often cold in various parts of the planet. For those areas that do experience snow, record heavy snowfalls associated with the air's ability to hold more moisture are possible. Of course, eventually, as the climate continues to warm, the chance of it snowing at all decreases and what once was a snowstorm will inevitably be a future rainstorm.
Precipitable water may not be as common a term as heat index or wind shear, but in many ways it's incredibly important and something I would bet you'll be hearing more about in the coming years.
