Rain comes, rain goes, but lately, when it rains it doesn’t just pour — it pours like never before. The reason? Man-made climate change.
It’s a fact that the atmosphere is warmer so it can hold more water vapor. That means that when it does rain, it can rain more heavily. Climate change is intensifying hurricanes, because ocean waters are hotter, and that’s the power source for hurricanes. The jet stream is more “wavy” and tends to get stuck in place because of changes in atmospheric circulation caused by the disappearance of Arctic sea ice, and when heavy rain systems hang around longer, they dump more rain.
It’s all real, and it all came together in Houston, Texas during hurricane Harvey. I found three weather stations in Houston with reasonably long records of daily rainfall amounts that include the time hurricane Harvey hit. One of them is Hobby airport in Houston, and here’s the data:
Note that the day with the most rainfall was August 26, 2017 — during Hurricane Harvey. They were hit with over 306 mm of rain (over a foot!) in one day.
Then there’s Westbury in Houston:
They got their heaviest on August 27, 2017, enduring over 323 mm (again, over a foot!) in one day.
Then there’s North Houston:
Their heaviest day was not during hurricane Harvey, it happened on June 9, 2001, at 268 mm (about 10.5 inches). Hurricane Harvey only brought a one-day rainfall of 263.7 mm (about 10.4 inches) on August 27, 2017.
Does that mean that at least some part of Houston has had a worse rain event before? NO. It does not.
Sometimes rain events last longer than just one day. At Hobby airport, hurricane Harvey didn’t just bring the heaviest rainfall day on record, it also brought the 2nd-heaviest and the 5th-heaviest — all three in a row.
I tallied the cumulative total rainfall during consecutive rainfall days, to see what the load was during each rainfall event whether it covered only one day or more than one in a row. For Hobby Airport, it looks like this:
At Hobby airport, Harvey beat the 2nd-heaviest rain day by a noticeable amount. But the rain event that was hurricane Harvey beat the 2nd-heaviest by a giant margin. In a consecutive string of rainy days, hurricane Harvey dumped 940 mm of rain on this location. That’s over three feet of rain — from one rain event.
Here are the rain event cumulative totals for Westbury:
Once again, the “significantly heaviest day” was part of the “ridiculously heaviest event” with 796 mm (over 31 inches) of rain.
How about North Houston? This:
Note that although hurricane Harvey didn’t bring the single heaviest rain day at the North Houston station, it did mark the heaviest rainfall event, more than twice as much as any other on record. That’s slightly more than 701 mm (27.6 inches) of water.
Any one of the listed climate change impacts makes heavy rain heavier, making flooding worse. When they all come together, destruction becomes disaster becomes mega-disaster.
My message to the people in Houston: You saw it with your own eyes. When you go to the voting booth next month, remember it.
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