Extreme Weather 101: Drought
Platte River Evaporates
Let it Rain, but Not Too Much
Have you seen a drought shift to a flood, or vice versa, in what seems to be a blink of an eye?
This can often occur in the summer. When persistent domes of high pressure aloft squelch rainfall for weeks on end, it can turn what had been a wet spring into a flash drought. Conversely, when an area in drought suddenly receives the remnants of a tropical cyclone or a front stalls in the summer with a deep moisture plume, cracked ground can suddenly be covered by feet of water in a flash flood.
"The weather has quickly gone from drought to deluge in the past, but in recent years there have been particularly dramatic contrasts between exceptionally wet and exceptionally dry, both in terms of switching from one to another at a location in a short period of time, and with those extremes geographically juxtaposed close to each other at the same time," says senior meteorologist Stu Ostro (Twitter | Facebook).
There's increasing evidence that stronger, more persistent blocking upper-level high pressure systems, as well as increased water vapor in a warming world, will lead to more of these shifts in the future.
"The new normal in the coming decades is going to be more and more extreme flood-drought-flood cycles," said Weather Underground's Dr. Jeff Masters in an April 2013 blog. "We'd better prepare for it, by building a more flood-resistant infrastructure and developing more drought-resistant grains, for example," says Masters. From 1980-2012, four of the top 10 costliest weather disasters in the U.S. were either droughts or floods, not counting flooding from tropical cyclones.
On the following pages are a few recent examples of rather extraordinary drought-to-flood shifts over the past few years, starting with a New Mexico reservoir's dramatic change in just a couple of months.
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