Wet in Washington
On Friday, July 28, Washington, D.C., recorded more than 3 inches of rain in what turned out to be a pretty big deal, statistically speaking. That day, 3.31 inches of rain fell at Reagan National Airport. This was the seventh wettest July day on record, with records there going back to 1872.
I did a little math and came up with the fact that the period of record contains a total of 4,526 July days. So to be the seventh highest out of 4526 is impressive indeed. And it’s made even more so because it was not one of those “localized” storms that can send torrents of water everywhere, but only over a small area, nor was it a system of tropical origin, well-known for their ability to produce broad swaths of heavy rain. Instead, this storm was a late-July coastal storm — what in wintertime we’d be calling a Nor’Easter. It affected a fairly large area with 2 to as much as 6 inches of rain. Winds from the Northeast gusted to over 50 mph on the Jersey coast.
Incidentally, Nor’Easters are called Nor’Easters because the wind is often blowing from the Northeast during the “meat” of the storm. This type of storm is quite unusual for late July, but certainly not unheard of. Having grown up on the East Coast, I can recall a number of summer Nor’easters.
Given that we’ve just been talking about how 3-plus inches of rain in a day can be a big deal, I imagine that this next fact will probably amaze you. In 1947, on June 22, Holt, Mo., was deluged with 12 inches of rain in, astoundingly, only 42 minutes.
Now, 12 inches represents about one-third of the total precip (rain plus snow) that Caribou sees in one year. And those folks got what we get in one-third of a year, in only 42 minutes. Incredible.
Of course, too much rain can lead to tragedy, as happened when that family was swept away from a swimming hole by a flash flood out in Arizona several weeks ago. Nowadays, so many people are “app-dependent” for their weather, while all the while, real life, real-time clues are all around them. All folks have to do is simply look at the sky and know which clouds they are looking at, and what those clouds might be telling them about the coming weather.
By the way, I strongly recommend the Audubon Society’s Field Guide to North American Weather. It is a wonderful guide to use to learn how to differentiate different types of clouds, and to understand what they might be telling you. I use it in the class I teach at UMPI.
Back to the topic of flash flooding: If you ever do any hiking out west, and if your hike is taking you through dry riverbeds or washes, or if you are hiking in the fabulous slot canyons, be sky-aware, and if you see a thunderhead, or even just a trend toward cumulus clouds turning into tall towers, be hyper-vigilant. It need not be raining where you are for a flash flood from upstream to strike quickly. If you see that a storm is up in the mountains and you are in a dry creek bed at a lower elevation, again, be super alert.
Sometimes flash floods first announce their arrival with a sound like a rumbling. When water gets to moving fast, it need only be half a foot deep to knock you off your feet, and then you’re just moving wherever the water takes you. Not good. Water weighs around 1,700 pounds per cubic yard, and when it gets to moving, it exerts a LOT of force.
We’ll wrap it up for this column by acknowledging the approach of the 48th anniversary of the Hurricane Camille-caused deadly flash flooding that literally liquified some Virginia mountainsides with more than 2 FEET OF RAIN, leaving behind bedrock scars which can still be seen today. Trees and boulders and liquefied soil followed gravity down to the valleys, where the people lived.
The flood calamity commenced on the night of Aug. 19, 1969, and lasted into the morning of the 20th. Sadly, 156 people in sparsely populated Nelson County, Virginia, perished in the flooding. This was before modern radar. The old weather radar just showed forecasters that there was an area of rain to the southwest of D.C., but there was no indication of its extreme intensity. An unheard-of rainfall of 27 INCHES was recorded in ONLY 8 HOURS at one gauge, and a farmer, measuring in a previously dry barrel, came away with 31 inches.
Some people in Nelson County simply call this terrible disaster “the Nineteenth.”
One final thing: If you are going to view the partial solar eclipse on the 21st, you must have special eclipse glasses. They must meet the safety standard, ISO 12312-2.
Ted Shapiro holds the Broadcast Seal of Approval from both the American Meteorological Society and the National Weather Association. An Alexandria, Va. native, he has been chief meteorologist at WAGM-TV since 2006. Email him at firstname.lastname@example.org.