Now that we’ve all learned what a derecho is, this is as good a time as ever to remind you to follow RealCrozetVA on Twitter – I’m posting there much more often than I can here, in part because it’s much, much, much easier to post tweets from my phone than it is to write a blog post. I’m trying to post on the RealCrozetVA Facebook page, but that app is so remarkably slow and dysfunctional that it drains my iPhone’s battery super-fast.
The traditional definition of a derecho is a thunderstorm complex that produces a damaging wind swath of at least 240 miles (about 400 km), featuring a concentrated area of convectively-induced wind gusts exceeding 50 kts (58 mi/h, or about 93 km/hr). Some studies add further criteria, such as a requirement that no more than 2-3 hours separate any two successive wind reports. Derechos typically possess a high or rapidly increasing forward speed. In addition, they have a distinctive appearance on radar (known as a bow echo) with several unique features, such as the rear inflow notch and bookend vortices, and usually manifest two or more downbursts.
Update 1 July: every day brings further affirmation that Facebook is, for events such as this fine for conversation. Bit for disseminating timely information. twitter is infinitely better.