What Exactly is A Derecho?
Regions of South Jersey and South Eastern Pennsylvania experienced a series of storms on Wednesday afternoon and night that caused some serious damage. Many were referring to it as a "mini-hurricane" or a tornado. The type of storm to hit those areas actually has a name and you've probably never heard of it. It's called a "derecho".
The name is so unrecognizable that spellcheck doesn't even register that "derecho" is a real word. So, what exactly is a derecho?
The National Oceanic and Atmospheric Administration identifies a derecho as a windstorm combined with thunderstorms and heavy rain that causes damage in a straight line. Basically, contrary to that of a tornado or hurricane, the damage left behind by a derecho can normally be traced by a straight line leaving experts to conclude that the specific wind pattern of this type of storm is, in fact, a straight path.
That's what South Jersey experienced yesterday. The storms were moving so fast and, if you paid attention to the radar, it looked like it basically traveled in a straight line down the both pikes and the AC Expressway.
The NOAA says that "falling debris" and "cloud-to-ground lightening" are what you most need to worry about if you're caught outside during a derecho:
"Falling debris is the most serious hazard posed by a derecho to those without shelter; cloud-to-ground lightning strikes are an additional hazard. Lie flat and face-down on low ground, protecting the back of your head with your arms. If possible, avoid trees; even relatively small branches can become lethal when blown by storm winds."
They also offer an explanation as to why so many South Jersey residents lost power and why it may take a while for it to be restored:
"...It is the vulnerability of overhead electric and communication lines to high winds and falling trees that makes derecho winds especially problematic in urban areas. In addition to posing a direct hazard to anyone caught below the falling lines, derecho damage to overhead electrical facilities sometimes results in massive, long-lasting power outages that can affect hundreds of thousands of people; in the worst events, power may not be restored for days. The complex and dense networks of overhead distribution lines --- and their proximity to large trees --- make urban and suburban areas especially vulnerable to significant derecho-induced electrical and communication outages. In addition, unlike the localized damage produced by a tornado, derecho damage may be widespread, with repairs requiring considerably more time and effort to accomplish." - NOAA
The best way to be prepared for this fast-moving storm is to, quite plainly, pay attention to warnings and weather reports.
Source: SPC.NOAA.GOV