Thunderstorms on the Summit

2014-07-13 18:18:29.000 – Tom Padham,  Weather Observer/Meteorologist

Hail outside the sub door after the 2011 storm

With the prospect of thunderstorms over the next few days, I am reminded of some of my experiences with storms on the summit, many of which have been some of the most exciting weather I have seen during my work here. Individual thunderstorms tend to take the past of least resistance, and often skirt around Mount Washington and the Presidential Range and either head north into the Gorham/Berlin area or south towards North Conway. Rarely storms are actually aided from the lift of the mountains if the storm is forced to rise up and over the range, with one very impressive lightning display coming to mind when a storm slowly built up over Mount Adams and then proceeded to strike the summit with continuous lightning and heavy rain. Luckily Mount Washington happened to be not in the fog and we were able to witness a pretty spectacular lightning show.

Typically the best setup for a severe thunderstorm on the summit is when a line segment, or squall line hits the summit. A strong line of thunderstorms is typically too large to completely miss the summit, and a portion of this line is then forced to rise up and over Mount Washington. Severe thunderstorms that form into a line segment tend to bow out and form more of a comma shape; a sign that strong winds have been forced downward from aloft to the surface. With this setup and often the enhancement of the wind from the mountain, the summit can see some very strong wind gusts during thunderstorms, often with a dramatic increase in wind speed over only a few minute period. A storm in June of 2013 comes to mind, with winds jumping from only about 20 mph to a peak of 101 mph in only a few minutes, along with nickel sized hail. Needless to say this would not be a storm one would want to be caught outside in!

Lastly, the best thunderstorm I’ve seen up on the summit happened back when I was an intern in 2011. A line of thunderstorms approached the area from the northwest, and then actually got hung up right over the mountain for nearly an hour, keeping us right in the middle of the storm. Winds were not especially impressive but did gust to around 60 mph, however the hail was the most impressive display I’ve seen. Hail lasted for nearly 45 minutes straight, varying in sizes from about pea sized to quarter sized. The hail even coated the ground to about 2 inches in depth, making for a wintry scene on the summit in the middle of Summer. Here’s hoping to many more awesome storms to come!

Tom Padham,  Weather Observer/Meteorologist