At its peak, there were more than a quarter of a million power outages across Massachusetts yesterday caused by a strong line of thunderstorms that moved from Ontario, Canada, all the way across southern New England. As the cleanup continues, you might wonder what caused all the tree damage and resulting power outages.
First of all, what occurred yesterday was not a tornado. Tornadoes are a specific wind phenomenon in which the wind is rotating; we did not have any rotation yesterday. What we did see were microbursts. A microburst is just a small downburst that is usually less than 4 kilometers across. You can contrast this with a derecho, another severe wind phenomenon, which is a line of straight-line winds that lasts a longer time and moves across a wider area. One might even argue that yesterday’s line of microbursts was in a sense a derecho, but I will