By Peter Collins Brown
Editor’s Note: The Bedford Citizen is pleased to welcome back its occasional meteorologist!
What a week to be attending a weather conference! All this week, I’ve been at an American Meteorological Society Symposium in Boston. Imagine my surprise when my phone vibrated on Monday afternoon with a text exclaiming: Tornado Warning for Bedford. Although the presentation I was listening to was interesting, I couldn’t pass up the opportunity to see if I could catch a glimpse of the forecasted storm. So I packed up my materials, sneaked out of the conference and hopped into my car for the ride home. As I drove up Route 2, I could see the dark clouds and the lightning flashing off to the northwest. And as I reached the top of the hill in Arlington, I noticed that the clouds were almost on top of the trees. This was going to be quite a storm.
As it turns out, we know now that it wasn’t a tornado but a microburst that ravaged parts of Bedford on Monday. So, what exactly is a microburst? Let’s start with the weather conditions in Bedford on Monday: it was HOT and HUMID—you could cut the air with a knife; just walking from your car to the front door left you drenched.
The storm that struck us started out in central Worcester County. As it moved east, it fed on the hot, humid air it encountered. You remember how it felt—like you could wring the water out of the air. Well, hot, humid air is buoyant and rises rapidly into the atmosphere. As it climbs, the air gets much colder; the sticky air begins to condense and rain eventually falls. As a liquid, the water is very dense, and it can push air quickly ahead of it as it falls. Think of standing on a subway platform in Boston. You can feel a strong rush of air as the heavy train makes its approach through the tunnel—it’s pushing the air ahead of it out of the tunnel. Now think of all this rain bursting out of clouds and falling at great speed pushing the air downward like the train pushes the air out of the tunnel. This storm pushed a huge mass of air ahead of it at speeds of up to 90 to 100 mph. When the air hit the ground at that speed, it bulldozed everything in its path. And unlike a tornado, these were what are termed straight-line winds, meaning that the winds didn’t rotate, but swept across the area in a straight line. That also explains why certain parts of town only experienced torrential downpours while a few streets away there was considerable damage due to uprooted trees and downed power lines. This is because, despite the extensive damage they cause, “micro”-bursts are typically no larger than 2.5 miles wide.
For those of you who were watching the storm’s approach on television, you may have seen the radar—where you could now see the storm and what its intensity would be at the street level. This technology gave everyone at least a 30-minute window to prepare. The National Weather Service issues “warnings” when a storm is actually “imminent in the immediate area.” It’s not a maybe situation. Whether it’s a severe thunderstorm or tornado warning—it’s very important to heed the warnings. Remember to follow instructions to stay out of the water and get to a sturdy shelter. If you’re in your car try to stay away from low-hanging trees and power lines.
No one likes a really good storm more than I do, but I know what kind of damage they can do. Don’t think as I headed up Route 2 that I wasn’t watching and wondering where the storm was headed and how I could keep a safe distance away. We were just lucky that it didn’t score a direct hit on the Great Road at rush hour. Think of how much worse it could have been. At least there were no reports of serious injuries. Just remember—never think you can outfox or outrun Mother Nature.
Correction: This story has been changed to reflect the correct date of the storm in Bedford. The microburst struck on Monday, July 7, 2014, not on Tuesday.