What Happened? Connecticut Weatherman On Historic Flash Flood

Connecticut's recent flash flood caused millions of dollars in damage, claimed two lives and took the entire state by surprise. We had a tough time putting all of this in perspective for the radio show so we reached out to our Meteorologist Jack Drake for some help.

Get our free mobile app

You can hear Jack's storm recap below, he also shared the the following words on how this happened and why we were not warned.

Flash flooding is the least glamorous of all severe weather events. There aren't Hollywood hits made about flooding like there are for tornadoes, and Glen Powell certainly isn’t chasing after flash flood warnings on his quest to "ride" the storm. Flash flood events don’t even get names or headlines like hurricanes do, and they often garner little attention in the eyes of the public. Despite this, flooding accounts for a significant share of property damage and fatalities every year in the United States. As a meteorologist, flash flooding also creates headaches since it can be challenging to forecast until it is happening and can often be very localized. For example, last Sunday, there was significant flash flooding on the eastern side of Danbury, but hardly any issues in the normally flood-prone Mill Plain area.

The consistent message I've heard after the deadly August 18th flood event is that it was not well forecast, and that’s true. However, that is also one of the inherent risks in flash flood events, which often occur on a scale smaller than most weather models can accurately resolve. Late last week, models had much of the rain staying about 50 to 100 miles west of Danbury, but they made a significant last-minute shift to the east. It became apparent that we were in trouble as the storms formed on Sunday morning, and I, for one, scrambled to get alerts out.

The cause of the flooding was a slow-moving frontal system that triggered repeated "training" thunderstorms through the area. Rainfall was enhanced by a stronger-than-expected low-level jet (LLJ), which can be thought of as a river of moisture through the atmosphere. The term "firehose effect" is also used to describe this process.

It’s no secret that Danbury has issues with flooding. The city sits in what is essentially a bowl, with tall hills on all sides. While the swampy lands were great for beaver pelts back in the day, they’re not so great in terms of urban flood risk. Whenever I go into an elementary school for a weather visit, I always ask the kids if they can name any areas in Greater Danbury that flood a lot. Without fail, they’ll rattle off the Danbury Mall, Federal Road, and Newtown Road by Walmart. On Sunday, an estimated 7 inches of rain fell near the Shelter Rock area, triggering a landslide and gas leak at the bottom of Shelter Rock Road.

Even with how bad the flooding was in Danbury and Bethel, where 7 to 8 inches fell, the flooding in some of the Housatonic River towns was catastrophic. An estimated 12 to 15 inches of rain fell on parts of Newtown, Southbury, and Oxford. Those numbers are enough to make this a once-in-a-1,000-year event, although personally, I prefer to look at it as an event having a 0.1% chance of occurring each year. With flood events on the rise in recent years, it’s only a matter of time before this happens again.

My advice for flash flooding is always simple: Know the areas in your community that are prone to flooding, take flash flood warnings seriously, and PLEASE never drive through flooded areas or around barricades.

Check out the Ethan, Lou & Large Dave Podcast on Apple and Spotify

Be sure to follow Jack Drake on Facebook @Jack Drake - Western CT Weather