The Flash Floods This Summer Have Been Incredible

Flooding near Islip, Long Island Wednesday.  

As I write this during my latest visit to Yankton, South Dakota, it's raining like CRAZY one state above me, up in North Dakota.    

More than five inches of rain have fallen in some areas, and it's still pouring up there. It's yet another example of a summer that has had some pretty incredible rain events.

Last week takes the cake. Especially on Long Island, where Islip had 13.57 inches of rain in one day.

Of that, 9.71 inches fell in two hours. To put that in perspective, Islip normally gets less rain than that over the course of two entire Augusts.

According to weather historian Christopher Burt, the narrow corridor of incredible rains on the East Coast is almost unprecedented. Certainly, the Islip rain was the heaviest 24 hour rainfall in New York State History.

Other areas of the East got clobbered, too. Green Haven, Maryland got 10.32 inches of rain, and Scarborough, Maine got 6.59 inches.

The rainfall rates were the big story, because in many areas, like Islip, the bulk of the rain came in two hours, three at the most. For instance, in Portland, Maine, 4.21 inches of rain fell in just two hours.

In the Northeast, rainfall in the amounts that happened in one day last week come during tropical storms or hurricanes. And it is hurricane season. However, this incredible rain had nothing to do with any tropical storm. Tropical air, yes, but not a tropical storm.

Super wet air from the tropics went up and over a weak weather front draped along the East Coast, At the points twhere the soggy, warm air had to rise over the cooler air on the other side of the weather front, the air rose, the moisture condensed, and down came the torrents.

It was also interesting to see how narrow the area of flash flooding and heavy rain was. That actually happens quite a bit in flash flood situations. One town gets blasted by the flood, and one or two towns over, there's not much to talk about.

In this case, 40 miles west of Islip, an unremarkable. 0.78 inches of rain fell during the storm. About 40 miles to the east of Islip, they only got maybe a half inch of rain. Yawn.

Damage patterns were interesting, too. On Long Island, most of the flooding was on highways and streets, and most of the damage was to cars, and some basements.

A similar torrential storm of 4.57 inches hit the Detroit area and other parts of southeastern Michigan the day before the East Coast got nailed. In the Detroit area, damage estimates are up to $1.2 billion and about 18,000 houses had flood damage, says Christopher Burt.

It all depends upon the topography, where the streams are and where the parking lots, streets and roofs prevent water from soaking into the ground.

Of course, in these extreme rain events, everybody asks if global warming has anything to do with this. Like Burt, I'm turning to Dr. Marshall Shepard, who has a great explaination about this.

Basically, he's reluctant to attribute one weather event like this to climate change, but climate change does make extreme rainfall events more likely, so we'll be seeing more of these big local flash floods.

Shepard also points out that in recent decades, a lot more urbanization with its giant parking lots, huge roofs, sprawling suburban tracts and highways mean there's too much concrete and asphalt out there to allow rain runoff to soak into the ground. Instead it pours off the parking lots and roofs and causes worse flooding.

Interestingly, social problems might have made the Detroit flooding worse, according to CBS Detroit.  The cash-strapped region had antiquated pumping stations to remove water from freeways, and thieves stealing copper pipes rom pumping stations of course made them unable to function.

So, we'll keep watching these local, devastating flash floods keep popping up worldwide. Today it's North Dakota. Who else will get washed away tomorrow.?