More Big Flooding, And Will Tropical Storm Make It Worse?

What might become Tropical Storm Bill
forming over the Gulf of Mexico Sunday. 

Flood and flash flood warnings and watches were scattered across different parts of the nation this morning as a wet early summer continues in many areas.

It's about to get worse, and some place - like Texas and Oklahoma - that suffered enormous floods last month are going to get slammed again.

There's two main ingredients to this latest bout of flooding. One is a strong ridge of high pressure causing a torrid heat wave in the southeastern United States.

That high pressure is steering lots of moisture from the Gulf of Mexico toward the Texas and Louisiana coast,  up into the southern Plains, then into the Ohio Valley.

Worse, a tropical storm is trying to form in the western Gulf of Mexico. If it forms, they'll name it Bill. 

Hi, Bill.

Bill will never be a powerhouse in terms of wind, but boy will it bring a lot of rain! That's true even if it doesn't get strong enough to get the name Bill.

A great huge arc from eastern Texas, on up into Missouri, the Ohio Valley then east to maybe the New York City area, New Jersey and southern New England could get at least four to eight inches of rain in the next week. Locally more, even, especially the more south you go.

Since most of these areas are already quite wet, the flooding over the next several days could get quite intense. People in this great huge arc of predicted wetness might want to build an ark.

Here's a geeky, interesting thing about would-be Tropical Storm Bill.  Tropical systems and hurricanes rely upon warm ocean water to maintain their strength. Virtually always, tropical storms and hurricanes weaken quickly once they get on to land, largely because the friction of the land slows the winds, and the ready supply of moisture from the ocean isn't there anymore.

(However, tropical storms remnants can cause heavy rain and flooding far inland, well after the winds have died down.)

In would-be Tropical Storm Bill's case, there's a chance it could maintain its strength well inland into Texas and Oklahoma.

This has happened at least once before. In 2007, Tropical Storm Erin moved ashore in the western Gulf of Mexico and quickly weakened once it got over land, as most tropical storms do.

Once it got into Oklahoma, though, favorable upper level conditions helped maintain it. Also, the flat ground of Oklahoma was very wet from previous rainfall. Erin pretty much redeveloped into a tropical storm, complete with winds of 60 mph, spiral rainbands and an eye characteristic of tropical storms and hurricanes.

The National Hurricane Center called it just a low pressure system at this point, but it had all the characteristics of a tropical storm.

Atmospheric scientists Theresa Anderson and Marshall Shepherd studied this, and said wet, flat earth can mimic the ocean's rich moisture source  in some cases to encourage inland tropical storms like Erin. They called this the "Brown Ocean Effect."

Since Texas and Oklahoma are so wet right now, maybe Bill will become or maintain itself as a tropical storm in the southern Plains like Erin did eight years ago?

Maybe.  If the "Brown Ocean Effect" helps Bill maintain its strength once it's well inland, that would likely worsen the flooding that's already almost a sure bet.