Study: Tornado season starts earlier

A group of scientists from Montana State University issued a report Tuesday that says the tornado season is starting a week earlier than in the past across a part of the Midwest known as Tornado Alley.

The report looked at tornado statistics from 1954 to 2009 and focused primarily on Oklahoma, northeast Texas and Nebraska. Scientists said they found that the peak of tornado season in recent years has been around May 19, compared to May 26 in the early and mid 1950s.

"If we take Nebraska out (of the data), it is nearly a two-week shift earlier," said John Long, a Montana State researcher who was lead author of the study.

The scientists found a link between early tornadoes in Oklahoma and the presence of stronger El Nino conditions. You'll remember that El Nino is a condition of warmer-than-usual surface water temperatures in the eastern Pacific.

El Nino conditions tend to put a lid on hurricane development in the Atlantic and Caribbean, but they also tend to produce a lot of rain and storm activity in the winter and early spring months across a corridor stretching from California and Arizona to Texas, Oklahoma, Louisiana, Arkansas, Tennessee, Mississippi, Alabama, Georgia, and the Carolinas.

So it makes sense that El Nino years would produce early tornado outbreaks.

The Montana State researchers didn't spend a lot of time in the study looking for causes of the early tornadoes, but they said it is in line with what you'd expect from a warmer climate.

Hurricane activity: As we expected, hurricane activity in the Atlantic remains rather quiet this season. The strongest storm so far, Category-3 Hurricane Edouard, is moving across the central Atlantic Ocean this week.

It is expected to curve east of Bermuda and head back toward Europe, possibly threatening the Azores with strong winds this weekend as it turns into a post-tropical storm.

Meanwhile, Odile has weakened from a strong hurricane to a tropical storm as it pushes northward through the Gulf of California, between Baja California and the Mexican mainland. That storm is forecast to make landfall in northwest Mexico and then move northward -- in a much weakened state -- into Arizona.

Look for plenty of news coverage in coming days about flash flooding in Arizona and New Mexico. Parts of those states could get very heavy rain later this week.

Yes, that's snow falling up north

Was it really only a week ago when it felt like summer wouldn't end?

Now the Charlotte area is looking at high temperatures only in the 70s for much of next week, and some residents in the northern-most United States awakened to snow on the ground Friday.

Up to 8 inches of snow accumulated in the Black Hills of South Dakota, and the National Weather Service in Sioux City said it was the earliest accumulating snow in the region since 1888. Snow also accumulated the past two days in Canada's Alberta province and in Montana.

Low temperatures are expected to reach the upper 20s Friday morning in parts of Minnesota and the Dakotas, and Great Lakes locations like Cleveland and Detroit will see the mid and upper 40s.

Here in the Carolinas, the heart of the cold air won't arrive. The cold front will stall along the coast, and while cooler air will be sweeping into the eastern United States, the truly chilly conditions will never get into the Southeast.

Meanwhile, it's still tropical weather season in the Atlantic and Caribbean. And there are two areas of interest.

A tropical depression developed Thursday about 700 miles west of the Azores. This system could turn into a tropical storm by early Friday and a hurricane soon after.

However, computer models indicate that the system, which would be be named Edouard if it reaches tropical storm status will curve into the open Atlantic and never threaten the mainland United State.

The other system is crossing the southern part of Florida and will emerge into the Gulf of Mexico sometime this weekend. It will not have enough time to strengthen much, but it will bring heavy rain to parts of Louisiana and south Texas.

Cool, wet weekend; then maybe taste of fall next week

Those of you who have been griping about hot weather can celebrate.  It looks as if a real change to cool conditions is on the way, although it might make the weekend rather unpleasant.

The first real shot of chilly air is expected to push out of Canada and into the northern edge of the United States over the next few days. There will even be a bit of snow in the northern Rockies, and scattered frost over parts of Montana and the Dakotas.

That autumn-like air mass will push eastward, bringing much cooler air to the Great Lakes over the weekend and then the Northeast early next week.

The edge of that cool air will move through the Carolinas on Friday, but there are some real questions over whether the cold front will have enough of a push to reach the Deep South.  That means the front could stall over Georgia and South Carolina, setting the stage for a cool, cloudy, wet weekend.

In September and October, it's not uncommon for these late-summer and early-autumn cool air masses to get hung up near or just south of the Charlotte area. When that happens, small low pressure systems develop on the stalled front and move eastward, bringing a mix of drizzle, light rain and even moderate rain showers.

It's a version of the cold air wedge, and it could be in our future this weekend.

By early next week, computer models indicate that the front finally will push south, allowing skies to clear in the Charlotte region. If that happens, we could be in for a real taste of autumn, with daytime highs in the mid 70s and morning lows in the low and mid 50s.

A sure bet: Speaking of cold air wedges ... Tuesday was another example of how you could make a lot of money betting against the computer models when it comes to wedge patterns in the Carolinas.

The models almost always are too optimistic in predicting when the wedge will weaken and allow the clouds to break and sunshine to return. On Tuesday, the models showed sunshine returning by midday Tuesday to Charlotte, with temperatures climbing into the mid 80s.  Naturally, the clouds hung tough all day.

That happens nearly every time in these wedge patterns.

Assuming the wedge breaks down Wednesday, we'll see a brief return to summer-like weather, with highs reaching the mid 80s.  Temperatures could hit the upper 80s Thursday, but then the cold front will arrive Friday and bring it all to an end.