Wednesday, July 3, 2013

Why this strange weather?

The pattern which has been the dominant player in Carolinas' weather this week (and, really, a lot longer) is expected to break down this weekend.

But the real question is whether things really will change for very long.

We're accustomed to seeing weather systems move west to east, or northwest to southeast. This time, the pattern is moving east to west.

Throughout the week, the Carolinas -- and much of the eastern United States -- have been in the combat zone between Bermuda high pressure and a large upper-level low pressure system centered somewhere near the Mississippi River. A third player in the weather has been an old stationary front, stuck across North Carolina.

The Bermuda high's clockwise flow of air and the Mississippi Valley low pressure's counter-clockwise flow met over the eastern United States. That strong southerly flow brought plenty of moisture into the Carolinas. And occasionally, weak low pressure systems moved along the same channel.

All of that combined to create an extended period of unsettled weather.

We've talked a lot about the heavy rain and storm damage. The rain totals actually are amazing, and I'll report on that later this week. But another part of the story has been the temperatures.

A year ago at this time, we experienced three consecutive 104-degree days in Charlotte. This year, our high temperatures have struggled to reach 80 degrees. It's because of the thick cloud cover. Believe me, if the clouds weren't there, we'd be in the upper 80s and low 90s, which is typical for this time of year.

Instead, we're about to experience a very unusual Independence Day in Charlotte.  Our highs probably won't climb above the lower 80s.

Anyways, back to the pattern change.

The Bermuda high is strengthening, and it's pushing the upper-level low farther to the west. As the Bermuda high grows stronger, it's spreading drier air into the Carolinas and along the rest of the East Coast.  Gradually, day by day, larger chunks of the eastern United States are experiencing a decrease in storm activity and an increase in sunshine.

It happened Wednesday on the Carolinas coast.  By Thursday, I expect places like Raleigh and Fayetteville to see the sun for at least part of the day. That pattern reaches Charlotte by Friday.

As that happens, the wettest weather gets pushed westward.  The mountains are in for a soaking Fourth of July, and that pattern will move back into Georgia and Tennessee over the next few days.

My question is:  Will the pattern shift back again?  Will the Carolinas and the rest of the eastern United States find itself back in the atmospheric war zone again soon?

As I've written before, the location and strength of the Bermuda high makes me a bit nervous about hurricane season.  The clockwise flow around the high could serve as a very effective steering mechanism for tropical storms and hurricanes, sending them into the Southeast Coast.


Regular Irksome said...

Weather, like love, is strange.