Tuesday, October 5, 2010

Record heat to record cold?

Vince DiCarlo, who retired last year from the National Weather Service office, reminded me frequently that "averages are what you get from two extremes."

For example, Charlotte's rainfall total in September was about 4.1 inches -- above the monthly average.

But who thinks September was a wet month around here?

Our lawns turned brown in a relentless string of hot and dry days, until the last few days of the month, when it rained cats and dogs. Overall, though, rainfall was a big above average.

Our recent temperature swing is another example. A week ago Saturday, we broke a record (for Sept. 25) in Charlotte with a high of 94 degrees. Tomorrow (Wednesday) morning, we could be near record-low temperatures, with the thermometer in the vicinity of 40 degrees.

The record low for Wednesday is 38, set in 1935. This morning, we flirted with a record, dropping to 40 degrees (the record was 38, set in 1974).

The average high and low temperatures at this time of year are in the upper 70s and mid to upper 50s. But it seems as if we're mostly at one end or another of the extremes.

By the way ... I did a little checking of recent years, to see if our 40-degree reading this morning was unusual. Looking at the record book since 2006, it does appear as if it was a bit early to be that chilly.

Last year, our first day of 40 or colder was April 18 (35 degrees). October 2008 was a chilly month, as it dropped to 42 on Oct. 2 and got down into the upper 20s by the end of the month. In 2007, temperatures didn't fall to 40 or below until the end of the month. In 2006, it was the middle of October.

Either way, we can expect dry weather and a gradual warm up for the rest of this week. High pressure is taking control of the eastern United States, and we could be near 80 degrees for afternoon readings in a few days.

Talking Tropics: There's another system in the Caribbean, and the National Hurricane Center gives Invest 97L a 60 percent chance of becoming a tropical depression or tropical storm. It's north of the Virgin Islands, but the system is taking a beating from upper-level westerly winds (shear) and is not forming very quickly.

Some meteorologists speculate the area of disturbed weather could become two separate tropical systems -- one north of the Virgin Islands, carried back out to sea; and other south of the Dominican Republic and Haiti.


Anonymous said...

I remember October 2007 very well. We had a 90-degree day around the 12th or somewhere near there, after it being 100 degrees all summer.

This summer felt worse than 2007 - I think the number of days where the dewpoint was above 70 topped those of '07 with its 100-degree days. I can't tell you how overjoyed I was to have to pull a jacket out of the closet this morning.