Tuesday, July 22, 2014

Dreary weather pattern preparing to change

I feel sorry for anyone who's tried to take vacation days since last weekend -- assuming those vacation plans involved anything outdoors.

Charlotte-area weather has been rather unpleasant. It's been wet in many places, the humidity has been high, and sunshine has been scarce. Temperatures have been cool, but I realize some people are pleased with that development.

That cool high pressure system that we talked about 10 days ago set up shop over the Northeast, and that provided the area with the below-average temperatures last weekend. Then an upper-level low pressure system moved into the Florida Panhandle area and became stationary for a few days.

The Charlotte region was on the boundary between the influence of high pressure to the north and low pressure over the Gulf coast. Along that boundary, showers and thunderstorms developed. The Florida low pumped enough tropical moisture into the area that heavy rain fell. At my home in Matthews, we've recorded as much rain in the past week that we normally get for all of June and July.

Now all that is ready to change, for a few days, at least.

By Tuesday night, the Florida low will backtrack to the west, and the prevailing east-southeast flow in the Carolinas will switch around to the southwest and west.  That will help dry things out.

The results should be obvious Wednesday, with more of a typical summer pattern -- highs in the upper 80s, humid conditions, and afternoon thunderstorms. But "typical" won't last long.

Another cold front is forecast to barrel into the area Thursday, and drier conditions will follow Friday and Saturday.

One key player in the weather pattern has been a large area of stifling hot high pressure over the Southwest. That strong high has been nearly stationary, and it has helped set up a blocking pattern over the United States.

Much of the Great Lakes has been rather cool this month. Energy use in parts of Indiana, Michigan and Illinois is 25 to 30 percent below seasonal averages.

While Charlotte has seen some cool weather in recent days, we're only about 1 degree below average for the month. The number of cooling days -- a measurement of how the weather affects air conditioning use -- is down about 5 percent for the month in Charlotte.

It looks as if the cold front that moves through Charlotte later Thursday will dissipate after reaching the coast. Then warm and humid conditions with afternoon thunderstorms will return for next week.

Paul Pastelok, a long-range forecaster for Accu-Weather, thinks August could mark a return to more typical summer weather. He said a Bermuda high pressure system likely will establish itself off the Atlantic coast and dominate Eastern U.S. weather.  That Bermuda high, a fixture of summer weather in the Southeast, has been missing in recent days.

Sunday, July 13, 2014

Polar vortex this week ... in July?

Monday morning update: Well, common sense has taken over. The latest computer models show high temperatures for the middle and end of the week, after the cold front passage, in the mid 80s. This is certainly cooler than average, but it's also not anything in the "remarkable" category.

It'll be a break from the recent 90s, but it will still feel like summer. After all, this is July and we're in the Carolinas.

Earlier post: There has been a lot of conversation in weather circles about a rather unusual meteorological event that is likely to take place this week in the eastern United States.

Some are calling it the return of last winter's "polar vortex" -- a deep low pressure system over eastern Canada that drags cool air into the eastern part of the United States. Back during the winter, especially in January, when Charlotte averaged nearly 5 degrees below seasonal norms, the polar vortex was blamed for the extremely cold weather that settled into the East.

It was responsible for temperatures that plummeted far below zero in the Great Lakes and Northeast. The Carolinas weren't immune either.  My birthday, Jan. 7, featured a morning low of 6 degrees that ruptured a lot of water pipes.

If you look at the weather map, this week's forecast conditions bear some resemblance to last winter. Once again, a deep low pressure system will move across Canada and take up residence in the eastern part of the country. The Washington Post's weather crew, the Capital Weather Gang, examines the situation in this article.

The National Weather Service office in Greer, S.C., began discussing the situation late last week, when it appeared as if the Eastern Canadian low would drive a strong cold front through the Carolinas and off the coast.  In that situation, Charlotte could experience high temperatures at mid and late week in the upper 70s and lower 80s.

But now the computer models suggest the cold front won't make much progress south of the Charlotte region and eventually will stall just to the south. That seems more logical, given the time of year and our location in the South.

Still, it appears as if we're looking for unusually cool weather this week for the middle of July. And to the north, farther away from the stalled cold front, this week's temperatures will be unusually chilly. Some of the Great Lakes cities like Cleveland, Detroit and Chicago might struggle to get into the low 70s at midweek.

It's not really a "polar vortex," because the source of the system will be Alaska, not the polar regions. But this week apparently will give Charlotte-area residents a definite break from the type of mid-July heat we're accustomed to.

Saturday, July 12, 2014

Check out the 'super moon' tonight

With skies mostly clear tonight across the Charlotte region, you'll get another chance to see the so-called "super moon."

That's the term given the moon when it is full at the time of its closest monthly approach to the earth. Scientists at NASA say the "super moon" can be 30 percent brighter than a regular full moon.

Interestingly, we'll have three consecutive months of a "super moon," with upcoming events on Aug. 10 and Sept. 9.

The full moon actually was Friday night and Saturday morning, but we'll still have a moon that's 95 percent full tonight.  The moon is scheduled to rise at 8:44 p.m. and set at 7:43 a.m., which will put it high in the sky for the overnight hours.

The moon's orbit is not a perfect circle around the earth.  Rather, it's an elliptical orbit, and when the moon is at its closest approach (called the "perigee"), it's about 32,000 miles closer than at the farthest point ("apogee").

As I said ... the weather apparently will cooperate Saturday night and Sunday morning, and it should be easy to check out the "super moon."  Some fog could develop in the hour or two before sunrise Sunday, but otherwise, it should be good viewing weather.

Wednesday, July 2, 2014

Storms will precede a much nicer 4th of July

It's another oppressive day in the Charlotte area, with temperatures above the 90-degree mark and humidity levels that are difficult to tolerate.

But better days are ahead ... as in Friday, Saturday and Sunday.

Conditions are shaping up for a beautiful Independence Day weekend across the Charlotte region. While the coastal sections of the Carolinas worry about approaching Tropical Storm Arthur, the central and western parts of the two states will feature some great weather.

The Fourth of July in Charlotte is usually synonymous with heat, humidity and evening thunderstorms.

But a cold front is forecast to push across the area Thursday, and it will take the heat and humidity with it.

The 2 p.m. temperature Wednesday in Charlotte was 91 degrees, and the 70-degree dew point temperature produced a heat index of 97 degrees. That's not pleasant, and it's the second straight day we've dealt with those conditions. It's even worse in Raleigh, where a 95-degree air temperature and high humidity is producing a heat index of 103 degrees.

Thunderstorms are forecast to break out Wednesday afternoon and evening in the mountains and spread eastward into the Piedmont. A few severe storms are possible.

Additional thunderstorms are likely Thursday as the cold front approaches. Once again, some severe weather is probable, and people attending the Charlotte Symphony Pops Concert and fireworks display at SouthPark will need to keep tuned to weather forecasts.

Friday, behind the front, we can expect lower humidity levels, mostly clear skies, and temperatures in the upper 80s. There won't be any heat index issues, and if all that isn't enough, the warm weather will be tempered by a fairly stiff northerly breeze around the back side of Tropical Storm (or Hurricane) Arthur as it moves up the East Coast.

Morning lows will be in the mid 60s both Saturday and Sunday, and daytime highs will only reach the middle 80s.

For this time of year, that kind of weather is a treat.