Monday, August 18, 2014

Plenty of question marks in this week's forecast

At first, it seemed so easy.

A strong high pressure system would build over the Carolinas, and we'd experience a week of hot weather -- perhaps our hottest week of the summer.

The heat would extend through the week and possibly into the early part of next week, with only a few chances of thunderstorms. The greatest chance of storms would come Monday afternoon and evening.

Scratch that idea.

As it turns out, Monday's thunderstorms affected the mountains during the morning, then split apart and developed in the afternoon over the South Carolina Midlands and up in Virginia. The Charlotte region could escape without a drop of rain.

And as for the rest of the week?

Well, it figures to be warm, but not at the kind of levels -- mid and upper 90s -- that we first expected. Instead, it appears as if the Carolinas might wind up being right along the path of several clusters of showers and thunderstorms being shunted from the Great Lakes southeastward.

High pressure that has dominated the western United States has shifted a bit to the east, and the computer models indicate that the Carolinas will be on the eastern edge of the high. Often, clusters of storms -- known to meteorologists as mesoscale convective system (MCS) -- form on the edge of the high pressure systems and are steered around that edge.  It appears as if the Carolinas could be on that edge.

That means these clusters of storms could move into the Carolinas at times during the week. For meteorologists, that's a headache.  It makes forecasts of more than 36 or 48 hours a bit risky, and that could be the case this week.

And later in the week, there are growing signs that another cold air wedge could push into the Carolinas. Those wedges, formed when cool and moist air is pumped from the Atlantic Ocean into the Piedmont by high pressure systems over the Northeast, have made frequent appearances this summer in our region.

If that happens, forget about the 90s this weekend.  We could be looking at thick overcast and temperatures in the mid and upper 70s.

Thursday, August 14, 2014

Summer is about to deliver some heat

I hope you haven't caught yourself thinking that maybe we're done with the heat this summer.

The computer models are pointing toward a warmup over the next few days, and that could be followed by some even warmer temperatures by the end of next week and into the start of the kids' school year Aug. 25.

We're not talking about 100-degree weather, but temperatures in the mid 90s will feel hot, after the kind of weather we've experienced since mid-July.

Carolinas' temperatures -- and, in fact, readings across the eastern two-thirds of the country -- have been well below average for the last four or five weeks. In Charlotte, we're nearly 3 degrees below the monthly average temperature so far.

It's been wet, too. While the rainfall numbers at Charlotte Douglas International Airport haven't been noteworthy, there have been several heavy rain events across the region recently. Beachgoers know what I mean. Rain has fallen three straight weekends on the Carolinas coast.

I spent last week at Sunset Beach, and rain fell all seven days I was there.

It only makes sense that things will change, and now that seems to be taking place. Our pattern for the past month has been wet and cool, but the computers are hinting at a change -- warm, with only scattered daily thunderstorm activity.

The Global model was producing forecasts this week that point to 100-degree weather in the Carolinas around the Aug. 23-26 period, but with all the rainfall we've had since mid-July, it doesn't seem likely that we'll get that hot. Some of the heat will be expended drying out the ground, so we'd probably see mid 90s instead.

We'll also be watching the Atlantic, because the tropics have been quiet so far this season.

That was the prediction, with an intensifying El Nino in the Pacific basin expected to limit the development of tropical storms and hurricanes in the Atlantic and Caribbean. But we've had only two named storms so far this season, and that's the smallest number at mid-August since 2009.

Once again, it makes sense to expect some development in the Atlantic next week.

And what about autumn? The government's Climate Prediction Center seems to be pointing toward a warm autumn for the Carolinas.

The forecast for August through October calls for average temperatures, but the September-November and October-December forecasts show a strong chance of above-average temperatures -- and above-average precipitation.

In other words, expect warm and wet weather for September, October and November.

And that ties in with a couple of autumn forecasts I've seen in recent days.

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.

Monday, June 30, 2014

A dry and pleasant July 4 ... is that possible?

The Carolinas coast is getting most of the attention from meteorologists this week, as they watch the possible development of a tropical low pressure system east of Florida.

But back here in the Piedmont and foothills, conditions are shaping up for what might be an unusually nice Independence Day holiday. If everything develops the way the computer models indicate, our July 4th could be dry and pleasant.

High temperatures in Charlotte might climb only into the upper 80s, humidity levels might be tolerable, and skies might be clear.

Scott Krentz, of the National Weather Service's office in Greer, S.C., said Monday morning that the computer-generated forecasts seem to be pointing toward one prediction -- that a fairly vigorous cold front will push across the Charlotte region late Thursday and be followed on the Fourth of July by a high pressure system.

Under that solution, Thursday would be a stormy day, especially in the afternoon and nighttime hours.

For several days, the Carolinas have been under the influence of an unsettled pattern, as an easterly flow off the Atlantic brought a lot of moisture into the area. Some locations in the North Carolina mountains got 6 to 8 inches of rain over the weekend. A vigorous thunderstorm Friday night dumped about 3 inches in parts of southeastern Mecklenburg County.

Additional showers and storms developed Saturday and Sunday, and more of the same is forecast for the first few days this week -- although storm activity will be scattered, forecasters say.

The chances of thunderstorms probably will increase into the "likely" category Thursday, as the cold front approaches. Anyone planning outdoor activities Thursday night -- and there are plenty of concerts, festivals and fireworks displays scheduled -- would have to keep an eye on the forecast. The storms could continued into the overnight hours.

Then the cold front is predicted to push all the way to the coast Friday. Under that scenario, the cold front would serve as a pipeline for the tropical weather system expected to move up the East Coast. If you're planning to spend the Fourth of July at the coast, that's a problem.

But for those remaining in the Piedmont, foothills or mountains, the holiday could be really nice.

Independence Day typically in the Charlotte area is hot and humid, with a scattering of late-afternoon and evening thunderstorms. Highs in the low 90s are common.

But we could be looking at a holiday with highs from 85 to 88 degrees and no worries about whether a thunderstorm will interrupt the holiday fireworks displays and other evening events.