Thursday, December 30, 2010

Mild weather: Long-lasting, or a temporary reprieve?

After a month of the coldest December weather in many years, the Carolinas finally are getting a break as we head into the New Years holiday.

A weak low pressure system is crossing the area today, bringing clouds and a few sprinkles, but skies will clear later Thursday night and usher in a very nice New Years Eve. Fans heading to Friday's Meineke Car Care Bowl at Bank of America Stadium will have sunshine, temperatures in the upper 50s, and -- judging from the tepid ticket sales -- plenty of room to spread out.

Nice weather will continue through New Years Eve, and relatively mild conditions are expected to continue through next week.

That raises the question: Is this the long-awaited breakdown of the pattern that brought us cold, sleet and snow in December? Will our La Nina winter -- mild and dry -- finally get under way?

Or is this just a temporary reprieve?

Based on what long-range forecasters are saying, it's the latter. The cold and stormy weather is returning, they say.

The Greenland block -- a strong high pressure system that brings cold and storms into the eastern United States and into Europe -- is making a comeback. The consensus seems to be a wintry pattern will return around Jan. 10, and the eastern United States will face another extended period of nasty conditions.

So whatever happened to La Nina?

I asked two experts, and they agree ... the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) have been far too strong for La Nina. The pattern of the jet stream, sending cold air and storms on a roller-coaster ride southward from the Arctic into the U.S. and Europe, has cut off the predicted west-to-east pattern of milder conditions that we'd expected.

It shows, once again, that long-range predictions are tricky. When we're told to expect an El Nino (cold and chilly) or La Nina (mild and dry) winter, those Pacific Ocean conditions are only part of the story. The NAO and AO have a big role in what happens, along with some other factors.

To be fair, some of the long-range winter forecasts (I'll give Accu-Weather's Joe Bastardi credit for this) said there'd be occasional episodes of arctic blasts intruding on La Nina. But December was a lot more than an "episode." It was nearly the whole month.

So if all this is true, we'll get about 10 to 12 days of seasonal weather here in the Carolinas before we head back into the deep freeze.

One cautionary note ... forecasters are only 1 for 2 on recent predictions of cold weather. They were 100 percent correct about December, but some meteorologists had called for a cold weather outbreak in late October. That didn't happen.

However, with solar energy very low now, a return to cold weather doesn't seem too far-fetched.

Monday, December 27, 2010

A white Christmas, or not?

After all the talk last week about the chances of Charlotte getting its first white Christmas since 1947, now we're left with a debate.

Was it a white Christmas, or not?

Rain changed to snow about 7 p.m., and reliable sources tell me the ground was coated with snow by midnight. I was dreaming of sugar plums by that time.

Snowfall was even heavier to the north and of Charlotte, where there were several inches on the ground by midnight.

However, the real answer isn't quite to easy.

"Officially, it will not go into the record books as a white Christmas," says John Tomko, a meteorologist at the National Weather Service office in Greer, S.C. Tomko is responsible for keep weather data for the western Carolinas, and he says that according to the rules, Christmas 2010 was not white.

"The snow depth for the day is measured at 12 UTZ (12 noon Universal time, or 7 a.m. in Charlotte," Tomko says.

At 7 a.m. Christmas Day, the sun was still shining through a layer of broken clouds. The precipitation didn't arrive until at least eight hours later.

So in the record books, Charlotte's last white Christmas was in 1947. Who knows how long it will be before we have another opportunity?

Tomko acknowledges that some people don't care about the weather rulebook.

"I'm sure a lot of people had a dusting of snow in the evening," he says. "To them, it was a white Christmas. And I'm not going to argue with them. They'll probably remember it as a white Christmas.

"But according to the rules, it was not."

Tomko says Charlotte had 2 inches on the ground at 7 a.m. Sunday, the official measuring time for Dec. 26. But between 3 and 4 inches actually fell from the storm.

Friday, December 24, 2010

Snow drama ... behind the scenes

If you've followed the news stories I've written, and those written on the TV websites in Charlotte, you can tell that there's been an awful lot of back-and-forth adjustments the past few days regarding the Christmas storm system.

All along, we kept saying it would be the final 24 hours before we really had a good idea where it would snow, and how much would fall.

The latest run of the Global (GFS) model has taken us back into Snow Central again.

It shows a more potent storm system, with a lot more precipitation than the computer had indicated in its runs Thursday night and early Friday morning. And while there are still question marks about the temperature -- it'll be close to freezing Saturday during much of the precipitation -- the chances for a significant snowfall are climbing again.

I just saw a GFS panel that shows potential snowfall accumulations by the end of the weekend, and it shows a solid 2-4 inches in our area, with 5 inches or more in a swath along the U.S. 1 corridor -- Raleigh-Durham, Sanford and maybe even Fayetteville.

That panel shows an inch of snow as far down as Atlanta, in fact.

Predicting this storm has been a real pain.

Initially, the European model predicted a monster storm developing off the Carolinas coast. The GFS showed a moisture-weak system moving across the Gulf of Mexico, keeping its moisture far south of Charlotte. Then the European began weakening the system, and it looked like the chances of a white Christmas in Charlotte were dimming.

Now, at noon on Christmas Eve, there's this latest GFS run.

Stay tuned ... this could be interesting.

Wednesday, December 22, 2010

Latest forecasts ... whiter than ever

The latest computer model runs -- from midday -- are in, and they continue to paint a snowy picture in the Charlotte area and elsewhere across the Carolinas for the second half of Christmas Day.

The newest trend is for a low pressure system to strengthen very rapidly off the Carolinas coast and deliver a blizzard from Virginia northward.

Under this scenario, we wouldn't escape in the Charlotte area.

Before we go any farther, let's introduce a new wrinkle -- the timing of the storm. If it should arrive fairly late Saturday, temperatures might have climbed above freezing. That means the first few hours of precipitation could fall as rain, before a changeover to snow in the evening. And that would limit the accumulations somewhat.

The Global (GFS) and Canadian computer models' latest runs continue to show limited precipitation for Charlotte, which means light snow accumulations (a few inches, at most).

The latest run of the European computer model shows up to a foot of snow falling in Charlotte and even more in the Raleigh-Durham area. North of there, they could be measuring snow in feet, and they'd have howling winds of 40 mph and stronger to deal with.

All of this is 72 or more hours away, and you know how this winter forecasting business goes. A lot can change between now and then.

But the computer models, which are based on the science of meteorology (including weather history), seem to paint a picture of a major snowstorm affecting the eastern United States.

Let me thank my brother Michael, who's much more the scientist than I am, for his help in this. But here's a very preliminary look at what could happen this weekend:

In Charlotte: Christmas Eve would be dry, and it would still be dry when you awake Christmas morning. Snow would move into the area sometime between midday and mid-afternoon, and it would continue into Sunday morning. Accumulations could be heavy.

In Raleigh: Precipitation might begin as rain early Saturday afternoon, but it would change quickly to snow. The latest European model shows more than a foot of snow in the Triangle area. Much of eastern North Carolina would be affected.

Columbia: It'll be a rain-snow mix, but temperatures would be cold enough Saturday night and early Sunday for some snow accumulations.

Myrtle Beach: The picture is that of a rainstorm, with temperatures near freezing and strong winds.

Atlanta: Some snow, but it's too early to tell how much might accumulate. The rain-snow line could be close to the Atlanta area.

More to come. Stay tuned.

Snow? Yes ... but how much?

All right -- let's all join Bing Crosby and Danny Kaye, and sing along ...

I'm dreaming of a white Christmas.......

The National Weather Service's computer models -- all three of them -- are singing the song today. There is now unanimous agreement among the computers, and most meteorologists, that snow is coming to the Charlotte area on Christmas weekend.

The big questions:

1. Will it actually fall on Christmas Day, or will it arrive early Dec. 26?

2. How much?

Yesterday, the GFS (Global) computer model was predicting the major storm system in the West would move across the Charlotte area, bringing us rain. The other two models forecast a track along the Gulf coast, which would mean snow.

But the GFS model is singing the "White Christmas" song today, so let's move on to the other questions.

Forecasters say one of the computer models, the European, is leaning toward a slower-moving storm, which might not bring snow to the Charlotte area until late Saturday night or early Sunday. The Global model predicts snow will start Christmas morning, while the third model forecasts snow in the afternoon.

Why is the arrival time important?

For historic reasons, I guess. The last major snowfall in Charlotte on Christmas Day was in 1947, when 5 inches fell. There has been a trace of snow -- which means flurries or sleet pellets -- a few times since then.

As for the amount, meteorologist Pat Moore of the National Weather Service was brave enough to make a rough and very early guess -- 3 to 5 inches. However, Moore notes, if the slower European model is correct, snowfall totals could be doubled.

Naturally, this is exciting news for anyone who wants a white Christmas and loves snow.

But this storm will have a nasty impact for travelers. The snow will cover Arkansas and Tennessee on Christmas Eve, and when the storm departs the Carolinas on Sunday and moves north, it will spread heavy snow up the East Coast.

If you're planning to travel back toward Charlotte from New York, New Jersey, Pennsylvania, Maryland or Virginia on Sunday or Monday, you'd better allow yourself an extra day -- just in case.

"If this forecast works out, it could be an event that will be talked about the rest of our lives," the Weather Service's Moore says.

Tuesday, December 21, 2010

Christmas snow? Let's be cautious

Yes, the National Weather Service forecast is mentioning that word for Christmas Day.

But will it really snow in Charlotte for the holiday? History indicates we should be very cautious before planning a sleigh ride down Providence Road on Saturday evening.

The computer models used for weather forecasting agree that a strong storm system hammering California today will cross the Rockies, dive toward the Gulf Coast, and then move up the East Coast by Saturday and Sunday.

There seems little argument that parts of the East Coast could get a major winter storm late Saturday and into Sunday. If you're planning a Christmas trip to Washington, Baltimore, Philadelphia, New York or even farther north, then snow is a good chance.

Roads could be in bad shape later Saturday and Sunday, and the flight schedules could be a mess both days.

Depending on the track of the storm, inland parts of the Middle Atlantic and New England could get hammered. If the storm hugs the coast, then heavy snow will fall in places like Frederick and Hagerstown in Maryland; the Harrisburg and Scranton-Wilkes Barre areas of Pennsylvania; and upstate New York.

But what about the Carolinas? Well, here is your lineup of computer model predictions. Take your choice:

GEM: This is the snow-lovers' computer model. It predicts the storm system will cross northern Florida, reach the coast near Charleston, and curve north. That would mean a significant snowstorm for the Charlotte region, starting as rain late Friday night but changing to snow by Christmas morning. Under this scenario, the snow-rain dividing line could be well into South Carolina.

ECMWF (European): This computer model takes the storm along the Gulf Coast. That would mean temperatures in Charlotte will be cold enough for snow, but most of the precipitation would stay to the south. We might see snow, but not enough for any significant accumulations.

GFS: Meet the Grinch, oh you fans of a white Christmas. The GFS predicts the storm's center will cross the Charlotte area. That means rain, except for snow in the mountains. In fact, the rain could be rather heavy, in this scenario.

Doug Outlaw, of the National Weather Service office in Greer, S.C., says forecasters there are leaning toward the GEM forecast, for snow in the Charlotte area. For now, they believe the best chance of accumulating snow would be northwest of Interstate 85.

The forecasters at private companies like Accu-Weather and the Weather Channel are following the GFS. They predict rain for Charlotte.

"It's simply too early to know for sure," Outlaw said. "In a day or two, I think we'll start seeing the models come more in line with one another. That's when we'll get a better idea of what actually will happen."

Either way, Outlaw says, the storm will be a newsmaker as it rolls up the East Coast after leaving the Carolinas.

"Some places up there will certainly get their white Christmas," he said.

In case you're wondering, the last serious white Christmas in Charlotte was in 1947, which was so long ago that even I hadn't been born yet. That year, 5.8 inches of snow fell in the Queen City. There also was a 4-inch snowfall in 1880 and 0.2 inches in 1909.

A trace -- we're talking about brief flurries -- was recorded several times, including 2007, 1998 and 1993.

Last year produced a major rainstorm in Charlotte, but there was a devastating ice storm in the N.C. mountains. Up to a half-inch of ice accumulated in Watauga and neighboring counties, knocking out power to tens of thousands of customers for several days.

Monday, December 13, 2010

Freezing rain might be on horizon

The worst thing about the latest outbreak of cold weather (I say "worst" for those who don't like these conditions) is that it apparently won't leave soon.

And this time, it could come with some added complications, in the form of frozen precipitation for the Charlotte area.

The immediate concern in the Charlotte area is cold weather and strong winds, but meteorologists are watching a system which could cross the region late Wednesday or Thursday. The last few times a storm system moved into our area, temperatures moderated above freezing, and the precipitation fell as rain.

This time, it will be a closer call.

Temperatures are expected to be below freezing when the precipitation arrives Wednesday night or early Thursday morning. For now, forecasters think this will be a weak low pressure system, which means light precipitation.

But it likely will start as snow or sleet, then change over to freezing rain for a while before turning to rain later Thursday morning. National Weather Service meteorologists have been referring to the system as a "nuisance" storm, which means sleet and icing problems are not expected to be big.

Thursday's system could be more of a headache along the Interstate 40 corridor (that means you, Hickory and Statesville!), where temperatures might not get above freezing until later in the day. That would give more time for ice and sleet to accumulate.

Yet another system could develop Sunday. Brad Panovich, chief meteorologist at WCNC-TV, the Observer's news partner, says that storm could produce a swath of snow as it moves from the Gulf of Mexico to the East Coast. Areas to the northwest of the low pressure system's center would get the snow.

It's far too early to get a good reading on the track of the low, but stay tuned.

Computer models paint a cold picture for the Charlotte area until Christmas. Some forecasts indicate we won't see 50 degrees for the next 12 to 14 day, and there could be another freezing rain threat around Christmas Eve.

If you're one of those people who's been yelling for cold weather, so you'd get in the holiday spirit, I hope you're happy.

Tuesday, December 7, 2010

Weekend storm, then more cold

I've heard people focus on the forecast for warmer temperatures this weekend, but they might be missing the bigger story of what's ahead for the Charlotte region.

Yes, it looks as if we'll get a three-day moderating trend from the brutal cold that has covered the Carolinas this week. High temperatures Friday will climb into the upper 40s, and with 55-degree readings Saturday and Sunday, it'll seem almost balmy.

But a big storm system will be crossing the East this weekend, and another surge of very cold air will follow the storm. It looks as if next week's temperatures will be every bit as cold as this week.

This week's weather is the coldest air in the Charlotte area since an arctic outbreak that stretched from mid January to early February in 2009. It dropped to 9 degrees on Jan. 17 that year, and there were several morning lows in the sub-20-degree range.

The big storm system this weekend appears as if it will follow a track north of Charlotte. That will keep any chance of snow to our north, but it means places in the Ohio Valley, the Middle Atlantic, and the Northeast could get walloped by heavy snow and wind. We'll get a better idea about that in the next few days.

Here in the Carolinas, heavy rain could fall, especially late Saturday and early Sunday. Once again ... we'll have a better idea on the timing and amount of precipitation in a few days.

Then behind the system, cold air will pour in again. High temperatures next Monday will remain in the 30s, and more of the same seems likely for next Tuesday.

No let-up in the cold pattern can be seen for the next two weeks, actually.

Those Big Winter Storms: A little more than a week ago, I wrote about computer-generated forecasts (from the GFS model) that indicated a chance of a major winter storm in the Carolinas for Dec. 8 and then again around Dec. 13.

As I wrote at the time, the long-range computer models are notoriously unreliable, and that is being borne out. Tomorrow is Dec. 8, and it'll be clear but very cold. The Dec. 13 storm (that's next Monday) seems headed for our area a day or two early -- as a rain-maker, not a producer of freezing rain or snow.

I've fallen victim to looking at long-range forecasts myself, and this is another reminder that we can't get too excited about what a computer says will happen two weeks down the road.

Saturday, December 4, 2010

Is Charlotte too cold for ACC title game, bowl game?

Well, the first ACC football championship game in Charlotte didn't exactly get Chamber of Commerce weather.

Sleet pellets and even a few snow flurries fell around daybreak and again Saturday afternoon in the Charlotte area, and while the precipitation likely will be cold rain -- not the frozen stuff -- for tonight's kickoff, it certainly won't be attractive weather.

I realize some people believe football should be played in Green Bay-esque weather, but I suspect the majority would prefer temperatures at least in the 50s for a championship game, and for the bowl game played annually in Charlotte.

All this begs the question (which has been raised many times before): Is Charlotte too far north for an outdoor football championship game? And is it too far north for a bowl game?

We'll dismiss the bowl game question immediately.

When the NCAA can sanction bowl games in New York City (the new Pinstripe Bowl) and Washington (the EagleBank Bowl) -- and, for that matter, the bowl game in Boise -- it's silly to question holding such a game in Charlotte.

Our weather is roughly similar to several other places that host bowl games, including Nashville and Memphis. And besides, the worst snow I ever saw at a bowl game happened once in the early 1980s, when North Carolina played Texas in the Sun Bowl in El Paso. I think it was in 1982. It was a whiteout.

But the ACC title game is another matter, because it was played the first five years at Florida sites, where sleet and snow almost certainly won't be a problem.

I went back and checked Charlotte's weather for the last seven years on the first Saturday in December, and I found -- perhaps not surprisingly -- that it's wildly inconsistent. The evidence:

2009 (Dec. 5): High of 47, low of 28, with .05 of an inch of rain. That's pretty crummy weather.

2008 (Dec. 6): 42 and 31 degrees, with a trace of rain. Once again, bad weather.

2007 (Dec. 1): 62 and 47 degrees. Fantastic!

2006 (Dec. 2): 59 and 36 degrees. Once again, fantastic.

2005 (Dec. 3): 50 and 27 degrees, with .05 of an inch of rain. Mediocre, but good enough.

2004 (Dec. 4): 35 and 33 degrees, with .21 of an inch of precipitation, some of it as freezing rain. Uhhh ... I don't think so!

2003 (Dec. 6): 82 and 66 degrees. That set a record for the latest 80-degree day in Charlotte history. Obviously, few people would have complained.

So over the past seven years, the weather was mediocre or better four times, and not good on the other three years.

Supporters of the effort to bring the ACC championship game to Charlotte note that the average temperature in Jacksonville, site of several of the league's title games, is only a few degrees warmer than here. That's correct, and I recall bad weather in Florida at least once.

The average high and temperatures at this time of year in Charlotte are 57 and 37, which is fine for football.

So let's hope the weather is better next year, and chances are it will be. Besides, as long as fans show up, the ACC will be happy, no matter what the weather.

Thursday, December 2, 2010

That 4-letter word ... snow

You can kiss the mild weather good-bye for a while, as a real outbreak of winter is taking shape over the Carolinas and much of the eastern United States.

Among the highlights (or lowlights, if you're not a winter weather fan):

1. A chance of snow mixing with rain for a few hours after midnight Saturday in the Charlotte area.

2. Very cold temperatures next week in the region, with daytime highs struggling to get out of the low 40s some days.

3. The lurking possibility of a winter storm sometime around Dec. 13.

The weather pattern in the Northern Hemisphere is undergoing a major shift, because strong high pressure has established itself over Greenland. That is blocking the typical west-to-east movement of weather systems, and instead, we're getting exaggerated dips in the jet stream.

One of those dips is over the eastern United States. Another is over the British Isles. Heavy snow has been falling the past few days over parts of England and Scotland, with up to 10 inches accumulating in some London suburbs. It's unheard-of weather for this time of year in that part of the world.

Closer to home, the cold weather we've experienced the past 24 hours is merely a tuneup for what's ahead.

It dropped to 23 degrees Thursday morning at Charlotte/Douglas International Airport, the coldest since a 22-degree reading March 7. But it could fall to near 20 degrees next week.

A low pressure system will dive southward Saturday, crossing North Carolina and bringing rain and snow showers. Meteorologists -- the National Weather Service, The Weather Channel and Accu-Weather -- agree that the precipitation will fall as rain over South Carolina and snow in the N.C. mountains.

It looks like rain showers will move into the Charlotte area Saturday evening, and they could mix with snow for a few hours early Sunday. Some forecasters think places like Winston-Salem, Greensboro and Raleigh could get a coating of snow from this system.

If you're going to the ACC championship football game Saturday evening, look for cloudy skies, temperatures in the low 40s, and a small chance of a rain shower.

The weekend low will usher in the really cold air. A northwest flow will establish itself, and while that type of pattern produces dry weather in the Charlotte region, it will be very, very chilly.

You can expect daytime highs in the low 40s and morning lows in the lower 20s for the first three or four days next week -- and that's despite full sunshine during the daytime hours.

The computer models continue to indicate the chance of a big winter storm around Dec. 13 (a week from Monday). I mentioned this earlier in the week, and the long-range forecasts continue to show such a system developing. The computer models haven't changed much for a couple days, putting Charlotte in an area that could get cold rain or frozen precipitation.

By the way ... the other computer model-predicted wintry storm was supposed to have developed Dec. 8. That's Wednesday, and it looks as if we'll have absolutely dry conditions, although it will be plenty cold enough for snow.

I mention that busted Dec. 8 forecast to remind all of us that Dec. 13 could wind up being dry, too.

Bastardi's White Christmas. I know some of you weather geeks are not big fans of Accu-Weather's Joe Bastardi, who specializes in long-range forecasts. But it's interesting to note that Bastardi is predicting that about half the country will have a white Christmas. That compares, he says, to an average of 25 to 30 percent of the United States having snow on Dec. 25.

His map of snow on Christmas includes parts of North Carolina, with the line drawn quite close to the Interstate 85 corridor.

I'll go with the averages. Snowfall is recorded in Charlotte, on average, about once every 25 or 30 years.