Wednesday, November 30, 2011

'Busy' hurricane season ends

Today marks the end of the 2011 hurricane season in the Atlantic basin, although the season really began and ended in the last week of August, when Hurricane Irene bulled up the East Coast.

The National Hurricane Center says there were 19 named storms, tied for the third-highest total since record-keeping began in 1851. The NHC also says that total is well above the average of 11 and continues a trend in recent years of above-average storm activity in the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico.

However .........

Unless you are a fish, it didn't seem like a big season.

There were seven hurricanes and three major hurricanes. Those numbers are only one above the seasonal averages. More important, only one hurricane -- Irene -- made landfall in the United States.

And no major hurricane (Category 3, 4 or 5 status) hit the United States this year. That makes it the sixth straight season without landfall by a major 'cane. The last big storm to hit the mainland was Wilma, late in the 2005 season. That year also included Katrina and Rita.

Irene did considerable damage to the eastern edge of North Carolina, and also in the Mid-Atlantic and New England states. It was the first hurricane to make landfall in the United States since Ike in 2008.

"Irene broke the 'hurricane amnesia' that can develop when so much time lapses between landfalling storms," said Jack Hayes, director of the National Weather Service.

Hayes makes a good point in noting that Hurricane Irene served as a reminder that tropical systems can strike anywhere -- in this case, Pennsylvania, New York and Connecticut took a rare hit.

Irene highlighted both the good and bad of hurricane forecasting. The National Hurricane Center nailed the storm's path, several days in advance. But the intensity forecast was off, as Irene weakened before making landfall.

For most of the hurricane-prone areas of the Southeast, 2011 was a quiet year, a lot like 2009 and 2010.

The strong ridge of high pressure over Texas prevented tropical systems from affecting that part of the country. That prevented massive oil and gas price increases that result from a hurricane crossing the Gulf of Mexico's petroleum beds, but it also kept the Lone Star State deeply mired in an extremely damaging drought.

A persistent trough of low pressure off the East Coast kept storms out at sea, much as in 2010.

Look for the 2012 forecasts to start appearing in a few months.

Monday, November 28, 2011

Where is winter?

I'm starting to hear a few complaints from the winter-lovers, especially the people who are anxious to start wearing their heavier clothes and who think it's impossible to talk about Christmas when it's 70 degrees out there.

I'd be happy to have 80 degrees on Christmas, but I realize my opinion is in the minority.

So where is the chilly weather?

First, it's not unusual to have 70-degree-plus conditions in late November. The same thing happened last year, and we had a string of near-80-degree days a few years ago around the beginning of December.

Last year, the warm weather ended abruptly with a cold front that arrived late Dec. 1. From Dec. 2 until Valentine's Day, with a few exceptions, conditions in the Charlotte region were quite cold.

Almost like clockwork, much cooler air is on the way. It will arrive early Tuesday, and our high temperatures for a few days will only be in the 50s. It won't be quite as brutal a change as last year, when daytime highs were held to the upper 30s and 40s for a couple weeks. But it is a change worth noting.

Yet I don't see a complete change to below-average temperatures, through the middle of December. The Climate Prediction Center, computer models, and private meteorological services seem to indicate that, on average, temperatures will be about average. A few cold snaps, lasting two or three days, are likely.

But an abrupt change to mid-winter conditions does not appear in the offing for a while.

Tuesday, November 22, 2011

Region's worst bad-weather roads

Between now and the start of 2012, many of us in the Carolinas will hit the road for a visit with friends and family members.

This is a tricky time of year to travel.

Storm systems occasionally move across the South. They can produce a drenching, soaking rain that last for many hours, or sometimes they trigger rounds of showers and even severe thunderstorms (such as last week).

Dense fog can be a problem.

And as we progress deeper into the holiday season, the possibility of snow and ice rears its ugly head.

Based on conversations with a number of other people who travel a lot during the holidays, here is a list of sections of major highways that are the worst to travel at this time of year. I'm sure you'll have others to add, but this list of interstate roadways (and we're talking about segments of the roads, not the entire route) can be a real pain in the neck:

1. Interstate 77 at the N.C.-Virginia line: This is more than a pain in the neck. It's downright scary at times. The biggest problem is fog, but high winds and ice or snow also can provide the danger.

It's a stretch of about 10 miles that climbs more than 2,000 feet. Once, about 30 years ago, I was in a northbound car that struck a large rock. The rock had tumbled into the road during heavy rain, and we didn't see it until the last minute because of fog. It damaged our steering system. But there have been fatal crashes on this part of the road during fog events.

2. Interstate 26, in Henderson County: Once again, an altitude climb creates conditions that can lead to dense fog or icing. Four people died in a multi-vehicle wreck in October 2010 in this area, and I-26 is closed frequently during winter storms in Henderson County because of ice and snow. A large number of trucks use this road, and the combination of trucks, cars and fog sometimes is not good.

3. Interstate 40, at Black Mountain: A familiar theme here. There's a 6% elevation grade over a five-mile stretch of roadway, and it's been the scene of some nasty wrecks in the past. If you're eastbound (going downhill), test your brakes before you start. Because of the altitude climb, wet roads at the bottom of the climb can be icy at the top.

4. West Virginia Turnpike, Bluefield-Beckley portion: There's an altitude climb around mile marker 25, but the bigger problem here is icing in the winter. West Virginia road crews do a good job of staying on top of conditions, but if you're headed north and a cold rain or even snow is falling in Bluefield, be prepared for worse conditions ahead.

And consider making a rest stop at the big turnpike center near Beckley, because the portion of the road from there to Charleston is twisting and yet another headache.

5. Interstate 85, Greensboro to Durham: There are no altitude issues here -- just tons of traffic. And when heavy rain is falling, be careful. A number of times in recent years, traffic during the Thanksgiving or Christmas holiday weekends has been brought to a standstill by a multi-vehicle collision.

6. Interstate 81, various areas between Roanoke and Harrisonburg: One problem is I-81 has only two lanes in both directions, except for a few places near larger cities. The second problem is that half the population of the United States seems to travel this interstate highway on holidays or summer weekends.

Oh, yeah -- and some of the people who drive on I-81 seem a bit reckless. Add bad winter weather to all this, and you have the makings of a travel nightmare. It happens from time to time.

In all these cases, the various states' transportation departments have toll-free information lines, Facebook and Twitter accounts, and other ways of informing the public about wrecks and bad weather.

Before leaving home, make sure you have a way of being alerted in advance.

Tuesday, November 15, 2011

Autumn see-saw continues

Having a difficult time figuring out whether to pack the warm-weather clothes away ... or deciding exactly what to wear each day?

Our weather pattern is a see-saw affair, switching from late-autumn to early-autumn conditions every few days. And we're about to go into another dip -- followed, naturally, but another climb.

This pattern is something you'd expect at the time of year when things are about to change in a big way.

Autumn will give way to winter soon, and what we're seeing now is a sort of back-and-forth of seasons. We have a few mild days, and then the temperature tumbles for another two or three days.

I got an email from Mecklenburg County commissioner Bill James, who noted that the current pattern is a working definition of Indian summer, and he's right. The traditional definition of "Indian summer" is a period of mild weather after a hard freeze. We've had freezing weather twice in recent weeks, and milder periods followed those freezes.

Temperatures today are expected to reach the middle 70s, with lower 70s again Wednesday as a cold front approaches the area. Then we fall, with highs in the lower 60s Thursday and the lower 50s Friday.

Then it's back up again, with 60 degrees Saturday, the upper 60s Sunday, and then the lower 70s Monday.

Guess what follows that?

How about cold weather for Thanksgiving (I saw one forecast of rain and a high of 42 degrees), followed by much warmer conditions on Thanksgiving weekend ... followed by (sigh!) a return to cold in the week after Thanksgiving.

Some meteorologists have predicted this back-and-forth pattern is what we can expect for much of the winter. Typically, though, we settle into more prolonged periods of cold and then mild temperatures.

Stay tuned.

Monday, November 14, 2011

Week of weather changes ahead

Don't look for consistent weather this week.

We'll have two very different air masses, starting with very mild conditions early in the week but ending with below-average temperatures.

In between, there will be a rainy transition day.

Most people will like the way the week starts.

Mild air will be in control today and Tuesday, with a light southwest breeze and temperatures reaching 70 degrees today. Highs on Tuesday will be in the lower 70s, or nearly 10 degrees above average.

Changes will begin to take place Wednesday, as a cold front approaches. Showers and possible a thundershower are expected to move into the area, although it appears as if the precipitation might not arrive until mid to late afternoon. It will be mild once again, with high temperatures in the low to mid 70s.

Much cooler conditions will spread into the region Thursday, with highs probably only reaching the mid 50s -- despite sunny skies. It might be even cooler Friday, with sunshine and highs only in the lower 50s.

A warm-up will begin Saturday, and at this point, the coming weekend promises to be very nice for the middle to end of November. High temperatures by Sunday will be back above average, possibly in the mid to upper 60s.

Monday, November 7, 2011

Imagine a hurricane with snow!

Alaska has some of the most amazing weather in the world, although I much prefer to marvel at it from afar.

It's a place where temperatures reach 90 degrees in the summer and 45 below zero a few months later.

And some of the storm systems that affect the state are incredible. Case in point: the storm that is expected to pound the western part of Alaska on Tuesday.

If you watched the Discovery Channel's "Deadliest Catch," you know what I mean. Storms repeatedly batter the Bering Sea and the far northern Pacific Ocean throughout the year, but especially from autumn into winter. Those lobster boat crews battle hurricane-force winds and mountainous seas.

I notice that the Weather Channel is launching a somewhat-similar series Wednesday night, with its "Coast Guard Alaska."

A Hurricane Force Wind Warning is in effect for the western coast of the state for Tuesday and Tuesday night, and where the storm is predicted to make landfall -- around Nome -- there's also a blizzard warning.

The low pressure system is expected to have a central pressure of 944 mb when it makes landfall. That's the equivalent of a Category 3 hurricane.

Winds in the western Aleutians, from the islands of Attu to Kiska, are forecast to be 75 to 80 mph Tuesday, with waves of 30 feet. In Nome, the forest is for 4 to 8 inches of snow and winds of 60 mph. Temperatures will be in the 20s while all this is happening.

The forecast for the town of Gambell -- on St. Lawrence Island, off the Alaskan west coast -- is for 75 mph winds and a mix of snow, rain and fog, with temperatures around 30 degrees. How can you have fog with winds of 75 mph?

The weather here in the Carolinas should be very quiet this week. I prefer "quiet" to 75 mph winds, snow and fog.

Friday, November 4, 2011

How good are our winter forecasts?

I've written several stories, and you've undoubtedly seen several predictions about winter 2011-2012.

It always makes great conversation, and meteorologists' ability to predict an upcoming season has improved mightily in recent years.

But will we ever be able to really get the winter forecast right?

It wasn't long ago that the Farmers' Almanac, the woolly worm and the groundhog were all we had to forecast winter. Then along came vast improvements in computer modeling and scientists' understanding of the various factors that create weather, and that gave winter forecasts a bit more clout.

Still, there are some obstacles.

Last October and November, all the talk was about La Nina, and what it would mean for winter in the South. The standard thinking is that La Nina means dry and mild winters in the South.

Lo and behold, arctic air blasted into the South on Dec. 2 last year, and for 11 weeks, the eastern two-thirds of the United States shivered. Snow fell several times in the South. Charlotte got its first Christmas snowfall in a half-century, and December 2010 was among the coldest months in recent years.

Some meteorologists had warned us that there were other factors in winter weather -- specifically, the Arctic Oscillation (AO) or North Atlantic Oscillation (NAO). When high pressure builds near the arctic, low pressure tends to form at middle latitudes (i.e., the United States). That sends arctic air blasting into the United States, and it also provides a nice little track for storms to form.

It's why there was a series of winter storms last year from Texas to the Southeast coast, and then up the East Coast into New England.

It was what meteorologists call a Negative NAO.

Around Valentine's Day, the Negative flow went Positive, and La Nina took over. The weather got mild, and in late winter and early spring, the track of storms went across the South. That led to the series of tornado outbreaks that killed hundreds.

The question is: Can we predict a Negative NAO or AO?

"Right now, it's really not something we can forecast more than about a week in advance," said Mike Halpert, deputy director of the Climate Prediction Center for NOAA since 2007. "It's the fly in the ointment for our winter weather forecast."

Halpert said that if scientists knew the NAO would be neutral or positive, then they'd forecast a mild, dry winter for the Southeast, due to La Nina. Instead, the prediction is for "an equal chance" or above-average or below-average temperatures.

As you might expect, scientists are working hard to improve their ability to forecast the Arctic and North Atlantic oscillations. There are theories, Halpert says. One links the amount of snow in Siberia in October and November. More snow means colder air and higher pressure near the Arctic -- hence, a Negative AO.

Halpert says another theory links the oscillation to the amount of sea ice or to sea water temperatures in northern latitudes.

"We're looking at the research," he says. "This is an area of study for us."

Some meteorologists, like Brad Panovich at WCNC, the Observer's news partner, have predicted this winter will have a similar pattern to last year -- a very chilly start, especially in December and early January. Then the indication is for a milder trend later in the winter, followed by the possibility of another bad tornado season in early 2012.

This AO and NAO situation is a reminder that meteorology is a science, but one in which there are still many questions without answers.

Thursday, November 3, 2011

Wet night coming, but weekend should be OK

A rather vigorous low pressure system is expected to swing across the Carolinas later tonight and early Friday, and it will mean a rainy overnight period.

The rain might extend into the early part of Friday morning's commute.

But if your weekend plans include some outdoor activities -- football, for example -- the rain should be long-gone before the first kickoff. It will be chilly, however, and it could be breezy for the high school games Friday night.

The low pressure system predicted to move eastward -- somewhere near the N.C.-S.C. line -- overnight is rather interesting.

The computer models hint that moist air will surge into the area near the center of the low overnight. Coupled with rising air near the low, that could trigger a few overnight thunderstorms. At this time of year, overnight storms that form near strong low pressure systems need to be watched.

Either way, a good drenching is likely tonight, and most areas will get a half-inch or more.

The rain should end by mid-morning Friday, and a few peeks of sunshine are possible before sunset.

Don't look for temperatures to climb much Friday, after overnight lows in the lower 50s. Highs probably won't get much above the mid 50s.

Saturday and Sunday look to be mostly clear and cool, with daytime highs in the upper 50s and lows in the mid 30s.