La Nina's gone. Now what?

NOAA's scientists made it official this week, burying the La Nina conditions that have been in control for about two years.

Meteorologists say water temperatures in the eastern Pacific basin have warmed, and the La Nina has become what is called Enso-Neutral. What that means is we're in between El Nino and La Nina.

La Nina was one of the factors in our incredibly mild winter, and it played a role in the very mild late February and March in 2011. It also was considered a factor in the above-average number of hurricanes in the Atlantic and Caribbean last summer, although nearly all those storms never hit the United States.

So now what?

NOAA's forecast is for Neutral conditions to continued through September, although meteorologists say a few of the computer models predict an El Nino could form by late summer.

And beyond that? The forecast is for an equal chance of Neutral or El Nino conditions for the end of the year, taking us through autumn and into next winter.  La Nina conditions are not expected to develop again in the near future.

So here's what that means:

HURRICANE SEASON ... Just about all scientists expect fewer tropical storms and hurricanes in 2012 than in 2011. In La Nina seasons, the low-level winds from the Pacific to the Atlantic are weak. That allows thunderstorm clusters to develop in the Atlantic and Caribbean, which helps tropical systems develop.

There are plenty of other factors at work, such as Atlantic Ocean surface water temperatures. But La Nina is one player involved.

This season, those winds across the United States won't be as weak. That means conditions won't be quite as ripe for tropical storms and hurricanes to form.

Of course, only one storm -- Hurricane Irene -- affected the United States last year, even though there were an above-average number of systems.  If there are only two hurricanes in all of 2012, and both of them hit the U.S. mainland, we'll consider 2012 worse than 2011.

NEXT WINTER ... In La Nina winters, conditions in the South tend to be warm and dry. That's pretty much what happened this past winter.  Once again, however, there are other factors involved.

La Nina was in place for the winter of 2010-11, but there also was a Greenland block -- strong high pressure over Greenland, sending cold air funneling southward into the eastern United States. The result: a very cold December and January, and then a warm mid and late February when La Nina took control from the Greenland block.

But with no La Nina next winter, it's safe to say we won't have it as mild as in the winter of 2011-12. Then again, few winters are as mild as 2011-12.  You can pretty much count on using the heat at home a lot more, and we'll probably be at least looking at the chances of snow and ice more than we did last winter.  

Same old story ... where's the rain?

It seems like we can't go more than five or six months around the Carolinas without having to talk about drought, but it's back in the conversation again.

Conditions are nowhere near as bad as a few years ago, when much of the Charlotte area was classified by NOAA as being in "exceptional drought," but the entire region has now moved into the "moderate drought" area -- the second-worst of five levels of dry soil conditions.

And there's isn't a lot of rain in sight.  In fact, we have only one really good shot at it in the next week, on Wednesday.

What happened Saturday is typical of how things unfold in drought conditions. Two separate systems could have brought thunderstorms to the Charlotte area, but the storms instead drifted over Winston-Salem and Greensboro and then into the Raleigh area. Granted, that kept the weather nice for the Wells Fargo Championship and other weekend plans, but we need the rain.

So far this year, precipitation is 5.22 inches below average at Charlotte/Douglas International Airport. To put that in perspective, we've received less than two-thirds of what we usually get.

A cold front is predicted to cross the region Wednesday, and computer models suggest there could be a fairly widespread outbreak of showers and thunderstorms. In fact, rainfall predictions are between a half-inch and an inch for Wednesday. Thunderstorms are also in the forecast for Tuesday, but those will probably not move out of the mountains.

After the frontal passage later Wednesday, we'll be under the control of a fairly strong high pressure system, and that means dry weather through Sunday. Temperatures will be a bit cooler than we've seen recently, but they'll be around seasonal averages, and at this time of year, seasonal averages are pretty nice (highs in the upper 70s, lows in the upper 50s).

A tricky Saturday forecast

Meteorologists are having a tough time getting a handle on what will happen Saturday afternoon and evening in the Charlotte area, and it has a little more importance than usual, with about 35,000 people outdoors at Quail Hollow Club for the Wells Fargo Championship.

The bottom line is that forecasters are expecting thunderstorms to develop at some point in the afternoon, but there are several moving pieces to the weather situation, and we could wind up with absolutely nothing happening.

One piece of the puzzle are the remnants of a thunderstorm cluster that moved into northwest North Carolina early Saturday from Kentucky and Tennessee. Those storms died out, but the outflow boundaries -- the unsettled air at the end of the storms -- has pushed into the Carolinas Piedmont. Those outflow boundaries often are a trigger for storms.

And that outflow boundary is expected to cross the Charlotte area early Saturday afternoon.

Another piece of the puzzle is a weak low pressure system, expected to move across the region a bit later in the afternoon. With an unstable atmosphere today, such a system could serve as the trigger for storms.

Meteorologists at the Storm Prediction Center in Norman, Okla., have part of the Charlotte area in the "Slight Risk" zone for severe thunderstorms today. That zone includes the immediate Charlotte area and points east and south. In other words, we're talking about Mecklenburg, Union, Stanly, Anson and Richmond counties of North Carolina, and all of South Carolina.

But nothing had developed, as of late Saturday morning, and it's possible the afternoon will remain  storm-less.

However, if you're at the Quail Hollow Club, or if you're planning any other kind of outdoor activity today, be forewarned ... the risk of strong thunderstorms is there.

Sunday, by the way, should be much calmer.

2 views of our summer forecast

The start of meteorological summer is still nearly a month away (June 1), but a lot of people already are talking about what type of summer we can expect in the Charlotte region.

Our unusually warm winter and very mild March stoked conversation that summer will be very hot. It's the old "If it's this hot in March, wait until summer" argument.

So I've taken a look at forecasts from NOAA's Climate Prediction Center and from Accu-Weather, and they seem to agree. Both are calling for warmer-than-average temperatures and a rather hazy prediction on precipitation. The CPC's rainfall forecast is for "an equal chance" of above-average, average or below-average precipitation. Accu-Weather, meanwhile, puts the Charlotte region at the southern edge of what it expects to be an area of wet weather with violent storm outbreaks.

Here are some highlights of the forecasts:

Warmth: There's pretty much a consensus on this. Meteorologists expect it to be warmer than usual across the region. Given the conditions we've had since winter, that's no surprise.

CPC rainfall forecast: That "equal chance" designation has been placed over most of the United States by NOAA meteorologists. They say it's difficult to predict rainfall, and it's especially tough this summer.

Accu-Weather's storm forecast: Meteorologists for the Pennsylvania-based company expect June and August to be the wettest months in our region. They also expect an active severe weather season from Indiana and Michigan southeast to Virginia and Maryland. That area includes the northern part of North Carolina (Greensboro and Winston-Salem, especially). Accu-Weather thinks that zone will separate warm conditions from cooler temperatures for a chunk of the summer.

Florida drought: Both NOAA and Accu-Weather expect rainfall to be rather plentiful this summer in the Sunshine State. That's good news for an area that is hard-hit by drought.

Where will it be dry?: The highest chances of hot and dry conditions appear to be in a band from southern Montana down to the Texas Panhandle. That includes much of Wyoming, Idaho, and Colorado, along with western South Dakota, Nebraska and Kansas.

Where's the cool weather?: New England and the West Coast.

How about hurricanes?: I plan to write about this subject next week, since several early-season forecasts are out. But meteorologists say they expect the atmospheric steering currents later this summer to be northward along the East Coast.  That could push tropical storms and hurricanes up the coast, similar to what happened last summer with Hurricane Irene.

It also means any system that develops in the eastern Gulf of Mexico could be steered up into Georgia and the Carolinas.

The Great April 15 Snowstorm

Charlotte's near-freezing temperatures Thursday morning seemed like quite a shock after weeks of 70s and 80s in March and early April, but it could have been worse.

In fact, it has been worse.

Mecklenburg County commissioner Bill James, who has a real interest and a good understanding of all things meteorological, passed along an item he found in a history book of Mecklenburg County. It was an excerpt about a big snowstorm on April 15, 1849.

I found several other accounts of the same storm, and interestingly, it appears to have developed in a year much like 2012. Temperatures had been unseasonably mild in March and April, but very cold air spilled into the South in the second week of April. It's not clear exactly what happened, but based on the results, we can guess.

There are published accounts of a big snowstorm that struck April 14 and 15 in parts of Louisiana, Florida, Georgia and the Carolinas. So we can assume that low pressure formed in the Gulf of Mexico and tracked across the Deep South, into the cold air that had pushed southward.

Mid-April snow in Florida? Just imagine that!

But the Carolinas took a hit.

The Mecklenburg County account, in the book that Bill James found, describes it this way:

"Everything in the way of vegetables was well advanced in the spring of 1849. The farmers were ready to give corn its first plowing when the snow came. It fell very gently, no crust on top.

"It was so piled up in the apple blossoms that they looked like snow balls. All vegetation was killed, no fruit that was in bloom escape being killed. The great crop of Mecklenburg blackberries alone escaped, of all our fruits.

"It was not until mid-summer that the trees made a respectable shade, or the cattle could make a tolerable living in the range at large."

That account says 5 inches of snow fell.

Meteorologist Don Sutherland, who has published a number of books and blogs, notes an account of the storm in the Camden (S.C.) Journal:

"It commenced with a slight fall early in the morning (April 15) and continued to increase in quantity until 2 or 3 o'clock in the afternoon, when it fell in large flakes, as in mid-winter ... The housetops were covered with snow, which had not melted on Monday morning (April 16). A mid-winter scene in early spring is a sight that we do not remember to have seen at any former period."

The S.C. Department of Natural Resources says 6 inches of snow was measured in that storm in Columbia.

So it appears the April 15, 1849, event was a storm that hit South Carolina and the southern edge of North Carolina.

The National Weather Service's records for Charlotte go back only to the winter of 1878-79. Since then, the record snow in April was 3.5 inches, on April 9, 1880.

Cool weather? We knew it was coming

Everyone has been saying it for the last few weeks, as we experienced day after day after day of temperatures far above seasonal averages.

"It'll cool down eventually. We'll get a cold snap in April."

And here it comes, although it's not clear exactly how cold it will get.

Canadian high pressure will take control of Charlotte-area weather Friday, and we'll notice the difference. Temperatures will struggle to get out of the 50s, unless enough sunshine breaks through the overcast Friday afternoon to allow a recovery into the low 60s.

Then we'll have morning lows in the upper 30s to near 40 degrees Saturday, and the low to mid 40s Easter Sunday. Afternoon temperatures won't be bad, with highs around 70 Saturday and in the mid 70s Sunday.

But there won't be a return to 80 degrees next week. Instead, another cold front is forecast to push across the area late Monday or Tuesday, holding afternoon highs to the 60s again for Tuesday and Wednesday.

National Weather Service meteorologists are closely watching for the possibility of frost on those chilly mornings. The unseasonably warm weather in March and early April caused strawberries to ripen early and fruit trees to blossom several weeks before they normally do. A freeze could be devastating to farmers.

The good news? At this point, it appears as if morning temperatures won't quite dip to freezing levels in areas where trees have blossomed.

Forecasters have predicted April will be warmer than average, overall, and that could happen, despite next week's cool down. Accu-Weather forecasts call for a return to the low 80s by late next weekend or early in the week of April 16.

March 2012 ... one for the record book

We've just completed the second-warmest March in Charlotte weather history, but that was nothing, compared to what happened over much of the continental United States during the month.

Dozens of cities, from Maine to Wyoming, broke records for the warmest March ever.

Some cities set daily high temperature records for a week in a row. In one Michigan city, a daily high temperature record was broken by 42 degrees -- and even the morning low was warmer than the previous record high for the date.

More of the same is expected in April, although the start of the month might be a bit cooler than we've seen in recent weeks.

In Charlotte, the average temperature -- calculated by averaging out the daily highs and lows at Charlotte/Douglas International Airport -- was 61.3 degrees. The only March that was warmer was in 1945, when the average was 61.6.

We had 10 days with highs of 80 degrees or warmer, which tied a record for the month.

But several Carolinas cities had the warmest March on record. And it was the same over much of the nation, except for the West Coast, the Southwest, Alaska and Hawaii.

Tampa set a record for the warmest March. So did Riverton, Wyo. So did Portland, Maine. For that matter, so did Winnipeg, in the Canadian prairie province of Manitoba. In fact, the average temperature in March for Winnipeg was 20 degrees warmer than usual.

Perhaps the most amazing event came March 21, when it climbed to 81 degrees in Marquette, Mich., up along Lake Superior on the U.S.-Canada border. The former record high for March 21 was 49 degrees. 49! And the high for the date was 81!

NOAA's forecast for April is a continuation of above-average temperatures in most of the East, although meteorologists also expect the month to be dry. March, while very warm, produced average rainfall totals in much of the Carolinas. The next week or two is expected to be cooler than average in the Carolinas, with a warm-up afterward.

Incidentally, before you get started on the Global Warming Chorus, be aware that March was very chilly on the other side of the globe. It was cold and wet over much of the United Kingdom and Europe.