Thursday, April 28, 2011

Sadly, storm specialists were correct again

If the Storm Prediction Center in Norman, Okla., ever puts your area at "high risk" of severe thunderstorms or tornadoes, go look for shelter.

The meteorologists in Norman once again nailed the forecast Wednesday, correctly predicting the massive outbreak of tornadoes that killed about 200 people. It's the second time this month that one of their rarely issued "high risk" forecasts panned out.

When severe weather is a possibility, the Storm Prediction Center classifies areas as being at "slight," "moderate" or "high" risk of storms. The "slight" risk classification is used most of the time. Occasionally -- maybe a few times a month -- they'll use the "moderate" tag.

According to a list I found, the "high risk" classification has been used 86 times in the last 27 years. By my Cleveland State math, that's about three times a year, so it's rare.

They've issued a "high risk" three days this month -- but, actually, for two events.

The first was April 16, when the Oklahoma-based meteorologists predicted a major tornado outbreak in eastern North Carolina and southeast Virginia. The result: dozens of twisters that killed more than 20 people. It was one of the worst tornado outbreaks in Carolinas history.

Then the Storm Prediction Center used the "high risk" tag on Tuesday and Wednesday -- Tuesday for the Arkansas and Texas area that was clobbered by tornadoes and flooding that day; and Wednesday for northern Alabama, southern Tennessee, northeast Mississippi, and northwest Georgia.

Thursday's forecast turned out to be the bulls eye for the storms that will turn out to be the deadliest in decades.

The risk classification is based on a number of factors -- the amount of lift in the atmosphere; helicity, or the spinning motion of the atmosphere; and shear, which is the term for winds blowing from different directions at various levels of the atmosphere.

They don't bat 1.000 in Norman, but the Storm Prediction Center scientists have a pretty good average. And this month, they've been incredibly accurate.

Wednesday, April 27, 2011

Just how bad tonight?

The last thing meteorologists need to do is warn people about severe weather -- only to have none develop. There already are enough skeptics out there.

But forecasters seem to be taking a bullish approach about the predictions overnight in the Charlotte area.

Typically, thunderstorms weaken at night, because one key ingredient -- the unstable atmosphere caused by daytime heating -- disappears. Occasionally, however, a weather system brings along its own trouble, and some meteorologists think that will be the case tonight.

A few strong storms developed Wednesday afternoon across the Carolinas, but they're not related to the system expected early Thursday morning.

Jeff Taylor, of the National Weather Service office in Greer, S.C., said late this morning that the atmosphere will have plenty of shear -- winds blowing from different directions at various altitudes. Helicity, or the spinning motion in the atmosphere, also could be significant. Thunderstorms that move into such conditions often turn severe.

Forecasters are strongly convinced that a major tornado outbreak will take place this afternoon and evening in northern Alabama, southern Tennessee and northwest Georgia. They think that same system will convert from a broken line of storms -- a condition in which tornadoes form more easily -- to a solid line as it moves into the Carolinas overnight.

Solid lines of storms don't produce many tornadoes, but they are very capable of the kind of damage we saw early April 5, when strong winds knocked out power to more than 300,000 customers in the region.

So pay attention to forecasts tonight.

Monday, April 25, 2011

No hurry for 90-degree days

A few months ago, I told someone who was relatively new to Charlotte that we usually get one or two 90-degree days in April.

The other day, I decided to check out the facts -- always a good thing to do. It turns out that I was wrong. I hate when that happens.

In fact, 90-degree days in Charlotte are rather rare. The closest we've gotten so far this year, not including Monday, was a pair of 86-degree readings -- on Easter Sunday, and back on April 11. It looks as if it will be at least May before we have a 90-degree days this year.

But that wouldn't be unusual.

In 132 years of weather record-keeping in Charlotte, it was reached 90 degrees on an April day only 28 times. That comes out to about once every four or five years.

It happened last year. In fact, the first 90-degree days last year was among Charlotte's earliest. It happened on April 6, when the thermometer hit 90 for a high. But in 2009, it was June 20 before we had a 90-degree day. It hit 94 that day.

The first 90 days were May 31 in 2008; May 30 in 2007; and April 27 in 2006. Just eight years ago, it didn't hit 90 until July 8. That set a record for the latest in Charlotte for the first 90-degree day.

Eventually, it will get there. And when it happens, a lot of Charlotte-area residents will complain. But it's a part of life around here.

Wednesday, April 20, 2011

Mecklenburg ... a tornado magnet

I wrote a few days ago about three recent Charlotte tornadoes, and a closer look at the archives shows something interesting -- Mecklenburg County has been hit with more tornadoes than any other North Carolina county in the region over the past 60 years.

The Storm Prediction Center's records show 20 tornadoes in Mecklenburg since 1950. For those of you into averages, it means the immediate Charlotte area gets a tornado about once every three years.

You'll notice I said Mecklenburg leads the area's North Carolina counties. That's because Chesterfield County in South Carolina has been hit with 22 tornadoes during that time.

I'll get into the county-by-county totals later, but this whole topic resulted from readers' questions about whether twisters ever hit the immediate Charlotte area. The classic perception of a tornado is a storm that rampages across farmland, but urban areas are not safe.

Christopher Burt, a meteorologist who has written a great book, "Extreme Weather," assembled a list of the 10 most tornado-prone cities, based on their location in parts of the country that received a large number of twisters.

No. 1 on his list is Oklahoma City, which he says has been hit more than 110 times, including an EF5 (the strongest level) in May 1999. No. 2 on the list is the Dallas-Fort Worth Metroplex, which also has been hit dozens of times. Only one city in his top 10, Chicago, has never taken a direct hit.

So urban areas get their share of tornadoes.

Atlanta and the rest of Fulton County have been hit 27 times since 1950, including an EF3 in March 1975 that killed three and injured 152; and the March 2008 twister that hit during the Southeastern Conference basketball tournament, killing one and injuring 30.

Columbia and Richland County have recorded 34 tornadoes, the worst of which was an EF2 in May 1976 that caused one death.

Raleigh, which took a direct hit Saturday, had recorded 30 tornadoes before last weekend. That included an EF4 in November 1988 that caused two deaths, 105 injuries, and $250 million in damage.

Charlotte-Mecklenburg's 20 tornadoes include a pair of EF2's -- on Sept. 7, 2004, caused by the remnants of Hurricane Frances; and on March 10, 1992. That storm hit in southwest Charlotte, causing 18 injuries and $2.5 million in damage -- the most ever for a Mecklenburg twister.

Here is a look at the tornado history of other counties in the region:

Anson: 4.

Burke: 6.

Cabarrus: 11.

Caldwell: 6 (includes and EF4 near Dudley Shoals on May 7, 1988).

Catawba: 15.

Chester: 12.

Chesterfield: 22 (the Carolinas' biggest recent tornado outbreak, on March 28, 1984, produced an EF4 that caused $25 million damage and 24 injuries).

Cleveland: 17.

Gaston: 13.

Iredell: 16.

Lancaster: 11 (includes an EF4 in that March 1984 outbreak).

Lincoln: 19 (includes a killer storm during the big May 4, 1989, outbreak; the F4 tornado caused four deaths, 19 injuries, and $25 million in damage). Lincoln County is tied for third (with York County) in the area, behind Chesterfield and Mecklenburg, in tornado frequency.

McDowell: 3.

Montgomery: 7.

Richmond: 3 (this number was surprisingly low, because Richmond is in the Sandhills and more prone to the significant tornado outbreaks in the springtime).

Rowan: 9 (does not include Saturday's EF1).

Rutherford: 7.

Stanly: 10 (this county is living a charmed life, with no recorded tornadoes in 12 years).

Union: 16 (includes a killer storm May 5, 1989 -- an EF4 with one death and six injuries; the total does not include Saturday's EF0).

Watauga: 2.

York: 19 -- tied with Lincoln County for the third-highest total in the area.

Monday, April 18, 2011

Charlotte has a tornado history

The tornado that struck Raleigh on Saturday has caused a couple readers to ask if twisters ever have hit the incorporated Charlotte area.

I'll try to go into more detail on this Tuesday, but the quick answer is "Yes."

There have been about two dozen tornadoes in Mecklenburg County over the past 60 years, and most of them were inside the Charlotte city limits.

The most recent was May 9, 2008, when an EF0 tornado (weakest on the Enhanced Fujita scale of 0 to 5) hit northwest Charlotte. That twister developed in Gaston County and crossed into Mecklenburg after 1 a.m. It knocked down some trees, but to be honest with you, I don't remember that one very well.

Two other tornadoes in Charlotte are more memorable.

On March 8, 2005, an F1 twister touched down near 36th and North Tryon streets. That storm followed an eastward path, damaging roofs and snapping off the tops of trees for a few miles. It knocked down a tree on the campus of Cochrane Middle School in northeast Charlotte before lifting up.

About $50,000 damage was caused.

And on Sept. 7, 2004, an F2 tornado struck southwest Mecklenburg and southwest Charlotte. That storm caused about $150,000 damage. You might remember stories at the time, of teachers and students huddling in the hallway of Lake Wylie Elementary School with the tornado nearby.

That twister was caused by the remnants of Hurricane Frances as it pushed northward from Florida into the Carolinas. The remnants of Frances produced a single-day tornado record in South Carolina that day.

Friday, April 15, 2011

Boo! Bad storms are coming

I'm not sure who gets more excited during an outbreak of severe thunderstorms -- those who are mesmerized by bad weather, or those who can't stomach the people mesmerized by bad weather.

Whether it's severe storms, tornadoes, hurricanes or snowstorms, the media coverage of bad weather (or predicted bad weather) seems to rile some people.

From what I've gathered, the critics' chief complaint is that meteorologists, or those who report on the weather, tend to sensationalize.

I've made a special attempt to use some restraint in covering the weather. Sometimes, I've used too much restraint. On April 4, I wrote that there was a chance of a few heavy storms overnight. Other media outlets were much more bullish in their advance coverage. They were right. I downplayed the threat too much.

The same thing last Saturday, when hail caused millions of dollars of damage locally.

A special target of the critics are the TV meteorologists, particularly during tornado events, when the stations usually go to full-time coverage. Those silly severe storms and tornadoes have no sense of timing. They have a bad habit of coming along in the afternoon and evening, which means weather coverage sometimes cuts into coverage of basketball, football, golf tournaments, NASCAR races, or maybe your favorite program.

I don't deny that meteorologists -- including amateurs who are fascinated by weather -- get excited in big events. However, I've also met political junkies who think the whole world should be fascinated by a big election, or sports fans who think their favorite event is the biggest thing in the whole world.

TV meteorologists say their coverage during severe weather is designed to save lives. I believe them. Don't try arguing that advance warning of tornadoes and hurricanes doesn't save lives. That ship has sailed. The statistics show how the toll of injuries and deaths has plummeted in recent decades, due to warnings.

The problem, perhaps, is when the big event -- a tornado, hurricane, snowstorm -- doesn't develop as anticipated. Maybe the critics feel they have been manipulated somehow.

Meteorology is a science, but as one National Weather Service veteran once told me, "It's not an exact science. There's still a bit of art mixed in."

The Storm Prediction Center in Norman, Okla., and the National Weather Service -- and many other meteorologists -- predict an outbreak of severe weather Saturday in the Carolinas. If it doesn't happen, I won't complain.

It means my car won't be damaged by hail, or those two big trees along the creek won't come crashing into my fence or onto my roof.

It also means people outdoors Saturday -- playing baseball, softball, soccer, tennis or golf -- or the parents and children at Easter egg hunts will be safe.

But people who know a lot more about atmospheric science than me say there's a threat. My job is to report that.

Thursday, April 14, 2011

Another stormy Saturday?

This won't be good news to the thousands of people who have plans Saturday morning -- the youth baseball, softball and soccer players; the golfers; the tennis players; the gardeners; and those planning to participate in Easter egg hunts.

But it looks like we're facing another stormy Saturday.

Last weekend, the bad weather arrived in the evening. This time, it looks like a morning event.

The computer models can't agree on the exact timing, but most meteorologists are looking at a time frame of 5 a.m. until 1 or 2 p.m., with the 7 a.m. to noon period most likely.

A cold front will be crossing the area, and the Storm Prediction Center in Norman, Okla., says atmospheric conditions will be conducive to the development of severe thunderstorms. A major outbreak of severe weather is expected Friday in parts of the South, and that same system will be moving into the Charlotte region by Saturday morning.

As we move into Friday, the picture should become clearer. But you might want to have a backup plan on your Saturday schedule.

Friday, April 8, 2011

Spring break outlook: Very promising

It's looking more and more as if chances of frost and cold weather are on the ropes, and if you're thinking ahead to the upcoming vacation week for many area public school students, there's good news.

The outlook for the next two weeks is for consistently mild weather. By that, I mean daily highs of 70 degrees or warmer -- in most cases, warmer.

Students in the Charlotte-Mecklenburg Schools and many other nearby systems will have spring break the week of April 18, the week before Easter. I've checked advance forecasts from several private companies and the Climate Prediction Center (the government folks), and the outlook is for temperatures at or above average for this time of year.

Average highs are now a bit above 70, and those averages will be in the low to mid 70s by the end of the month.

A couple of people have asked me whether it's safe to plant flowers and vegetables that can be damaged by frost. On average, the date for the last frost in Charlotte is April 7 ... which was Thursday. So if you follow statistics, it's safe.

But given that no chilly weather is on the horizon for the next 10 days or so, I'd say the odds are even more in your favor.

Don't forget ... we've had frost in early May in years past, and there will be a few more outbreaks of cold air in the North that could push near the Carolinas.

But all indications are that we've might have turned the corner.

Wednesday, April 6, 2011

Was that a record storm outbreak?

We might never know if the outbreak of severe weather late Monday and Tuesday was a record, but several meteorologists I've read indicate it could have been.

At the least, the number of severe weather reports is among the biggest in history.

Take a look at the graphic on this post -- a graphic of reports received by the Storm Prediction Center in Norman, Okla., between 7 a.m. Monday and 7 a.m. Tuesday. The reports show locations of tornadoes, winds of 70 mph or more, or large hail.

First, a couple of caveats:

1. I noticed in a couple stories that the Storm Prediction Center recently changed its report policy. It now lists reports from nearby areas as separate incidents, so that might increase the overall number.

2. The storm outbreak happened in an area with a lot of populated cities, rather than in the Great Plains. More people = more reports.

3. While the storm outbreak was significant, let's remember that the death toll, fortunately, was far below that of many past outbreaks. From what I saw, there were six deaths from this week's storms.

Still, it was quite an outbreak.

The Storm Prediction Center says there were 1,377 reports between 7 a.m. Monday and 7 a.m. Tuesday, plus another 52 after 7 a.m. Tuesday. Of those, 43 were tornadoes. There were another 1,290 or so of strong winds.

There was one tornado in North Carolina -- a twister which struck about 12:15 a.m. Tuesday in Surry County, near the Virginia border. That storm damaged about 35 to 40 homes.

Friday, April 1, 2011

It's hurricane forecast season

For the people who follow hurricanes, there are two times of year -- Hurricane Season, and Hurricane Forecasting Season. And we're coming into the prime part of Hurricane Forecasting Season.

Over the next six weeks, we'll get forecasts from Accu-Weather, the Colorado State University specialists, a team from N.C. State University, and the National Hurricane Center -- among others.

The first of those predictions is in. If I were aiming for exciting headlines, this blog entry would have said, "Carolinas In Hurricane Bulls-Eye This Year." But I didn't, because if we learned anything from the last few years, it's that hurricane forecasts are far from a science.

In 2007, the forecasts over-estimated the number of storms. Last year, the predictions of an above-average season were on target, but several forecasters said the U.S. coast would take a beating. That didn't happen. Not a single major hurricane made landfall on our coast, even though several big storms churned in the Atlantic and Caribbean.

So take this with some caution ... Accu-Weather is predicting above-average hurricane activity this year, with a higher-than-normal chance of tropical storms and hurricanes hitting the Florida and Carolinas coasts. Accu-Weather's reasoning is the position of high pressure systems in the Atlantic. Last year, strong high pressure served to steer hurricanes westward through the southern Caribbean, into the coasts of Mexico and Central America.

If I understand it correctly, the thinking this year is that high pressure will be farther east. That will allow tropical storms and hurricanes to bend northward near North America.  

Accu-Weather predicts the Gulf Coast, especially Texas, will be at risk early in the season, with south Florida and the Carolinas feeling the brunt of activity in mid- to late-season (roughly, from late August through October). You can read all of this at Incidentally, William Gray and Phillkip Klotzbach, the kings of long-range forecasting, issue their prediction from Colorado State on Wednesday. They put out a preliminary forecast last December, and it also called for above-average activity.