Kevin Myatt

Latest entries from the Weather Journal blog

• Weather Journal taking a long break
• Yes, there's still an Atlantic tropical season going on
• Freezing temperatures likely tonight

About Kevin

Kevin Myatt grew up in Arkansas to the tune of tornado sirens and the rhythm of hailstones, aspiring to be a meteorologist before his studies and career were turned to journalism instead. Though he often chases storms, he prefers living in the cooler, more tranquil weather of the Blue Ridge. He moved to Roanoke in 1999 to take a job on the copy desk of The Roanoke Times; writing headlines and editing copy is his principal work for the newspaper today.

Each May, Kevin assists Pulaski County High School / Virginia Tech meteorology instructor Dave Carroll in leading college and high school students to the Plains to observe severe weather firsthand. The accounts of many of his storm chases can be found here on the storm chasing page of his weather blog on roanoke.com.

Kevin was an editor for "Hurricanes and the Middle Atlantic States," a book written by D.C.-area weather enthusiast Rick Schwartz and published by Blue Diamond Books that documents hurricanes striking the mid-Atlantic states since colonial times.

The Weather Journal column began in 2003 and appears on Friday's Virginia section front in The Roanoke Times. The Weather Journal blog began in 2006 and follows weather day-by-day between the larger columns.

Thanks to August, the record books get an update

Correction: Roanoke's 27 days of temperatures at or above 90 degrees in August was four more than the previous highest number of such days in a month, 23 in July 1987. The margin between the new record and the old one was incorrect in Saturday's Weather Journal column in the Virginia section.

When a long jump or pole vault record is broken in the Olympics, it usually happens by a fraction of an inch. When a record falls in a running event, it is often by a tenth of a second.

Imagine if a long jumper or pole vaulter sailed a foot past the old mark, or a sprinter raced through the tape two seconds faster than anyone before.

August 2007 is that kind of massive record-breaker in Roanoke's weather history. You have just lived through the hottest month in nearly 60 years of official weather records -- and second place isn't close.

See graphics: August's high temperature records | August '07 high and low temperatures

"'Unprecedented' is the most appropriate word that comes to mind in the context of the number of overall records that were broken, which speaks more to the persistent hot pattern than any unusual extreme situation of shorter duration," said Stephen Keighton, science and operations officer at the National Weather Service in Blacksburg, in an e-mail.

Monthly temperature records typically fall by a tenth of a degree, maybe two-tenths -- or if it's really extreme, half a degree.

The average temperature for August of 82.2 degrees -- figuring in both the sweltering days and the sultry nights -- is 2 degrees above the previous hottest month, July 1993. The month's average low temperature outpaced the old record by 1 degree, while the month's average high temperature topped the old mark by nearly a degree.

And if that isn't enough to make it the runaway champion of heat, August also had 27 days at or above 90 degrees, four days more than the highest number in any other month (23 in July 1987). We haven't had that many days in the 90s in four of our last seven entire years, let alone in a single month.

We've had more 100-degree days before -- eight in July 1977, compared with four in the month just past. We've had more extreme heat -- 104, 105 and 104 on consecutive days in August 1983, compared with a maximum of 102 this time around. And we've had seasons with heat over an even longer period of time -- 65 days of 90 or above, stretched from May to September, in 1953; we're at 45, and counting, this year.

But never before, since the Roanoke Regional Airport official weather records began in 1948, have we had a month so consistently hot. No day this month had a high below 86, and 20 days had low temperatures in the 70s.

The heat was remarkable not just in Roanoke, but throughout Southwest Virginia. Blacksburg set eight daily high-temperature records.

What caused the heat?

On a regional scale, the heat wave was driven by the combination of a persistent high-pressure system parked over us and long-term drought.

Keighton explained that the strong high-pressure system, which typically forms over the central United States, shifted east twice in August. He added that as long as it stays dry, it is conceivable the high could move back over us, bringing periods of heat in September.

"When the weather gets hot, soils dry out more quickly; therefore, a heat wave can act as a catalyst for drought," said Chip Konrad, a former Roanoke resident who is the deputy director of the Southeast Regional Climate Center, in an e-mail. "As drought conditions are observed, much less water is available to be evaporated thus a higher portion of the solar energy can be used to heat the surface. So the resultant drought conditions further increase temperatures during the day.

"It is a kind of snowballing effect that requires a big and persistent circulation change to break. Oftentimes it requires a change of season."

At the local level, you can throw in winds blowing down the mountain slopes and the urban heat island effect as likely contributors to Roanoke's hottest days and warmest nights.

Winds blowing from the west down mountain slopes compress and dry out, intensifying heat. Such winds were observed on Roanoke's hottest days in August. Asphalt and concrete within a city hold in more heat than do ground, trees and grass in the country, so nights are often warmer and days have a head start with the heating stored up from previous days.

Was it global warming?

The inevitable question that will come up: Was Southwest Virginia's blazing August associated with global warming?

"It cannot be said with any confidence at this point that global warming contributed to the record heat," Keighton said.

"It's true that one of the predictions associated with global climate change is more extremes in some parts of the globe, and so there is always a chance that a summer like we've had (significantly cool stretches in July followed by these significantly hot stretches in August) could be something that's seen more and more in the coming decades, but to relate any relatively short term weather pattern or extreme weather system to global warming is probably not good science."

Southwest Virginia has not experienced a pattern of extremely hot summers in recent years.

In fact, August broke us out of an unusually long period -- eight years -- in which Roanoke did not have any 100-degree temperatures or months with at least 20 days in the 90s.

"However, if we see more and more heat waves over the next 20 years or so, a case can made for this trend to be associated with greenhouse warming," Konrad said.

Never mind 20 years -- what's ahead in the months and weeks to come?

We're waiting to see if tropical systems or seasonal changes can punch a hole in the heat and drought.

The next week looks a little cooler, but there are some signals that heat could return after that.

But don't look to summer temperatures for any indication on what will happen in winter.

Some summer heat waves are followed by mild winters, others by cold winters.

With an eight-year streak of no 100-degree temperatures now over, can ending an 11-year streak of no foot-deep snowstorms be far behind?