July 29, 2003
LITTLE CHANGE
The closest we've been able to come to a drought in 2003 has occurred over the past two weeks.
Of the last 14 days, no rain has fallen at the Roanoke Regional Airport on 10 of them. Contrast that to the first half of the month, when there was measurable rain on all but 2 days!
It's been that kind of year.
We had a stretch in June where there was measurable rain on nine straight days.
We had a stretch in May where it rained 14 of 16 days.
And we had our once-a-week snows through January and February.
It's also been a cool year. Except for March, every month this year has been average or below average in temperature. And even March, 2.2 degrees above normal, squeezed out a last-gasp snowstorm to ruin our blooming Bradford pear trees.
Of course, when it clouds up and rains as much as it has, it doesn't get very hot. Look outside today for Exhibit 1.
And there's just no real indication that things are going to change that much in the second half of the year.
It looks like the heat ridge in the West may retreat westward instead of expanding east. It looks like we'll have recurring cold fronts at least through early August. La Nina, often correllated with dry autumn and winter weather, looks like a fizzle. And there's plenty of meterological speculation that hurricane season is about to go bonkers, so we might be dealing with a Gulf or Atlantic storm threat every couple of weeks that could dump yet more rain on us.
We're now past the annual peak sunshine, so that means that slowly and surely we'll be plodding toward autumn. August, however, has often produced our hottest weather, including Roanoke's all-time record of 105 back in 1985. But that kinda stuff usually occurs when there's been a consistent pattern of hot, dry weather in July, drying out all the vegetation and the ground. Two weeks of slightly less moist weather haven't done nearly enough in that regard.
July 25, 2003
IT DOESN'T TAKE A TWISTER
There's often an assumption made that straight-line winds in thunderstorms can never do as much damage as a tornado.
Memphis, Tenn., is a prime example of why that is wrong.
On Tuesday, at about 7 a.m., a ferocious thunderstorm ripped across the Mississippi River into the city of about 600,000. Over the next few minutes, winds of up to 100 mph shredded the city. Roofs of some building came off. Century-old trees toppled into houses. Half the city was without power. Damages are expected to top $6 million; cleanup costs may top $40 million. And not a single tornado caused any of it.
What hit Memphis was called a "derecho" (pronounced "day-ray-show"). In simplest terms, it's a line of thunderstorms that gets really out of hand in soupy summer air. The energy it gathers causes it to race rapidly forward, and that forward speed adds to whatever winds are blowing out of the storm clouds. A radar echo often seems to take on a "bow" shape. Derechoes sometimes seem to become their own animals, almost independent of surrounding weather patterns, steering their own atmospheric currents as they plow through stagnant summer air.
Officially, a thunderstorm system must have 58 mph winds over a 250-mile length to be a derecho. While there are many thunderstorm complexes that develop in the hot months, called "MCS's" (mesoscale convective systems), only a few erupt into full-fledged derechoes. Mostly, they hit grass, wheat and cattle in the Great Plains. Rarely do they plow into the heart of a large city like Memphis.
The same system, much weakened, ended up in Roanoke late Tuesday, mostly a rain producer by the time it got here. The Appalachian Mountains sometimes shred thunderstorm systems that approach from the west. But not always. Atmospheric turbulence and moisture piled 10 miles in the sky is just not impressed with humps of rock less than a mile high.
On Aug. 9, 2000, Western Virginia was slapped by two separate derechoes. Check this Web page, courtesy of the National Weather Service, for a radar loop on those storms.
METEOROLOGIST JOHNNY CASH
"Love Is A Burning Thing
And It Makes A Fiery Ring
Bound By Wild Desire
I Fell Into A Ring Of Fire
I Fell Into A Burning Ring Of Fire
I Went Down, Down, Down
And The Flames Went Higher
And It Burns, Burns, Burns
The Ring Of Fire
The Ring Of Fire"
An AP story about the Midwest's storminess and the West's heat reminded me of an old term that explains our weather pattern this summer: "the ring of fire."
"Ring of Fire" is a Johnny Cash song, lyrics above, and it's also a term used to describe the volcanoes that ring the Pacific Ocean. But in summer weather, it's also a phrase that has been applied to a huge high pressure heat dome that circulates thunderstorm systems around it. We've been talking about this since June, but haven't slapped this colorful term on it.
The high is out West, which is absolutely sizzling. The "ring of fire" surrounds the high, across the far north and then diving south into the Ohio and Tennessee valleys. We have been a little east of the actual ring, so our storminess hasn't been that of Iowa, Illinois and Tennessee. But we are more on the stormy side rather than under the hot, dry bubble.
All the suspense we really have in our summer weather is whether this heat dome, which routinely expands and contracts, will finally make a move on us, or if it will just sit out over Denver and Phoenix and sling storms at us. And that's why I have to keep talking about, because until there's a tropical system or a really strong autumn-arousing Arctic cold front, there's not much else going on. We're moving into the dog days. We've still got three long months before we can even speculate about snowstorms.
July 22, 2003
SEVERE WEATHER
Mix July sunshine with an unusually strong cold front for the season, and the ingredients are in place for severe weather.
That's what is in the offing this afternoon over our region. As a strong cold front moves into warm, humid air, thunderstorms will develop, and some of them could reach "severe" limits.
What is severe, you ask? A severe thunderstorm, according to the National Weather Service, contains winds of 57 mph or higher and hail 3/4 inch in diameter or greater. Severe thunderstorm warnings are usually issued on radar observations that lead forecasters to believe a storm has one or both of these characteristics, rather than actually waiting for someone to call in and say "Hey, I just had 3/4 inch hail and 57 mph winds."
Another factor will be all the leftover "outflow boundaries" from thunderstorms to our west on Monday. These are like mini-cold fronts, puffs of cooler, drier air here and there that have poured out of collapsing thunderstorms, scattered around like confetti after the party. Each one of these outflow boundaries creates a new place for convection to develop in the summer heat.
And then there's always the mountains to further help focus thunderstorm development.
What happens after this potentially stormy day will be an early taste of fall. Temperatures might struggle to reach 80 on Wednesday and Thursday. That'll be a nice respite.
HEAT OUT WEST
There's no doubt the heat center of the nation this summer has been out West.
Monday's high in Aspen, Colorado, where it's typically autumnlike at 7,000 feet, was a toasty 91, 3 degrees hotter than Roanoke. (But Aspen's low was 51 -- ours was 67)
The desert, of course, is even hotter. Laughlin, Nevada, was 116. Bullhead City, Ariz., was 118. Death Valley, Calif., hit 124, after a morning low of 95. (The National Weather Service climate chart shows zero snow depth for Death Valley ... you don't say?)
The summer heat ridge I talked about in June has parked itself, all right -- out West.
What remains unknown is if this ridge will ever make a serious move to build eastward or even relocate. Toward the end of the week, there are signs it will push into the Plains and Midwest. Will it come farther east and give us a heat wave? With each passing summer day, it becomes less and less likely.
And just as we speculated here in June, if we are on the east side of the high, it will keep slinging fronts and storm systems out of Canada onto us. That will break even the regular low 90s kind of summer heat we get from time to time.
If you're into heat waves, it doesn't look good in 2003. I'm not. Bring on fall and winter.
July 18, 2003
FREAKY HEAT
Would you be freaked out if the winds started picking up and the temperature shot up 11 degrees to a balmy 92 -- at 1:30 in the morning?
Dalhart, Texas, experienced this early Tuesday morning. With winds gusting to 38 mph, the temperature rose from 81 degrees at midnight to 92 degrees an hour and a half later. Now, that's freaky!
Dalhart's early morning heat wave was the result of an uncommon phenomenon called a "heat burst." It's caused when a dying thunderstorm collapses, forcing air from the middle of the atmosphere toward the ground. Typically, we experience this as a cool burst of air that drops the temperature, but if enough dry air has been pulled into a storm, this air can be forced and compressed as it approaches the ground and will heat up. In the plains and desert regions of the West and Midwest, enough dry air sometimes gets pulled into thunderstorms to cause a heat burst.
It's kinda like a big hair drier in the sky.
The Dalhart heat burst was pretty mild compared to one that occurred in Kopperl, Texas, in 1960. That one produced 75 mph winds and temperatures so hot that vegetation was turned to ashes in the heat. No official thermometers were around, but it's estimated temperatures may have exceeded 130 degrees. (The world record is 136, by the way).
Geography and climatology would seem to preclude such an event occuring in Western Virginia. It's doubtful enough dry air could get pulled into a thunderstorm with so much Gulf, Atlantic and river moisture around. Even our drought periods are moist compared to the West. I would think an Eastern heat burst would be no more than a slight warming at best.
DULL WEATHER
The next several days promises weather that will be extremely average for this time of year -- highs in the mid 80s to low 90s, partly cloudy skies, scattered afternoon showers and thunderstorms.
At least we're not getting soaked constantly like in May and June ... but those under heavier thunderstorms each day may get a brief soaker.
If you're in our "hottest day" contest, the current hottest day is 91 on July 5 and 8. I'm still really doubting we'll be able to establish a heat wave for very long this summer, but my guess stands at 97 on Aug. 12.
TROPICAL STORM DANNY
Unless you're going in a ship across the Atlantic, Danny will be a non-player in your weather.
Danny has 65 mph winds and is about 700 miles south of Newfoundland, moving north-northeast. He may make it to hurricane status, but he is what weather buffs like to call a "fish storm" -- he'll stay out over the ocean with fishies.
July 15, 2003
HURRICANE CLAUDETTE
First, a quick word about what has become the first landfalling hurricane of the season on the U.S. coast. Hurricane Claudette has made landfall today at Matagorda Bay, Texas, with winds of about 80 mph. A minimal hurricane, yes, but you know how much havoc even 50 or 60 mph thunderstorm winds can cause around here.
Claudette will not be a factor in our weather as she will head off west across the plains of Texas and Mexico to die a slow, rainy death somewhere near El Paso.
Our weather this week is about as typical and stagnant as possible: Highs in the 80s, lows in the 60s to near 70, and a slight chance of showers and thundershowers each day. The low pressure trough that has brought us a period of cooler weather is breaking down but it does not appear a big heat ridge is waiting in the wings to take over. Without any large-scale weather features being dominant this week, we'll revert to default and have typical summer weather.
GLOBAL COOLING, ANYONE?
The media is rampant with dire predictions of global warming -- melting ice caps, droughts in wet places, mega-hurricanes. But one well-respected meteorologist is suggesting we may be at the cusp of a period of global cooling.
Joe D'Aleo -- perhaps better known as "Dr. Dewpoint" on intellicast.com -- is a global warming skeptic. He believes that evidence cited frequently for global warming does not show worldwide warming, but instead is the result of local factors such as urbanization that raise temperatures in a small area. If you think about it, most weather reporting stations are in or near cities, usually near lots of heat-absorbing concrete (usually real close to airport runways, in particular). So if a lot of these local areas of urban heating were averaged together, it would raise the average accordingly.
Though his views are in the minority among atmospheric scientists, Joe is no crackpot. Last winter, using historical research into past seasons that had very similar large-scale atmospheric factors, Dr. Dewpoint produced a winter forecast that so closely mirrored what actually happened that it was stunning. Nor is the idea of global cooling a new one. In the 1970s, when several severe winters froze the nation solid, global cooling was a media buzzword almost the way global warming is today. The idea then was that we were headed toward another ice age.
Anyway, if you're interested and your computer has Adobe Acrobat Reader, check out his piece. It is technical at times but not incomprehensibly so.
The core of his argument is that several large atmospheric oscillations have now switched into a different gear than they were previously, and this would signal the start of a period of atmospheric cooling.
While I would not characterize myself as a global warming skeptic, I am skeptical of the hysteria that seems to surround it.
My take has always been that man greatly overemphasizes his importance in the physical realm. When compared with solar phenomena, volcanic eruptions, and all manner of meteorological, astronomical and geological events that we have only the barest grasp of, our minivans and mall parking lots are pretty puny stuff to be basing an entire theory of climatic change on.
I'm not saying we don't have some impact, I just don't believe it is the most important one for predicting decades of climatic change to come.
I also believe the planet has been intelligently engineered by a divine creator to balance out extremes ... but that in no way excuses us from our responsibilities to take care of the Earth and find less-intrusive and less-destructive means to live out our lives. Having dominion over the planet demands responsibility, not just wanton use and abuse.
So there you have it. I'm not quite ready to make reservations for my tropical vacation in Maine. Nor am I setting my mind on an Everglades cross-country skiing expedition. We have a lot of work to do to master forecasting tomorrow's weather accurately. When we get that nailed down, maybe then we can more confidently expound on what it will be like in 2103.
July 11, 2003
COOLER, DRIER ... BUT NOT TOTALLY DRY
I'm sure few of you reading this column have ever read a National Weather Service forecast discussion. But the age of the Internet has made these discussions available to all, whereas only professionals and perhaps a few weather-crazed amateurs with access to a weather wire used to see them.
Each National Weather Service office issues forecast discussions a minimum of twice day -- at about 3 a.m. and again at 3 p.m. with updates as needed. The discussions provide a behind-the-scenes insight into what the meteorologists are thinking with a given forecast. They're filled with jargon, strange abbreviations and grammatical issues, but any literate person can sift through one and get an idea of what's going on. Check it out for yourself at this Web page.
The forecast discussion issued this morning by the National Weather Service in Blacksburg is telling. I've quoted a paragraph below, altered into sentence-form with fully spelled-out words:
"Upper trough is fairly impressive for mid-July with full latitude characteristics. All models are trending stronger with the upper trough which suggests surface front should easily make it to the coast and inroads to the Deep South. Given this scenario ... you would think we should maintain mainly dry weather across our forecast area. What is becoming more problematic however is uncertainty of how cooler air at upper levels aided by lift from multiple short waves impulses that are forecast to move thorugh the long wave trough over the next several days will interact with the relatively moist boundary layer and mid-July surface heating. For this reasoning ... it is hard to completely omit probability of precipitation from any given forecast period."
Here's the layman's translation:
(1) The jet stream, the fast-moving current of air that steers storms, is dipping much farther south than it usually does this time of year, and the computer forecast models are suggesting that it will even be stronger in upcoming days. This will allow milder weather than is typical for mid-July to slip south from Canada.
(2) Typically, this would mean it would be dry, but the atmosphere continues to be so moisture-charged that, with any kind of turbulence or afternoon heating, rain can't be ruled out for any of the next several days.
That about says it all. Temperatures will back off into the low to mid-80s the next several days, and it will indeed be much less humid, but we just can't knock out any and all chances of rain. Such is life in a year in which we're a foot above normal in rain.
ON THE WANE
Two meteorological events I've commented on in recent weeks are presently on the wane -- but either could make a comeback, and maybe a vigorous one at that.
Tropical Storm Claudette is re-entering the Gulf of Mexico after an encounter with Mexico's Yucatan Peninsula. She was already flagging when she hit the coast and is now re-emerging with 55 mph winds. The question now is whether Claudette will regenerate into a hurricane and then threaten the U.S. Gulf Coast.
La Nina has piddled out in the central Pacific as water temperatures there are about neutral -- which means it's neither an El Nino (warm) nor a La Nina (cool). Climate forecasters are now suggesting conditions may not be favorable in the next few months for either an El Nino or a La Nina. It would be hard to get either really raging by wintertime, when they seem to have the most impact on our day-to-day weather. Therefore, we may not get any signals from the Pacific on what our fall and winter will be like.
July 9, 2003
CLAUDETTE
Tropical Storm Claudette has blown up quickly in the Caribbean. Sweeping south of Jamaica, it's already up to 65 mph winds, though little strengthening appears likely in the next few hours. It's moving west at 24 mph, which is really booking for a hurricane.
The question over the next 24-36 hours is whether this storm will hit Mexico's Yucatan Peninsula -- the land mass that juts north into the Gulf of Mexico and shipwrecks many a storm that would hit the U.S. -- or whether it will curve northward in time to miss it.
If the latter is true, this would become a serious threat to the U.S. Gulf Coast as a hurricane later in the week, especially if it slows down and starts stewing in the juicy Crock Pot we call the Gulf of Mexico.
If it hits the Yucatan, it might do as Isidore did last October and never regain its feet in the Gulf. Going as fast as it is now, it might be hard to hit the brakes in time to miss the Yucatan.
A movement into the Gulf, either as a hurricane or as a damped down tropical storm, could make it a rain threat for us. The way this year is going, it almost seems a lock to do that. For now, it's just something to keep an eye on.
July 8, 2003
PATTERN SHIFT
A significant pattern shift appears likely this weekend.
We've been on the backside of a high pressure ridge over the Atlantic Ocean, and as a result we've had hot, muggy days with scattered afternoon downpours as this high has pulled warmth and moisture across us from the southwest.
It appears the pattern will shift to move a low pressure trough over us. This low pressure trough will at first sling a series of atmospheric disturbances at us from the northwest that will trigger -- yes -- more showers and thunderstorms, and quite heavy at that, especially Wednesday through Friday.
By the weekend, a cooler, drier air mass may settle in, with highs dropping into the 70s and low 80s. I say "may" because the question in the summertime is always how far south a front will really drop. Stagnant summer air masses tend to stall these boogers, and that can lead to yet more unneeded rain day after day. But either way, it appears we'll get a break from our recent attempt at real summer weather and get a taste of, well, maybe late summer, instead.
VISIBILITY
When I awaken to haze-choked July scenes here in the Roanoke Valley, marring my usually gorgeous view of the western skyline running from Bent Mountain to Tinker Mountain, I presume that the visibility is much worse today than it was two, three or four decades ago because of increased urbanization and all its foul fumes.
But what if the data runs completely counter to that assumption, which I would take almost as common knowledge? According to the Virginia State Climatology Office, it does.
I find the agency's reports to always be interesting reading. They're written in such a way that even someone other than a weather geek might find them worth a gander. The folks at the climatology office know their Virginia climate patterns. They also tend to be highly skeptical of any and all popular buzzwords about climate and weather, such as El Nino and global warming. Check it out yourself sometime at climate.virginia.edu.
The climatology advisory I refer to is from August of 2000, where the subject of visibility at various Virginia and West Virginia cities is discussed. Data show that Roanoke's average visiblity has improved significantly since 1936, not declined. The trend is obvious on a chart of observed conditions back to that time.
A closer inspection of the data shows that it is visibility in the cooler months -- from fall through winter and early spring -- that has improved dramatically, not so much the summer visibility. Hence, the chalky summer skies I abhor have always been with us.
The climatologists' off-hand explanation is intriguing. They suggest that the end of the coal-fired engine era could be a leading factor in this visibility trend in Roanoke. The Norfolk and Western railroad, which was headquartered here not so very long ago, phased out coal-burning locomotives in 1960. They produced a lot more soot and smoke than the current diesel engines. The diesels probably join auto exhaust in creating more ozone -- a key ingredient in summertime mucky haze -- but not the lingering black smoke the coal-burners left behind.
The article is interesting on many other points. Check it out for yourself on the Web, charts and all.
July 7, 2003
Copyright 2003