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Kevin Myatt grew up in Arkansas to the tune of tornado sirens and the rhythm of hailstones. Chasing twisters like he did in 1999 and getting within a quarter-mile of one was exciting, but he finally tired of 5-month-long summers and 2-inch snowstorms and moved to the cooler climes of Southwest Virginia's mountains in 1999. Kevin thought he was going to be a meteorologist growing up but he credits divine intervention with continually detouring him to a newspaper career instead, landing him in an managing editor job of a small Arkansas paper before coming to The Roanoke Times as a copy editor in 1999. But his love of weather continues to this day, and at the beginning of 2003 he began this weather column in addition to the hiking page he has updated occasionally on Roanoke.com since early 2000. He now works the copy desk for The Roanoke Times and is its principal weather geek, offering weather reporting training classes to reporters and advising the newsroom on upcoming weather stories. He updates this column most Tuesdays and Fridays -- and other times as conditions warrant. Email your weather or comments questions to kevin.myatt@roanoke.com For more on Kevin
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WEATHER JOURNALApril 29, 2004 THAT WINDY FEELING FLAGS WHERE IT COUNTS One of the recurring questions I've received from readers and people I know is to explain why it's so much more windy now than it used to be. Having been here not quite five years, it would be impossible for me to judge whether it is or not, and therefore much harder to offer an explanation. So I turned to the folks whose job it is to keep up with things like this, the Virginia State Climatology Office in Charlottesville. It also allows me plausible deniability should the data not match readers' perceptions. Guess what? The numbers at Roanoke Regional Airport over the past 5 years not only fail to show it has gotten more windy, but in fact, according to the climatology office, show that it is less windy over that period than over the average of the full 44-year period of record. In the 60 months between 1999 and 2003, only four -- September 1999, March 2001, November 2002 and January 2003 -- have had wind speeds above the monthly average over a 44-year period. Two others -- July 1999 and October 2001 -- were right on the average. In the remaining 54 months, wind speeds at Roanoke Regional Airport were below the 44-year average. So what does that mean? That all the people wondering about the wind are crazy? Not necessarily. First off, remember that no one lives at the Roanoke Regional Airport. The airport's rain gauge is regularly reviled by readers around the area as a notorious dry spot, often getting a few tenths of rain when Boones Mill or Cave Spring or Vinton or even Downtown Roanoke get deluged. This is a question for another day. As for the wind, it is possible that wherever you live may in fact be windier than it used to be, whatever the anemometer at the airport is showing. The climatology office offers its own caveats, one being that the location and the elevation of the wind-measuring equipment changed in 1996, when Roanoke adopted an automated system and relocated it on the airport grounds. Another larger caveat is that this analysis is not as thorough as it would need to be to prove or disprove the conclusion, and such an analysis is beyond the reach of the available data. Even with those askterisks, it is the opinion of the climatology office that it is unlikely that average wind speeds have increased at the airport in recent times, and may have decreased slightly. One idea I have is there have been several memorable high wind events of late driving the perception that it is more windy. Last fall, for instance, gave us Hurricane Isabel and two 60-mile-per-hour cold front wind blasts in a period of 6 weeks. What do you think? Is it more windy or less where you live? E-mail or call me. April 26, 2004 You can't look out of an airplane and see state lines neatly printed on the surface. Similarly, you can't look up in the sky and see blue or red wavy lines, or giant H's or L's, but weather people talk about fronts and pressure systems like they're family pets or in-laws. Let's take a few moments today and consider fronts. The blue lines on the weather map with pointed triangles represent cold fronts, while the red lines with rounded humps are warm fronts. A line that alternates between the two is a stationary front. There are also occasionally occluded fronts, but let's leave that complication for another day. One of the pointed blue lines is sweeping over us from the west today. Our air will become much cooler and drier after this rain, so cool in fact that some areas will probably see frost on Tuesday night. The symbols for fronts were adopted from military planning. The lead positions of various armies are often depicted by lines embedded with triangles or humps pointing the direction of their movement. You can think of fronts in the same way: The leading edges of "armies" of air, heading in the direction the triangles or humps point. Almost all of the warm fronts that pass through Southwest Virginia are the forward thrust of warm, moist air originating in the Gulf of Mexico. But we have at least three different flavors of cold fronts. Most of our cold fronts would more properly be termed "cool fronts" and are the leading edge of air masses originating in the northern Pacific Ocean. Even though this air has originated in an ocean, by the time it has crossed nearly 2,000 miles of land and been wrung out by at least three major mountain ranges, the air is dry. These fronts usually bring temperatures only a little cooler than on the front side, but because they bring dry weather, daytime temperatures in sunshine may be just as warm or a little warmer than what was experienced before the frontal passage. Other cold fronts are termed "Canadian" cold fronts because they bring air originating in the bowels of our northern neighbor. This air is usually about 10-20 degrees cooler than what preceded it. A third group, the dreaded Arctic cold fronts, originiate near the Arctic Circle and often plunge temperatures 30 or more degrees. Though we get a few Canadian cold fronts even in the summer, Arctic cold fronts are almost entirely limited to late fall, winter and early spring. Quite often, a warm front or a cold front will run into resistance and stop moving. These are stationary fronts. When a front hangs up like this, it can be a continuous train track for storminess. A stationary front last week was responsible for repeated rounds of severe weather and flooding in Oklahoma, Arkansas, Missouri and Illinois. Stationary fronts frequently would be better termed "flip-flop fronts" because they waffle back and forth as the armies of warm and cold air advance and retreat at one another's expense. This can be a deeply confusing and frustrating situation for meteorologists. A difference of 30 miles or less can mean the difference between stable and stormy. For the record, the front that is passing was a Pacific front when it stalled in the Midwest, but then got a push from Canada and is going through as a Canadian front. Even though you don't see blue triangles overhead, you still should consider covering up your tender vegetation on Tuesday night. April 22, 2004 REAL SPRING, RIGHT NOW You can think of all weather as a quest for equilibrium, always in motion, only occasionally realizing its goal. We have been experiencing that over the past week. After several days of cold, damp weather that even produced some snow at higher elevations, we suddenly sprang out of winter's encore into summer's preview. The high pressure ridge built overhead over the past week and we've seen several days of temperatures in the 80s, with even a few 90s here and there in Virginia and the Carolinas. The "normal" temperatures for this time of year -- averaged out over 30 years between 1970 and 2000 -- are around 70 for a high and the mid-40s for a low. On April 12, Roanoke had a high of 46. That's close to our average low this time of year, and about what our average high is on any given January day. In sharp contrast, the high of 87 that Roanoke recorded on Sunday is about equal to our normal high in August. So the question remains: Where is spring? Did we just skip from winter to summer? When temperatures are swinging far above and below seasonal norms, it's a sure sign of atmospheric energy that makes large-scale storminess a distinct possibility. Cooler air has had a hard time moving southward and eastward against the hot air dome over the Southeast. A cool front has become stalled roughly from Oklahoma to Pennsylvania, rippling back and forth with each successive push of cool and warm air. The collisions of the air masses along this indecisive front have triggered some serious thunderstorms. On Tuesday, a deadly tornado ripped through Utica, Ill, part of an outbreak of twisters, high winds and hail that have been raking several Midwestern states. In Virginia, the warm air has been steadily getting more moist, until finally on Tuesday, a very weak cool front backing in from the north was enough to touch off showers and thunderstorms. Nothing like Illinois experienced, but a sign that it's that time of year when the seasons fight until summer finally pins winter to the mat. But it's too early for summer to win just yet, and the cool air will ultimately win this week's battle, as high pressure to our west and northwest will finally gather enough strength to push a cold front through over the weekend. We'll see some rain, maybe hear some thunder, though it looks doubtful now that all the conditions will be ripe for really heinous thunderstorms. Always something to keep an eye on, though, when air masses collide. Here's the good news, for many of you: This front will not be so powerful as to return us to winter's chill, but should actually bring us very close to our seasonal norms, with highs around 70 and lows around 50 much of next week. So spring will finally arrive, with at least a few days of precious "normal" weather. Not too hot, not too cold, just rare equilibrium. It won't stay that way, so enjoy it while it lasts. April 19, 2004 IT DOESN'T GET WORSE THAN BANGLADESH Mount Washington, N.H., often gets tagged with the title of the "World's Worst Weather" for its 200-mph wind gusts and brutally cold temperatures. But for sheer human tragedy, nowhere can compete with Bangladesh, the small, densely populated nation immediately east of India on the Bay of Bengal. Bangladesh holds the dubious distinction of having suffered the most deadly tropical cyclone (estimated 300,000 killed in 1970) and tornado (1,300 killed in 1989) on record. The nation also gets regularly raked by hailstorms and massive flooding. Last week, 70 people were killed and some 15,000 were left homeless when a series of tornadoes ripped through northern Bangladesh, wiping out rural farming villages of mud huts. A Virginia native is on the vanguard of studying tornadoes in Bangladesh. Jonathan Finch, a Lawrenceville, Va., native who got his undergraduate degree at the University of Virginia, is a meteorologist at the National Weather Service in Dodge City, Kan., right in the heart of America's "Tornado Alley." On the side, he has become the first forecaster to issue tornado watches and convective outlooks for Southeast Asia on his Web site, bangladeshtornadoes.org. The site also contains a history of major tornadoes in the region and detailed information on the weather patterns that cause them. The big reason Bangladesh is such a target for high-intensity bad weather is the Bay of Bengal to the south. Its waters are above 80 degrees all year long. Our chief moisture sources, the Gulf of Mexico and the western Atlantic, only retain those kind of water temperatures for a few months in summer into early fall, and then only in certain areas. The Bay of Bengal's warmth easily cooks up mighty cyclones (we call them hurricanes) and supplies tons of sultry air for heavy rain, thunderstorms and tornadoes. Dry winds move from west to east across India, often originating in Afghanistan and Pakistan, and roar off the Himilayas and the Tibetan Plateau to the northwest. This dry air then collides with warm, wet south winds off the Bay of Bengal to create supercharged thunderstorms with lots of spin. It has many similarities to the weather pattern that exists in America's "Tornado Alley," where about 90 percent of the world's tornadoes occur. In the U.S., dry air blowing down the Rockies encounters warm, moist air from the Gulf of Mexico. America's version covers a wider area for a longer time, so there are many more tornadoes in the U.S. But the juxtaposition of 29,000-foot mountains with 85-degree sea temperatures in such a small area may in fact make a greater percentage of tornadoes violent in Bangladesh, a nation packed with 2,580 people per square mile. (By comparison, Virginia averages 181.5 people per square mile) So the next time the weather turns rough here (not this week, with lots of dry warmth under that high pressure I told you about last week), just know that no matter how bad it is, it's almost certainly been worse in Bangladesh. April 15, 2004 LET US COUNT THE DAYS Was four days of cold and damp weather worth it for possibly as much as a week of sunny, warm, dry weather to come? That's the tradeoff we are making in the highly amplified, slowly progressing weather pattern that has set up this early part of spring. What I mean by highly amplified is that the jet stream, riding west to east across the country, is taking huge rises to the north and dips to the south. So the chilly, wet periods are especially chilly and wet, while the warm, dry periods are also especially warm and dry. The dips in the jet stream represent low pressure troughs, areas of rising air where convection and condensation tend to be centered. These troughs have been digging particularly deep this spring, so much so that they become lethargic and don't want to move with the jet stream. Sometimes they even become cut off entirely from the jet stream, as we've discussed before. This is the slowly progressing part, where a given low pressure area may hang over a certain area for days on end. This was what happened over the past four days, as a low that nearly became cut off just took its sweet time moving across us. We ended up with 2 1/2 inches of rain stretched over the period, and some unseasonably cold weather where our daytime highs were near what our average lows should be. Most remarkable about this past storm was its pool of cold air aloft that was so deep it triggered the latest accumulating snow on record for parts of western Kentucky and Tennessee. Some places got up to 6 inches, and these are places many hundred feet lower than our 900-foot elevation at the base of the Roanoke Valley. There was some snow at elevations above 3,500 feet around here, and lower than that in West Virginia. But now what has happened is the huge cutoff low in the northern Pacific that we talked about before is drifting into the Pacific Northwest. As it does this, the pattern is progressing subtly so that cold, wet, storminess will be centered over that part of the country, while a high pressure ridge builds in the East. Air sinks in a high pressure area, killing convection and moisture buildup. As a high pressure area remains in place, the air under it gradually warms. In the summer, these high pressure ridges can become really stagnant, and trap hot and hazy conditions under us for weeks on end. For now, it'll just bring several days of warm, dry, spring weather to make you forget the damp chills of early in the week. The flip side of this warm spell is that it may in turn lead to another cold, damp period down the road, maybe this time next week or later. Sometimes we're in a fast jet stream pattern where systems zip through and give us a quick hit of rain every few days. We're in an different scenario now, where systems move through slowly and drag a lot of weather with them. Which is better -- three days of nice weather followed by a day of rain, or a week of dry followed by four days of rain? You be the judge. April 12, 2004 HEAVY LIFTING KEEPS US UNDER THE WET When it rains here, like Monday's soaker, it always needs a lift. Something has to raise the moisture in the atmosphere, causing it to both encounter cooler air and bunch together, condensing it from vapor into droplets. There are many different mechanisms for that lift, four of which I will discuss here. Often, two or more of these factors are working at once. In the early and middle part of this week, all four may have a hand in our rain. The chilly, steady rain we got on Monday is often the result of "overrunning." This is when warm, moist air from the Gulf of Mexico is carried aloft on top of a cool air mass at the surface. The lift is created by weather systems high in the atmosphere. On Monday, the counter-clockwise circulation of a strong upper level low developing to our west over the Mississippi River valley did exactly this. The cool air became trapped on the east side of the mountains, as it so often does here, and the warm, moist air came over it. A second factor that is often in play in rain production is orographic effects, or what mountains do to lift moisture and cause precipitation. Upslope winds are a common cause of precipitation in our mountainous region. In the winter, the focus is often on northwest winds blowing over the mountains of West Virginia, causing snow squalls. In spring and summer, more of focus is on east and southeast winds bringing Atlantic moisture up the Blue Ridge. Monday's rain, though primarily caused by overrunning triggered by large-scale weather systems, also had an upslope element with east and southeast winds ahead of the low riding up over the mountains. Fronts also lift moisture. A cold front plowing through a moist air mass is like a plow blade, pushing the juicy air in front of it high into the atmosphere. We'll have a cold front pushing through over the next 24 hours, and this could aid in shower and thunderstorm development. Finally, there is convection, which becomes more and more at work as we get deeper in the warm season. Convection is simply warmer air at the surface rising into cooler air aloft. Come the hot summer months, convection by itself is often a trigger of afternoon showers and thunderstorms. It can team up with orographic effects -- the difference in heating between the mountaintops and valleys -- to create rumbles and downpours on otherwise sunny, sultry summer days. On Tuesday, with a warm front working in to bring milder air at the surface, it is possible that this 60ish air will push upward into the cold pool of air aloft with the upper level low, causing some thunderstorms to form. Convection doesn't require hot air, just air somewhat warmer rising into other layers that are somewhat cooler. All this heavy lifting will mean we stay wet through at least mid-week. April 8, 2004 A MOIST KIND OF DRY Somewhere along the way, we got a little dry. Drought comes upon us stealthily. It doesn't announce itself with dramatic flair like a hurricane or Arctic cold front, it just creeps on us, deceiving us with piddling little rain showers that don't really amount to anything, and then, there it is. The ground turns chalky, acre-sized brush fires spread into miles-wide forest fires, reservoirs start dropping, and before long, they're telling you not to water your yard or wash your car. Let me emphasize, we're not having a drought, and we're not really close to one, for now at least. But we are almost 5 inches below normal in rainfall for 2004. Carvins Cove slipped below full pond for the first time in many months on Wednesday. Considering that parts of the Southeast are much drier, it makes one wonder if our soggy 2003 wasn't an aberration in a long-term pattern of dryness in our corner of the United States. Since the late 1990s, we've had an alarming propensity for drought in our neck of the woods. The near-record rainfall of 2003 wiped out our last round of drought, filling parched Carvins Cove and even leaky Mountain Lake to the brim. It's a bit too early to declare that we're headed toward a drought this summer. For one thing, the immediate weather pattern doesn't support it. You may even be seeing some rain as you read this on Thursday as an upper level low -- what was once a cutoff low spinning its wheels in the desert sand of the Southwest, causing severe flooding in Mexico and burying Texas in hail drifts -- approaches from the west. Yet another cutoff low, or upper level low pressure separated from the jet stream, will be driving a weather pattern that could bring us a soggy, chilly Easter weekend. But this time, instead of spinning over us as it did last week, it'll be way out in the Pacific ocean below Alaska. Yes, that far away, it will affect our weather. This closed low (another term for a cutoff low) will do a couple of things: (1) serve as a roadblock for any kind of large systems that could break the weather pattern down and (2) with its counterclockwise spin help "pump up" a high pressure ridge in the western United States. When the ridge is in the west, the trough develops in the east. The jet stream will rise high up over the high in the west and dive southeast toward us, digging as deep as the Gulf of Mexico. Unlike last week, when the cutoff low got stuck over us and spun showery weather and mountain snow showers on us in pitiful monotony, a series of smaller disturbances will ride the jet stream through this trough, each one scooping up moisture and triggering occasional rounds of rain through the weekend and early next week. There is some concern that one of these disturbances about Monday or Tuesday could fire up a larger surface low, possibly a semi-nor'easter-like storm that could spin a lot of rain inland -- maybe even some snow in the high elevations of West Virginia, Pennsylvania and points farther north. But even if that doesn't transpire, it looks pretty wet over the next week. It may not be enough to catch us up to normal, but it should be enough rain to end any thoughts of an ongoing dry-out that lasts mercilessly into summer. This high-in-the-west, trough-in-the-east pattern is what we've been stuck with through most of the last 18 months, including those drippy months of 2004. There's still plenty of time to turn the tide of expectations from drought to deluge, though I'm sure we've all grown weary of either extreme and would prefer an unremarkably average year of rainfall this time around. April 5, 2004 OUTBREAK ANNIVERSARY The United States has been raked by many, many tornado outbreaks. But only one is called the Super Outbreak. April 2, 2004 CHILLING EFFECT When there’s a cutoff low hanging around, don’t wear your cutoffs.
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