Top 5 Weather Whoppers of 1999
When you look back on 1999, what stands out? Michael Jordan’s retirement? Star Wars: The Phantom Menace? Ricky Martin crooning “Livin’ La Vida Loca”? Speaking of loca, what could be crazier than ’99’s wild weather?
In January a blowout blizzard dumped up to two feet of snow from Minnesota to Texas. In May, savage tornadoes pummeled Oklahoma, killing more than 40 people. Last summer’s drought parched northeast farmland, costing farmers more than $1 billion in crop damage. Then on September 16, Hurricane Floyd lashed Atlantic coast states from South Carolina to New England, causing massive flooding and 56 deaths. What’s going on?
“Weather is by nature extreme–hot, cold, wet, and dry,” says Sam Champion, a meteorologist (weather scientist) and New York City weatherman on ABC-TV. “When it comes to understanding how complex weather patterns work, we’ve only started putting the pieces together.”
Some scientists think one source of ’99’s wild weather could be La Nina, a Pacific Ocean weather cycle in which fierce winds have caused colder ocean surface waters in the last two years. La Nina may trigger drought conditions followed by hurricanes in the eastern U.S. But Champion cautions: “Maybe one, 20, or 120 different weather patterns in combination cause cycles of droughts and hurricanes. We still don’t know. Still, 1999 was an extremely active weather year.” Just how active? Check out ’99’s top weather whoppers.
1 HURRICANE FLOYD
September 16, 1999: East Coast
Hurricane Floyd roared out of the Atlantic Ocean to pound the U.S. Eastern Seaboard with gale force winds of 160 kilometers per hour (100 miles per hour). Floyd had calmed down from the day before, when its storm clouds spanned an enormous 1,000 km (600 mi), and winds raged at 225 kph (140 mph). Meteorologists rated Floyd a Category 4 hurricane out of a rating system that runs from 1 to 5 based on wind speed. (Category 5 hurricanes pack winds of 155 mph or more).
Three million coastal dwellers evacuated their homes. Floyd struck hardest in North Carolina, dumping 20 inches of rain, and flooding half the state before rolling northward.
Floyd became a hurricane (see diagram, left) after starting off as a small rainstorm off western Africa. The Atlantic’s warm water (30 [degrees] C, or 86 [degrees] F) fueled the small depression, or storm. Seawater evaporated and men condensed to form clouds. Trade winds, low-altitude tropical winds, combined with high-altitude winds to blow westward. Then winds pushed the growing storm into a vast spiral shape.
When Floyd hit land, it weakened into a tropical storm (ocean-borne storm with winds of 30 to 74 mph). “It’s hard to predict a storm’s exact path and fury,” says Jack Beven, a hurricane specialist at the National Hurricane Center in Miami, Fla. To forecast hurricanes, meteorologists study wind patterns and track areas of low pressure (regions with warm evaporating air) across the Atlantic. But many factors alter hurricane forces, so sizing up a hurricane is a guessing game.
Birch of a Hurricane
Hurricanes form over oceans. 1. Warm water evaporates and rises, condensing to form rain clouds. 2. Humid air rises, creating a vacuum that draws in outside air. 3. This mixed air heats up, creating more clouds and expanding the storm. 4. Trade winds (low tropical winds) and high-altitude winds (winds at 40,000 feet above Earth), blowing in the same direction, send the storm spiraling around a center, called the eye.
2 OKLAHOMA TORNADO
May 3, 1999: Oklahoma
More than 40 tornadoes swept the outskirts of Oklahoma city for 20 hours, leveling entire communities in a swath of fury. The twisters rank among the worst in decades, injuring 750 Oklahomans, killing 42, and causing more than $1 billion in property damage. One tornado spawned record-breaking winds of 511 kilometers per hour (318 mph) and lasted four hours! An average twister fizzles in minutes.
In mid-afternoon of May 3, meteorologists spotted small, tightly packed storms west of Oklahoma City. Changing wind patterns around the storms spun the air fast enough to create a funnel with a vacuum, or low-pressure area, inside the spinning air. Result: twisters (see diagram above). As the tornadoes whirled faster, the pressure inside their funnels dropped. That increases twisters’ suction force. The tornadoes sucked up everything in their path!
On average, 1,000 tornadoes hit the U.S. each year, most of them between late spring and early summer in Tornado Alley–an area that stretches from Texas to South Dakota. So the Oklahoma twisters came as no surprise to forecasters. But the funnels of most tornadoes usually measure less than 500 meters (1,640 feet) wide, whereas these monsters had funnels measuring 1.5 km (.9 mi) wide!
How Twisters Form
1. Tornadoes occur during thunderstorms, when cold dry wind meets warm humid wind. 2. The two winds, moving in different directions and speeds, spin around one another. 3. The spinning effect lowers the pressure inside the storm, creating a vacuum in the storm’s center. 4. The vacuum sucks up moist air from below which rises and becomes part of the storm.
3 SUMMER DROUGHT
June-August 1999: Midwest, Northeast
Summer ’99 parched much of the U.S. In Connecticut, rainfall totaled only 2 inches in June–8 inches is normal. In Maryland, average dally temperatures in July soared to 90 [degrees].
By mid-July, small lakes from Ohio to Maine dried up. By August, many states imposed water restrictions: in Maryland you could go to jail for six months if you watered your yard. The summer’s drought proved one of the worst in decades, costing West Virginia alone more than $100 million in crop damage. “All the bushes and trees began to die,” says Christina Andreadakis, 12, of Lutherville, Maryland.
The drought began when a high-pressure system (weather pattern in which dense dry air keeps out rain) stalled over parts of the Midwest and Northeast for two months (see diagram, above). “Droughts occur somewhere in the nation every year,” says Michael Hayes, weather scientist with the National Drought Mitigation Center in Lincoln, Nebraska. “The problem is that our vulnerability to them is increasing.”
As urban and suburban populations grow, the dependence on water sources increases. Farmers were hardest hit, losing $1.5 billion in crops and livestock.
Eventually, with the landfall of Tropical Storm Dennis on August 31 and Hurricane Floyd, parched states became wet again. “The fact that hurricanes follow droughts may be nature’s own `moisture delivery system,'” says forecaster Sam Champion. “It’s nature’s way of replenishing land starved for water.”
How Droughts Form
1. Droughts start when an area of high pressure (densely packed air molecules) remains motionless for a long time. 2. This prevents the passage of rain clouds, which then must move around the high-pressure system. These high pressure areas bring cold dry weather in winter and hot dry weather in summer.
January 2, 1999: Midwest
The year was two days old when the worst blizzard in decades blanketed states from Minnesota to Texas, killing more than 20 people, and snarling road and air travel. In a matter of hours, Chicago saw 24 inches of snow–an all-time city record. Deaths included a handicapped college student in Pennsylvania who froze to death when his wheelchair stranded him in snow.
Blizzards are torrential downpours of snow combined with strong winds–in this case, winds of more than 60 mph. To form, a blizzard needs frigid air blowing from Canada and plenty of moist air, usually blowing northward from the Gulf of Mexico or eastward from the Pacific Ocean. “If it’s cold enough, and a significant amount of moisture is pumped into a storm, you can get a blizzard,” says Paul Kocin, a winter storm expert with the National Weather Channel. When frigid and moist air collide, as they did that bitter January day, get ready for a snow load!
5 WARMEST WINTER ON RECORD
January – March 1999: Most of U.S.
Dozens of ski resorts in New England could barely afford to stay open last winter due to the balmiest weather on record. In Maine, the country’s coldest state, temperatures in February were on average, 7 degrees higher than usual. Virginia saw record-breaking temperatures for the month of January–6 degrees warmer than average.
“We don’t know whether this overall warming trend is simply a natural cycle, or one affected by human activity, like pollution,” says forecaster Sam Champion. “We’ve only recorded weather data for less than 200 years.”
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