Copyright © 2011 by Ralph Couey
Motorcyclists of all stripes look forward with great anticipation to the end of winter and the return of sunshine, warm weather, and clear roads. Spring can be a glorious time to ride, but changing weather patterns can develop dangerous conditions.
Spring in the Midwest and high plains is a time when war breaks out between warm, moist air surging up from the Gulf of Mexico and cold, dry air making its stubborn retreat into Canada. The resulting battleground can generate strong to severe thunderstorms, some of which may spawn tornadoes.
There are different types of thunderstorms, and it’s important to know the difference. There are isolated storms, the ones meteorologists like to call “garden variety” or “pop-up” that develop, rain themselves out and dissipate over a couple of hours or less. The hazards of these storms are torrential rainfall, extremely limited visibility, strong wind gusts, and lightning. Most riders are familiar with these, a regular encounter on afternoon rides. Probably the biggest danger is the heavy rain, which can induce hydroplaning, a wave of water that builds up at the front of your tires that can actually lift the bike off the road’s surface, sending the machine skidding across the asphalt. Don’t think for one moment that rubber tires protect you from lightning strikes. It has happened, last year in Kentucky for example. Also, the heavy raid restricts visibility for drivers as well. We know how hard it is for them to see us on a good day. In a downpour, trying to peer through a windshield and wipers, it’s even more difficult. Since these storms are isolated, i.e. fairly small in footprint, the best thing is simply to pull off and wait for them to pass, or change your route to go around them.
A severe thunderstorm is characterized by the National Weather Service as one with 58-mph wind gusts and at least 3/4-inch hail. I’ve been caught in two hailstorms in my riding career, and I wore those bruises for a long time. But hail in these storms can range up to the size of golf balls or larger. These are life-threatening, and no place for a motorcycle.
Supercell thunderstorms are the largest, covering a huge swath of sky, thousands of cubic miles. The tops of these storms can reach as high as 60,000 feet. These are the storms that are most likely to produce a tornado. Twisters are fairly rare events. Each year, some 100,000 thunderstorms rumble across the U.S. Tornado counts are a bit more difficult, but the best estimate concur that around 1,000 tornadoes occur in the U.S. annually. So, a tornado is, in essence, something that occurs only one percent of the time. Still, they need to be taken seriously.
Besides the obvious danger of getting sucked up into a funnel, other hazards include hail from the parent thunderstorm, inflow winds nearby which can be over 100 mph, and one most people don’t think about. Debris.
Tornados are constantly picking things up, mostly dirt and rocks. But they can also pick up debris from houses and commercial buildings and vehicles. There is a video that was taken of a twister in that tore through an industrial park in Pampa, Texas in 1995. The video clearly shows a full-size pickup truck whirling around the outside of the funnel about 100 feet up in the air before being thrown to the ground. Debris has been known to fall out of the sky as much as a mile and a half from the actual storm. So a rider (and a motorist or pedestrian) really faces a three dimensional threat.
There are ways to avoid getting caught in severe weather. One way is to check the weather reports before venturing out. Forecasting, while still challenging, has gotten much better in recent years with the advent of sophisticated computer modeling of the atmosphere. If there is a severe weather threat, it will be known at least a day in advance.
Another way is to learn how to “read” clouds. Thunderstorms are “built” by warm air rising into the atmosphere. The higher the air rises, the more severe storms become. You can see towards the afternoon when regular cumulus clouds start to throw up “towers.” What you’re seeing is that rapid rise of warm, moist air. This is a process called “convection.” When you see that, the atmosphere is destabilizing and bad weather is on the way. Once you begin to hear thunder, head for home, or some other shelter. Lightning researches say that if you can hear thunder, you’re in danger of being struck by lightning.
If you should be caught out in the open facing a supercell, there are signals in the atmosphere you can look for, based on hundreds of eyewitness accounts.
The air, which was already hot and humid, will become very still and oppressive. Animals will have gone to ground, so there may be almost no sound. Some people have reported a smell similar to natural gas. Looking up, you may see the entire storm rotating. In the southwest quadrant of the storm, you may see a cloud segment lower out of the base, roughly shaped like a foot. This is called a wall cloud. If conditions are just right, a funnel will form and begin to reach for the ground. Sometimes the funnel may be invisible and you’ll have to look for telltale signs of dust and debris along the ground. And if the local officials are on the ball, you will hear the hair-raising sound of sirens spooling up around you.
Most storms move from southwest to northeast, though there are exceptions. The best escape route is to move away at a ninety degree angle to the storm track, preferably south. Don’t try to out run the storm, but move towards the nearest likely shelter. Avoid highway overpasses and tunnels, which can compress winds and create a funnel for debris. If there’s no time to get to shelter, then find a ditch or depression, lay face down and cover your head. Obviously, if you wear a helmet, you’re already a leg up.
Of course, once the twister is past, start looking for people to help. If the storm passed through a populated area, there will be damage and injuries, and people trapped in the rubble of their homes. First responders, trying to navigate roads made impassable by damage and debris, may take a little extra time to arrive.
No rider enjoys being caught in bad weather. But in careful planning before the ride, and keeping your head up and wits around you during the ride will help to mitigate the risks.