Looks Like Stormy Weather

by MSgt Julie Meintel
445th Airlift Wing, WPAFB, OH

2/5/2014 - Spring 2014 -- Of all the changes of the seasons, it sure seems like everyone is happiest to see the arrival of spring. I don't know of that many people who really look forward to the arrival of cold temperatures and piles of snow that winter usually brings, but I know there are some who do! In the spring, flowers begin to bloom, the grass begins to turn green again, and we can put our winter jackets away. Spring, as everyone knows, brings warmer temperatures and leads right into summer, with its longer days, plentiful sunshine, and slower pace. We do relax a little in the spring, but one way we can't let down our guards is with relation to flying and the weather. Getting from the snow and ice of winter to the clear, sunny days of summer means a sometimes-bumpy trip through the unpredictable spring weather patterns.

Perhaps no season is quite as erratic as spring, with its increased thunderstorm activity, fog, high winds, and tornado potential. Weather changes more day to day during the spring than in any other season. Air Force Handbook 11-203, Vol 1, Weather for Aircrews, is a valuable resource for all things weather related and should always be your first stop for weather questions. Here in southwest Ohio, typical springtime weather usually involves some push-and-pull between cold air masses from the north and warm, moist air from the south in the Gulf region. This can cause severe, sometimes violent, storms with high, unpredictable winds, hail, or even tornadoes. If that weren't enough, even after temperatures begin to climb, it is quite possible that they will drop again. It's not at all uncommon to see icing into March and even April.

Our purposes here are not really to go in-depth into thunderstorm producing weather conditions but simply to get you thinking about shifting gears with your flight planning and paying attention to seasonal changes. Thunderstorms and tornadoes aren't the only weather conditions that might trip you up; those high winds that behave unpredictably can also turn into wind shear and microbursts very quickly, and those are guaranteed to ruin your day. When doing flight planning, of course you start with Plan A, but you need to be sure that you don't take off without Plan B, C, and D in your pocket, just in case.

To touch briefly on a few of the weather conditions you're most likely to see, no matter where you are leaving or where you are headed, let's look at thunderstorms and high winds for a few minutes. It says right in the introduction to the thunderstorm chapter in AFH 11-203, Weather for Aircrews, that thunderstorms contain the most severe weather hazards to flight. It also goes on to list these hazards: strong winds, severe icing and turbulence, frequent lightning, heavy rain, and hazardous wind shear. And oh yeah, don't forget large hail, microbursts, and even tornadoes. Each of those is worthy of its own chapter and its own article, but just be aware that in flying near a thunderstorm, those are some of the things you can encounter. The best possible thing you can do when a thunderstorm is in your flight path is avoid it to the greatest possible extent. When you have around 44,000 thunderstorms happening every day somewhere in the world, avoidance is sometimes just not possible. The next best thing if you can't avoid it altogether is to stay far, far away from it and depart the area as quickly as you can.

High, unpredictable winds can quickly and easily turn a moderately bumpy flight path into far more dangerous conditions like wind shear and microbursts. Wind shear, simply put, is any rapid change in wind direction or speed. It is especially dangerous during takeoff and landing when the aircraft is operating close to stall speeds, when any loss of lift could be catastrophic. Wind shear has caused aircraft crashes and fatalities, and being ready to counteract it is critical. A microburst, in a nutshell, is a short-lived and powerful downdraft associated with convective activity. Microbursts and wind shears go hand in hand; microbursts often cause strong wind shears, and meteorological observations show that about five percent of all thunderstorms produce microburst activity.

When the strong winds of a thunderstorm become violent rotating winds in a column, then you have a tornado. This can happen quickly; this is one reason it's important to avoid the vicinity of the storms in the first place. We've all seen the damage tornadoes can do; they are devastating. Winds within the funnel-shaped circulation can reach 300 mph, and the tornado's forward speed averages about 30-40 knots, which equates to about 35-45 mph. That's a fast-moving storm and definitely one to steer clear of!

As if the winds weren't enough danger to accompany thunderstorms, they can also bring hail and lightning. Hail is a solid ball of frozen ice, although hailstones are not always spherical; they are often irregular in shape and size. A general rule of thumb about storms and hail: the larger the storm, the more likely it is to produce hail. It has been known to be present as high up as 45,000 feet, in clear air, and it can be carried as much as 20 miles downwind from the thunderstorm's core. Hailstones can get large and do a lot of damage to an airplane in a very short time.

Lightning can strike at any level in a thunderstorm. Most lightning discharges never hit the ground but occur either within a cloud or between clouds. Lightning can also occur in the clear air above or below a storm, as well as all around it. Depending on the severity of the strike, structural aircraft damage is generally minor, but severe damage can occur. Beyond the structural damage, lightning can also affect the way the aircraft's electrical systems work, along with avionics, instruments, and radar. It can cause bomb doors to open or activate wing folding motors, and it can call your electronic flight control navigational systems' accuracy into question. After a lightning strike, the best thing to do is have your aircraft's systems checked out, and don't trust the instruments' readings until they can be verified.

Like most safety warnings, much of this is "worst case scenario" territory, and you may never encounter anything as severe as these situations. But you are just about guaranteed to encounter a thunderstorm at some point in your flying career, and you will need to be prepared to deal with it. Read AFH 11-203, plan ahead, talk to the weather shop for forecasts along your flight path, and give PIREPS for other crews transiting the area. Don't be surprised by bad weather. Be ready for it!