To a student pilot, weather is usually not a concern. The flight instructor checks the reports and forecasts alongside, and helps to make the critical go/no-go decision. Flights are often limited to within 10 miles of the airport and last only an hour, so it's likely the weather prediction will hold true. But all flying isn't done in the comfortable environment of the airport with a flight instructor. Pilots fly in the real world, and the real world is full of real weather.
As pilots, it's our prudent duty to seek out weather reports and forecasts, determine whether they meet our personal minimum criteria, and then make a go/no-go decision. But since weather is an inexact science and the combination of all the separate factors add up to an infinite number of possibilities, it takes skill and experience to know whether what's on the screen or coming from the flight service briefer is what really will happen. In other words, we must make a two-dimensional guesstimate of the weather come alive in three dimensions.
Developing good weather judgment begins on the ground. Before any flight, it's imperative to check the weather with a full briefing. Besides being a required task (see Federal Aviation Regulation 91.103), it's just good sense.
Making a decision on whether or not to fly is easy when the weather is either really good or really bad. The challenge is the gray area between those extremes. The first step in seeing through the gray and making a go/no-go decision is to identify key factors in the briefing that suggest larger issues. Hundreds of these little tidbits are scattered throughout weather reports and forecasts, and it's up to each pilot to identify which ones matter. Here are a few examples:
VFR not recommended. This may seem obvious, but it's important to understand VFR not recommended is put in briefings for a reason. Conversely, the warning against VFR is issued for weather covering a wide area, and the conditions in any specific local area may be conducive to safe flight.
Close temperature/dew point spread. Just like you learned in the weather theory books, a close temperature and dew point may mean fog, drizzle, rain, or freezing precipitation. Another key indicator of fog is the close temperature and dew point spread the morning after a particularly wet cold front goes through. The abundant moisture almost guarantees morning fog.
Pressure falling rapidly and strong southerly winds. Those two factors add up to a cold front. A deep trough, especially for those on the east side, is also a good indication of a frontal zone. A front probably won't develop in the next hour, but it will eventually.
Close pressure gradients. The closer the isobars (lines of equal pressure), the stronger the winds. Bank on that.
The 850-mb chart. Meteorologists say that as a rule of thumb the peak wind at 5,000 feet will be the peak wind on the surface later in the day. If the windsock is flat against the pole at 8 a.m., check the 850-mb chart for a predication of what it may look like at 11 a.m.
These are clues to help guide you to a broad picture, which is a good thing. When looking at weather, start big and go small. Not only will the larger picture often give clues to the local weather, and thus make you better at predicting it, but it's usually more accurate. Large-scale patterns are easier to forecast than micro areas and short time frames. There's a reason why flight service briefings go big to small--follow its lead.
To help further interpret the weather, assume two things about your briefing. First, the information will be wrong; second, the weather is often over-forecast. To the first point, if you go into the briefing assuming that what you're about to hear will be wrong, it will get your mind on edge and help you be critical of what's being said. To the second, although it always pays to be safe and careful, most forecasts are overly so. Does it look like clear blue sky but the terminal area forecast says five miles visibility for the next two hours? Use common sense to know that probably won't happen.
After receiving all the available information, the challenge is knowing what to do with it. You need is a framework, or a set of criteria called personal minimums. Establish a set of weather criteria beyond which you will not fly--a weather budget, per se. Consider the weather briefing a nice dinner. Your personal minimums are your bank account. If dinner is going to cost more than you have in the bank, don't go to the restaurant. Likewise, if the wind is forecast to be 20 knots and your personal minimum is 10 knots, don't launch.
Before you set your personal minimums, consider that there are a few fundamental problems with the concept. Personal minimums need to be realistic, meaning they should be conservative, but also workable in the real world. Sticking to your minimums in an absolute sense just isn't practical. Let's face it--someday you will be stuck 500 miles from home and something will be beyond your limit. If you've never pushed yourself and your limits, you won't have the confidence to fly or the experience to know if you can truly deal with it. Also, remember to revisit your limits. If your wind limit is 10 knots and you land consistently well in 10 knots, up your criterion to 15 knots. Just try and do it on a controlled day, say one with a low crosswind component.
You have to be honest about your abilities and pragmatic in your approach. That's why it's safe and smart to sometimes push or break your personal minimums. Sure, you could fly up against the limit five times before you decide to up the criterion incrementally, but that isn't practical. To know if you can handle the real world, you need to push it. It's silly to be stuck those 500 miles from home just because winds at your departure are eight knots over your limit--something most pilots can easily handle if need be.
This is where experience and judgment come in. Pushing it isn't a license to take unnecessary risks. Listen to the voice in your head and recognize the difference between fear or concern, and trepidation. Listen to the voice, understand why you're feeling the pullback, and follow its warning. A refresher lesson with a flight instructor can help with this as well.
Remember that flight training is like a learner's permit. While you're in training, your instructor will limit you to certain wind, visibility, and ceiling values--consider these your first personal minimums. But when you earn that pilot certificate, you are free to go wherever you want and whenever you want, provided you follow the regulations. Just because new drivers can go 70 mph on the Interstate during rush hour doesn't mean they should. Nor should a new pilot blast off with his newfound freedom into three-mile visibility for a cross-country.
Let's go flying
Ready to go test your judgment? Remember the reports and forecasts were likely wrong, at least in some small way. Knowing this is important when making the flight in question. It puts you in the mindset of looking out for any adverse weather. Consequently, you'll be mentally prepared to divert, turn around, or implement another backup scenario.
Sometimes personal minimums are conservative enough, and nothing on the flight comes as a surprise. But the reality is there will always be some surprises, sometimes even to your benefit. The ceiling will be higher than forecast, the wind will be stronger than expected, or the visibility will be lower than forecast. Discrepancies between expectation and reality are a key reason to have personal minimums. If you stay within your boundaries, you'll be better off when the weather does turn worse because you gave yourself a buffer. As an example, if your personal visibility minimum is seven miles and conditions drop to five, you'll be fine. But if you don't have minimums beyond the FAA requirements and the visibility goes down just a mile or two, you have a real problem.
Approach weather like the science it is. Take what the briefer said as the theory, go do your experiment by flying the trip, and after your flight analyze the results. Were the winds stronger than forecast? If so, why? What did the clouds tell you about the smoothness of the air? Why did certain places along the route have cloudier weather than others? At a minimum, make sure you understand why the forecast was different than the actual weather and imagine a few key factors such as temperature or cloud cover that would have changed the conditions.
As you drop your minimums, remember there are some conditions that you shouldn't ever fly in--thunderstorms, freezing rain, and ice are a few examples. Not flying in a thunderstorm may seem obvious, but they can fool you. One time you'll fly near one and nothing will happen. Then the next time you might get a little closer, and the third time you'll fly under one. Don't forget that thunderstorms are unpredictable, violent weather events. No amount of training or experience ever changes that dynamic. The same goes for icing and freezing rain--that is, until you fly an airplane equipped and certified to handle the frozen stuff (and even then, getting out of those conditions can be a priority). Learning to fly in ice by first-hand experience is a bad idea in an airplane not equipped to handle it.
Flying in a little bit of weather can be a beautiful, almost spiritual experience. But work your way up to that day. Experience is acquired over time, not all at once.
Deputy Editor Ian J. Twombly is a commercial pilot with multiengine and seaplane ratings. He is a CFII.
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