Wx Watch: Getting the Big Picture

Ever heard of synoptic weather? It's a term used to describe the positions and behaviors of lows, highs, fronts, and other large-scale weather events. In other words, it's "the big picture," and meteorologists pay a lot of attention to it.

Unfortunately, many pilots give synoptics short shrift. We're all taught to pay attention to synoptic features in our pilot training, but how many of us actually bother to sketch in the positions of fronts or lows on those little maps printed on so many flight planning forms? How many of us really read area forecasts? How many of us read the forecast synoptic summaries appended to low-altitude significant weather prognosis ("prog") charts? How many of us can briefly describe the synoptic situation affecting a proposed route of flight? Based on personal experience, I'd have to say that the answer to those questions would be "not many at all."

A friend whose job is to teach tactics for dealing with adverse weather once told me an amusing — if a bit disturbing — story about a class that he conducted. The goal of the class exercise was to get the participants to make a go/no-go weather decision concerning a flight along a particular route. Instead of having all 50 students (all of them certificated at least to the private pilot level) make 50 different calls to flight service, a videotape of a real, standard briefing, for a real weather situation along a real route, was played. The class was to listen to the briefing; write down METARs, TAFs, and other pertinent weather information; then come up with their ideas about the flyability of the weather.

Guess what? The class gaped at the video monitor and never wrote down a thing. It was as though the briefing exercise was some sort of visual Muzak.

The same sort of thing can happen when some pilots watch The Weather Channel — which is an excellent source of synoptic weather, by the way. The Muzak's on, and the mind's on hold. If you were to turn off the TV and ask viewers to recount what they'd just been told, chances are that they couldn't do it.

Telephone briefings from flight service? DUATS printouts? Internet sessions with weather providers? When it comes to synoptic weather, I think that it's more of the same. The wealth of information seems to encourage passivity rather than active involvement in a learning process. Pilots seem to ignore the big picture in favor of concentrating only on the reported and forecast conditions along a thin line stretching from departure to destination.

That's not to say that METARs and TAFs aren't important. They most certainly are, of course. But the big picture can provide vital details about the characteristics of any nearby fronts and also give clues about the weather for the following day. Most important, a knowledge of the synoptic situation builds a weather-oriented situational awareness that can't be beat.

Here are some potentially nasty features to look for in synoptic summaries:

• Any fast-moving (more than 30-knot groundspeed) cold front. These can sprout some mean thunderstorms. If the temperature and humidity contrasts between the air masses on either side of the cold front are great, get ready for some real fireworks.
• Stationary fronts. As the name implies, this type of front can linger for days, with widespread precipitation, low ceilings, and lousy visibilities. It will take a strong high, or another storm system, to move a stationary system.
• Troughs aloft. These southward-dipping masses of cool air can both create and intensify any surface disturbances. They serve as great forecasters of rotten weather. Look for graphic presentations of troughs aloft on the 500- and 700-millibar constant pressure charts.
• Any onshore movement of cool air. This can create dense fog at coastal airports, as well as fog that can reach well inland.
• Occlusions and winter warm fronts. Snow, ice pellets, and other precipitation that falls from colder air aloft can transform into freezing rain when it hits warmer air below. Also, the multiple freezing levels so often observed with occlusions can create some of the worst icing conditions. These phenomena are most prevalent in the eastern half of the United States.
• Stagnant highs. The southerly flow around the "back side" (i.e., the western half) of a high pressure system is a great haze and thunderstorm producer in the eastern United States.

To some extent, the Federal Aviation Administration's own guidelines for pilot written examinations are to blame for a deemphasis on synoptics. Pilot written exams have comparatively few questions about aviation weather. Those that do appear on these exams tend to focus on interpretation of METARs, TAFs, and a few weather graphics. An understanding of synoptics, and the forecasting skills that implies, is downplayed.

That's too bad, because every pilot should be able to generate a basic surface analysis chart after reading an area forecast or a DUATs briefing. Every pilot should be able to look at a surface chart and explain what conditions might be expected along a given route. It's all a part of knowing the "whys" of flying weather, something every bit as important as deciphering the "whats."

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