Weather Charts

Pilots are well-armed with weather information before they go flying, or at least they should be. In this age of Internet access to massive databases of weather charts and forecasts, there’s no excuse for being uninformed about the weather before setting out on a flight.

Even without the Internet, the FAA maintains a network of Flight Service Stations where pilots can look at charts and forecasts. With the help of an FAA specialist, pilots can get preflight briefings that include every important detail of weather that might affect a flight.

To be sure, local weather is highly changeable, often making a mockery of forecasts just a day or two into the future. That’s why weather charts have life spans of just a few hours. Then, weather specialists publish updated ones that reflect changes in the atmosphere’s variable currents.

If a pilot can’t visit a Flight Service Station in person, a toll-free phone call will connect him to a specialist who will give the same weather briefing right over the telephone.

What do raindrops look like? They don’t look anything like raindrops as we draw them in doodles. They begin as tiny, spherical globules, and as they combine with other raindrops, they begin to flatten on the bottom. When they grow larger than a quarter inch, they elon­gate and begin to get skinny in the middle until they are two drops separated by a thin tendril of water. The tendril eventually breaks, leaving two droplets half the size of the large one, and the process starts again.

Whether by Internet, in person, or by telephone, the preflight weather briefing is crucial for a safe flight. Here are a few of the charts and forecasts that pilots should become familiar with:

• Surface weather observations. These local weather reports don’t attempt to forecast the weather, they simply report current conditions. In pilot shorthand, one might look like this: KBOS 202254Z 12008KT 11/2SM BR. After some basic training, pilots are able to translate easily: At Boston on the 20th of the month at 22:54 “zulu” time (as pilots refer to Greenwich time; that’s 5:54 p. m. Boston time), the wind is blowing from 120 degrees, or the southeast, at 8 knots. The visibility is 1% miles in smoke and mist, as indicated by “SM” and “BR.”

• Area forecasts. These forecasts look at large regions the size of several states. They try to predict what sort of conditions are going to move through the region in the next 18 hours. These forecasts are meant to give a broad sense of weather rather than specific information about particular airports.

• Surface analysis and weather depiction charts. These maplike charts depict the locations of weather fronts and rain or snow storms across the mainland U. S. Major airports are represented by symbols denoting general weather conditions. These charts don’t attempt to forecast the weather; they just report conditions in the past couple of hours.

• Other charts, including the significant weather prognostic chart, winds aloft chart, composite moisture stability chart, and constant pressure analysis chart challenge pilots to become weather forecasters. These charts are typically left to flight service specialists to interpret, but over time pilots can become remarkably adept at reading and understanding them.

The Visible Atmosphere.

Despite the dangers of flying in rough weather, pilots who do so are privileged to experience some of the most eye-catching, breathtaking sights on earth. But be warned. As Mark Twain wrote, “We have not the reverent feeling for the rainbow that a savage has, because we know how it is made. We have lost as much as we have gained by prying into the matter.”

With that caveat, here are a few of the strange and beautiful phenomena that meteorologists call “atmospheric optics” that the sky has in store for all of us. Pilots, however, have a front-row seat.