Weather

Flight instructors and students can make a good case for winter being the worst time to begin learning to fly, especially across the northern United Sates. Winter’s cold, often cloudy, and sometimes downright stormy weather challenges would-be pilots and their instructors.

Even so, winter’s shorter days are as likely to keep student pilots out of the air as the season’s storms and snow. Almost all beginning flight instruction has to be given during daylight, visual flight rules conditions when the student can see the ground and the student and instructor can see for at least a few miles around their airplane.

DAY DEFINED. Federal aviation regulations (FARs) say that only time at the controls of an airplane between the end of “evening civil twilight” and the beginning of “morning civil twilight” can be logged as night flying time. In both practical and legal senses, daylight is the time from the beginning of morning civil twilight until the end of evening civil twilight.

Morning civil twilight begins when the center of the sun is 6 degrees below the horizon and ends at sunrise, which is when the top of the sun first peeks above the horizon. Evening civil twilight begins when the top of the sun goes below the horizon at sunset and ends when the center of the sun is 6 degrees below the horizon. In general, in the middle latitudes civil twilight begins about a half-hour before sunrise and ends a half-hour after sunset.

A common unofficial and practical definition of civil twilight is that it’s light enough for outdoor activities, such as playing softball or landing an airplane, without the aid of artificial light. Weather conditions and the position of the sun are involved here.

The FARs say the times of civil twilight are found in the Air Almanac, which you aren’t too likely to find at most airports. You can buy the CD version from the U.S. Naval Observatory.

Unless you are a keen amateur astronomer, or want to use a sextant for celestial navigation—as pilots who flew overseas did in the pre-GPS days—it’s easier to look up the times of civil twilight, sunrise, and sunset on the U.S. Naval Observatory’s (“Complete Sun and Moon Data for One Day” on the Internet).

SEASONAL DIFFERENCES. Places along the 40 degrees north latitude line, which runs across the United States roughly from Philadelphia to Indianapolis to Denver and on to Cape Mendocino on California’s northern coast, offer a good example of the differences between summer and winter daylight.

On June 21, places along the 40th Parallel have 16 hours, five minutes of daylight between the beginning of morning civil twilight and the end of evening civil twilight. On December 21, these places have only 10 hours, 22 minutes of daylight.

A student pilot trying to squeeze in flight instruction after work in a 9-to-5 job who can get in an hour or two of flying after work on weekdays in summer is limited to flying only on days off during the winter.

NORTH-SOUTH TEMPERATURE CONTRASTS CREATE STORMS. The big differences in winter’s daylight around the country means weather patterns vary.While the northern part of the country is rapidly cooling off in the fall, the south cools much more slowly. In Galveston, Texas, for example, the June high and low averages are 87 and 78. In January, Galveston’s average high and low are 62 and 50.

With the shorter winter days in the north, temperatures rapidly fall, which increases north-south temperature contrast. Between Des Moines and Galveston, for example, the June difference in average high temperatures is only 5 degrees. By January, the average high in Des Moines is 33 degrees cooler than in Galveston.

Such temperature contrasts supply almost all of the energy for the extratropical cyclones (storms) that follow various routes across the country from late in the fall until early spring with snow, sleet, freezing rain, and ordinary rain.

Winter’s clouds and storms that reduce the time available for visual flight rules (VFR) are one of the big reasons why military flight training has been concentrated in the southern United States since before World War II.

Shorter days offer winter’s first challenge to student pilots. The darkest days of winter around December 21 bring roughly two hours less sunshine on clear days in the northernmost states compared with those in the south.

Clear days are harder to come by in the north, especially east of the Mississippi River. For example, in Cleveland, Ohio, the sky is cloudy (nine-tenths or more is covered by clouds) an average of 69 percent of the time in December but only 28 percent of the time in July. To the south, Dallas-Fort Worth averages cloudy skies only 38 percent of the time in December and 13 percent of the time in July.

You can escape many cloudy days, but not long nights, by heading west, farther away from oceans and large lakes that add moisture to the sky that makes clouds. In Denver, the sky is cloudy only 26 percent of the time in December, compared with 16 percent of the time in July.

If nothing else, learning to fly during a northern winter gives a student pilot plenty of practical experience in obtaining weather briefings during “interesting” weather. (The last thing a pilot wants to hear is a meteorologist saying, “We’re going to have some interesting weather.”)

Learning about weather begins with learning the basic science behind it. Learning more about meteorology is a good way to spend the time when darkness and winter weather ground a planned flight.

Flight instructors and students can make a good case for winter being the worst time to begin learning to fly, especially across the northern United Sates. Winter’s cold, often cloudy, and sometimes downright stormy weather challenges would-be pilots and their instructors.

Even so, winter’s shorter days are as likely to keep student pilots out of the air as the season’s storms and snow. Almost all beginning flight instruction has to be given during daylight, visual flight rules conditions when the student can see the ground and the student and instructor can see for at least a few miles around their airplane.

DAY DEFINED. Federal aviation regulations (FARs) say that only time at the controls of an airplane between the end of “evening civil twilight” and the beginning of “morning civil twilight” can be logged as night flying time. In both practical and legal senses, daylight is the time from the beginning of morning civil twilight until the end of evening civil twilight.

Morning civil twilight begins when the center of the sun is 6 degrees below the horizon and ends at sunrise, which is when the top of the sun first peeks above the horizon. Evening civil twilight begins when the top of the sun goes below the horizon at sunset and ends when the center of the sun is 6 degrees below the horizon. In general, in the middle latitudes civil twilight begins about a half-hour before sunrise and ends a half-hour after sunset.

A common unofficial and practical definition of civil twilight is that it’s light enough for outdoor activities, such as playing softball or landing an airplane, without the aid of artificial light. Weather conditions and the position of the sun are involved here.

The FARs say the times of civil twilight are found in the Air Almanac, which you aren’t too likely to find at most airports. You can buy the CD version from the U.S. Naval Observatory.

Unless you are a keen amateur astronomer, or want to use a sextant for celestial navigation—as pilots who flew overseas did in the pre-GPS days—it’s easier to look up the times of civil twilight, sunrise, and sunset on the U.S. Naval Observatory’s (“Complete Sun and Moon Data for One Day” on the Internet).

SEASONAL DIFFERENCES. Places along the 40 degrees north latitude line, which runs across the United States roughly from Philadelphia to Indianapolis to Denver and on to Cape Mendocino on California’s northern coast, offer a good example of the differences between summer and winter daylight.

On June 21, places along the 40th Parallel have 16 hours, five minutes of daylight between the beginning of morning civil twilight and the end of evening civil twilight. On December 21, these places have only 10 hours, 22 minutes of daylight.

A student pilot trying to squeeze in flight instruction after work in a 9-to-5 job who can get in an hour or two of flying after work on weekdays in summer is limited to flying only on days off during the winter.

NORTH-SOUTH TEMPERATURE CONTRASTS CREATE STORMS. The big differences in winter’s daylight around the country means weather patterns vary.While the northern part of the country is rapidly cooling off in the fall, the south cools much more slowly. In Galveston, Texas, for example, the June high and low averages are 87 and 78. In January, Galveston’s average high and low are 62 and 50.

With the shorter winter days in the north, temperatures rapidly fall, which increases north-south temperature contrast. Between Des Moines and Galveston, for example, the June difference in average high temperatures is only 5 degrees. By January, the average high in Des Moines is 33 degrees cooler than in Galveston.

Such temperature contrasts supply almost all of the energy for the extratropical cyclones (storms) that follow various routes across the country from late in the fall until early spring with snow, sleet, freezing rain, and ordinary rain.

Winter’s clouds and storms that reduce the time available for visual flight rules (VFR) are one of the big reasons why military flight training has been concentrated in the southern United States since before World War II.

Shorter days offer winter’s first challenge to student pilots. The darkest days of winter around December 21 bring roughly two hours less sunshine on clear days in the northernmost states compared with those in the south.

Clear days are harder to come by in the north, especially east of the Mississippi River. For example, in Cleveland, Ohio, the sky is cloudy (nine-tenths or more is covered by clouds) an average of 69 percent of the time in December but only 28 percent of the time in July. To the south, Dallas-Fort Worth averages cloudy skies only 38 percent of the time in December and 13 percent of the time in July.

You can escape many cloudy days, but not long nights, by heading west, farther away from oceans and large lakes that add moisture to the sky that makes clouds. In Denver, the sky is cloudy only 26 percent of the time in December, compared with 16 percent of the time in July.

If nothing else, learning to fly during a northern winter gives a student pilot plenty of practical experience in obtaining weather briefings during “interesting” weather. (The last thing a pilot wants to hear is a meteorologist saying, “We’re going to have some interesting weather.”)

Learning about weather begins with learning the basic science behind it. Learning more about meteorology is a good way to spend the time when darkness and winter weather ground a planned flight.