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Training Tip: What's up with the wind?Training Tip: What's up with the wind?

Weather conditions pilots focus on most in preflight planning vary by season as summer convection and high density altitudes give way to cold-weather concerns like slippery surfaces, frosted-over aircraft, or a temperature inversion that can change rain into treacherous airframe ice if it strikes an aircraft flying in below-freezing air below.

Image courtesy of Jeppesen.

In any season it takes dedicated delving into details to assess flight conditions. Fortunately, one aspect of weather analysis that applies at any time of year is being able to check a surface analysis chart and get a big-picture idea about one of a light aircraft pilot’s main concerns: wind.

Fronts, high and low pressure systems, and isobars (lines of equal atmospheric pressure) are the prominent features on a surface analysis chart. Isobars convey wind data in two main ways. They show the direction of wind flow, which roughly parallels the isobars if you visualize northern hemisphere wind flowing clockwise around high pressure and counter-clockwise around low pressure. Isobars also suggest the intensity of wind, with tightly spaced isobars portraying a strong pressure gradient and, therefore, a lot of wind. Isobars widely separated, as they appear in New York State and New England on this surface analysis chart, imply light winds—as indicated by this data-rich METAR excerpt from a Maine airport: "081153Z 00000KT 1/4SM R15/1000V1400FT FZFG VV002 M02/M02 A2988 RMK AO2 SNB31E38."

If this were a ground school class, a precocious student might raise a hand and challenge the notion that a METAR issued so early in the morning satisfies the example, because at that time of day, winds tend to be light before thermal activity fires up.

A fair point. So let’s look in on that same airport later. At 1853Z, the station reported, "35006KT 10SM FEW045 SCT095 BKN200 02/M01 A2971." An airport 50 miles southwest reported, “VRB06KT 10SM OVC100 03/M02 A2971.” Still light winds across the region.

What wind speeds and direction might you observe in the Midwest based on this surface analysis chart? 

Check your “gustimate” against the 1854Z METAR at Iowa’s Des Moines International Airport: "30018G25KT 10SM BKN024 M06/M13 A3050."

Were you close?

A surface analysis doesn’t give a complete picture of weather. However, it should provide a general answer to the first question on many pilots’ minds before flying: “What’s the wind doing?”

Dan Namowitz

Dan Namowitz

Associate Editor Web
Associate Editor Web Dan Namowitz has been writing for AOPA in a variety of capacities since 1991. He has been a flight instructor since 1990 and is a 30-year AOPA member.
Topics: Flight Training, Weather
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