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Training Tip: One windy dayTraining Tip: One windy day

The typical weather chart is a notable exception to the rule that one picture is worth a thousand words. But that all changes when a surface-analysis chart pictures isobars wrapped tightly around an area of low or high pressure.

Photo by Chris Rose.

What are tight isobars on a surface-analysis chart trying to tell you to expect?

You’ll find the answer in the headline above. If a surface chart seems covered with orb-shaped spider webs—or by one big web, as on Oct. 18—you can bet on a breezy day for flying, so be sure to consider the local impact.

The surface-analysis chart gives you a head start on that part of your planning too. Recalling that in the Northern Hemisphere, wind flows clockwise around highs and counterclockwise around lows, you can guesstimate, for example, that in Maine, there was strong wind from the northwest.

Good guess, according to this early afternoon observation (note the peak-wind remark at the end of the data): KBGR 181653Z 30016G26KT 10SM SCT060 04/M08 A3000 RMK AO2 PK WND 33031.

If “tight” isobars indicate strong wind, don’t mistake widely spaced isobars as assuring light winds. “Microscale” exceptions could come as a rude shock to a pilot tricked into complacency by a benign forecast. Remain alert to signs of visual cues that surface winds are increasing as you fly.

Whatever causes a sudden wind increase on a flight—perhaps a front moved in faster than expected, or the winds aloft forecast overshot the altitude at which higher wind speeds were expected—many pilots can share an experience of encountering strong winds that seemed to come from nowhere. Once you’ve had such an experience, you will never again let your guard down.

As if unexpected winds were not enough of a surprise, they are likely accompanied by wind shear. When a front barges into an area of stable air, or when you climb or descend into a zone where winds aloft differ drastically in speed or direction, expect wind-shear-generated turbulence. That means hitching up the seat belts, flying at the recommended airspeed for turbulence penetration, and providing air traffic control with a pilot report describing what you encounter.

Descending from the traffic pattern, defenses against low-level wind shear include readiness, exceptionally precise directional control, maintaining enough airspeed to ensure firm control responsiveness, and being ready to execute a quick go-around if the approach becomes destabilized.

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: Weather, Takeoffs and Landings, Flight Planning
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