A CLOSER LOOK: Forecasting for the skies and impacts from weather on aircraft

A CLOSER LOOK: Forecasting for the skies and impacts from weather on aircraft
Meteorologist Terry Lebo with the National Weather Service in Wilmington, NC (WMBF)
A cross-section diagram that meteorologists use to see how the wind speeds change with height through the atmosphere. (WMBF)
A cross-section diagram that meteorologists use to see how the wind speeds change with height through the atmosphere. (WMBF)

MYRTLE BEACH, SC (WMBF) - With the Wings Over Myrtle Beach Air Show in town, the weather impacts above the surface are just as important as the weather spectators this weekend will experience at the surface.

For National Weather Service meteorologists, there's a multitude of forecast scenarios that can cause travel headaches and sometimes cancellations. Terry Lebo, a meteorologist with NWS office in Wilmington says the most common disruptive aviation weather is fog, a common phenomenon across the Pee Dee and Grand Strand.

If the fog reduces visibility below 3 miles or the clouds are lower than 1,000 feet, the NWS advises that flights rely on instruments to take off and land.

Lebo explains: "The difference between visual flight rules, (VFR) or instrument flight rules (IFR)  has to do with the visual cues you use. Visual flight rules is exactly what it sounds like: you're flying based on terrain where you see trees, buildings versus instrument flight that means your visibility is restricted, whether that's because of darkness, clouds or fog so you're basically flying based on instruments."

Outside of fog and reduced visibilities, other inclement weather issues for aircraft come from wind and ice. With regards to wind, Lebo says the most problems from wind arise from not only the speed, but the change of wind speed or direction with height.

"The thing we are concerned with as far as forecasting parameters have to do with Low Level wind shear. So if you have light or calm winds at the surface, and then just above the surface you have very strong winds," says Lebo

Low level wind shear can develop ahead of cold fronts and within storm systems.

As for ice, planes can have major issues if they fly through precipitation near freezing, the ice can shift the weight of the plane and cause it to become unbalanced.

Another common irritation passengers can experience is turbulence. Lebo adds that forecasting turbulence can arise from many different situations.

"You can have turbulence on clear days, if you have good heating, so you get strong upward motion because the ground heats up and you have cooler air aloft. That's when you can get turbulence. You don't necessarily have to see clouds to have turbulence."

For more on aviation forecasting, the NWS Wilmington issues updates four times a day here in their forecast discussion

For travel weather forecasts and where aviation weather problems may arise, follow this link to the Aviation Weather Center, a branch of the NWS that is a one stop weather information shop across the U.S.

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