Behind the Forecast: Turbulence

Behind the Forecast: Turbulence
GF Default - Science Behind the Forecast: Turbulence

Listen to Science Behind the Forecast with Meteorologist Tawana Andrew every Friday on 89.3 WFPL at 7:45 a.m.

LOUISVILLE, KY (WAVE) - Turbulence; it’s the reason so many are afraid of flying. Turbulence is the irregular motion of the air resulting from eddies, think swirling motions in the atmosphere, and vertical currents.

Turbulence can range from some slight rumbling to enough motion to significantly damage the aircraft. The severity of the turbulence depends on what instigates it and the stability of the atmosphere.

There are a few types of turbulence.

  • Light turbulence: This may cause slight altitude changes.
  • Moderate turbulence: This slightly more intense but the aircraft does not lose control. Inside the aircraft, unsecured objects may be dislodged. 
  • Severe turbulence: An airplane will have to deal with drastic and large changes in altitude and airspeed. An airplane may lose control for a moment and passengers may be shifted violently in their seats.
  • Extreme turbulence: In this situation, an aircraft will be tossed violently and pilots will find it hard to control. Structural damage is possible. 

Now that we’ve covered the worst case scenario, what causes turbulence? There are four main causes.

  • Frontal Turbulence: As warm air lifts over a front and two air masses interact, friction occurs causing turbulence. Turbulence is more significant when there is a warm and unstable air mass in place and will potentially become extreme if thunderstorms form. This type if turbulence is most common with cold front but could be experienced with warm fronts too.
(Source: National Weather Service)
  • Wind Shear Turbulence: Wind shear is defined as the change in wind speed or direction with height. Wind shear is found near areas of low pressure, jet streams, and near temperature inversions. Near areas of low pressure, turbulence is mainly due to horizontal directional and speed shear.
  • Mechanical Turbulence (Turbulent eddy motions): This type of turbulence is caused by the friction between the air and the ground. Air flowing over irregular terrain or man-made objects like cities causes eddies and turbulence in the lower levels of the atmosphere. Turbulence’s intensity is dependent on the type of surface, atmospheric stability and the strength of the wind at the surface. Stability is the most important factor. Heating from below causes more intense vertical motion. When the air is unstable eddies tend to become larger. The stronger the wind, rougher the terrain and unstable the air, the more intense the turbulence will be.
(Source: National Weather Center)
  • Thermal Turbulence or Convective Turbulence: You’ll find this type of turbulence on sunny, warm summer days. The Earth’s surface is heated unevenly by the sun. Urban areas along with sandy and rocky areas a heated much more quickly than areas will more vegetation. As warm air rises and cooler air descends, an airplane flying through these will experience rocky conditions. If there are cumulus clouds, the turbulent layer of the atmosphere will stretch from the cloud tops to the ground. Thermal turbulence will drastically impact the path of a plane that is about to land. Thermals may cause a plane to shift from its normal flight path and possibly undershoot or overshoot the runway.
(Source: National Weather Center)

Clear air turbulence (CAT) is defined as turbulence not associated with clouds at or above 15,000 feet. Contrary to the name, the skies do not need to be clear of clouds for clear air turbulence to occur. It can occur in cirrus clouds, near lenticular clouds and even close to some thunderstorms.

If you’re ever worried about turbulence before a flight, you can always check a turbulence report here.

Science Behind the Forecast: Turbulence

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