Avoid it! – The Weather Radar

Airborne Weather Radar - Source:  Wikimedia

Airborne Weather Radar – Source: Wikimedia

The Weather Radar is one of the most valuable tools that we have on board an aircraft to avoid / navigate areas of thunderstorms.  Without it, in many parts of the world, like the one I fly now, it would be impossible to comply with scheduled flights in areas of active or forecasted convective weather.

The Weather Radar has saved many lives, but has also caused many accidents due to misinterpretation or because some have mistakenly thought that with the only fact of having it on board, they can fly with all kind of weather.  A weather Radar is only useful is the crew is capable of fully understand the system and interpret the screen display.

Correct use of a Weather Radar requires correct use and understanding how severe weather works.  Weather reports obtained at Flight Dispatch or Flight Service Station – FFS, as well as in flight reports provide valuable data to the crew of hazardous weather.  The best use of Weather Radar is to use it in conjunction with weather reports and weather forecasts.

 Understanding Weather Radar principles:

Radar echoes returns are proportional to the droplet size and precipitation intensity, although reflectivity of precipitation not only depends on the intensity of precipitation, also in the type of precipitation. 

Weather Radar Principles - Source:  Airbus

Weather Radar Principles – Source: Airbus

Precipitation that contains water will return a stronger echo than dry precipitation.  Dry hail for example will reflect far less than wet hail.  The upper level of a thunderstorm that contains ice crystals provides weaker returns than the middle part, that is full of water or wet hail.

The Weather Radar does detect:

·         Precipitation.

The Weather Radar does not detect:

·         Clouds, fog or wind.

·         Clear air turbulence – CAT , no precipitation.

·         Windshear.

·         Sandstorms

·         Lightning.

Reflectivity according to droplet size. - Source:  Airbus

Reflectivity according to droplet size. – Source: Airbus

The Weather Radar depends on signal returns, heavy precipitation may indicate stronger weather, the major part of the signal is reflected by the frontal part of the precipitation, the aft part will return weak signals that are displayed by green or black areas, the crew may wrongly interpret that these areas are safe, this phenomenon is called Attenuation.

Modern Weather Radars are capable to apply a correction to the signal when is suspected to be attenuated behind a cloud, however a black hole behind an area shown in red in the Weather Radar Display should always be considered as an area very active.

Attenuation behind two very active cells - Source:  Airbus

Attenuation behind two very active cells – Source: Airbus

 

 

 

 

 

 

Remember, The Weather Radar should not be used as a tool to penetrate or navigate around areas that are displayed as severe.  The Weather Radar should be used for weather avoidance.

 

“If you don’t have Weather Radar on your airplane, the best way to flight through a thunderstorm is on the ground and inside of a hangar”

By Ivan Paredes

Recommended reading:

– Airbus – Flight Operations Briefing Notes

 

Bookmark the permalink.

Leave a Reply

  •   GDL 39