Page 20 - Volume 19 Number 10

Twenty miles from where?The old advice about avoiding thunderstorm activity–to remain 20 miles from the edges of any storm cell’s radar return, and to stay in visual conditions if at all possible while doing so–is just as valid now as it was in the days before weather data uplinks and moving map displays. The true purpose of these technoloiges is not to help us penetrate areas of precipitation returns; it’s to make it easier for us to stay 20 miles or more away.There are additional factors of Base Reflectivity vs. Composite radars (the former reads only what is happening at the base of the clouds, while the latter depicts precipitation in the cloud in cross- section, providing advance warning of heavy precipitation), and the time between radar observation and transmission through NEXRAD uplinks (the latency period, which isn’t as bad in areas of active radarreturns as has been reported). Even the colors used to identify specific levels of precipitation activity are very different from one weather radar data provider to another.Dr. David Strahle developed an operating logic in the 1960s that pioneered digital transmission of weather radar information, eventually into the cockpit in flight. Dave is known as “the father of datalink radar.” A very active IFR pilot, he is an expert on weather radar interpretation and regularly consults with Government and private authorities and air crash investigators. His profession is as a radiologist...who better to analyze radar cross-section returns with a fresh, new outlook than someone whose industry-leading career is interpreting cross-section imagery of cancer patients?Dr. Strahle is the extremely-rare authority who not only knows his stuff, but is also makes it extremelyeasy to understand the very advanced topics as a speaker and lecturer. I’ve heard him speak on inflight radar uplinks four times, and would do so again in a minute. I highly encourage you to watch for him on the speaking circuit and attend his presentations. In his Oshkosh 2015 talk, he emphasized: It’s generally safe to fly through areas of light precipitation (“green” returns on most radar plots), if there is no moderate or greater precipitation associated with those clouds. However, Dr. Strahle tells us, if there is any moderate precipitation in the radar plot (generally yellow), you need to remain at least 10 miles away from even the light (green) returns that surround the heavier precipitation. If there is heavy (often, but not always, orange or red) or extreme (darker red, white or other) precipitation, remain at least 20 miles away from even the light (green) returns.Why is this? Research shows that individual thunderstorm cellsHartzell Engine Half Page4/C Ad18 • TWIN & TURBINEOCTOBER 2015