I very much enjoy your magazine. I have a question I would like your opinion on.
Reading “Riding The Storm Out” (September 2024) was very informative. However, the question I have is this: What weather would be safe to fly through? I have asked many experienced pilots the basic question: What specific weather should I not fly through? I have received different answers from just about every experienced pilot I ask.
One will say, “I’ll fly through anything that is not a thunderstorm” (red on a Nexrad display like ForeFlight’s). Another will tell me, “I do not cross through any fronts.”
Still others tell me they will fly through light and moderate rain, green and yellow.
I know there is not one right answer for every pilot, but for a well-trained pilot who is not looking to take unnecessary risk, what would you all say the answer is?
This is my conundrum: When I’m flying and see Nexrad weather blocking the destination. Part of it is green (light rain), part of it is yellow (moderate rain) and of course there is the red portion, which is the heaviest. How would a safe pilot proceed?
How accurate are the weather screens available to us? Is it possible to fly through a yellow portion and actually end up in a thunderstorm? Is turbulence a major factor to consider? Can yellow turn to red? These questions are keeping me up at night!
Thanks for your help—I’m just trying to come up with a consistently safe way to proceed with my flights.
—Charles Riley, Via email
There’s a lot going on in your questions, and—as with the pilots you consulted—there’s no single, “right” answer for every occasion.
First, though, the best way to avoid flying into a thunderstorm is to stay in visual conditions, period, even if you have to turn around and/or land short of your destination. The article you reference is focused on what to do if you inadvertently fly into one.
A major factor to consider is Nexrad’s latency. It can easily take 20 minutes for Nexrad to scan its environment, process the data, convert it to imagery and then transmit it to your airplane. When considering a developing storm, 20 minutes can be an eternity. Note that the “age” value various Nexrad presentations display starts counting when the data is received, not when it was obtained. As the FAA’s Advisory Circular on thunderstorms (AC 00-24C) states, data-linked Nexrad imagery “shows where the weather was, not where the weather is.”
Note also that the color-coding corresponds to reflected radar energy—how much precipitation is present, not turbulence. The ForeFlight Nexrad color-coding range is detailed in the legend excerpted below.
As AC 00-24C states, “weather radar detects only precipitation drops; it does not detect turbulence. Therefore, the radar display provides no assurance of avoiding turbulence.” To the best of our knowledge, there is no direct correlation between the precipitation observed by a Nexrad site and the severity of turbulence a pilot might encounter, if any. That said, moderate and heavy precipitation—including hail—are always to be avoided.
Given the latency of in-cockpit Nexrad weather data and a thunderstorm’s dynamic nature, we’d be very careful flying into any area depicted in yellow, not just because it presents elevated risk—which it does—but because it easily can intensify beyond the 40 dBZ levels into red or purple before appearing in your cockpit.
Nexrad is a strategic tool, showing us what to go around, not a tactical one showing us the way through the soft spots, if they even exist.
Send your thoughts, comments or questions to avsafetymag@gmail.com.
