Dangerous Radar Data

Tim Vasquez

Tuesday, February 23, 2021 at 11:41 AM ET

Verified

This is the NEXRAD image from the exact time of the crash.

Key Takeaways:

In-cockpit weather systems like XM Weather (NEXRAD) have significant data latency (often 10-20 minutes or more), meaning they display where weather *was*, not its current real-time location or intensity, which can lead to critical misjudgments of rapidly developing or moving storms.
Fast-moving squall lines, particularly those with bow shapes and high reflectivity, are indicative of severe turbulence, damaging winds, and downburst potential, even if formal warnings are not issued, posing extreme hazards to aviation.
The safest practice is to avoid entire thunderstorm areas, as relying on in-cockpit NEXRAD to navigate through or near storms is dangerous given data latency and the inherent unpredictability of severe weather phenomena.

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Another season of turbulent spring weather is just ahead, so it’s a good time to go over storm safety. We’ll do that once again by discussing a pertinent weather-related accident. Although at first glance the lessons might seem obvious, we’ll use this fateful ride-along to discuss some key concepts I’ve observed as a meteorologist, and point out some techniques that you might find useful someday during a rough ride.

Not the Best Day

Our case study takes us to the pre-dawn hours of a stormy March morning in western Tennessee. The accident aircraft was a Eurocopter AS350, registered to a regional hospital network. The helicopter was state of the art, equipped with MFDs, EGPWS, and night vision equipment. During this unsettled night, it arrived at Jackson-Madison County General Hospital with a patient airlifted from a nearby town. After dropping the patient off, the pilot prepared for the westward return flight to its home base in Brownsville, Tennessee, 23 miles away. The time was 0540L (0540 local).