Nexrad, Rain and Flying

I think it’s wonderful that the internet and satellites and smart phones have given everybody the ability to see Nexrad radar pictures almost anytime and anywhere.

Stancie and her golf buddies study the Nexrad returns as closely as I do before a flight. Sailors, joggers, farmers and almost everybody else stays up to date on the precip shown on Nexrad. But do we understand what we are looking at? Especially when it comes to flying weather?

When we see those colorful Nexrad returns we are probably looking at some form of precipitation. But we can’t be sure the precip is reaching the ground, is obscuring visibility, is caused by a thunderstorm, or know if turbulence is lurking in the radar echo.

That was the challenge for a trip back home from Sun n Fun last week. The Nexrad mosaic picture showed hundreds of miles of radar returns over a broad swath of the middle of the country.  The area was at least a couple hundred miles north and south, but about a thousand miles east to west. Going around in a piston airplane wasn’t an option.

The precip was associated with a slow moving cold front that had become nearly stationary. Thunderstorms–clearly indicated by lightning returns overlaid on the radar image–were moving northeast at 35 to 45 knots along the southern edge of the weather.

But what about that 150 miles or so of solid yellow Level Two return on my satellite weather that was behind the thunderstorms? Was it turbulent? If I found a gap in the storms could I fly on home to Michigan through all of that “yellow” radar return?

My conclusion was yes, the huge swath of yellow radar returns would be wet, maybe bumpy, but flyable if I got past the leading edge storms. The reason I believed that is because there was no gradient. The area, at least 100 miles wide, was solid yellow. The returns didn’t change from yellow to green, or yellow to red, just solid yellow. It was the biggest area of one level of radar return I can remember seeing.

With great cooperation and advice from ATC, and using both the satellite  weather and onboard weather radar to confirm, Stancie and I found a gap in the line of thunderstorms between Cincinnati and Columbus. We watched a cell on the radar pass off the left wingtip, and just to prove it meant business, the storm pumped out quite a cloud to ground lightning show.

Past that cell we turned northwest toward Lake Michigan. All radars showed moderate to heavy rain, but the radar returns didn’t vary from solid yellow. I felt a little like I was flying a submarine as for nearly an hour the rain beat on the airframe, found leaks around the door, and created some P-static on the radios. But the ride was smooth, we were mostly between layers at 4,000 feet and by the time I neared home and Muskegon Airport conditions had improved enough to fly a visual approach.

When I climbed out of the airplane water was pouring out of the many scuppers under belly and tailcone. And I’m sure a little more paint had been knocked off. But we had a good trip, the Nexrad didn’t lie, and it’s something that would have been a real worry before Nexrad in the cockpit. When everything on radar is green or yellow in very large areas with no red or many changes from green to yellow you can’t be assured good visibility and decent ceilings, but you can be sure the wings aren’t going to break off.

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7 Responses to Nexrad, Rain and Flying

  1. Roger Halstead says:

    One of the smoothest (and most colorful) flights I’ve ever taken was almost entirely in red and yellow returns. The returns most of us see are nothing more than the intensity of the precipitation. You also need the Doppler returns, stability, and pireps.
    You also need to know how old the returns are that you are seeing. At best they are 5 minutes old and can be 10 minutes or more. If you are in front, stay as far as possible. Thunderstorms can spit hail and lightening as much as 10 miles out front.

    One telltale for a bad area is red spots, surrounded by yellow, surrounded by green. It’s not an absolute, but a pretty good sign of individual cells. Another is a rather narrow gradient between the colors. One to definitely stay away from is a line that bows out in the middle. If there is a clear gap and then a line of green, it’s a sure sign of a gust front.

    It was one of my last dual IFR flights as an instrument student before taking the flight test. It was basically KIKW, LAN, AMN, KIKW. The briefer had quipped that I’d save a lot of gas by just going around the pattern.

    The view between LAN and AMN was almost surrealistic and reminded me of a scene from the animated sci-fi movie Titan AE . I was between layers that were connected by many columns plus quite a number of cotton like clouds floating around in there. The light was green having been filtered through all that water. I would have loved to have been able to fly around in there VFR, but being on an IFR flight plan, I resisted the temptation.

    On the VOR app to AMN we were just skimming the tops and penetrating a few extensions of the bottom layer outbound. The feeling of speed was tremendous.
    We were in very heavy precip as soon as we started down. I was preparing to go missed as we broke out right at minimums. There was the runway straight ahead, right where it was supposed to be.

    As we headed back to 3BS, now KIKW, MBS app told us to expect the visual. All we could see ahead was a solid wall of cloud with some lightening flashes comfortably off to the left, so we respectfully declined, gave a pirep, and requested the VOR 06 approach. Most of the approach inbound only offered glimpses of the ground, but it opend up to VFR about 3 miles from the runway.

    It was one of those flights you can’t appreciate until you’ve done it, particularly so as a student.

    Being in Michigan, I think a third of my flights were in actual, by the time I took the test.

    • Sarah A says:

      The comment on the delay in the data making it to the cockpit is very important. It is imparative that pilots, both IFR and VFR not try to use this delayed data as a guide to penatrate weather but more as a guide of where to avoid while keeping that delay in mind. Whith that in mind having weather in the cockpit is noe of the greatest recent advances in flying safety. I think back to my days as a student pilot doing those first cross country solo flights and how great it would have been to know just what those dark clouds represented and how far they extended. That never ended on through getting my IFR ticket and not having the fortune to fly aircraft with on-board radar (that is probably 99% of us out here) I always had to keep my fingers crossed that the weather I saw during the briefing had not changed too much. That prompted more than one safety stop to take another look at the current weather before deciding if it was safe to proceed to the intended destination.

  2. Peter Timmins says:

    Access to Nexrad in the cockpit has become so universal that it’s time the FAA incorporated training into the Instrument Rating and reviewed the validity of the contract weather briefers. Too many pilots (all maybe?) are self trained on this technology with varying degrees of success but still rely on it for safety. Factoring the possible delays in returns and interpreting what the colors really mean is something of an art and requires judgement gained through experience. Personally, I self-brief on weather and only call FSS to create a record of briefing. In over 50 cross countries, I have NEVER heard something in an FSS brief that I didn’t already know. I’m sure Nexrad training will show up just as soon as the FAA takes the baro-altimeter and Loran questions off the test…..

  3. Chuck W says:

    I agree with MAC and thanks for showing that green and yellow most likely won’t kill a fellow. Something I seem to often repeat to family and flightcrews flying with me as I gauge the threat on is it building or dissipating. I do this by watching for any orange and is it increasing or decreasing, with ATC , works well. Don’t be surprised if asked for a pirep for the next guy trying to shoot the gaps.
    But alas, at night doing the same thing is much spookier as the bumps, rain and the towering cumulus being backlite by lightning strokes shows Mother Nature can whip things up fast. I remind myself that the image on the screen is history and even with help from ATC, the same procedure during night IMC, isn’t for the weak of heart. Those lightning strokes burn striking images into to the psyche, that last. Although never in danger, one is always danger close and a deviation to the flank and never in front of the event is always a good option…

  4. David Medders says:

    While your observations regarding NEXRAD reflectivity are correct, you are ignoring two far better convective weather indicators provided by XM Weather:

    - Echo tops shows how high precipitation extends above the ground. It is similar to cloud tops but not quite the same since, in most cases, the top of the cloud will be somewhat higher than the top of the precipitation echoes. Echo tops are useful in identifying a region of strong convection. Echo tops are transmitted by XM Weather at 7.5-minute intervals. In my experience, the ride below echo tops 25,000 feet or lower is acceptable in a light single or twin.

    - Cells/storm track shows intense storm cells. Identified cells include maximum reflectivity, echo top, speed, and direction of movement. By using raw radar, this product provides the most current data for severe weather avoidance. Cells are transmitted by XM Weather at 1.25-minute intervals.

    My primary weather display is configured for concurrent display of reflectivity, lightning and cells. I typically show echo tops on a secondary display or switch the primary display as necessary. Practice with your configuration prior to flight, as Garmin units will silently drop some weather data based on zoom and de-clutter settings.

  5. Cary Alburn says:

    After 4 decades of flying and with an IR for most of that time, I still feel like an infant when it comes to on-board weather–I’ve had ADS-B in Nexrad weather for about 10 months. So I look at it via the Internet every morning at home, and now that it works below pattern altitude at GXY, my home port, I have it up every time I fly. But understanding what it’s telling me is still a bit foggy.

    Pretty marvelous stuff, although so far it hasn’t changed the way I fly much. Neither did having color radar in a 231 Mooney I used to fly in the 80s, which also took me quite awhile to learn to use.

    So yeah, I think much of what most GA pilots know about weather depiction in the cockpit is self-taught, which means the knowledge is incomplete and full of gaps. What I’ve learned has come in fits and spurts and bits and pieces, from a myriad of different sources, mostly because there doesn’t seem to be any really good source that puts it all into an understandable package, emphasizing “understandable”.

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