Using historical weather data to learn

As pilots, we spend a lot of time reviewing the weather before a flight–you might even say some pilots obsess about it. But very few pilots spend any time looking at the weather after a flight. That’s a shame, because there’s much to learn from a post-flight analysis and there are some new tools that make it quite easy.

Thunderstorm from airplane
If it looks bad, it is bad.

Comparing a forecast to actual conditions is what weather flying is all about. That is, did things unfold as you (or the forecaster) expected? If not, why not? If so, were there any trends that you can learn from? As we gain experience making these comparisons, hopefully our judgment improves and our weather decision-making muscles get stronger. It does take practice.

One of the main benefits of this type of analysis is that you can do it without even flying. Here are four ways I use historical weather for training:

  • Plan a flight, then “fly” the weather map. I regularly plan flights that I have no intention of flying, simply to think through the weather decisions to be made (see our Go or No Go series). Try to simulate a real flight – look at the weather forecast three days before the intended departure date, then the night before and finally the day of. Watch how the forecast changes as the timeline gets shorter. Then check the weather as it unfolds during your simulated flight time: look at the radar, read METARs and check pilot reports. Do you feel good about your decision?
  • Fly a flight, then go back and look at it. This is the most obvious, but also the most ignored, opportunity. If you made a flight, especially if it involved some weather, go beyond a simple “we made it” analysis and spend a minute examining the weather you flew threw. Take a look at all the different weather products and compare them to what you saw in person. I sometimes go a step further and take pictures in flight–screenshots on my iPad showing the radar, cell phone pictures of clouds we passed–then compare those to the overall weather map. There is a lot to learn this way, and I’m often surprised by how different a line of weather looks in person compared to the national radar map.
  • Cancel a flight, then look at the conditions. Here’s one I hadn’t considered until a pilot friend suggested it to me a few years ago. After I canceled a flight, and while feeling the inevitable guilt that comes with not completing the “mission,” my friend sent me the pilot reports map for my route of flight. Not a pretty picture, with moderate to severe turbulence and lots of icing PIREPs. It made me feel much better about making the No Go call, and I learned a lot about how this particular winter cold front had developed. We often talk about negative reinforcement (we made it, the weather must not have been that bad), but this is a great opportunity for positive reinforcement (we canceled and we were right to do it).
  • Recreate accident reports. This may not be for everyone, but if you view accident reports as a valuable way to learn from experience (as I do), then re-flying an accident flight with the weather reports from that time can be very instructive. Try to put yourself in the cockpit with the pilot, and don’t fall into the trap of blaming the pilot or assuming it couldn’t happen to you. What specific actions would you have taken to avoid the accident pilot’s fate? Are there procedures you can change or add to your flying to prevent such a situation?

All of these are great ways to learn real world weather flying, but how do you find the weather data to do this type of training in the first place? There are dozens of online resources, some good and some quite bad, but almost all of them are free. Here are a few that I find particularly helpful:

  • WxRewind – This is an all-in-one resource for pilots, as the site archives radar, AIRMETs, satellite imagery, prog charts and icing forecasts. It’s nothing fancy, but it’s a great way to get an aviation-specific snapshot of the conditions aloft. You can choose any date and time going years into the past.
    Wxrewind
  • Weather Underground METARs – This popular weather site has a number of helpful resources, including very detailed weather reports for most airports in the US. This includes the hourly METARs (in both raw code and plain English), plus weather trends, temperature graphs and sunrise/sunset data. If you’re tracking trends in ceilings or visibility, this makes it easy to follow. There is simply a huge amount of information here.
    METAR 600
  • Interactive Radar – While WxRewind has radar images also, this is a more powerful tool, with different radar levels, a zoomable map and lat/lon coordinates. There’s a bit of a learning curve, but if you want to see how a line of thunderstorms developed, this NOAA website is hard to beat.
    AF Radar map feature 600
  • Satellite This website is not as useful as some others, mainly because you cannot zoom in very tight, but one major strength is its worldwide coverage. In one place, you can view satellite imagery for any place on the planet, going back to 1978. You can also choose visible, infrared or water vapor images – a great way to understand the differences between these products.
    Satellite 600

Understanding weather is one of the biggest challenges any pilot faces, and it’s one that never ends. If we embrace this challenge, it can lead to enjoyable, lifelong learning. And fortunately, there have never been more resources for pilots. Set aside some time on a regular basis to fly the weather map – whether you get in the airplane or not.

2 Comments

  • This is great information. I have sometimes tried to research past weather to see if my own No Go decisions were valid. I found the process difficult, but I was unaware of all of these tools. I am going to look at this problem again and see if I can learn something new. Thank you for sharing this.

    On a side note… I had a BFR today and mentioned to the instructor about AFJ and some of the weather articles and how I use the 7-day forecast to plan VFR xc trips. One thing I pointed out was my lack of anxiety over my own No Go decisions because I know the weather was or would have been unacceptable to complete the flight.

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