Navigating instability

Flying during convective season requires some knowledge, experience, and understanding of how to use all the tools available to us. You don’t always have to cancel a trip on a day with convective weather, but you may have to modify the trip by adjusting departure times or building in some stops to wait out some thunderstorms. Check your “get-there-itis” at the door.

My first recommendation is a bit of a no-brainer. Plan your flights in the morning. Most convective weather develops during the heat of the day. Climatologically, most thunderstorms develop between 2 p.m. and 6 p.m. An early morning or evening flight will make your turbulence-phobic passengers happier too.

When planning a trip during convective season, I begin looking at the weather days in advance. You can do this several ways. Watch your favorite local TV meteorologist. Typically, broadcast meteorologists will have a strong focus on upcoming stormy weather. You also have more resources these days than ever. The forecast discussion available from the National Weather Service and at your fingertips on ForeFlight is a great tool. The forecast discussion will shed some insight on what local weather service meteorologists are thinking. Another resource for those with a penchant for meteorology is a weather model site.

Visiting a site, such as pivotalweather.com, can be useful for your flight planning. By focusing on the European Centre for Medium-Range Weather Forecasts (ECMWF) or Global Forecast System (GFS) models reflectivity product, you can develop an idea for the timing and also the intensity of rain and thunderstorms days in advance. Models are not exact, but they can give you a strong idea for your planning.

When you are within 48 hours of your flight, a wealth of higher resolution weather tools is available including the High-Resolution Rapid Refresh (HRRR) model. The 1 km agl reflectivity is similar to having a future radar view. The model is self-correcting because it ingests current radar data to enhance its accuracy. I use the HRRR and the latest Nexrad data right up until launch time. You can also go to the Storm Prediction Center website and examine the severe weather outlooks for the next few days. Where those marginal, slight, enhanced, moderate, and high-risk areas are outlined will often impact your flight. Slight and even marginal days can be hazardous to general aviation aircraft.

The night before your flight, read a detailed weather brief and take a close look at TAFs—not just TAFs for your origin and destination, but also points in between. TAFs are a better resource than model output statistics forecasts. MOS is raw model output where TAFs have been created by meteorologists at local National Weather Service offices. This is also good time to look at the weather maps including a surface analysis and a prognostic chart. Remember those from your private pilot checkride? Despite being legacy tools, they still come in handy to give you the big picture of the weather.

What if there is convective weather between you and your destination? Take a close look at any convective sigmets, their times, and location. Does that mean you need to abandon your trip? Not necessarily. Is the weather moving? Will it be gone before you get there? Do you have a good place to land and wait it out if things don’t go as planned? These are all questions you have to ask yourself before your flight.

Case in point: I had a friend who recently was trying to get home to Alabama before severe weather arrived. He was flying back from Sun ’n Fun in Florida. It was a very active weather day, but the line of storms was moving slowly at only around 5 to 10 mph. While the view on radar was pretty scary, we agreed to continue to the flight because based on the movement he would arrive at his destination before the storms did. I also recommended having an airport to land away from the storms and well to the east just in case there was a change with the weather. You get the idea; always leave yourself a way out with plenty of fuel reserve to get to that alternate. Backed in a corner with dwindling fuel and stormy weather is not comfortable.

Watching the weather doesn’t stop when you take off. Anyone will tell you I am keenly focused on the weather while in the air. SiriusXM or ADS-B weather is a fantastic strategic resource. While the data is often not the resolution you will have on the ground with many weather apps and the data can be delayed as much as 15 to 20 minutes, it gives you a fantastic look at the big picture. The data you receive in the air is often a composite radar product that often looks more intense than reality. This is why: A composite product takes the maximum reflectivity from each elevation angle and meshes it into one image. Listening to ATC reports and monitoring pilot communications can also help paint a picture of what is going on.

In the air, how do you know the difference between harmless stratiform rain or dangerous convective weather? First, when in doubt don’t go or consult others with more experience for a discussion. I recently crossed a pretty significant looking line of weather that didn’t even result in a bump. On that particular day, I already knew the atmospheric conditions did not favor convective storms based on my experience and background in meteorology. I also asked the Jacksonville Center controller if any aircraft were flying through the weather at my altitude. I cross-referenced with the cloud top product on XM to verify the weather was not composed of towering cumulus clouds. Visually, I was also able to navigate around many of the buildups at 10,000 feet. Your eyes can be one of the best tools available when convective weather is present. I also left myself several outs just in case the weather was developing worse than forecast.

Forecasts are a prediction into the future. Sometimes the weather can be better than the prediction, and sometimes it can be worse. The worst piece of information you can have is an old weather forecast. Weather data is highly perishable. As a pilot, it is key you always have the latest weather information. Your life may depend on it.

JP Dice is a veteran meteorologist, flight instructor, and corporate pilot flying a Gulfstream G150.