Monday, August 22, 2011

The Forecast That Cried "Thunderstorm"

I'm at an airport in the afternoon and the goal is to be at another airport early tomorrow morning. Ideally we should have left several hours ago, before the summer afternoon thunderstorms developed in the mountains, but the goal didn't exist then. Or at least I hadn't been apprised of it. This airplane does not have the service ceiling to fly over these thunderstorms; flying under them in the mountains is not a winning proposition; flying through a thunderstorm would probably mean icing and turbulence beyond the limits of the aircraft, so I'm plotting a route around them. Or at least up to them, so that tomorrow we won't have to go as far.

We could leave super early to go tomorrow instead. I do the math as to when we should get up to be where we need to be when we need to be at seven am. It's something like half hour to get ready, plus half hour to the airport plus half hour preflight, plus fifteen minutes for engine start, runup and taxi, plus three hours en route, plus an hour to land, pee, refuel, taxi and take off again, plus half an hour for generally screwing up somewhere in there. That adds up to leaving at 12:45 a.m., or just enough time for me to reset my duty day. But neither of us really wants to do that, so I look again at the going around the weather option. I chat to a flight services specialist to get his interpretation of the latest radar imagery. Together we select a route that should keep me free of the storms without too much inefficiency, and I file it.

Depart, call the departure frequency, fly a heading, maintain an altitude, fly direct a fix and cleared own navigation as filed. I'm through the lower level stratus with a good view and there are no TCUs en route as far as I can see. A centre controller calls me and offers me direct destination, but I decline, citing weather concerns. The next controller says, "You're not negative RNAV today are you?" Now I'm not exactly going to the most popular airport in the country, but surely someone else is getting diversions for this weather. I call up flight services, give them a position report and ask for an update on the area of thunderstorms. The specialist says they are still a threat and describes the locations of the largest-painting cells. What the hey? We're past the biggest one, and I passed that little thing without a second glance. I ask centre for the vector direct they have been trying to give me for an hour, and then we never see anything we have to avoid the whole way.

Darn you, weather forecast. If there's nothing dangerous going on, don't make me look stupid and waste time and fuel going all the way around when i could go straight. I go straight from here on in, skip over the proposed intermediate airport and land at airport B for the night. We're in position for the morning's mission and we have enough time for dinner and a good night's sleep, despite incredibly slow restaurant service.


nec Timide said...

One of my pet peeves about weather forecasts is how specialists deal with forecasted convective activity. Until the phrase VFR not recommended was deprecated it was difficult to get a weather brief on Ontario during July and August that didn't include the phrase.

That is the only real complaint I've ever had with specialists, so keeping in mind how dangerous T-storms can be to the airplanes I fly, not on the whole a big deal. There have been days when I've canceled flights that could have been made, or unnecessarily flown longer legs over more isolated teritory to avoid convetive activity that never materialized. On the other hand, during my solo cross country (in 1976) flight I got bottled up in a valley between Salmon Arm and Kamloops by T-storms long enough to start planning a precautionary landing. I guess what I'm saying is over cautious forecasts are better than none.

DataPilot said...

I was IFR and on ATC radar the one and only time I ever flew into a thunderstorm. Nasty experience, by the way.

Early in my flying days, our primary weather radar station was located on a small plateau about at 3000' elevation 100 miles away. Everybody knew that the information from that old station was flaky, so we flew VFR any time heavy convective activity was expected. We realized that ATC couldn't see the bad clouds and vector us around them.

Then a new NEXRAD station was built. We were assured that the new radar could display TS much more clearly, and in a complete 360-degree arc. Wow! It was supposed to be a huge improvement.

What we didn't know what that the new radar had been built on the summit of an extinct volcanic cone. Sure, it could see weather in every direction, but only at or above its own elevation. And since it was sitting on top of a 7000' mountain, and our airport was at sea level, the weather that we cared about was often invisible to the NEXRAD station. In our area, it's not unusual for thunderstorms to top out around 7000'.

I guess the moral of the story is to use your best judgement when thunderstorms are in the neighborhood. If ATC is more reliable than your eyes, use them. If not, stay VFR. If you're not sure, well, maybe it's best to stay on the ground.

dburlison said...

When I was flying my greatest concern was always the weather..

Well done site-very interesting/informative..


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