Hi there,
How do other people here decide which fronts aloft are safe to fly through (IFR…) and which aren’t? Let’s keep the conversation relatively simple by excluding icing, thunderstorms so as to focus on what is possible for a majority of the fleet.
DMEarc
I don’t think there is a sure way because the weather data doesn’t exist in a good enough form.
Also you can’t exclude icing in any IMC – unless you fly below the 0C level, which is fairly well forecast (well, within say 2000ft).
So if you want to fly above the 0C level, there is always going to be a risk of ice, and convective stuff. The only solution is what I usually do: fly VMC on top. That obviously needs adequately good wx at the two ends, cloud tops not too high / adequate aircraft performance, and probably oxygen.
I will do IMC enroute if the OAT is below about -15C and (from the various images e.g. IR, sferics) it is clear there is nothing convective in there. Risks however remain even then because you can get ice, and you can definitely get icing of the air intake system of the engine (I’ve had that 2x). However, these conditions are rarely predictable from wx data; the times I have done this was an airborne decision to continue.
I’m assuming the question is about pre-planning rather than actual flight.
Nowadays I tend to rely on 4 sources to see if a front will be fly able or not:
- gramet
- mslp
- sigwx
- the BBC’s weather map
The last one may sound very amateur, but it’s actually very accurate in my experience. If I see a strong line of white stuff on there, I know I’ll likely need to go around. If it’s in chunks, I’ll fly tactically through it. If it’s dark or light blue, I’ll fly over it.
I crosscheck what Topmeteo makes of it in terms of significant weather and clouds. This gives you a good idea of how active a front is supposed to be. Then you can check METARs of fields where this front is currently at as well (if it’s not long before you go). And it can be interesting to check multiple MSLP/frontal charts of different weather services. One service’s front can sometimes be someone else’s trough line.
Topmeteo, like all free wx websites in Europe, is still serving only the same GFS data.
Troughs are bad news. They tend to mean convective wx which will be very rough to fly through. I have gone over the top of a lot of it, though often at FL200, and only just made it. However, different forecasters will draw the troughs in different places, so their presence e.g. here
is no more than indicative of such wx in the whole area shown.
