"Richard Kaplan" wrote
OK so suppose you are traveling due West on a 160 nm trip from Pittsburgh PA
to Columbus OH and in between there is an occluded cold front with a 250
mile vertical line of thunderstorms associated with the front. The line of
storms includes level 3 through 5 cells and the largest break in precip
would be a circuitous path at times only 15 miles wide.

Well, that would be the day I would need up to a 125 nm deviation, now
wouldn't it? How often does this actually happen?

And no, spherics alone would not cut it for that kind of penetration.
In fact, in my entire flying career, I've only encountered similar
situations three times. Twice I followed another (RADAR equipped)
aircraft while also getting RADAR assistance from approach control.
In both cases, I had been maintaining a steady watch on what the
weather was doing and was confident that it wasn't going to get much
worse in the few minutes the penetration would require. The other
time this wasn't an option. Remember the one time I needed a
deviation in excess of 100 nm? Well, that was it. To be honest, I
don't even think of it as a deviation if it only adds 30 minutes to my
trip. After all, car trips and airline flights are routinely delayed
that much.

Usually, my trips are significantly longer than 160 nm (if that was
typical for me, my airplane would be overkill) and so the deviations
are less significant. Also, having my course line directly
perpendicular to the front, while not particularly rare, is still a
minority of cases.

Michael