Hi Bob,

Just a quick one, I have just completed four of your online CMET exams which are fantastic! However, the following question has confused me. See below; the online exam says that "B" is the correct answer, but in Test #2 in the back of your text book the exact same question is asked but the correct answer is "A"?
Could you please clarify this one for me.
Cheers
Matt

Low level jet streams can be hazardous because they produce -
Select one:
a)strong horizontal wind shear near the surface
b)strong vertical wind shear near the surface
c)strong vertical wind shear at high altitudes
d)strong horizontal wind shear at high altitudes

There was some confusion about the terms 'horizontal' and 'vertical' wind shear. According to the Manual of Meteorology, horizontal wind shear is wind shear encountered when the aircraft's flight path is horizontal. That is, the shear is produced by a sudden change of speed between two air flows moving vertically. The worst case would be one air stream moving vertically upwards while the adjacent one moves vertically downwards such as in a thunderstorm cell. That's called horizontal wind shear nowadays.

Vertical wind shear is wind shear encountered when the aircraft's flight path has a vertical component such as climbing or descending. That is, the shear is produced by a sudden change of speed between two air flows moving horizontally. An example would be cold air at the surface that is almost stationary with a fast moving warmer air stream running across the top of the stationary layer such as is the case in a strong surface inversion.

The earlier versions of the Met book has them the other way round - which was the accepted definition when I did Met!!

Thanks for your feed back - I'll make any necessary changes in the book.

Bob