Wow, some serious and wierd ideas floating round here.
I'll help clarify, I hope.
Ok. winds are created by variations in pressure. Air would like to rush into low pressure areas, but alas, in the northern hemisphere the air is turned to the right. Thus the rule, BACK TO THE WIND LOW ON YOUR LEFT.
BUT, Upper winds are a little different, the pressure upstairs is determined by temperature downstairs. Cold air makes pressure fall very rapidly with altitude, so therefore a lower pressure than normal would be found upstairs. Warm air does the reverse and creates higher pressures in the upper atmosphere.
So, the upper wind rule is BACK TO WIND COLD ON YOUR LEFT (because it's the old air making the low pressure in the first place).
Lets say there is a massive temperature variation downstairs on the surface of the earth, then there would be a massive pressure variation in the upper atmosphere and this would result in a whopper wind!!!. An upper wind >60kts is a jetstream.
Now, a "front" is a boundary between airmasses of different temperatures. So whenever you have a front, you will have a big pressure difference in the upper atmosphere. The stronger the front, the stronger the pressure variation upstairs and the stronger the wind.
Weak fronts, weak upper wind et etc
Phew, bit much after easter, but hope it helps. Or just buy my cd (hey hey)
Steve