Originally Posted by drummer81
- So the "tails" of low preassure are a common thing at this time of year on atlantic? (or even common to all low pressures) ?
- And the speed and the direction that they move is about the same as with the "moteher" low pressure?
- have I still understood correctly that the movement of low pressures is going to move northwards (still from west to east) during next few months as it comes southwards during winter months. ?
I will try to answer here much as my knowledge and skills are limited. You will be able to get more accurate answers from Google
. You can also contact any Uni with a met faculty, or NOAA forecasters staff. I found people out there are very very helpful when they find they are not all alone ;-)
Here, my take:
- The tail (the S-most part) of a front (in this case we imagine a cold front, but in the lower portion it may in fact be a cold/warm front) (oftenmost trailing behind a Low up N) seems to travel SLOWER than the 'mothership'. Think of it: the distance up North is SHORTER (imagine you are trying to sail rtw twice: one time along 80 degs north, the other time along 10 degs North: is the distance traveled the same at these two latitudes?). The Low up North will try to get on top of the associated High, (if one is present), meanwhile the tail will travel more or less at the speed of the two adjacent Highs below (if both are present). I am not sure on this one, but I think this may be the explanation of why we see the long fronts getting even longer - the Low is traveling fast over shorter route
while the trailing front has more distance to cover AND it also travels slower. Long fronts with long tails seem to get shorter and fewer in the summer - but only if and when the High pressure builds high enough to settle down and become what is called the Azores
High. The High is then so big, stable and stationary that no front can penetrate the area. Should the high disappear, be it June or July, you will see Lows and fronts flying thru the area as if they had something personal against nice Azorean people.
- The direction is Eastward, following the associated (at times also dissociated) Low. The Low tends to 'escape' the front. The front may actually get stuck out there, alone, almost sad, becoming stationary too (you will see a stationary front has different marking too on a radiofax.
- The whole wx thing will be moving upwards now BUT it will also evolve towards summer (summer here but winter in NZ!) patterns. But yes - it all is moving up and down following the Sun. If you look at where the wx equator is (not the Equator) you will see that not only the whole thing shifts N and S following the Sun but also (interestingly) that the wx equator is N of the Equator most of the year!!! (at places: throughout the year (sic!).
I am attaching some more images
that I think explain things much better than I can.