Frontal RejuvenationAdded : Thursday at 8:24 Right, it's one of those scenarios which probably only meteorologists find interesting, but we thought we would share the charts and physics going on behind the scenes in the hope you find it interesting too....
This is the area of low pressure in question. Granted, it's a flabby old low sitting out off the coast of Portugal and not doing anything particularly interesting, but later today it throws up a warm front from the South which then stalls across parts of Southern England with increasing cloud :-
Still not interesting? OK, well on the other side of the Atlantic we have some cooler air coming out of the Labrador Strait and heading across the Atlantic. Remember the word cool, as this air will have traveled thousands of miles across the Atlantic ocean and will be heavily modified at the boundary layer :-
Guess you are still wondering what is so interesting about this eh? The "interesting" stuff happens tomorrow evening as the frontal system stalls across the UK and we have light winds coming up from the South and cooler air approaching from the Northwest. You can see the tentative signs of "interesting" here :-
If you look at the jet stream forecast for tomorrow you can see this :-
A weak jet streak which runs in from the South ahead of the cooler air coming in from the Northwest and running over the top of the frontal system which has stalled. This does two things, firstly it draws out air from the upper atmosphere which is then replaced by air at the surface which causes the air to rise (we call this upper level divergence) and secondly it promotes air to converge at lower levels which again allows the air to rise.
The result?
The frontal system rejuvenates with some heavier rain developing across Central and Western areas where this process takes place. You can see this in the chart above as the blow of yellow.
Nothing amazing or incredible about it, but it's just forces of physics in action and if you wonder why the front suddenly springs to life overnight Friday and into Saturday you now know why... Still not interesting? Well, we tried our best..
METEOROLOGIST : MARSH |