Zonal To MeridionalAdded : Tuesday at 13:45 By now, you should realise that the weather changes. Obviously we don't mean the weather where you are, of course that does. But, the overall patterns shift from one type to another and for meteorologists we pretty much lump these into two types :-
1. Zonal - Which means wet, windy, changeable etc
2. Meridional - Which means blocked, persistent weather patterns etc
The thing is, because one type will eventually create the other, it's pretty rare to see any one pattern dominate for anything more than a couple of weeks. Take a look at the charts at the moment :-
You can see low pressure in control and a fairly flatlined jet stream across the Atlantic. This is a zonal pattern and means our weather remains changeable for the next few days. What tends to happen though, is that these low pressure systems develop, mature and then head North towards the pole where they in turn start to buckle the jet stream and this then creates a more wavy pattern.
You can see this if you look at the jet stream for the end of next week :-
This is a meridional pattern and tends to mean the weather is moving slower at the surface level. If you look at the chart for next weekend :-
You can see low pressure across Scandinavia and this is a slow moving feature which brings in some cooler air from the North. Regardless of whether it's high or low pressure across the UK, the pattern is rather sluggish and allows warmer and cooler air to be transported further North/South which in turn affects the temperature gradient which eventually fires the jet stream back up and we return back to a zonal pattern.
This is pretty much par for the course for our part of the world and why our weather remains something we love to moan about so often. It's also why when the UK or Western Europe sees the same weather for more than even a couple of weeks, we tend to be on the lookout for the pattern change as this rather unusual.
METEOROLOGIST : MARSH |