Ana and KataAdded : Tuesday at 13:10 Whilst this may sound like a slightly European 1970's police duo like Starsky and Hutch in the USA it isn't. These two little words are important when meteorologists come to describing frontal systems which are heading in.
Last week we had an ana cold front which brought heavy rain in from the West and retained its intensity as it swept across the UK.
Tomorrow, we have another frontal system coming in from the Atlantic, but what type is this?
Is it an anafront or katafront? We will come back to that in a second or two. If we run ahead into Thursday you can see the GFS ► keeps it cool and fresh with a decent wake behind the system and a blustery Westerly wind with showers :-
Then on Friday evening the GFS ► brings in a secondary low in from the Southwest with some rather heavy rain on the leading edge :-
OK, back to anafronts and katafronts and a good way to remember these is Ana with a capital "A" and the shape of that and then kata with a little "k" and the shape of that. Got it? Good.
If you looked at a frontal system from the side then you would be able to tell, but unless you are a pilot then you probably won't be able to do that. The secret of knowing the difference between the two is whether you know air is rising in front of the cold front and also rising near where the warm front reaches the surface.
If it is rising, then we call this an anafront, but if air aloft is sinking then we call it a katafront.
Because the air is rising we find that these fronts are far more active. You know the warm fronts which have lovely wispy cirrus and mares tails which lead to heavy rain a few hours later? They are anafronts, but the ones which come with stratocumulus and then drizzle? They are katafronts.
As for cold fronts? The ones which come through and make you grumble and get your brolly out are katafronts, but the ones which suddenly give heavy rain or hail etc and gusty winds before suddenly clearing to blue sky and you can see the rear edge of the front? They are ana ones.
To forecast these we usually use the 500-300mb charts to see whether there is enough wind strength aloft to help the air rise at the surface. As for tomorrow?
The jet stream runs aloft and it's likely that tomorrow you will see anafronts come in from the West before turning to a katafront as it heads further East.
METEOROLOGIST : MARSH |