Zonality?

[Potent Gust]

Hi guys

Loving the site and forum!

Could somebody explain zonality to me please? I read lots about it and people do not seem to like it in the winter. As a cold lover I guess I shouldn't either!

Thanks

[grab my graupel]

Hi guys

Loving the site and forum!

Could somebody explain zonality to me please? I read lots about it and people do not seem to like it in the winter. As a cold lover I guess I shouldn't either!

Thanks

Hi Potent Gust

Zonality simply put is when we basically have a flat West to East Jet Pattern and Low

pressure bringing Westerly/South Westerly Winds.

This type of pattern can lock itself in for a long time and eat into a large portion of our

winter if it were to occur. That is why most people want to avoid it.

Hope that helps a little.

Brian

[Potent Gust]

Hi Potent Gust

Zonality simply put is when we basically have a flat West to East Jet Pattern and Low

pressure bringing Westerly/South Westerly Winds.

This type of pattern can lock itself in for a long time and eat into a large portion of our

winter if it were to occur. That is why most people want to avoid it.

Hope that helps a little.

Brian

Yes that does help

Thankyou

[Lettucing Gutted]

Hi guys

Loving the site and forum!

Could somebody explain Zonality to me please? I read lots about it and people do not seem to like it in the winter. As a cold lover I guess I shouldn't either!

Thanks

The main problems with it is that the worst zonal warmth in all seasons comes from Maritime Tropical airmasses. This airmass is responsible for many "stuffy nights" throughout the year eventhough Continental Tropical is often just as bad.

However Zonality needn't be so bad for cold lovers.

Maritime Polar Zonality on the other hand often gives us cool weather in all seasons with very comfortable nighttime temperates. We can even get snow from Returning Maritime Polar air as shown by January 1984.

We have Maritime Polar air at the moment as well but there is a very big problem.

Warmer than average Sea surface Temperatures in the North Atlantic.

The problem with warmer than average SSTs is that a Maritime Polar airmass can bring 10+ maximum temperatures and frost free nights even in winter.

Just look at the chart below to see the modification of Returning Maritime Polar airmasses from warmer than average SSTs

The chart shows a Returning Maritime Polar airmasses over most of the UK on Christmas Eve 1997 which is upwind of the cold front situated over the south midlands.

http://www.ecn.ac.uk/Education/images/cold_front.gif

However those stupid warm SSTs in the North Atlantic warmed the Returning Maritime Polar airmass as the low pressure pushed it from the North Atlantic to the UK so that noon temperatures over most of the UK still reached 10-12C even upwind of the cold front.

The problem of Maritime Polar airmasses being modified by warmer than average SSTs also occured in other winter months such as January 1999.

It is seriously getting to the point that you need a very potent northerly just to get temperatures slightly below average.

Warm than average SSTs thanks to Global Warming isn't just making marginal cold setups into mild setups it is also turning strong Northwesterly winds into warm synoptics.

[grab my graupel]

Thanks for that Craig :lol: You described it much better than me.

I forgot to mention about there being Cold Zonality too, as you have done.

I suppose it is much more of a rarity these days to get a decent cold spell

from a Zonal pattern.

Brian

[BrickFielder]

Typically the term zonal is linked to how the jetstream is behaving with zonal implying it is flowing in a strainght line. In contrast a meridional flow is where the jetstream arches north and dips south in troughs.

In terms of weather then the zonal flow tends to bring low pressure systems straight across the atlantic from the coast of America where temperatures tend to be quite warm. Meridional flow tends to involve high pressure (forming in the arch of the jet) at higher latitudes with low pressure systems diving south into troughs. Here air tends to come from the north or east which is colder. Neither mean weather is exclusively mild or cold and for the UK conditions usually conspire to bring milder conditions.