Cold Zonality synoptics (Polar Maritime vs Tropical)

[North-Easterly Blast]

With the models showing a flat jet zonal Bartlett setup for next week and according to the ensembles for the first ten days of December at least, and when it is similar to the pattern that prevailed for almost all of last winter, it is time to raise a similar thread to what I raised last winter, for a debate on why we always get the SW-NE track of zonal flow and a Bartlett High nowadays, and not cold zonality, NW-SE tracking depressions and no Bartlett High (Azores High well out to the SW)

An active Atlantic and zonality was not always a disaster for cold weather, and even occasionally it has been a very good setup. You only have to look at January 1984 to find a month where zonality truly delivered the goods. (Cold weather and snow was brought by a zonality that is usuallya mild setup), which makes from my personal point of view January 1984 my next most favourite weather month of the UK after the big freezes of 1947, 63, 79 etc. Of course January 1984 is not up there with the likes of the following three winters, and the late 70s, but it was nevertheless far more than we are getting these days and in recent years.

What makes Jan 1984 all the more special is that although the first half was generally mild with a couple of topplers, it turned particularly cold from the 15th to 28th with frequent great heavy snowfalls from the Midlands northwards, and it was a positive NAO and AO month. There was never any significant northern blocking in this period, it was just that the Azores High was well out to the SW and the air was of a polar maritime origin by the 15th and the zonal flow became very meridonal and a small high crossed the UK by the 19th and there were heavy snowfalls by the 23rd as a low pressure in a meridonal zonal flow crossed the UK.

What made January 1984 even more special is that no true "northerly" or "easterly" spell and no true Greenland or Scandinavian high ever developed that month and it was so cold and snowy for many during the second half, and that was with a positive AO/NAO. The key factor was that no Bartlett High was present and the zonal flow became very meridonal across the Atlantic instead of flat.

March 1995 was very similar especially the first ten days and even towards the end and featured a number of snowfalls even without a true Greeny or Scandy High. March 1st- 7th 1995 was a classic of cold zonality. January 1978 also had cold zonality, and so did December 1993 on occasion.

It is not only us struggling so much to get a proper northerly or easterly spell in winter nowadays, it is the fact that today's zonality is always mild and not cold like it was in January 1984, March 1995 etc.

I know last winter was very zonal almost throughout, and the first ten days of December this year look set to be, but my big question is if we have to have zonality, for goodness sake why can it not be like January 1984? Meridonal, and no Bartlett High.

[The PIT]

Just one or two comments. At present there isn't a Bartlett on the chart and last year part of the problem was the Euro High which wouldn't shift.

[sundog]

Some one mentioned last year (i forget who it was) something about the hp belt moving further northwards, would that have something to do with it?

[AtlanticFlamethrower]

North Atlantic SSTAs in

January 1984

March 1995

January 1978

It would seem to be pretty self-explanatory.

Today there is a vast zone of +2 degrees celcius anomalously warm water where in those years there was not, or even a negative anomaly present.

Don't under-estimate modification of air temperature close to the surface due to ocean surface temperature.

Edit: An anomalously warm North Atlantic would presumably also have the effect of moving the polar jet northwards.

Edited November 29, 2007 by AtlanticFlamethrower

[nick sussex]

An excellent post NEB and very interesting. To be honest I cant remember the last time we had any colder zonality and this is why whenever models hint at this at post 144hrs we know what will happen, with time the track of the lows is taken further north and then the jet eventually sets up sw/ne, of course to give just one reason for this would be a little simplistic but the polar front does seemed to have moved north and perhaps its now default to run at a higher latitude and it now takes much more to get this to run further south, what would have perhaps given us colder zonality 30 years ago now wouldnt able to bring the jet far enough south and perhaps the recent warming trends have culminated in the new default polar front at a higher latitude. Not the most scientific of explanations but just something to throw into the mix. :lol:

[AtlanticFlamethrower]

North Atlantic SSTAs in

January 1984

March 1995

January 1978

It would seem to be pretty self-explanatory.

Today there is a vast zone of +2 degrees celcius anomalously warm water where in those years there was not, or even a negative anomaly present.

Don't under-estimate modification of air temperature close to the surface due to ocean surface temperature.

Edit: An anomalously warm North Atlantic would presumably also have the effect of moving the polar jet northwards.

So here's a link to the current SSTAs

In the Atlantic it's not a pretty sight.

[Norrance]

January and early February 1984 are one my favouriute Winter memories. 24 inches of snow in my back garden in the central highlands on the 16th that lasted a month with frequent top ups.[Not unusual for lying in that era but unusual in its depth.] Lots of PM air, the Polar front a little further South and later in the month lows tracking across the country giving temporary cold Easterlies to the North. Tried to post charts for 24th and 27th Jan to show this but for some reason the link would not copy.

Unfortunately Jan 1984 was not good for the whole country as milder air fed into the South and the PM air was also more modified. From Trevor Harleys site snow lying days for Jan were 30 at Kindrogan in Perthshire, 20 in Glasgow and Edinburgh, down to 6 in Manchester and only 1 in London so for the snow lovers in the south not such a good year.

Why cold zonality seems to be off the charts now is unclear but the sst's posted above must play a part. The location of any highs to the North and North West must also influence the tracks of the low pressure systems as they now tend to be further North and also spawn secondary features that prevent the colder air getting to us.

I would love a repeat this winter but I better not get my hopes up. However the last 6 months have been unpredictable so we never know. :lol:

[Jonnie G]

January and early February 1984 are one my favouriute Winter memories. 24 inches of snow in my back garden in the central highlands on the 16th that lasted a month with frequent top ups.[Not unusual for lying in that era but unusual in its depth.] Lots of PM air, the Polar front a little further South and later in the month lows tracking across the country giving temporary cold Easterlies to the North. Tried to post charts for 24th and 27th Jan to show this but for some reason the link would not copy.

Unfortunately Jan 1984 was not good for the whole country as milder air fed into the South and the PM air was also more modified. From Trevor Harleys site snow lying days for Jan were 30 at Kindrogan in Perthshire, 20 in Glasgow and Edinburgh, down to 6 in Manchester and only 1 in London so for the snow lovers in the south not such a good year.

Why cold zonality seems to be off the charts now is unclear but the sst's posted above must play a part. The location of any highs to the North and North West must also influence the tracks of the low pressure systems as they now tend to be further North and also spawn secondary features that prevent the colder air getting to us.

I would love a repeat this winter but I better not get my hopes up. However the last 6 months have been unpredictable so we never know. :lol:

I remember Jan 84 very well, it was so frustrating to see all the systems giving snowfall after snowfall to Scotland, whereas here in the north midlands it was just loads of rain - that was until about the 20th when a system ran far enough south and gave 8'' of snow, then another the next night gave a further 4''. Several weeks later and long after it had turned mild I remember Ian macaskil commenting 'Eskadalemuir still has 22'' of lying snow' .

[chionomaniac]

.

Edit: An anomalously warm North Atlantic would presumably also have the effect of moving the polar jet northwards.

[Norrance]

.

Edit: An anomalously warm North Atlantic would presumably also have the effect of moving the polar jet northwards.

Evening all

Can anyone explain how the warm NA has the effect of moving the polar jet northwards? Also how does anomalously warm/cold seas favour cyclogenesis or high pressure formation? I feel getting to grips with this would help me understand why we no longer seem to achieve sustained cold anymore.

Many thanks

c

I don't have the knowledge to answer that but a look through the learning area might provide an answer and I am sure the demise of cold zonality has been discussed before. One link about formation of Atlantic lows may be of a little help.

http://www.netweather.tv/forum/index.php?showtopic=35356

[AtlanticFlamethrower]

.

Edit: An anomalously warm North Atlantic would presumably also have the effect of moving the polar jet northwards.

Evening all

Can anyone explain how the warm NA has the effect of moving the polar jet northwards? Also how does anomalously warm/cold seas favour cyclogenesis or high pressure formation? I feel getting to grips with this would help me understand why we no longer seem to achieve sustained cold anymore.

Many thanks

c

Polar jet stream simply marks the tumultuous barrier between tropical and polar air. If through warmer North Atlantic tropical air can creep further north than usual then the polar jet stream will move with it.

Warm anomalies tend to favour high pressure. However the warm/cold anomalies will affect temperature whatever the synoptic set up.

There should be no low level Polar-Maritime snowfall this winter unless a system follows a potent easterly - in which case warm air skims over the top depositing its moisture through the cold layer below as snow.

[North-Easterly Blast]

Next week's zonality is certainly of a mild type, and I would refer to the setup for next Tue-Thur 4th - 6th Dec as a Bartlett as well. What ECM is latching on to is cold zonality though. If the zonal flow is NW-SE and the Azores High is well out to the SW then that type of cold zonal setup will deliver snowfalls.

Did the SSTs in January 1984 play a part in driving the zonal flow from NW-SE with the Azores High well out to the SW?

Also does anyone know what went wrong last winter and as to the reasons why we got a mild zonal (SW-NE flow) Bartlett setup? What prevented us last winter from getting a cold zonal setup like January 1984? An equally active Atlantic / positive NAO & AO as last winter brought us great cold zonality in January 1984, whereas last winter the flow tracked SW-NE and there was a Bartlett to go with it with the same sort of active Atlantic / positive NAO/AO. What were the reasons behind all this? Will we ever see a month like January 1984 ever again?

[kold weather]

No way would I cal lthe set-up between the 4-6th a bartlett, I'd say its just a mild zonal pattern with a weak Azores ridge being forced to head into Europe as the low digs down and east. A real bartlett would have a closed high of its own over Europe which isn't the case, the closest we get is this chart:

http://www.wetterzentrale.de/pics/Rtavn1201.png

textbook +ve NAO mind you but with a bartlett that core high pressur ewould be shifted eastwards ciompletely over Europe with another closed high near the Azores or Bermuda region.

[Norrance]

The zonality will not all be mild this week. For the North it is cool at present and only Tuesday to Wednesday morning can be described as mild. On the other days there will be snow on the hills and mountains and frosts on several nights.

[North-Easterly Blast]

Frosts maybe for north Scotland is possible on some nights this coming week, but south of Edinburgh/Glasgow it is definitely mild zonality - certainly far from a cold zonal setup similar to Jan 1984!

[damianslaw]

Frosts maybe for north Scotland is possible on some nights this coming week, but south of Edinburgh/Glasgow it is definitely mild zonality - certainly far from a cold zonal setup similar to Jan 1984!

Yes not for next week but the potential is there for the following week - if the azores high ridges north and west and pulls its influence away then the floodgates would open for cold zonality but unlikely to be on the same level as Jan 1984 yes I admit.

[Norrance]

]certainly far from a cold zonal setup similar to Jan 1984!

[Weather-history]

December 1993 could be described as cold zonal month for northern parts. Here in Manchester, we saw 12 days of falling sleet/snow, that month. Stornoway had 14 such days and 7 days of lying snow at 9am

http://www.netweather.tv/forum/index.php?s...l=December+1993

Edited December 1, 2007 by Mr_Data

[Eugene]

Give it a chance guys it's just very early Dec, i'm sure the zonality will cool down next week then run out of steam after the 15th as we head towards christmas day.

Early to mid Dec is usually the warmest part of the winter on average.

[North-Easterly Blast]

It is not only us struggling so much to get an easterly or northerly, its the fact that zonality is always mild that bothers and dstresses me. It would cheer me up if zonality in the UK was of the cold variety such as similar to Jan 1984, Mar 1995, Dec 1993 etc and other examples outlined in this thread. In my view also cold zonality is one of the most interesting type of weather pattern there is (after Scandy Highs and easterlies of course). Cold zonality offers the chances of wind and rain, temperatures never too mild and often below average when there is good sources of polar maritime air, and even the chance of snowfall for some areas.

[Thundery wintry showers]

The 'spoilers' are pretty much the same regardless of the cold source:

1. The global temperatures are higher and the SSTs surrounding Britain are higher. Thus, we need, on average, to tap into more cold air than we did before, for all cold air sources; this is especially true of maritime based (W, NW, N) cold snaps, but as Februarys 2005 and 2006 showed, it's also relevant to easterly incursions too.

2. Higher SSTs encourages more shortwave feature development, particularly around the Iceland area. This helps to cut off northerly flows, making them more transient and modified. Cool zonal weather is similar; the shortwaves periodically cut off the polar flow and/or force it to 'return' a longer distance over the Atlantic, such that the airmass is more heavily modified by the time it reaches us.

Easterly incursions in recent years have tended to be scuppered by low pressure to the NW causing Scandinavian/Siberian Highs to remain stuck there rather than extending to our north and bringing spells of cold wintry easterly weather. I remember the months January 2006 and February 2007, when in my LRF I went for a cold easterly spell in the last third of the month, and thought it was too good to be true when the GFS was throwing up the very scenario I had envisaged; as it turned out, it was. But fundamentally these are the same shortwaves that also scupper our incursions from W/NW/N.

We can still get cold zonal weather. December 1999 was in many ways similar to December 1993, though not generally as snowy, it was cold in Scotland, while we had short-lived but potent W/NW blasts on 3 February 2003, and an excellently timed one on 25 December 2004. But the odds against are greater now, certainly more than in the mid 1990s when the winters 1993/94 through 1995/96 featured numerous decent cold zonal interludes.

[Snowyowl9]

Yes dec 1999 was the last time we had cold zonality at this time of year at the begining of the month.

This day gave hail,sleet and snow showers with W-ly gales with the snow showers (rare now) and a dusting of snow here max temps 3c lower than todays actually here.

http://www.wetterzentrale.de/archive/ra/19...00119991204.gif

http://www.wetterzentrale.de/archive/ra/19...00219991204.gif

But as TWS said this was the last great cold zonality to remember with prolonged heavy snow shower with 2.5inches with slight drifting and what a perfect time for it to come 4 inches by boxing day.

http://www.wetterzentrale.de/archive/ra/20...00120041225.gif

http://www.wetterzentrale.de/archive/ra/20...00220041225.gif

A different situation to what we have currently with those anyway.

http://85.214.49.20/pics/Rtavn001.png

[summer blizzard]

Bumped up because it is quite relevant to the synoptics of the last week, proving that zonality is not always mild, even nowadays!

[Snowyowl9]

It was great to see cold zonality making it work last week with 6 days I`ve recorded sleet and 3 with snow falling(very brief on one day)and 1 day settling giving a covering during that cold strong SW-ly on wednesday night into thursday.

As for that december 2004 snowy christmas that was more of a NW-ly flow.

I`ve been looking at this last night and January 1999 was even more S/SW with 3 inches with gave 2 days of hail/sleet then snow showers the first day then heavy snow showers with drifting followed by rain/sleet showers followed by a thaw with temps 1c higher to last wednesday 3c(average max) and the previous day shown here,but 1c lower at night to last week on 1 of these nights.

http://www.wetterzentrale.de/archive/ra/19...00119990117.gif

http://www.wetterzentrale.de/archive/ra/19...00219990117.gif

And some places in the south had lying snow during friday with that S-ly tracking low aswell.

Pity it`s looking so good for next week as the high in the south moves to the wrong place.

Edited January 13, 2008 by Snowyowl9