Synoptic Patterns

[SP1986]

Frontal snow in winter itself is actually quite rare now, we usually seem to get showers and the odd troughs but that is all. Polar lows are also quite rare too, though we did have one one January 28th 2004:

http://www.wetterzentraleforum.de/archive/...cka20040128.gif

A recent lack of these events are mainly why we havent had countrywide snowfall for many years. The polar low in 2004 dissipated and swerved south-eastwards so many areas of the south only recieved a dusting.

<{POST_SNAPBACK}>

Quite true, frontal rainfall has also declined for the convective/showery type of rainfall.

[summer blizzard]

The reason frontal rainfall has declined is because in recent years, frontal systems have aproached from the north west rather than the south west and as a result have had to travel over more land and have decayed, especially during winter, the reason for this is because in recent years, the Jet Stream has been much further north of the British Isles than is usually expected.

[SP1986]

The reason frontal rainfall has declined is because in recent years, frontal systems have aproached from the north west rather than the south west and as a result have had to travel over more land and have decayed, especially during winter, the reason for this is because in recent years, the Jet Stream has been much further north of the British Isles than is usually expected.

<{POST_SNAPBACK}>

Maybe this is true, but with a strong low pressure available, much of the moisture is available to reach the SE.

However High pressure may have been to 'fault' for the lack of fronts and high pressure has been quite close to the UK and generally low pressures have been quite shallow.

[summer blizzard]

If the Jet Stream is to the north of the British Isles then there is usually high pressure to the south of the British Isles.

[SP1986]

If the Jet Stream is to the north of the British Isles then there is usually high pressure to the south of the British Isles.

<{POST_SNAPBACK}>

I think High pressure been just about everywhere it could have been the last 5 years , However your idea that fronts died is valid when you take into consideration that high pressure would have taken a lot of moisture away from the south, instead replacing it with a high theta-w and ultimately convection (hence most of the rain has been convective on troughs.

[summer blizzard]

At least the south will see some rainfall over the weekend as a fairly deep low goes over the British Isles, it seems that the lack of rainfall is most evident in winter, most likely due to the fact that the sea is favoured for the heaviest frontal rainfall.

[shuggee]

Those '68 charts, with 1045mbs over to the North and West illustrate the achilles heal of the modern winter - how not having a stable, strong Greenland High leaves us with little more than SW'ly and W'ly zonality.

Anyone remember those pesky little 'Channel Lows' or an equivalent say across the Midlands - introducing an artic or E'ly blast behind as they move off into the Low Countries?

Edited August 1, 2005 by shuggee

[londonsnow]

Those '68 charts, with 1045mbs over to the North and West illustrate the achilles heal of the even larger teapot - how not having a stable, strong Greenland High leaves us with little more than SW'ly and W'ly zonality.

Anyone remember those pesky little 'Channel Lows' or an equivalent say across the Midlands - introducing an artic or E'ly blast behind as they move off into the Low Countries?

<{POST_SNAPBACK}>

i remember them well shugs

[SMU]

Those '68 charts, with 1045mbs over to the North and West illustrate the achilles heal of the even larger teapot - how not having a stable, strong Greenland High leaves us with little more than SW'ly and W'ly zonality.

Anyone remember those pesky little 'Channel Lows' or an equivalent say across the Midlands - introducing an artic or E'ly blast behind as they move off into the Low Countries?

<{POST_SNAPBACK}>

Interesting you mention that Shuggs... If you look at my post in the Autumn thread you MAY not have much longer to wait to see those artic winds digging in bring Cold snowy weather...

S

[londonsnow]

Interesting you mention that Shuggs... If you look at my post in the Autumn thread you MAY not have much longer to wait to see those artic winds digging in bring Cold snowy weather...

S

<{POST_SNAPBACK}>

i cant find that steve. can you point me in the right direction? cheers LS

[SMU]

i cant find that steve. can you point me in the right direction? cheers LS

<{POST_SNAPBACK}>

Autumn thread

S

[SP1986]

Interesting you mention that Shuggs... If you look at my post in the Autumn thread you MAY not have much longer to wait to see those artic winds digging in bring Cold snowy weather...

S

<{POST_SNAPBACK}>

I would agree that this winter is half setup, but the SST anomalies need to take a massive dive first. However having said that, the anomalies above the UK would give us snow on a low in winter as opposed to rain we may have seen in the past (the borderline issue), first we have to hope the NAO stayed negative - which it should do as I saw an interesting little charts earlier today which showed the NAO in decline since the new millenium. However whether we get the right setup come winter is the real question, until then all we can do is speculate unfortunately (and trust me I wouldn't mind finding out that winter would be a corker right now)

[SMU]

I would agree that this winter is half setup, but the SST anomalies need to take a massive dive first. However having said that, the anomalies above the UK would give us snow on a low in winter as opposed to rain we may have seen in the past (the borderline issue), first we have to hope the NAO stayed negative - which it should do as I saw an interesting little charts earlier today which showed the NAO in decline since the new millenium. However whether we get the right setup come winter is the real question, until then all we can do is speculate unfortunately (and trust me I wouldn't mind finding out that winter would be a corker right now)

<{POST_SNAPBACK}>

Hi Steve-

In JB's post he ( I think once I translated his post into English) mentions that the Neutral Signal in the pacific & the +VE signals across the atlantic will ASSIST the prospect of a negative NAO- A Little confusing for those that thought that colder SST's would assist the development of the Greenland high.....

S

[SP1986]

Hi Steve-

In JB's post he ( I think once I translated his post into English) mentions that the Neutral Signal in the pacific & the +VE signals across the atlantic will ASSIST the prospect of a negative NAO- A Little confusing for those that thought that colder SST's would assist the development of the Greenland high.....

S

<{POST_SNAPBACK}>

Actually having read the post you send a link to, it physically makes sense, because the ITCZ is further North so in essence these hurricanes are forming in slightly cooler air, and this in turn is going to cause a conveyer belt of low pressure (due to the warmer than average water (strange really), and then this leads onto cooling the atmosphere. it does fit together i'll give it that.

The Greenland High would cool water, but this may only produce more anticyclonic development - of course we know a polar low develops better in warm water, but of course warm water can modify the 2m airsource to slightly warmer (I think that may be what people are worrying about) but if it's cold enough, it may not matter.

[SMU]

Actually having read the post you send a link to, it physically makes sense, because the ITCZ is further North so in essence these hurricanes are forming in slightly cooler air, and this in turn is going to cause a conveyer belt of low pressure (due to the warmer than average water (strange really), and then this leads onto cooling the atmosphere. it does fit together i'll give it that.

The Greenland High would cool water, but this may only produce more anticyclonic development - of course we know a polar low develops better in warm water, but of course warm water can modify the 2m airsource to slightly warmer (I think that may be what people are worrying about) but if it's cold enough, it may not matter.

<{POST_SNAPBACK}>

Agreed- It will be interesting if we get any Polar Low scenarios this winter- I will be looking for a 500 HPA temp of about -35C over the shelf and that long drag of northerlies across the Country-

With a High frequency of Strong Driving Troughs Cutting through Scandi recently I would say we have a good chance of seeing at least one this Winter-

Eastern Ireland, The North west and Sometimes the Home Counties do well out of those-

Regards

Steve

Edited August 1, 2005 by Steve Murr

[SP1986]

-Well the good points for now are to the north of us we have -SST's - I'm not sure why this is beneficial - but apparently it is...

-The NAO looks like being negative for the forseeable future

- High pressure looks like it will create a certain amount of cold pooling over and around Greenland.

I just hope southern Greenland cools down, it's had a very very warm summer so far.

Steve, is there any information on any melting ice in the Arctic regions at all? - this may also enhance high pressure ridging from the north.

[SMU]

-Well the good points for now are to the north of us we have -SST's - I'm not sure why this is beneficial - but apparently it is...

-The NAO looks like being negative for the forseeable future

- High pressure looks like it will create a certain amount of cold pooling over and around Greenland.

I just hope southern Greenland cools down, it's had a very very warm summer so far.

Steve, is there any information on any melting ice in the Arctic regions at all? - this may also enhance high pressure ridging from the north.

<{POST_SNAPBACK}>

No-

Grey Grey area that one.....( I doubt anyones conducted a survey of how Ice levels/melt effects the BI)

I messaged Atmos a few times and we had discussed it- only to the level of if there is a decline then it has usually recovered by the next year-

If i remember the rightly ice coverage has had a greater decline against the Norm over the western side of the Artic as opposed to the Eastern Side-

'Perhaps' Its all to do with the intense WAA pumped up the South and western side all summer Long-

Im guessing/Hoping that this winter will continue the theme of very Low MSLP averages over the western side (against the norm) to assist in the displacement through CAA to the South & South-west-

You never know-

Regards

Steve

Edited August 2, 2005 by Steve Murr

[SP1986]

Interesting this really, this charts shows that actually this year, the west of Greenland is actually quite cool, and the east shows some cold off the coast of Narsaasuaq which may also be encouraging.

[kold weather]

I think the reason why this year has been so warm in some regions of Greenland high,is because of the Greenland high,which every now and again is linking u pwit hthe Azores and sucking up a fair amount of warmer weather up the western side,coupled with clear skies thanks to the Greenland high and that is reason enough for some warm weather there.

0z is nowhere near as impressive as 18z with it taking longer for any cold pooling to really occur,although we do get a 1035mb Greenland high.howevr,looking at 0z FI,it forms a tropical cyclone and moves it northwards,and so very little confidence must be put in anything beyond 144hrs at this time of year and after that,anything can happen.

[Bottesford]

Surely hyping up 'cold pooling' is pointless in early August- maybe look for that sort of thing late September!

[TEITS]

In JB's post he ( I think once I translated his post into English)

S

<{POST_SNAPBACK}>

Im glad you have Steve im still working my way through it!!

I must admit I don't usually like Autumn as I usually cannot wait for winter to start but this year is different and I cannot wait to watch the developments during Sep/Oct/Nov to see what kind of winter we shall have.

[Thundery wintry showers]

Re the points about cold winters, there have been a few notable differences between cold snaps of the modern winter and winters in earlier decades, owing mainly to a northerly tracking jet and cyclogenesis around Iceland.

Easterly setups.

The historic easterly blasts either had high pressure moving out of Siberia into Scandinavia and then moving further west towards Greenland, or a high transferring south within the Greenland-Scandinavia sector, bringing easterly winds originating in Russia. That pattern can lead to prolonged cold spells, as the high can oscillate in position between Greenland and Scandinavia bringing a combination of easterly and northerly incursions and some fronts for the south. The ideal setup for snow lovers in the south and east is probably a ENE'ly of northern Russian origin, with frontal snow in the south, and instability picked up from the long track over the North Sea resulting in sunshine, snow showers and even thunder for north-eastern districts.

In recent years, cyclogenesis around Iceland has usually prevented the high getting west of Scandinavia, ensuring that our easterlies did not come from a particularly cold source and bringing dry cloudy weather. The exception was in late February 2005, which many of us will remember, but the cold air sources were 10-15C above average then.

Northerly setups.

The standard "northerly topplers" were also common in earlier decades, but there tended to be less cyclogenesis around Iceland, and a block around Greenland would have a greater chance of holding. Sometimes a northerly could persist for 2-3 days, or there could be multiple northerly blasts in succession- or, it could be followed by easterlies as HP built to our north. Large snowfalls could result when Atlantic systems pushed against the cold air. However, northerlies tend to need to sustain for at least 2-3 days in order to bring any widespread snowfalls/polar lows etc.

Recent years have seen the standard toppler 36 hour events, with a straight northerly bringing snow showers to Aberdeen, and then mild weather arriving from the north-west, the fronts having little resistance from the cold air.

Returning polar maritime setups.

For these to sustain, they usually need to be quite "northerly oriented", although January 1978, Janaury 1984 and March 1995 contained examples of setups where Atlantic depressions dominated but the air they carried was repeatedly cold enough for snow. However, for widespread snow events, a large High over Greenland is again useful, as it pumps large amounts of cold air into the mid-Atlantic, which then becomes embedded in our Atlantic depressions. In recent years, the prominent Icelandic Low has traditionally forced the cold air to take a much longer track over the ocean, so the resultant incursions haven't generally been snowy except in northern Scotland. The only good "tasters" of what this setup can bring, in recent years, occurred on the 3rd February 2003 and on Christmas Day 2004.

[summer blizzard]

Does anybody have the link to Joe laminate floori's column.

I believe that the reason for those warm sea surface temperatures to the south of Greenland is because of westerlies coming off a warm Canadian continant, if i am right, then once the continent starts to cool in September, the sea surface temperatures will also cool, it is good to see that there are no posotive anomolies to the north of us.

Also, is that a slight La Nino that i can see developing.

[summer blizzard]

With the Greenland High getting stronger and the Azores High getting weaker, i believe that the Azores High will no longer be a factor by September.

[SizzlingHeat]

in the winter, i have noticed that the azores high can get up to 1045mb which is extremely strong.