Best time of year for cold synoptics - when?

[NorthantsSnow]

Frosty just made a good point on the Model Output Thread which inspired me to start this thread. What we've experienced over the past 24 hrs is a fairly potent Northerly, especially given the season we are in. This resulted in some very low mins across the board, whereas maxes haven't been all that low, and were close to average for much of the UK yesterday. I assume though if this same setup occurred again in three months time, there would be a considerable difference in temps compared to the past few days, is that correct? So what I want to know is, when would be the ideal time for cold synoptics to occur? And before someone is clever and says "the winter" - I was hoping for something a little more specific than that, if possible.

[Thundery wintry showers]

I tend to think of northerlies as being most 'ideal' for wintry weather around December, because the sun is weakest at that time of year, and one issue with northerlies is that they're often associated with high sunshine totals, therefore meaning a potential thaw in the sun, which tends to become a major issue from mid-February onwards.

Easterly types are most ideal in February, I think, because the continent is almost as cold as in January, on average, while the SSTs are traditionally at their lowest in late February/early March.

[stormforce 10]

i'd say between mid december and late january because the sun is at its weakest.

[sundog]

I think the coldest time of the year is between mid jan to mid feb so that would be the best time to get cold synoptics. However my fav time to get them is around xmas to give that real seasonal feel and the chance of a white one.

[BLAST FROM THE PAST]

I've always based any chance of very cold and prolonged synoptics on one timescale. If by the last week of Jan cold synoptics haven't shown their hand then winter is likely not to really arrive. By this I mean that we must have had or experiencing cold weather and right synoptics by then otherwise it will be too late in feb. Yes some cold may arrive but nothing prolonged or of note. In reverse this summer is classic example, by Aug there was no real summer weather or synoptics of note...and they didn't arrive. We had some warm weather but nowt of note.

BFTP

Edited September 18, 2007 by BLAST FROM THE PAST

[saint]

between december and late feb in my opionion

saint

[Iceberg]

A slightly different POV, northerlies are best in March, this is the point where SST's and 500 temps are at there lowest encouraging PL's. You also have the thermal effect which helps to increase shower extent.

More lying snow for the favoured areas, but for 80% of the country your unlikely to see anything in dec or Jan.

Easterlies Jan and Feb.

NE eg direct from scandy land I'd probably go for Dec. This is the time of lowest isolation where temps can get really low, coupled with a still warmish north sea you get a lot of lake effect snow and the chance of a small meso surface low forming.

[I remember Atlantic 252]

id say the best time for cold synoptic charts is from 15th dec to 15th jan, long nights, sun shines on less surfaces so thaws less sn0w and very cold nights. love snow in feb and march but it soon thaws as sun is higher and stronger, the sun is really high at the end of feb and id say the time of year is not all that cold

snow at end of nov is better than end of feb as days are shorter

[Thundery wintry showers]

I have to admit, while I'm certainly not one of those who suddenly loses all interest in wintry weather as soon as March arrives, I do have more enthusiasm for autumn snowfalls than spring snowfalls. I find November to be a particularly dark, drab, uninteresting month for most of the time (though you do get rare sunny exceptions like 1996/2005/2006), and so a bit of the white stuff makes November seem less unappealing to me.

[Geordiesnow]

A slightly different POV, northerlies are best in March, this is the point where SST's and 500 temps are at there lowest encouraging PL's. You also have the thermal effect which helps to increase shower extent.

However though as TWS quite rightly says, snow thaws quicker in March so it would be rather pointless showers falling and the showers during mid day could turn back to rain so more snow thaw even in shaded areas but for me personally its still interesting.

For me personally i like Northerlies anywhere between Nov-Feb and Easterlies to occur after mid December though this will vary on how cold the continent is.

[damianslaw]

On a personal note the best time for winter synoptics for me to occur is from about the 20th Dec right through to the New Year i.e. the christmas period 1995, 1996 and 2000 and to a certain extent 2001 delivered the goods.

The long dark nights combined with the christmas period and a good winter synoptic ahh perfect!!

However, anytime in January is probably the best time as the sun is still very weak and the cold has usually by then sufficiently built up over the continent -so this is the best time for a sustained potent easterly and lasting snow cover.

However, I would agree early March is a good time for a northerly as the arctic is at its coldest by then and the extra strength from the sun can power up some very beefy snow showers admittedly snow cover doesn't tend to stick in March for long.

[disco-barry]

Just take it as it comes as from what i've learnt off here in the few years is that nothing is what is seems, people talk up there theories on why it's going to be cold etc. but i don't think i've seen one come off yet.

Steve Murr is a good one to listen to, very in depth forecasts throughout the winter

[Don]

I think the best time for cold synoptics is late January/early February when Europe's generally at its coldest and SST's are low. The trouble with mid February onwards as we've had in recent years is that the sun is gaining strength, so any snow doesn't tend to lay for very long, and the fact that Europe is starting to warm a little too.

[Nick F]

Well if you're into old fashioned weather prediction, you could always take note of the 'Buchan's Cold Spells' of 7-14th Feb, 11th - 14th April, 9th - 14th May, 29th June - 4th July, 6th - 11th August and 6th - 13th November. Though unfortunately, the weather is rather more random for cold synoptics, than the 19th Century Scottish Meteorologist proposed.

On a more serious note, I find the period between Boxing day and New Years' day seems to be particularly favoured for cold spells for some reason. Also i find Nerlies tend to take precedence over Easterlies for cold during November and early December, probably because the PFJ is more likely to introduce cold arctic air than cold continental air - as E Europe/W Russia often hasn't cooled down sufficiently until late December. Otherwise cold synoptics occur pretty randomly during the rest of winter.

[Bottesford]

Well Dec 21st is the shortest day meaning Nov 21st-Jan 21st is when we receive the least radiation (thus energy) from the Sun.

Thermally - around early February is when we experience our lowest temperatures on average.

SSTs - lowest in March.

So overall - 10th Jan - 10th Feb I guess. Depends what you're after - if it's more frequent heavier snow showers but not sticking so much, go for March; if it's rarer sticking around kind of snow - go for earlier in the season. I like snow only if it does one of the following - a) snows a load then it stays cold enough to stay as snow. or It snows then all melts in the spring sunshine. Living in an urban area means it doesn't take much for it all to become filthy & dangerous slush which is absolutely no fun at all.

I can take or leave snow but what I'd love to see is some really cold but dry air coming in from the east in say late Jan. Clear skies with temps ranging from -15c by night to -3c by day and very low humidity. If snow comes along, even better. Would be quite an experience although not much fun in the mornings that's for sure.

[Gavin P]

I'd go for mid January through to mid February.

[Rollo]

If we are fortunate to get the correct synoptics around mid to late december then any melt of the lying snow is minimal and one good fall will last as long as the cold spells duration-however this as we know is a very rare occurence.

[kentish_sally]

Being pedantic - Would we be suggesting UK-Wide or more localised? Surely we would have a difference of opinion (as welcome as it is) based upon what benefits us more and the time of arrival.

General setups such as polar lows or easterlies work well for North Kent and more recently ive seen snowfall happening, though not nessecerily from the above setups - more and more around the start of spring as flowers are begining to bud, where as people in Scotland fair better in Northerlies (obv!) and it seems these can occur generally on what would be described as mid-winter so early january

[phil nw.]

Over the years i have seen lying Snow anytime from November to April,however,these days with warmer seas around us a Northerly rarely brings a prolonged snowy spell.Therefore i would have to say late January to end of February would be be best for an Arctic blast for the UK when the sea is almost at its coldest and the sun still not too high.

As for Easterly`s then i guess the window of cold is larger say from from December to early March as the landmass to our East can cool much quicker earlier in the season and ,with right sypnotics, can still be quite cold as late as early March.

Unfortunately in recent years the right sypnotics are less common,certainly compared to my younger days of the 60,s and 70,s.

[BLAST FROM THE PAST]

Just bolt on Northerly to start the ball rolling in Dec [mid Dec onwards] ie 62, 81, 95 and easterly in Jan to very beginning of Feb a latest...86, 87, 91 as examples.

BFTP

[Weather-history]

Over the years i have seen lying Snow anytime from November to April,however,these days with warmer seas around us a Northerly rarely brings a prolonged snowy spell.Therefore i would have to say late January to end of February would be be best for an Arctic blast for the UK when the sea is almost at its coldest and the sun still not too high.

.

The trouble is a lot of northerlies tend to bring just cold and clear skies inland with any snow showers tending around coasts that are exposed to the wind during the high winter months.

You are more likely to see snow inland during March and April northerlies when showers can be generated. Only if its a vigorous northerly with troughs and polar lows are you likely to see snow inland during the high winter months.

[Roger J Smith]

You can see the answer to this question fairly clearly in the daily CET data available on the Metoffice site (from 1772 onwards).

The colder the winter, the more likely it is that the second half of January is notably cold. This is the core of the cold period in almost every case of a cold winter in the UK. There are of course exceptions. 1981-82 had almost all of its below freezing days before the middle of January. 1946-47 had its coldest period in February, as did 1894-95.

But the majority of cases have a few brief periods of sub-freezing weather in December followed by a more permanent plunge below zero around the 5th to the 10th of January which then reaches a minimum around the 15th to 25th of January before relaxing to more intermittent cold in early February.

Incidentally, I was unable to spot even one day when the mean CET was below -10 C, perhaps I missed one or two, but the range from -6 to -8 C seems to be the standard for cold daily means in various cold winters, the degree of cold for a month or season depends mostly on how long that lasts rather than how intense the cold becomes. Clearly the trigger for such low temperatures is radiational cooling over snow cover, you can see in milder winters that there are usually a few spells close to zero daily means, the sign probably of cold highs with no snow cover.

If you want to see a complete contrast between months, look at Jan 1795 and 1796. There was just one very brief thaw in Jan 1795 near the end of the month, but in Jan 1796 the lowest daily mean was 4.0 -- even higher than last January by quite a margin.

And not to get carried away, but since February the daily CET in 1794 has never been that far off this year -- hmmm.

[Rollo]

Are you hinting at something there roger? I still think that after a northerly plunge in December (and I am old enough to remember one or two) followed by the high settling over the country then very low temperatures both maxima and minima would and indeed have been achieved,certainly in my locality, which as you know is fairly rural.

[Roger J Smith]

Not really hinting, but it struck me looking at 1794 that, although January of that year was quite a bit colder than 2007, the rest of the year from February to the present time was broadly similar, even quite warm in April like this year, and in fact a bit warmer in July than this year, so in other words, the platform from which the winter will soon be diving is similar if not a bit closer to the water, so to speak. There appeared to be a fairly strong northerly around the 25th to 29th of September in 1794 after a bland September, so that's fairly similar too. You can always hope, I suppose.

That large area of open water northeast of Siberia is really a total wild card in the set-up, in my opinion, so much so that it could over-ride almost any analogue process at work, and I really think that all bets are off about the next few months with this in the complicated machine of global climate, my first impression was (as stated on another thread) that this should create high-amplitude flow over North America which at least puts some pressure on the flow over Europe to resolve away from a complicated set-up and provides all kinds of opportunities for arctic air to mass anywhere else but its most favoured position over Siberia for a change. But that could just as easily be central to eastern North America as Europe, I suppose.

I blame it all on the aliens behind the Moon, as you know.

[BLAST FROM THE PAST]

I blame it all on the aliens behind the Moon, as you know.

Roger

They not Aliens...its me and my family

BFTP