Uncle_Barty

A classic case of this was in January, when despite the model output being very bullish on a snow event from the west (not an undercut from the SW) even right down to the coast, I was 90% certain (based on experience) that we would only get rain or sleet on the coastal 10 miles or so. I was not the only one - I remember Old Met Man posting a similar opinion. Even the night before, dewpoints were still too high to support snow. We simply don't get snow in these setups!! I was asked the day before what I thought was the likelihood of snow and I said "10%". It was only that high because the models were so bullish predicting it. What happened was that as the front moved in from the west, it engaged colder drier air off the continent and we did get snow in all areas bar the coastal few hundred yards as dewpoints fell low enough. I have never seen that before in nearly 40 years of weather watching. Often, instinct based on experience does work, but in exceptional circumstances you can get caught out. This coming week may well provide more instances of this.....

It wouldn't take much of a correction west to put us back in the oven again. This is a little reminiscent of 2003 when we had some very warm weather followed by a less settled spell in late July/very early August before everything shuffled a little westwards again bringing the heat in. There isn't much sign of the Atlantic train getting going properly a la the past few summers. Things becoming changeable rather than unsettled, and usually better in the South and East. Things are on a knife-edge and it's going to be a fine line between changeable and another heatwave. I wouldn't like to predict at this stage as to which we will get.

I remember July 91 as being changeable but often pretty warm, and the August and first half of September as being warm and sunny. By mid-Sept that year much of the grass round here had gone brown. I'd settle for a repeat of those months this year after the last few summers we have had even down here. Despite the nice start to June here I'd say it's been drier and sunnier than usual but often feeling pretty cool out of the sun with the low dewpoints giving the breeze a cutting edge. Best so far is 24c here. If there is a bit of encouragement among the rather poor model output, it's that there doesnt seem to be a lot of northern blocking at the moment, and as there is often (from my recollection) a shift in the longwave pattern around the end of June give or take a week or two, I think there is every chance we could find ourselves on the warmer and more settled side of the pattern come July. But who really knows!

Point of order... June of 2007 had a very decent start with plenty of warm sunshine and reasonable temperatures, but went downhill quickly as the heights leaked away northwestwards, and the rest is history. Not suggesting that the same will happen this time, of course, but we do look set for a more than reasonable spell of weather for a time at least. Anything showing a breakdown to more unsettled weather afterwards is deep FI of course, as John in the post above points at in the comments about the long wave upper pattern.

Northern blocking, limpet trough just over or close to us. unsettled weather and suppressed daytime temps. (opposite to a Bartlett in winter, in other words, if you like......) Seems to have been our lot in recent summers.

I wish I could be so confident in your assertion of such an improvement in this era of the Modern Summer..... Models keep promising better but then the northern blocking rears it's ugly head.

Temp here 2.7c (highest of the day) in a light SE'ly that's picked up. Another site in Southbourne showing 4c. Little bit of microclimate here! Temps at airport -3 and at my other site in West Moors -3.7. Other local sites only a little further inland are below zero, including Wareham.

Despite the forecasts, I am amazed. Never before in nearly 40 years of weather watching have I gone to bed with temps of 5c outside, only to find temps FALLING in advance of a low from the west and winds from a southerly quarter, and snow setting in. Amazing.

No need - just that it was good to know that I'm not going completely mad with my thoughts seemingly going against what theMO is saying, etc. and hearing your thoughts coming from an ex-pro based down here. This sort of setup generally doesn't deliver snow here.

Exactly the points I have been making over the past 24-36 hours or so, even quoting the Dec 81 event.

Do you mean "back southeasterly"?! We have a southerly here at the moment (170°), if it veers it will go more SW or even westerly. Veer = swing clockwise Back = swing anticlockwise.

Temps rising here all day here now 5.1c with a southerly wind. Barring a change of wind direction to easterly, and advection of colder temps overnight, I can only see rain falling here tomorrow.

I'm not ruling it out as there is always the exception to the rule as I pointed out in my original post, but experience tells me to expect rain tomorrow. It's not cold enough today as it is, never mind when the wind comes round to south of east and off the sea. The only thing I can see that will increase snow chances for us would be if DPs drop with air off the Continent, otherwise it's just the wrong side of marginal.

4c in Bournemouth today. Unless there is a definite cooling of the airmass before/with the precip, I am now 99% certain it will be rain tomorrow for the coastal few miles in this area. Odds of snow here have lengthened. Like I have said before, we just don't get snow in these setups here 99% of the time. Only exception I can think of was 13th Dec 81 when we had a colder airmass to bump into and we had 4-5h of wet snow followed by heavy rain.

From my experience over 35 or so years living here is that usually is (rain/sleet) under these setups. Dewpoints look very marginal. We usually need deep cold air/easterly fetch/channel low to get a good dumping here. SW/ly incursion usually doesnt do it as once those winds get to an onshore direction, it's bye bye snow. In any case this "cold" spell has been a bit 'meh' down here so far. Didn't even get to -1 last night and temps a bit up on this time yesterday. Just a bit chillier than usual. Any cloud/precip coming in will push temps the wrong side of marginal.

OK, next week...... What would concern me (if I were a coldie) is that One, there is not cross-model agreement at D5+, and Two, that the fly in the ointment is the GFS. Being an American model and therefore probably more focussed on what happens Stateside, and what happens there is likely to affect us downstream. Three, the 'default'/most common setup is Atlantic and zonal. For those reasons, i think that the most likely outcome is that the rest of the models will fall into line with GFS in time and that the GFS is most likely to verify at the moment. I know that there are those will say "..but the Strat events go against what GFS are showing...." but that is for beyond the end of next week. I'm not saying it's "game over" after Tues, I could be proved completely wrong, of course. but gut feeling (for the reasons I've explained above) tells me we are likely to have a repeat of the December shenanigans, but without the rampant zonality that followed for the rest of that month. Whatever, we live in interesting times.

It's the usual thing of some taking note detail of every run every 6 hours. "Upgrade! " "No, now it's a downgrade! " Instead of looking at the bigger picture, the overall pattern, the hemispheric pattern, and knowing that there will be swings in the model output. Overall, over the past few days, it's still a story of a good chance of a cold pattern for the UK (about 50:50 IMO), but confidence on detail is low - so there is little point on getting hung up on detail.

Just goes to show, don't dwell on the finer points of each and every run!! And especially when a SSW is in progress and the full implications have yet to be realised...... I'm just keeping an interested eye on an overview of all the major models - we are in for a facinating period of model watching and for my money most things are possible, with a Bartlett scenario the least likely. Edited cos I put "most" instead of "least" in the last line. Wishful thinking !

Why?

A what??? Sounds painful! That 16c will need a good bit of sunshine to achieve - a lot will depend on how much cloud is round this high. SW'lys under HP can be pretty cloudy in winter.

you'll get one allright. For three months...... ...beginning May 15th!

My sentiments, entirely. Until there is a definite pattern change, cold fans are going to be chasing northerly topplers in FI. My money is on such a change, but not until at least the end of the first week in Jan, and if the forecast strat warming comes off. To that end, I would not expect to see much wholesale (i.e. over several runs and several models) change in the model output until the very turn of the year at the earliest.

It's in the right sort of position to be a Bartlett, but in my book, to "qualify" as such, it needs to be in situ for some time (perhaps 2 weeks plus) and seemingly immovable. Good summary here: http://weatherfaqs.org.uk/node/117 In my opinion, despite the appearance of an Iberian high showing in some of the model output, I think a Bartlett scenareo is unlikely in the foreseeable future (unfortunately, IMHO!)

Thanks John. Need to find a good source of reading online or a decent book on the subject. Might be able to find something in the works library, though that is aimed at aviation.

Thanks for this, John. Did you mean 'to the right of the jet entrance' in the graphic. Positions of the circles you put in suggests right rather than left? I've always assumed that the surface patterns are the result of the upper air ones, rather than vice versa? Which is way I usually scratch my head when I see something like "that shortwave is stopping the blocks from meeting/moving east" or whatever, whereas I always thought "the shortwave is there because the position of the blocks allows it to be there.."!