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Lake District Blizzard

Why Is The Upcoming Spell Of Weather Forecast To Be So Cool?

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Looking at the charts for friday, saturday and sunday, given it being early august with a lovely big high pressure system giving SE'ly winds. Surely high 20s widely would be expected with low 30s in the hotspots. For where i am only 21 / 22c is being forecast which is only a couple of degrees above average, likewise only 22c - 24c is forecast in parts of the south, which is also only a couple of degrees above average...

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Well, the beeb were predicting maxes of 26-27C tomorrow?

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Who cares? It's a pleasant outlook.

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Because it isn't.. warm spells have always been forecast too cool running up to them, and it's only just now that more realistic temperatures are being forecast. The GFS is poor at forecasting temperatures, but that's to be expected... the BBC and Met-office though, I'm not sure.

Yesterday the temperature reached circa 22C, it was forecast to be 19C. Today the temperature reached circa 25C, it was forecast to be 18C by the Met-office, and only 20C by the GFS... so the reality is, as far as temperatures go, in this situation, you have to wait and see what the temperature actually is.

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The upper temperatures look conducive to high 20s temperaqtures too so its very puzzling. BBC Weather site also showing low maxima too and rather a lot of cloud around??

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I'm not sure where this cloud is going to come from over the next two days, as the satellite images suggest that yesterday's front over SW England has fizzled and that all that remains is patchy convective cloud plus some patches of wispy high cloud in the north. Cloud will of course arrive associated with the Sunday/Monday breakdown, but not

It's possible that the GFS's low temperature projections for northern Britain may arise from overestimating the extent to which south-easterly winds bring suppressed temperatures and low cloud from the North Sea. I think "haar" will certainly become an issue over eastern Scotland and coastal NE England but it is hard to see temperatures being held back at 16-18C in inland regions.

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Its fairly easy to see where the models get their lower values from ASSUMING the models have the wind flow correct.

Simply look at the Met O Fax charts. Note how the gradient increases quite markedly from what most areas have had today. Their later charts suggest a gradient of about 130-150 which would give surface winds and possibly up as high as about 1200ft from between 060 and 100 degrees. This would bring cooler air off the North Sea into many eastern and central areas, even with some cooler air infiltrating through the mountain chain down the centre of England. The afternoon visual sat picc showed little if any sign of low cloud over the North Sea so it is possible that the models are antcipating that to be a large part of the apparent depressed maximum temperature. But the theory of why the models have dropped the maximum temperatures especially on Saturday is fairly obvious it seems to me. Compare the values on Saturday with Sunday with a wind change for some?

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Indeed, I'm struggling to see where this cloud is coming from too.

As John Holmes suggested, an increase in surface winds would stimulate the movement of cloud from the north sea although judging by the lack of cloud on the Satellite picture I'm not seeing it. So while yes it does make sense why we would see cloudy skies the current satellite images suggested a largely cloud free picture. Perhaps the increasing 850 profiles added by a higher gradient would increase the moisture on sea level prompting low level cloud to form?

Models usually struggle to estimate the full extent of cloud cover. For inland areas at least I would be inclined to wait till the day actually comes, any north sea cloud may easily burn away to the far east.

Thanks for the explanation, something to look out for future reference.

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18z still forecasting cloudy conditions Saturday here, it seems so odd for it to appear tommorow night so randomly and so far west!

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Summers are cooling year on year, we rarely get near 25C here since 2005, whereas in the 1990s there were generally long runs of 25C+ days

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Summers are cooling year on year, we rarely get near 25C here since 2005, whereas in the 1990s there were generally long runs of 25C+ days

Summer of 2006 was one of the hottest on record though (and the Autumn that followed was the warmest) and 2010 was quite good at times too.

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Summers are cooling year on year, we rarely get near 25C here since 2005, whereas in the 1990s there were generally long runs of 25C+ days

Its all down to the frequency of warm/hot synoptics and the fact that they dont seem to occur as frequently as they used to. I believe when the right chart comes along it will be just as hot as if it had occurred back in the 90s. Take last June for example where we saw 33c on only the second day of the heatwave.

Also, its unlikely that this summer will be cooler than last year. August would have to be 15.3c of less. Perhaps the start of an upwards trend? We will have to wait till next summer to find out.

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Summer of 2006 was one of the hottest on record though (and the Autumn that followed was the warmest) and 2010 was quite good at times too.

2010 was only 'good at times' in the SE.. it was very cool up here, not that I'm bothered.

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2010 was only 'good at times' in the SE.. it was very cool up here, not that I'm bothered.

It wasnt cool in Leeds, a look at the metoffice climate summary charts shows it was around 0.7C above the 1971-2000 average, around 105-110% sunshine and 90% rainfall. It wasnt all that bad.

It was actually similar statistically to summer 2005 in temperatures, sunshine and rainfall overall.

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Hm, you might be right, I think my opinion of that summer is influenced by August which was downright cool. July was average, June was above.

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Summer 2010 here was just below normal but with below average rain.

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Its fairly easy to see where the models get their lower values from ASSUMING the models have the wind flow correct.

Simply look at the Met O Fax charts. Note how the gradient increases quite markedly from what most areas have had today. Their later charts suggest a gradient of about 130-150 which would give surface winds and possibly up as high as about 1200ft from between 060 and 100 degrees. This would bring cooler air off the North Sea into many eastern and central areas, even with some cooler air infiltrating through the mountain chain down the centre of England. The afternoon visual sat picc showed little if any sign of low cloud over the North Sea so it is possible that the models are antcipating that to be a large part of the apparent depressed maximum temperature. But the theory of why the models have dropped the maximum temperatures especially on Saturday is fairly obvious it seems to me. Compare the values on Saturday with Sunday with a wind change for some?

Worth noting that even if the feed is more continental, temperatures over the low countries and much of Germany are only average at best, there is no real heat built up at the moment.

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Temperatures could have been a lot higher under this high if it had originated from the Azores with a low pressure running over the top ushering in some very warm air. The high we have now is actually a combination of a cool air mass from the north west and a high building from the south which merged over the UK. This explains the coolish nights some are experiencing.

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Temperatures could have been a lot higher under this high if it had originated from the Azores with a low pressure running over the top ushering in some very warm air. The high we have now is actually a combination of a cool air mass from the north west and a high building from the south which merged over the UK. This explains the coolish nights some are experiencing.

Its producing much more pleasant and usable weather though. Temperatures in the low-20s by day and down to 11-13C at night with plenty of sunshine and little cloud will suit the majority.

With a high building from the Azores its possible to be much warmer, but with that comes humidity, sticky nights and a very high risk of cloudy skies and trapped fronts.

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Its producing much more pleasant and usable weather though. Temperatures in the low-20s by day and down to 11-13C at night with plenty of sunshine and little cloud will suit the majority.

With a high building from the Azores its possible to be much warmer, but with that comes humidity, sticky nights and a very high risk of cloudy skies and trapped fronts.

Oh yes, no compalints from me. I was in Hornsea right on the coast and it didnt feel chilly at all in the onshire breeze. Nights are cool but its not until it gets dark that we are seeing temperatures fall into the cool category. While its light its very pleasant.

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Temperatures could have been a lot higher under this high if it had originated from the Azores with a low pressure running over the top ushering in some very warm air. The high we have now is actually a combination of a cool air mass from the north west and a high building from the south which merged over the UK. This explains the coolish nights some are experiencing.

And I'm grateful for that, MH!yahoo.gifyahoo.gif

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Temperatures could have been a lot higher under this high if it had originated from the Azores with a low pressure running over the top ushering in some very warm air. The high we have now is actually a combination of a cool air mass from the north west and a high building from the south which merged over the UK. This explains the coolish nights some are experiencing.

Indeed, we saw a similar scenario in early June 2005..

Cool air mass - http://www.wetterzentrale.de/pics/archive/ra/2005/Rrea00120050606.gif

Merged high pressure - http://www.wetterzentrale.de/pics/archive/ra/2005/Rrea00120050608.gif

Bit too stuffy for my liking last night and today.

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Historically, many heatwaves have originated from this kind of evolution, where we get a build of pressure following a polar maritime incursion, giving generally dry sunny weather with modest daytime warmth and chilly nights, and then highest pressure transfers into the North Sea sending hot airmasses up from the continent. The reason for the lack of notable heat this time around is probably the short-lived duration of the southerly airflow plus the nearest hot airmasses being a long way away to the south (the further away the hot airmasses, the more sustained the S/SE airflow needs to be).

When we get the tropical maritime airmass scenario with high pressure coming in from the SW and low pressure over the top, the weather often starts off fairly cloudy with warm sticky nights- again the clearest route to a hot sunny spell from there has the high pressure extend eastwards pulling up drier continental air.

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SP1986 was right, today a maximum of 20c was forecast and cloudy.

There hasnt been a cloudy in the sky all day except for tiny cumulus bubbling up on top of the higher mountains. Max of 24.3c here, similar at Keswick

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Yep similar here, it clouded over for half an hour around 12pm, that quickly dispersed with sunshine and temperatures of 24.c

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