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Posted (edited)

Hello all, 😀

As we all know, the UK is currently in a heatwave (July 27th). It is remarkable so far for not only its strength of the heat but the duration of the heatwave too (Since around June 19th to July 27th (Current),). The media is reporting interviews from UK meteorologists, asking why we are currently in a heatwave, with many answering that it is due to the jet stream marandering North to the UK, thus allowing hot air from a situated high-pressure system over Central Europe to divert up North towards the UK.

That's all fine and dandy, but I ask "Why is the Jetstream maraundering North and why is it currently so weak?" đŸ€”

So, what do you guys think?

Why are we experiencing such a strong heatwave? As in, what weather drivers are causing it to happen in the first place?

Let's get this discussion going! 😁

Edited by mpkio2

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While  it has been great, the 'heatwave' has not been going since June 1st.

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Summer, long days, strong sun and a dose of luck for heat lovers....simples. 😁

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5 minutes ago, Mapantz said:

While  it has been great, the 'heatwave' has not been going since June 1st.

I probably overestimated. 😳

Looking back at the records, south-east of the country had an averaged temperature anomaly of around 25c since around 19th June.

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Its been pretty damn warm since may 5th that's an understatement.

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There was a documentary about Climate change on Canadian TV on Tuesday i think...there they stated the UK was enduring their hottest summer in centuries due to climate change...hottest in 20 years maybe not sure where they get centuries from??

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7 minutes ago, cheeky_monkey said:

There was a documentary about Climate change on Canadian TV on Tuesday i think...there they stated the UK was enduring their hottest summer in centuries due to climate change...hottest in 20 years maybe not sure where they get centuries from??

Load of rubbish as usual. This Summer, not to play it down as it already has a place with the best, is still not quite as warm as 1976  or 1995 even ( though we've still got more than a month to beat them I suppose). But that's still only the hottest Summer in around either a quarter to less than half a century (unless 1976 gets beaten, then I guess that statement would be true). That's probably about as often as is normal, on average, to expect a challenger for the UK's hottest Summer, I'd imagine. Besides hot dry Summers may be a bit rare in this part of the world, but we usually get at least one most decades. So though fascinating from a meteorological perspective,  I don't really buy into the idea this is anything so exceptional to have to look back centuries to find any precedent for either.

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The BBC are being a bit simple in describing the jet ect.. (the symptom, not the cause).

A strong wave crossed the Indian Ocean into the central Pacific during late April (the further they get, the more they drive the sub-tropical high pressure belts northward) and was followed by a second during late May and early June which completely crossed the Pacific. In tandem with this (and partly as a result) we saw the intervening time periods until early July commonly see strong trades over the Indian Ocean and western Pacific (Nino signal) which maintained the pattern. 

Since early July we have moved back to a more neutral/Nina look in terms of stronger convection over the Indian Ocean and stronger trades over the central and eastern Pacific which is why the pattern changed around mid month to a more cyclonic one however the stand off has not been enough to push the trough completely through which is why we've seen the trough struggle to get east of the UK and take over. 

In tandem with this in May and early July especially we saw a stonkingly abnormal +AO (be that a result of or independent of said pattern) which has only helped to keep the jet stream well away from the UK. 

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Is it not still an effect of the unprecedented SSW in February? The atmosphere seems to have never quite recovered from that. That's what I'd assumed anyway.

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One hot summer and suddenly it's climate change we have a different summer every year this year the combination of the southerly winds and the jet stream going north are the factors.

Iceland has had a wet summer due to the position of the jet stream in 2007 we had the floods as the jet stream sat over the central part of UK.

It's typical media hysteria to think one hot summer is climate change didn't they say about 10 years ago the UK would never see snow in the future.

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The sun plunges into another deep minima.  This year we have had 117 blank days thus far running at 56%, 30 of the last 31 have been blank.  This allows more prolonged coronal hole effects on Earth, In turn the jetstream reacts wildly to deepening minimas.......this is a very interesting year indeed.  This hot pattern likely to see us into September at least imo.  It’s certainly ready to challenge 1976.  Interesting though that with this pattern we are not smashing heat records all over the place.....the pattern is ripe but.....

See you guys in autumn....

 

BFTP

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56 minutes ago, BLAST FROM THE PAST said:

The sun plunges into another deep minima.  This year we have had 117 blank days thus far running at 56%, 30 of the last 31 have been blank.  This allows more prolonged coronal hole effects on Earth, In turn the jetstream reacts wildly to deepening minimas.......this is a very interesting year indeed.  This hot pattern likely to see us into September at least imo.  It’s certainly ready to challenge 1976.  Interesting though that with this pattern we are not smashing heat records all over the place.....the pattern is ripe but.....

See you guys in autumn....

 

BFTP

Morning Fred.

I'm sorry to say that you, me and nearly everybody-else has got it all wrong - and the guy who called LBC early this morning is a true genius: it's all because Donald Trump has put an end to Obama's HAARP machines and Chemtrail programme. I kid ye not!đŸŒ©ïžđŸ‘Œ

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I think the upshot of this thread is that there are a variety of reasons, yet we do not know the true cause. The atmosphere is so interconnected that it may take well beyond our lifetimes before we understand how all the players contribute to weather at a more local level.

Correlations with sun activity seem to be there.

Teleconnections play a part, but what causes the teleconnections to do what they do?

The SSW event seems to have also played a part.

A generally warming planet has probably (IMHO) had an effect.

Looking at it all together, it seems that all the cards fell in just the right place for the summer we have had so far. But, we do not yet know why all the cards fell as they did.

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15 hours ago, cheeky_monkey said:

There was a documentary about Climate change on Canadian TV on Tuesday i think...there they stated the UK was enduring their hottest summer in centuries due to climate change...hottest in 20 years maybe not sure where they get centuries from??

Using the estimated CET values (currently up to 27th July) the summer so far, from June 1st, is the second warmest on 17.74°C behind 1976 with 18.04°C.

Working backwards however, this year is the warmest for all periods from between March 3rd and May 27th to now (eg. May-July 27th, April-July 27th etc).

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I can’t understand how everyone keeps mentioned 1976, as the last time we experienced temperatures like this summer. 1983, 84, 89 and 90 had long periods of dry hot weather. 83 had the hottest July until 2006. And 1990 had the hottest August day until 2003.

So, it’s not like the heat of this current summer hasn’t been experienced at least every 4-5 years since 1976. 

 

The atmophere has changed since last winter, and the most noticeable thing since last December, is just how dry it’s been. The cold, and snow has also been a feature, while the early spring(March) was quite wet and dull. In short, 2018 appears to be a year of extreme weather at either side. It wouldn’t surprise me if we encounter another very cold winter spell during the next December-February period.

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9 hours ago, Sunny76 said:

The atmophere has changed since last winter, and the most noticeable thing since last December, is just how dry it’s been. The cold, and snow has also been a feature, while the early spring(March) was quite wet and dull. In short, 2018 appears to be a year of extreme weather at either side. It wouldn’t surprise me if we encounter another very cold winter spell during the next December-February period.

That's surely question in everyone's lips: will the current pattern influence our winter?

One of the many things that fascinates me about our weather is the way it can flip so suddenly which we saw in February. In the past such flips have led to cooler winters (1996 for example), but who knows? On the other hand, it can also flip back very hard. The dry period in the mid nineties was broken suddenly by June 1997 which was at that point the wettest on record I think.

The same goes for the dry period leading up to April 2012 which then ushered in the wettest summer.

As for this summer, it is not the heat that is noticeable, but how dry it has been. Temperatures may not have been record breaking, but we have seen a very long dry spell in many parts of the country. This does follow on from an April and May that did break some temperature records of course 

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March was wet and cold and parts of April were very dull and cool. It wasn’t until the latter stages of April, that we finally had a taste of warm weather. May was still cool at night despite the warm spells, and I’m hoping we return to that once we reach late August and September. Warm days, with cooler nights.

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Hi All,

I sit on the fence with GW, but I believe the GW view is that 'heat domes' to the left side of continental masses should be becoming more common - sea ice loss decreases the albedo of the polar region, gradient is less and so the jetstream slows down as a whole and becomes more meridinal, and likelier to get stuck in patterns. Current thinking is that anonomousely warmer sea areas far to the north due to sst changes  allow ridges to extend further north and energy propogates up to the stratosphere so ssw's will become more common, and pv displacements across continental regions. Like I say I still sit on the gw fence but it does look suspicciousely like the jet over the last 20 years has been tightning up against the shores of N europe, and recently our usual west east flow is not so common.

Samos

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On 27/07/2018 at 23:15, davehsug said:

Is it not still an effect of the unprecedented SSW in February? The atmosphere seems to have never quite recovered from that. That's what I'd assumed anyway.

I personally don't think so. Although it's anecdotally common to see long high pressure periods not long after the initial effects of an SSW, all an SSW does is reverse the stratospheric vortex which did become positive again in March before we saw the regular final warming send them easterly again. At best i think all it did was ensure a more seamless transition because it occurred pretty late. 

Incidentally zonal winds are slowly recovering again on schedule, we should see vortex reformation around months end.

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6 hours ago, Sunny76 said:

March was wet and cold and parts of April were very dull and cool. It wasn’t until the latter stages of April, that we finally had a taste of warm weather. May was still cool at night despite the warm spells, and I’m hoping we return to that once we reach late August and September. Warm days, with cooler nights.

Hence why May is generally my favourite month! I love warm days and cool nights. This May was truly exceptional taking the record for the highest average maximum.

So, I don't think the summer we have experienced so far is something we have experienced every four or five years. We may get hot spells or even exceptional months, but the longevity of this summer is what stands out, and even if temperatures were average between now and the end of August, it would still be in the warmest ten summers on record. The likelihood is that it will finish in the top five assuming the models are not completely wrong!

The weather has certainly seemed more continental this year since February; more like I used to experience in the US when spring would consist of a few weeks of chilly and wet days in late March to mid April and then heat would arrive.

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1 hour ago, WhiteFox said:

Hence why May is generally my favourite month! I love warm days and cool nights. This May was truly exceptional taking the record for the highest average maximum.

So, I don't think the summer we have experienced so far is something we have experienced every four or five years. We may get hot spells or even exceptional months, but the longevity of this summer is what stands out, and even if temperatures were average between now and the end of August, it would still be in the warmest ten summers on record. The likelihood is that it will finish in the top five assuming the models are not completely wrong!

The weather has certainly seemed more continental this year since February; more like I used to experience in the US when spring would consist of a few weeks of chilly and wet days in late March to mid April and then heat would arrive.

Maybe we get an August 85, 86, or 87. Lol that would be a kick in the teeth if that happened, with the kids off now. 

Hopefully something similar to August 83,84 or 95, or even 2013 would be good. 2013 being the last decent one. 2016 was sunny at times, but it was cloudy from time to time.

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Posted (edited)

A very poor heatwave in my opinion for Manchester because its not had a single day hitting 30C. All the other big heatwave years, 76, 83, 90, 95, 2003/06 saw 31 or 32C get hit across a number of days, 2018 very poor here as far as heat is concerned.

This summer will be remembered mainly for its dryness.

Edited by 38.5*C

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re OP

Seems we've had 'waves of extremes'

the 'beast from the east' - cold then warmish then another shocker cold that confused spring plant growth

Now we have dry oscillation - hot then little rain and what looks like another dry spell coming in thro August to further confuse crops

Maybe the jet stream is reacting to something higher up in the stratosphere, little of which i know about but there seems to be a pattern of decaying extremes with regard to winter and summer this year - esp in the south.

Might have an Atlantic driven turbulent start to autumn - repeat/rinse till winter - then who knows.. but very interesting to experience if your life doesn't depend on the weather !

 

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17 hours ago, WhiteFox said:

That's surely question in everyone's lips: will the current pattern influence our winter?

Well I, for one, would like to see a proper freeze up in December and January rather than the rather belated effort seen this year.

A Siberian style early-mid January freeze up thank you very much!

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7 hours ago, 38.5*C said:

A very poor heatwave in my opinion for Manchester because its not had a single day hitting 30C. All the other big heatwave years, 76, 83, 90, 95, 2003/06 saw 31 or 32C get hit across a number of days, 2018 very poor here as far as heat is concerned.

This summer will be remembered mainly for its dryness.

A good summer shouldn’t be defined by having to exceed 30c. A lon dry spell of 24-27c for example, as opposed to two weeks of 32c is still better. 

2015 had the hottest July day on record, but what good was it, as the summer that followed was awful.

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