Jump to content

Possibly severe heat wave looming for 25th to 29th June, also some local severe storms


Recommended Posts

Looks to me like there should be a discussion thread open for the impending severe heat wave that will begin to set up on Monday 24th and reach full intensity from Tuesday to Friday of next week, gradually ending from west to east on Saturday 29th on current guidance. (edit, later guidance shows a late Saturday breakdown for the southeast)

Upper parameters are near their limits for southern England, the 576 dm thickness contour is shown moving north as far as the Midlands and south Yorkshire, and various model runs depict 850 temps of 22 to 24 C. These values with any long intervals of sunshine would argue for mid-30s temperatures away from moderating influences of coastal seas, probably in just about all of southern and central England and some distance further north at times. With those temperatures will come rather high levels of humidity, in part because the month has been quite wet (twice normal rainfall so far) and this will give a source of low-level evaporation into the air mass even if it has lower dew points in its source region of France (where by the way temperatures could be as high as 38-40 C). 

Nights will not cool off much especially in larger urban areas. Some lows of 20 to 23 C are possible in greater London, 17 to 19 C in less urbanized settings. 

There will be zones of frontal contrast over the far southwest, Wales, Ireland, northwest England and southwest Scotland at times, both with the warm fronts moving up ahead of the heat wave Sunday night into Monday, and then when the heat wave is established, along quasi-stationary fronts oriented from Ulster southeast to south Wales and Devon. Outbreaks of heavy thundery rain seem likely with those. When the heat wave begins to break down late Thursday into Friday, slow-moving cold fronts will push further east raising the possibility of severe thunderstorms into the Thames valley, west Midlands and south central England. 

A final phase (according to 18z GFS) may be frontal intensification by Saturday 29th as pressure falls sharply over the Irish Sea, leading to more widespread heavy thundery rainfalls from northwest England to the Midlands and southeast England. 

This will be a complete changeover from the rather cool conditions so far in June (although those have been moderating recently). At one point recently, the CET for June was only 12.9 C (normal by end of June is 14.5). But some of these heat wave days may be threatening the all-time June record of 23.0 (average of max and min) set on 3 June, 1947. In a similar set-up of shorter duration, the daily CET on 1st July 2015 reached a record 24.6 C (the all-time July record is 25.2 from 1948, and for August, 24.9 in 1995). In the impending heat wave, daily records may be falling in many areas. Top maximum temperatures in England could reach as high as 35 or 36 C. Readings of 32 C or higher could be widespread. In the western regions closer to frontal zones, 25-28 C may be the top values. 

Edited by Roger J Smith
  • Like 1
Link to post
Share on other sites
  • Replies 152
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

Can anyone think of a potential hot spell that has been so downgraded ? The Met Office were really taking note of possibilities because they released a youtube video addressing their concerns for this

Not much chance of high temperatures this week now,only Saturday. Extremely wet now seriously wet after this morning, wettest month in living memory at 231mm smashed the previous record of july 2

So for the record, Heathrow and Northolt reported 34.0 C on Saturday 29th. The 576 dm thickness contour passed through parts of East Anglia on its way to its current location in central Europe. In Fra

Posted Images

10 hours ago, Roger J Smith said:

Looks to me like there should be a discussion thread open for the impending severe heat wave that will begin to set up on Monday 24th and reach full intensity from Tuesday to Friday of next week, gradually ending from west to east on Saturday 29th on current guidance. 

Upper parameters are near their limits for southern England, the 576 dm thickness contour is shown moving north as far as the Midlands and south Yorkshire, and various model runs depict 850 temps of 22 to 24 C. These values with any long intervals of sunshine would argue for mid-30s temperatures away from moderating influences of coastal seas, probably in just about all of southern and central England and some distance further north at times. With those temperatures will come rather high levels of humidity, in part because the month has been quite wet (twice normal rainfall so far) and this will give a source of low-level evaporation into the air mass even if it has lower dew points in its source region of France (where by the way temperatures could be as high as 38-40 C). 

Nights will not cool off much especially in larger urban areas. Some lows of 20 to 23 C are possible in greater London, 17 to 19 C in less urbanized settings. 

There will be zones of frontal contrast over the far southwest, Wales, Ireland, northwest England and southwest Scotland at times, both with the warm fronts moving up ahead of the heat wave Sunday night into Monday, and then when the heat wave is established, along quasi-stationary fronts oriented from Ulster southeast to south Wales and Devon. Outbreaks of heavy thundery rain seem likely with those. When the heat wave begins to break down late Thursday into Friday, slow-moving cold fronts will push further east raising the possibility of severe thunderstorms into the Thames valley, west Midlands and south central England. 

A final phase (according to 18z GFS) may be frontal intensification by Saturday 29th as pressure falls sharply over the Irish Sea, leading to more widespread heavy thundery rainfalls from northwest England to the Midlands and southeast England. 

This will be a complete changeover from the rather cool conditions so far in June (although those have been moderating recently). At one point recently, the CET for June was only 12.9 C (normal by end of June is 14.5). But some of these heat wave days may be threatening the all-time June record of 23.0 (average of max and min) set on 3 June, 1947. In a similar set-up of shorter duration, the daily CET on 1st July 2015 reached a record 24.6 C (the all-time July record is 25.2 from 1948, and for August, 24.9 in 1995). In the impending heat wave, daily records may be falling in many areas. Top maximum temperatures in England could reach as high as 35 or 36 C. Readings of 32 C or higher could be widespread. In the western regions closer to frontal zones, 25-28 C may be the top values. 

thats a very good summary imho, but what i dont get is why so many other sites are totally playing down the temp values.
take next thursday for derby, uppers of around 20c, predicted max temp from the met office of 22c! and in clear sunny skies... (met o)

i dont get it.... how can surface temps be so (relatively) low under such high uppers?

  • Like 2
Link to post
Share on other sites

Possibly their forecast is based on guidance with lower values for 850 mb temp, or they believe an easterly flow will persist to the extent that North Sea cooling effects will reach that far inland. The latest GFS 06z guidance appears to have downgraded slightly and is also more gradual with its northward push of the very warm air mid-week, on the other hand the breakdown is now pushed back to around Sunday 30th. 

  • Like 2
Link to post
Share on other sites

indeed the met o prediction for next thursday i mentioned suggests a slack northeasterly flow (surface), yet a cannot find much evidence of that. the mean upper flow @ 850 hpa suggests a southeasterly.

i dont get it.... everytime ive seen charts like the current outputs we have roasted... and im going back over 40 years.

Link to post
Share on other sites

Latest GFS reduces the heat somewhat a times but I think it's getting the temperatures to low considering the uppers. Any sunshine at this time of year and the temp will rise quickly. The only way cool to average temps on Tuesday over the midlands and Yorkshire are going to happen is that stays cloudy. The local met office forecast just shows very warm conditions for us and mostly dry. Net-weather hot and Thundery at times. So you pay your money and make your choice.

Link to post
Share on other sites

Netweather going for a record breaker yet bbc have been downgrading this alledged heatwave all day. Take wednesday for example,  this morning it was predicting 26 for my hometown Sheffield, then 23 and now saying 21. All very pleasant but not record breaking. 

Link to post
Share on other sites
19 hours ago, Roger J Smith said:

Looks to me like there should be a discussion thread open for the impending severe heat wave that will begin to set up on Monday 24th and reach full intensity from Tuesday to Friday of next week, gradually ending from west to east on Saturday 29th on current guidance. 

Upper parameters are near their limits for southern England, the 576 dm thickness contour is shown moving north as far as the Midlands and south Yorkshire, and various model runs depict 850 temps of 22 to 24 C. These values with any long intervals of sunshine would argue for mid-30s temperatures away from moderating influences of coastal seas, probably in just about all of southern and central England and some distance further north at times. With those temperatures will come rather high levels of humidity, in part because the month has been quite wet (twice normal rainfall so far) and this will give a source of low-level evaporation into the air mass even if it has lower dew points in its source region of France (where by the way temperatures could be as high as 38-40 C). 

Nights will not cool off much especially in larger urban areas. Some lows of 20 to 23 C are possible in greater London, 17 to 19 C in less urbanized settings. 

There will be zones of frontal contrast over the far southwest, Wales, Ireland, northwest England and southwest Scotland at times, both with the warm fronts moving up ahead of the heat wave Sunday night into Monday, and then when the heat wave is established, along quasi-stationary fronts oriented from Ulster southeast to south Wales and Devon. Outbreaks of heavy thundery rain seem likely with those. When the heat wave begins to break down late Thursday into Friday, slow-moving cold fronts will push further east raising the possibility of severe thunderstorms into the Thames valley, west Midlands and south central England. 

A final phase (according to 18z GFS) may be frontal intensification by Saturday 29th as pressure falls sharply over the Irish Sea, leading to more widespread heavy thundery rainfalls from northwest England to the Midlands and southeast England. 

This will be a complete changeover from the rather cool conditions so far in June (although those have been moderating recently). At one point recently, the CET for June was only 12.9 C (normal by end of June is 14.5). But some of these heat wave days may be threatening the all-time June record of 23.0 (average of max and min) set on 3 June, 1947. In a similar set-up of shorter duration, the daily CET on 1st July 2015 reached a record 24.6 C (the all-time July record is 25.2 from 1948, and for August, 24.9 in 1995). In the impending heat wave, daily records may be falling in many areas. Top maximum temperatures in England could reach as high as 35 or 36 C. Readings of 32 C or higher could be widespread. In the western regions closer to frontal zones, 25-28 C may be the top values. 

A repeat of August 6th 1981 is on the cards then. Will be interesting to see if we get daytime darkness and cloud tops of 50,000 feet. Imagine the amount of coverage that would get now, if that happens. 

Link to post
Share on other sites

Perhaps getting a bit ahead of ourselves here in terms of predicted temperatures.. when the models begin to downgrade depth of warmth before it has started you know when things are going the wrong way, its when they continue to show upgrades very nearer the timescale thats when you sit up and listen - those near timeframes are not until Monday.. so some time to go before we can call likely temperatures with any certainty. Cloud will be a major factor, regardless of degree of upper temps.

  • Like 3
Link to post
Share on other sites

Looks like it will be  a pleasant warm week up here, not hot but just a nice week feeling like summer. Hopefully there will be plenty of thunderstorm activity (very lacking around here) and actually that would interest me more than getting heat records which seems less likely as the core of the plume looks to go into the North sea anyway now.

  • Like 1
Link to post
Share on other sites

With the slight downgrades in some model guidance, I opted to edit the title of the thread and removed the word "severe" from heat wave, although have not edited any of the wording in the original post otherwise. 

We're still seeing 570 dm thicknesses into southern England and 576 dm almost into the southeast, so not a huge change, also each run seems to be angled a bit differently and holding back the breakdown a bit further. 

Some parts of Wales may be in for locally excessive thunderstorm rainfalls and that may be one of the bigger impacts of this event.

  • Like 1
Link to post
Share on other sites

Somewhat of a backtrack in terms of "severe heatwave" territory. Same thing happens in Winter - the best charts are always 5+ days away but get watered down nearer the time. I remember in July 2015 when London reached 36C there was some unbelievable charts being churned out a few days before - quite a few in here were confident that the all time record would be broken but alas it's still intact from August 2003. Back to the current weather I still think the usual suspects like London will reach 32 or 33C next week but that's nothing exceptional or we haven't seen before in June. Plus looking like a lot of cloud in the mix as well scuppering any huge max temps. Anyway tomorrow may bring "upgrades" to the upcoming weather. We'll see.

Edited by Frost HoIIow
Link to post
Share on other sites

Nice steady downgrades continuing may end up a pleasant spell yet. Still think the GFS is undoing the temps but there has been a shift with the uppers being pushed further east. If this continues could end up with my ideal conditions low twenties and a nice breeze.

As for nothing exceptional we haven't see much in the way of hot weather so such a big jump will be hard to adjust to.

  • Like 2
Link to post
Share on other sites

BBC app showing max's of 16-19 for the next week here, with one day hitting 20. Just a continuation of the below average temps we've seen for a good while now. The only record breaking temps seen here in June were record cold days max temp wise, referred to by many as 'cooler' weather!

I would love the BBC to be wrong!

Link to post
Share on other sites

ok... think ive got it as to why previous runs had shown 15c - 20c isotherm upper but only 22c on the surface with a northeasterly..

convection.

the thunderstorms were more likely in western areas then eastern, they are expected to be severe... so the hot surface air rises to form the thunderclouds... leaving a void on the surface, which will be filled from the areas of high pressure. so convection in the west = surface breeze from the northeast (as thats where the higher pressure was expected) and that undercuts the hot uppers in a southeasterly flow.

that would create the 'sunny day but only 23c instead of 33c' the uppers suggested...

  • Like 1
Link to post
Share on other sites

Looking hot to me by the looks of UKMO, I think that the GFS is over doing the PPN, anyway 30c should be breached at the very least around London and parts of the Midlands.

UW144-21.gif

UW144-7.gif

Link to post
Share on other sites
4 minutes ago, mushymanrob said:

ok... think ive got it as to why previous runs had shown 15c - 20c isotherm upper but only 22c on the surface with a northeasterly..

convection.

the thunderstorms were more likely in western areas then eastern, they are expected to be severe... so the hot surface air rises to form the thunderclouds... leaving a void on the surface, which will be filled from the areas of high pressure. so convection in the west = surface breeze from the northeast (as thats where the higher pressure was expected) and that undercuts the hot uppers in a southeasterly flow.

that would create the 'sunny day but only 23c instead of 33c' the uppers suggested...

I make you right there, showers could end up pretty much hit and miss though so some places could be hitting 30c and a few miles away only 22/23c.

Link to post
Share on other sites

Local forecast has 24C next Friday. Contradicts the weather warning by showing only light rain and perhaps heavy showers Monday.

Link to post
Share on other sites

Has anybody checked the wind direction at the upper and lower levels.

If the surface flow is heavily easterly but the low is pumping from the south or south east then that easily explains the temperature difference as the cooler air at lower levels will undercut.

  • Like 1
Link to post
Share on other sites
19 minutes ago, summer blizzard said:

Has anybody checked the wind direction at the upper and lower levels.

If the surface flow is heavily easterly but the low is pumping from the south or south east then that easily explains the temperature difference as the cooler air at lower levels will undercut.

Im afraid you guys east of the pennines will likely be plagued by north seamist next week.. t'other side of the hills tho..

?

Link to post
Share on other sites
5 hours ago, northwestsnow said:

Im afraid you guys east of the pennines will likely be plagued by north seamist next week.. t'other side of the hills tho..

?

I wish.. the coming week looks hellish. Bring on a 2017/2010 style collapse.

Link to post
Share on other sites
1 minute ago, summer blizzard said:

I wish.. the coming week looks hellish. Bring on a 2017/2010 style collapse.

Yes, you are right and a timely reminder for myself that not everyone enjoys intense heat, and i suspect thats what some places are going to see.

Im hoping for a few crackerjack storms to boot.

Link to post
Share on other sites
41 minutes ago, northwestsnow said:

Yes, you are right and a timely reminder for myself that not everyone enjoys intense heat, and i suspect thats what some places are going to see.

Im hoping for a few crackerjack storms to boot.

Heat is not so much a problem and i love the sun, although the heat in late June last year was OTT it was bearable. Most of July 13 while too hot in temperature was also bearable.

The problem is humidity which i think i feel more than some being born north of the wall. If its much above 50% (assuming my barometer which was showing 30-45% during most of June 2018 and July 2013 was correct) then i would rather the summer washed out.

Link to post
Share on other sites

On a note about the hot spell i would monitor the Cheltenham station. Away from London it is quite recurrent for the hottest temperatures when there is an easterly element at play.

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...