Heatwave Definition?

[damianslaw]

BBC are widely using the term heatwave to describe the impending warm/very warm spell.

Does anyone know what the bbc definition of a heatwave is.. is it simply when the temp somewhere in the country looks like hitting 30 degrees..

By my own reckoning two days of temps in the SE close to or at 30 degrees but nationwide hovering between 20-26 degrees does not in my book constitute a heatwave. It seems to be being used very liberally..

I call a heatwave at least a 3 day spell when temps nationwide are in the mid 20's or above throughout, alas the upcoming weather certainly does not constitue for those in scotland, n ireland, n england, wales and sw england - another case of the bbc being very SE centric..

[95 Degrees]

IMO a heatwave is anything at or upwards of 32C for a period of days and warm nights to go with that, for the SE anyway, for the North and North-West they may consider a heatwave 27C upwards for 2 days or more.

[Costa Del Fal]

I consider a true heatwave to be 30c or more for at least 2 days preferably 3. This temperature threshold maybe 27c or so for the North.

Its being used far too easily nowadays imo. Most of the SE wont quite reach 30c imo. London could definitely so though.

[feb1991blizzard]

BBC are widely using the term heatwave to describe the impending warm/very warm spell.

Does anyone know what the bbc definition of a heatwave is.. is it simply when the temp somewhere in the country looks like hitting 30 degrees..

By my own reckoning two days of temps in the SE close to or at 30 degrees but nationwide hovering between 20-26 degrees does not in my book constitute a heatwave. It seems to be being used very liberally..

I call a heatwave at least a 3 day spell when temps nationwide are in the mid 20's or above throughout, alas the upcoming weather certainly does not constitue for those in scotland, n ireland, n england, wales and sw england - another case of the bbc being very SE centric..

I dont know whether i am right with this definition but in my book the whole country does not have to have very warm or hot temps but the area that is predicted to have a heatwave IMO needs to be a long way above average for a considerable amount of time. EG for london to have a heatwave i would say a week of above 30c maxs and 17c Mins, maybe 27c and 14c for the North.

[TEITS]

BBC are widely using the term heatwave to describe the impending warm/very warm spell.

Does anyone know what the bbc definition of a heatwave is.. is it simply when the temp somewhere in the country looks like hitting 30 degrees..

By my own reckoning two days of temps in the SE close to or at 30 degrees but nationwide hovering between 20-26 degrees does not in my book constitute a heatwave. It seems to be being used very liberally..

I call a heatwave at least a 3 day spell when temps nationwide are in the mid 20's or above throughout, alas the upcoming weather certainly does not constitue for those in scotland, n ireland, n england, wales and sw england - another case of the bbc being very SE centric..

How can it be SE centric when the warning is only for the SE/E Anglia! The other locations aren't at risk hence no warnings.

Personally I feel the warning is appropiate because it isn't just the high temps but the high dewpoints that are a factor.

Have to say the anti SE posts on this forum become rather tiresome after a while. I feel this is mainly because the SE/E Anglia often see the highest temps and a majority of the storms and this causes envy.

[feb1991blizzard]

How can it be SE centric when the warning is only for the SE/E Anglia! The other locations aren't at risk hence no warnings.

Personally I feel the warning is appropiate because it isn't just the high temps but the high dewpoints that are a factor.

Have to say the anti SE posts on this forum become rather tiresome after a while. I feel this is mainly because the SE/E Anglia often see the highest temps and a majority of the storms and this causes envy.

If there are any anti SE posts on here as a result of envy of high temps then they certainly are not from me although i am envious that they bare the brunt of the classic scandi high / N france low combinations ala 87 and 91!

[Cheese Rice]

How can it be SE centric when the warning is only for the SE/E Anglia! The other locations aren't at risk hence no warnings.

Personally I feel the warning is appropiate because it isn't just the high temps but the high dewpoints that are a factor.

Have to say the anti SE posts on this forum become rather tiresome after a while. I feel this is mainly because the SE/E Anglia often see the highest temps and a majority of the storms and this causes envy.

LOL lets not go there!

Anyway a heatwave has and always will be a period of over 3-5 days where temperatures widely exceed 25.c+.

What parts of England will experience is not a heat-wave, three days of hot weather is not cause for concern.

[Optimus Prime]

IMO;

For a period;

2 days or more if temperatures exceed 32c over a wide area of the UK

4 days or more of temperatures fall in the 28-30c over a wide area of the UK

6 days or more if temperatures fall in the 25c-27c category

I think it should depend on how high the temperatures are. The higher the temperature exceeds the high end the less days needed for it to be considered a heatwave.

[Evening thunder]

Hmm, for the last 5 summers maybe this does seem like a heatwave

I just watched the BBC forecast and there was lots of mention of the heatwave and they said about the 'heat health warning' at the end but they didn't mention that not everywhere would see this, or that it was just SE'ern parts reaching 'heatwave' territory which I thought they should have done.

[Coast]

I'm not sure why it is that when the temperatures start to rise, the Daily Ex has to go overboard!

http://www.express.co.uk/posts/view/254888/Killer-heatwave

Mind you, on this occasion it wasn't PWS creating that headline.

[Thundery wintry showers]

The Met Office has its own definitions here for England and Wales (though it doesn't seem they have any for Scotland).

http://www.metoffice.gov.uk/weather/uk/heathealth/

I think their definitions are pretty reasonable, but I doubt that those temperature levels will actually be reached on Sunday and Monday. My suspicion is that they will probably just fall short in the SE, with maxima of 28 or 29C somewhere around London and a minimum of 17C. Perhaps the MetO are just covering the possibility that temperatures might be a couple of degrees up on what is currently expected- which is by no means unknown, even at just one day ahead.

[GMCA]

The Met Office has its own definitions here for England and Wales (though it doesn't seem they have any for Scotland).

http://www.metoffice.../uk/heathealth/

I think their definitions are pretty reasonable, but I doubt that those temperature levels will actually be reached on Sunday and Monday. My suspicion is that they will probably just fall short in the SE, with maxima of 28 or 29C somewhere around London and a minimum of 17C. Perhaps the MetO are just covering the possibility that temperatures might be a couple of degrees up on what is currently expected- which is by no means unknown, even at just one day ahead.

To be fair, the heat-health watch does say there's a 60% chance of these values being met, highlighting the uncertainty involved.

[damianslaw]

Hmm, for the last 5 summers maybe this does seem like a heatwave

I just watched the BBC forecast and there was lots of mention of the heatwave and they said about the 'heat health warning' at the end but they didn't mention that not everywhere would see this, or that it was just SE'ern parts reaching 'heatwave' territory which I thought they should have done.

Yes the BBC are not saying heatwave conditions for the SE/E Anglia - it is misleading the rest of the country. On there warning advert they should be saying for the SE/E Anglia - as it is the way they are forecasting it may appear that the whole country is in for a heatwave.

I also don't like them using that weather temp chart - again they show maximum temps for London and the SE when the rest of the country esp further north is always a few degrees down on what the maximum temp is showing. Those charts often mean absolutely nothing to Scotland, N Ireland and N Eng.

If they used words like 'for London and the SE' then fine, but the way they present things can be very misleading to the general public. Much better watching your local regional bbc forecasts.

I'm not being against the SE, but the BBC should make it much more clear in there forecasts where they are actually referring to when they announce 'heatwave warnings' and show the temp graph chart.

Thanks to all those who have posted in this thread and particularly the person who has stated the BBC definitions. In any case the upcoming 'hot' spell looks like only just qualifying a heatwave in London, parts of SE and E Anglia both in terms of temps and duration. A rather 'pitiful' heatwave it has to be said and certainly not a heatwave anywhere else.

[EaasmanG]

Heatwave definition for the Peak District: 2 days above 20°C.

[Summer of 95]

2 consecutive days with average max above 30C

3 " " " above 28C

4 " " " above 27C

5 " " " above 25C, with at least one day reaching 27C.

And at least 7 hours sunshine per day averaged over those periods.

I think the last time was July 2006!

[johnholmes]

http://www.metoffice...alth/index.html

all the official information to explain where and what etc in the link above

Edited June 25, 2011 by johnholmes

[MP-R]

For here I would say a heatwave would constitute at least 3 days where the temperature reaches 28C or more. A warmwave or warm spell at least 3 days where the temperature is between 24C and 28C. Anything below that would be typical for a West Conutry summer with daytime maxima between 19C and 23C.

[TonyH]

Whats wrong with calling a regionalised heatwave just that? Its already very warm and humid here in the west so certainly 2 days of fairly widespread heat is assured. 30c in the se today and 32c tomorrow my punt.

[Bottesford]

2 consecutive days with average max above 30C

3 " " " above 28C

4 " " " above 27C

5 " " " above 25C, with at least one day reaching 27C.

And at least 7 hours sunshine per day averaged over those periods.

I think the last time was July 2006!

I'd go with that too. Definitely not experienced a 'heatwave' since 2006 round here. About time we did!

[Rainy]

Yes the BBC are not saying heatwave conditions for the SE/E Anglia - it is misleading the rest of the country. On there warning advert they should be saying for the SE/E Anglia - as it is the way they are forecasting it may appear that the whole country is in for a heatwave.

I also don't like them using that weather temp chart - again they show maximum temps for London and the SE when the rest of the country esp further north is always a few degrees down on what the maximum temp is showing. Those charts often mean absolutely nothing to Scotland, N Ireland and N Eng.

If they used words like 'for London and the SE' then fine, but the way they present things can be very misleading to the general public. Much better watching your local regional bbc forecasts.

I'm not being against the SE, but the BBC should make it much more clear in there forecasts where they are actually referring to when they announce 'heatwave warnings' and show the temp graph chart.

Thanks to all those who have posted in this thread and particularly the person who has stated the BBC definitions. In any case the upcoming 'hot' spell looks like only just qualifying a heatwave in London, parts of SE and E Anglia both in terms of temps and duration. A rather 'pitiful' heatwave it has to be said and certainly not a heatwave anywhere else.

[Rainy]

I'm always grateful for Damianslaw's comments on the weather. Very relevant to us here.

Yesterday had a "day out" to the Midlands. Warmer down there. No need of the coat I wore here in the morning. Cloudy everywhere though, except parts of Cheshire in the evening.

But coming back into the hills, the last 6 miles or so, the shock of the return to the gloomy wet hit me. Puddles everywhere, rivers roaring, every blade of grass full of water, most hay meadows turned jungly and uncut. Clouds down on the fells. Chilly in the house. Had to put on a heater briefly.

Rain in gauge for the last 2 days measured 21.3mm.

We are longing for a long spell of DRY SUNNY conditions up here in the NW hills. A 2 day hot spell in the SE has no relevance to us. Looking at the BBCTV forecasts it appears the cloud will linger here. And what about Scotland. Looks a lot worse up there.

[dave.p]

It's very rare for the thermometer to rise above 24c here, so I guess a minimum of 2 or 3 days above 24c could be considered a heatwave.

[johnholmes]

the official guide to what constitutes a heatwave is very clearly laid down, see my link. Of course anyone may disagree with the values from their own point of view.

ah-will not copy so you need to go back a page and find the link I posted

repeating the link below

http://www.metoffice...alth/index.html

2 consecutive day and the intervening night it would seem and the values as per the link above.

Do remember its not promulgated for healthy young folk but for others older and less fit for one reason or another.

Edited June 26, 2011 by johnholmes

[Derp Patrol]

I find that it's far too overused. In winter it's fair enough that we've been seeing the term 'big freeze' mentioned a lot because we have had very cool winters recently and it is much harder for areas like say London to get ice days than get 30C in Summer IMO.

But for places like London where on average there are 4 or 5 30C days a year then I think it is overused, a heatwave should be a rare event and not just a one of very warm spell. Average London maxima for July are about 23-24C now (using 81-10 averages) so 30C is too low for heatwave territory I think. Also, I remember last year we had a period of about 3-4 weeks of temperatures 24C or above and people were labelling that a heatwave, but it's fairly common to get sustained 24C+ temps here.

For northern UK I think the definitions are slightly better as it is much harder to reach 28C-30C, but again i think 15C night temperatures is a bit pathetic to class as a heatwave! that's not far too off average night time temperatures here in July and August!

[Rob]

I class a heatwave as the following

A minimum of

Day 1 - 30c+

Night 1 - 15c+

Day 2 - 30+