I noticed on the Met Eireann Twitter account and website there was a mistake which stated if the UV index was 10 it was extreme. I contacted them using the form on their website and had emails asking me for evidence it was wrong. I took a screenshot from their website but they wanted more evidence so I took a screenshot from the World Health Organization website which stated the UV index is extreme if it is 11+. Met Eireann corrected it on their Twitter account and website before I sent the email and I am pleased it has been corrected but surprised by the mistake.
I have stated before the UV index does not exceed 8 in the UK as this is what I read on the Met Office website and DEFRA. I look at the Met Office website and the temperature forecasts are too low and this makes me think the UV forecasts are also too low. Two people on here have told me UV levels in the UK have been higher than 8 so I was wrong.

Nicholas
Meir Heath, Stoke-On-Trent 250 metres above sea level.

On Monday, May 25, 2020 at 2:25:39 PM UTC+1, Nicholas Randall wrote:
I noticed on the Met Eireann Twitter account and website there was a mistake which stated if the UV index was 10 it was extreme. I contacted them using the form on their website and had emails asking me for evidence it was wrong. I took a screenshot from their website but they wanted more evidence so I took a screenshot from the World Health Organization website which stated the UV index is extreme if it is 11+. Met Eireann corrected it on their Twitter account and website before I sent the email and I am pleased it has been corrected but surprised by the mistake.
I have stated before the UV index does not exceed 8 in the UK as this is what I read on the Met Office website and DEFRA. I look at the Met Office website and the temperature forecasts are too low and this makes me think the UV forecasts are also too low. Two people on here have told me UV levels in the UK have been higher than 8 so I was wrong.

Nicholas
Meir Heath, Stoke-On-Trent 250 metres above sea level.

The UV index regularly reaches 8 in Cornwall, and has reached 10 at Camborne (which is of course a MetO station) on a few occasions. 11 has been recorded out on Scilly. I believe Nick up in Devon (part of England I believe) has also recorded 10.

The very high readings are normally associated with a warm sector ridge & a very gentle SW airstream. Cold sector deep blue skies invariably give significantly lowing readings.

There have been discussions on why this is the case, whether it is due to low levels of ozone under warm sector conditions, or low level high humidity..

Certainly, the times I've been badly burnt have always been is sea misty conditions. Other people on here have made the same comment.

Graham
Penzance

On 25/05/2020 14:25, Nicholas Randall wrote:
I noticed on the Met Eireann Twitter account and website there was a mistake which stated if the UV index was 10 it was extreme. I contacted them using the form on their website and had emails asking me for evidence it was wrong. I took a screenshot from their website but they wanted more evidence so I took a screenshot from the World Health Organization website which stated the UV index is extreme if it is 11+. Met Eireann corrected it on their Twitter account and website before I sent the email and I am pleased it has been corrected but surprised by the mistake.
I have stated before the UV index does not exceed 8 in the UK as this is what I read on the Met Office website and DEFRA. I look at the Met Office website and the temperature forecasts are too low and this makes me think the UV forecasts are also too low. Two people on here have told me UV levels in the UK have been higher than 8 so I was wrong.

Nicholas
Meir Heath, Stoke-On-Trent 250 metres above sea level.



Away from coastal areas I think the UV forecasts are pretty accurate. I
am about 28 miles from the south coast (crow miles) and usually peak
summer is high 6s, maybe nudging a 7 very occasionally.

Here's a graph of my peak UV values by day for the past 12 months:
http://www.brianwakem.co.uk/misc/uv.jpeg



--
Brian Wakem

On 25/05/2020 20:00, Brian Wakem wrote:
Away from coastal areas I think the UV forecasts are pretty accurate.Â* I
am about 28 miles from the south coast (crow miles) and usually peak
summer is high 6s, maybe nudging a 7 very occasionally.

Thanks Brian. I can add that as well as being away from the coast, also
being away from the South West will also see lower UV levels.

I have recorded a UV of 10.0 as my highest.

Every year I will at some point record a UV over 9.0 (under conditions
described by Graham). My UV readings are usually matched by the official
station at Camborne.

Deep blue, crystal clear sky usually delivers a lower UV. Such as today
when my maximum UV was 6.8 , which is on the lower side for this date. I
see that Camborne recorded 7.5 today. I suspect my UV sensor is a bit
dirty as I haven't cleaned it for a couple of years (it's on a mast).

After living in London & Birmingham for a while, I can testify that the
sun's UV strength seems much weaker at these places. And when I do
travel Up Country, the inhabitants do seem paler away from the South West.

--
Nick Gardner
Otter Valley, Devon
20 m amsl
http://www.ottervalleyweather.me.uk

Camborne reached 8 back on the 18th May, and with more humid conditions it'll be around that today.

Graham

Penzance

On Monday, 25 May 2020 14:25:39 UTC+1, Nicholas Randall wrote:
I look at the Met Office website and the temperature forecasts are too low and this makes me think the UV forecasts are also too low.

You should be aware that there isn't a link between temperature and UV level, so the above logic is incorrect. UV level is a function of the amount of absorption that occurs in the atomosphere, and this is largely determined by the angle of the sun's rays.

The simplest demonstration of this is the fact that UV level peaks around local noon, whereas temperature peak is 2-3 hours later.

Also, the summit of, say, Snowdon will experience a higher UV level than, say, Llandudno, as there is less thickness of atmosphere above to filter out incoming UV.

Factors such as low-level moisture, the presence of some cloud, and ozone also play a part.

--
Freddie
Dorrington
Shropshire
115m AMSL
http://www.hosiene.co.uk/weather/
Stats for the month so far: https://www.hosiene.co.uk/weather/st...cs/latest.xlsx

On Tuesday, 26 May 2020 15:22:04 UTC+1, Freddie wrote:
On Monday, 25 May 2020 14:25:39 UTC+1, Nicholas Randall wrote:
I look at the Met Office website and the temperature forecasts are too low and this makes me think the UV forecasts are also too low.

You should be aware that there isn't a link between temperature and UV level, so the above logic is incorrect. UV level is a function of the amount of absorption that occurs in the atomosphere, and this is largely determined by the angle of the sun's rays.

The simplest demonstration of this is the fact that UV level peaks around local noon, whereas temperature peak is 2-3 hours later.

Also, the summit of, say, Snowdon will experience a higher UV level than, say, Llandudno, as there is less thickness of atmosphere above to filter out incoming UV.

Factors such as low-level moisture, the presence of some cloud, and ozone also play a part.

--
Freddie
Dorrington
Shropshire
115m AMSL
http://www.hosiene.co.uk/weather/
Stats for the month so far: https://www.hosiene.co.uk/weather/st...cs/latest.xlsx

I am aware there is no link between temperature and UV levels. I was stating the Met Office maximum temperature forecasts are low and I think the UV forecasts are also too low. Today the maximum temperature was forecast to be 18 C and the UV forecast was changed from 6 to 5.
I agree with most of what you state about factors that affect UV levels except humidity. I do not think it affects them.

Nicholas
Meir Heath, Stoke-On-Trent 250 metres above sea level.

I agree with most of what you state about factors that affect UV levels except humidity. I do not think it affects them.

Nicholas
Meir Heath, Stoke-On-Trent 250 metres above sea level.

Equally, I am sure it does. If Norman reads this I know he'll agree. In fact, anyone that spends a lot of time outdoors, certainly on the coast of SW England where high humidity is common, fully appreciates the fact.

How else do you explain the big drop in UV when a cold front goes through? Certainly lower high level ozone sometimes being associated with a warm sector ridge is partly the cause, but the whole thing? If you don't except it's the humidity, despite the evidence, you need to come up with an alternative explanation why it's so high in air which has none of the clarity of that behind the cold front.

Somewhere I'v got a list of times when the Camborne UV has hit 9, never in clear, clean sunny mP conditions.

Graham
Penzance

Graham Easterling wrote:


I agree with most of what you state about factors that affect UV
levels except humidity. I do not think it affects them.

Nicholas
Meir Heath, Stoke-On-Trent 250 metres above sea level.

Equally, I am sure it does. If Norman reads this I know he'll agree.
In fact, anyone that spends a lot of time outdoors, certainly on the
coast of SW England where high humidity is common, fully appreciates
the fact.

How else do you explain the big drop in UV when a cold front goes
through? Certainly lower high level ozone sometimes being associated
with a warm sector ridge is partly the cause, but the whole thing?
If you don't except it's the humidity, despite the evidence, you need
to come up with an alternative explanation why it's so high in air
which has none of the clarity of that behind the cold front.

Somewhere I'v got a list of times when the Camborne UV has hit 9,
never in clear, clean sunny mP conditions.

Graham
Penzance

I can't comment on actual UV measurements but, from personal
experience, for any given temperature I find that I burn more readily
in high humidity conditions than in dry conditions. In coastal, fairly
humid conditions, in this country with the temp in the low 20s I burn
much more than I do in 40° in very low humidity in inland Australia.
Indeed, I have to be very careful in this country on summer days when
there is a complete cover of low cloud but nothing above it. On such
days, if unprotected, I would burn very badly.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
https://peakdistrictweather.org
twitter: @TideswellWeathr

On Tuesday, 26 May 2020 20:09:50 UTC+1, Graham Easterling wrote:
I agree with most of what you state about factors that affect UV levels except humidity. I do not think it affects them.

Nicholas
Meir Heath, Stoke-On-Trent 250 metres above sea level.

Equally, I am sure it does. If Norman reads this I know he'll agree. In fact, anyone that spends a lot of time outdoors, certainly on the coast of SW England where high humidity is common, fully appreciates the fact.

How else do you explain the big drop in UV when a cold front goes through? Certainly lower high level ozone sometimes being associated with a warm sector ridge is partly the cause, but the whole thing? If you don't except it's the humidity, despite the evidence, you need to come up with an alternative explanation why it's so high in air which has none of the clarity of that behind the cold front.

Somewhere I'v got a list of times when the Camborne UV has hit 9, never in clear, clean sunny mP conditions.

Graham
Penzance

I have not seen any evidence UV levels are linked to high humidity. If UV levels are lower after a cold front it may be there is more cloud.

Nicholas
Meir Heath, Stoke-On-Trent 250 metres above sea level.