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B87 why do raw sunshine values need to be corrected?

Another clear blue start to 100% overcast by 10am. Worst climate ever!

Up here in Tromsø it’s been incredibly sunny the last weeks. Dry easterlies but fairly cold. Maximum temp so far this year was on 10th April at 7.8°C, but the last week temps have struggled to reach 3°C during the day and fall well below freezing overnight. Still over 60cm snow in the garden but roads are clear now thankfully. View from the office today

Derecho I'm sure that's coming our way. Forecast is for some rain later.

danm Meanwhile here it is drizzly and only 6C

Well a proper sunny morning! Shame it won’t last though…

Some angry but unthreatening skies yesterday.

Walked out with Sophie and she was excited. Look mummy pure blue sky. That's how rare it is here ... Even my child notices!

Walked out with Sophie and she was excited. Look mummy pure blue sky. That's how rare it is here ... Even my child notices!

Sunnyish start to the day. XC Weather forecasting that it will stay like this all day, whilst the Met Office says moderate rain from lunchtime onward. Jeez, how can they be so far apart in forecasting something that will happen in 3 hours?!

I mean, it could be worse, it could be battering down all day. Light rain on the dog walk this morning, but hat and gloves on. They're usually collecting dust already at this time of year.

Yes exactly, I just don’t understand why the Met Office only publish the raw figures but not the corrected ones. Without that calculation you can never really know the exact actual sunshine hours for a particular location, unless you look at the anomaly maps which give a percentage range.

Looking at the Sat image and the direction of cloud travel, there are a few breaks. If there's one saving grace, the forecast has overdone cloud amounts for the last few days here and it's broken more than expected.

A dry night with long clear periods until well into the early hours. Clouding over before dawn with an occasional spot of showery rain. At 0800 g.m.t Temp; 6.6c 24 hr max; 8.2c 24 hr min; 0.8c Grass min; -2.6c Rainfall in 24 hrs ending 0800 g.m.t; Trace Mean wind speed; 13 mph W 6 oktas Cu, Sc and Ac Vis; 15 miles

While today feels cold for late April, with a touch of frost first thing in some places, it's a far cry from the icy freeze of the 1981 blizzard. Read the full update here

So anything mild now appears to have been pushed back until early next week at best. 5/6c overnight isn't a problem but when it only rises to 7/8c during the day it feels just as cold. On a different note, just watched the met-office online forecast (for the first time) and apparently -3 in England in late April is 'nothing unusual'.

richie3846 As I said in the sunshine thread, that calculation won't work for Brize Norton or other stations. Every station, annoyingly has their own percentage of under-reporting. Some of the absolute worst stations for recording sunshine way under- Herstmonceux, Wakefield, Almondbury etc Poor under reporting of sunshine- Heathrow, Charlwood etc A touch under actual value- Shoeburyness, Leconfield etc Close to normal- Manston, Brize Norton, Tibenham etc

Dare i watch the GFS 06Z "But...but...but the SSW will be different this time guys!" There's no other way around it- SSW = Sudden Spring Wrecker. We don't get a Spring if we get an SSW. The earliest we can expect ANY kind of settled sunny weather would be late May now but it's still a roll of the dice depending on all this crap northern blocking nonsense so we may just get the dullest year ever, time will tell!

A lot of cloud but bright spells; slight rain shower 0500=0.2mm of rain; lowest temperature =2.3 C in the early hours

richie3846 Heathrow's adjusted values don't represent every station though so you have to be careful. Heathrow & Charlwood are underestimating sunshine figures by quite a bit but other locations such as Manston, Brize Norton etc probably only underestimate by a tiny fraction. The easiest way to figure how much of a deficit at certain stations, for me at least (and even that isn't 100% accurate) is to check values on the ensoleillement map on Meteociel when there has been wall to wall sunshine, particularly in Summer months & you can see which places are worse than others for sunshine reporting. Herstmonceux is by far the worst reporter as they only record something silly, like 11.6 hours of sun on a perfectly clear day, while Heathrow & Charlwood would get about 14.2, Shoeburyness 14.7 max & places like Manston, Brize Norton 15.1. It's way more complicated & very annoying that stations don't adjust themselves! I try to keep it as fair as I can in my sunshine tables by not adjusting the ones that only need miniscule adjustments & then adjusting a bit less than necessary, other stations like Heathrow & Charlwood & it seems to more or less work out about right- but still not 100% accurate of course!

....And there is it the classical HP over Greenland that spreads northwards up to the arctic, another completely useless spring month coming?

danm I've saved a screenshot shot of B87's calculation table for future reference. Very useful. I'm thinking a lot of the ongoing discussions about sunshine over the years, may have been unintentionally misleading and pessimistic because of this discrepancy. I'd say this topic needs bringing to the forefront from time to time, to remind people of the adjustments, and to check their sources of information for raw or adjusted data, where that is possible.

Andy Bown Yep, here it is on my way back, looking your way.

113.6 hours sunshine at Brize Norton, my nearest met office site. I'm assuming the weatheronline.co.uk figures are raw data. If so that'll be around 124 hours of adjusted figures. With 6 days left, it seems likely that we'll end up being only slightly below average, quite a turnaround from the opening week. The middle two weeks were quite sunny, more than average, so overall the month has felt quite reasonable here. So 365 hours this year so far. It appears we've not been as cloudy locally compared with some other areas. Thanks to B87 for providing the adjustment table. I'll use that from now on, I've saved a screenshot for future reference. Worth mentioning that when we're looking at sunshine folks, it may be useful to find out, or try and work out if the data source is raw or adjusted. I'm getting a vibe that sometimes people are looking at the raw data, and therefore believing it's cloudier than it is compared to average. I worked out that weatheronline.co.uk uses raw data, because their numbers don't match the met office climate summaries.

What I’m finding more astonishing than how poor and cold our weather is, is that there’s not a single day on the 00Z where temperatures anywhere in the UK at any given time are above 18C… and that goes out till the 10th of May, 3 weeks from the start of meteorological summer.