Why Can We Have Weeks Of Rain, But Not Weeks Of Sun?

[reef]

Its interesting, looking at the stats for sunshine in this location the 1971-2000 average is 1477hrs per year. To find a year with less sunshine than that value you have to go all the way back to 2002 and since 2005 every year has had over 1600hrs.

The Metoffice sunshine charts show a similar picture. Since 2002 every year has been generally average or sunnier than average apart from isolated pockets. I think when people are moaning about lack of sunshine they generally mean in July and August as there have actually been quite a number of very respectable sunny months recently including some which were record breaking.

[Gavin P]

As already stated, if the weather from late January to the late March had occured from late June to late August we'd have had an exceptionally hot, dry and sunny summer. It's just how the cookie crumbles, I'm afraid.

Sooner or later the right synoptics WILL occur in the right months and we'll have a hot summer. On average we get two warmer, drier and sunnier than average summers a decade (the 1960's didn't have any, whilst the 1990's had 6) so a good one should come along soon enough (its still possible this summer could even turn out to be a good one believe it or not)

Edited June 14, 2012 by Gavin P

[Weather-history]

the 1960's didn't have any

Summer 1969 had a summer index of 234 for Manchester, so it must have been a pretty ok summer

[Thundery wintry showers]

Indeed, Trevor Harley noted 1969 as "the best summer of the 1960s- which isn't saying a lot", and indeed taking the UK as a whole July and August were quite warm, June was notably sunny with July fairly sunny and August fairly cloudy, and all three months had rainfall close to or slightly below normal.

However the other summers of the 1960s were mostly characterised by relatively sunny Junes followed by dull wet weather in July and August.

[cheeky_monkey]

(its still possible this summer could even turn out to be a good one believe it or not)

True..June 1991 was pretty dismal and cool July and August were pretty good esp August summer overall was better than average.

[Interitus]

But a key difference being that Vancouver experiences over double the July sunshine that Shannon does.

Vancouver has much more sunshine than Shannon but not over double! - more like 50% more.

Two reasons - primarily it is further south, comparable with western France which has similar sunshine levels.

Also it is further inland from the open sea and sheltered by the mountainous Vancouver Island and Olympic mountains of Washington state, whilst air from other directions come from the dry interior of the north American continent.

If you look at weather stations further north in coastal British Columbia you will find that annual sunshine totals are absolutely comparable with the British Isles e.g

Port Hardy 50deg40'N - 1465.1 hrs

Sandspit 53deg15'N - 1498.1 hrs

Prince Rupert 54deg17'N - 1229.1 hrs

Stewart 55deg56'N - 981,4 hrs

[Aaron]

St John's in Newfoundland is 47 degrees north with around 1,500 hours of sunshine.. less than London despite being further south.. around 200 hours more than most of northern England.. quite gloomy

[Interitus]

Indeed, we are in a fairly cloudy area but it's not like we are alone in this.

For example consider the inhabitants of Lima in Peru, at 12 degrees south they are firmly in the tropics - and receive only 13mm of rain per year.

Sun-baked desert?

No, they only average between 1284 to 1425 hrs of sun per year..

Edited June 16, 2012 by Interitus

[Luke McDonnell]

One of the things that puzzles me is why is it that High Pressure can set up over Greenland/Iceland for weeks on end but not over the British Isles/NW Europe? It's like we get 9 days or so of HP over us at the end of May, it retrogresses to Greenland, and once thier it stays thier for more than triple the time it was over us for. Surely, if HP can set up over Greenland for a protracted period of time leaving us exposed to likely unsettled weather, then surely it can set up over the British Isles for a protected period of time giving us weeks and weeks of sun! Anyone agree?

Luke

[Evening thunder]

If you want somewhere really dull, try Campbell Island, south of New Zealand. Similar latitude to Birmingham, but only receives about 650 hours of sunshine a year. http://en.wikipedia.org/wiki/Campbell_Island,_New_Zealand

[I Cumbria Marra I]

No, the UK is crap for sunny weather and it always will be, enough said.

Edited June 17, 2012 by I Cumbria Marra I

[Evening thunder]

No, the UK is crap for sunny weather and it always will be, enough said.

^Not nearly as crap as Campbell Island... Anyway who said it was sunny, just posting stats from other places around the world showing we are not completely alone.

[johnholmes]

One of the things that puzzles me is why is it that High Pressure can set up over Greenland/Iceland for weeks on end but not over the British Isles/NW Europe? It's like we get 9 days or so of HP over us at the end of May, it retrogresses to Greenland, and once thier it stays thier for more than triple the time it was over us for. Surely, if HP can set up over Greenland for a protracted period of time leaving us exposed to likely unsettled weather, then surely it can set up over the British Isles for a protected period of time giving us weeks and weeks of sun! Anyone agree?

Luke

meteorologically there are a number of reasons why that is unlikely.

A simple answer is to look at an atlas, sea currents and temperatures for a quick if incomplete answer.

[johnholmes]

No, the UK is crap for sunny weather and it always will be, enough said.

Perhaps you should consider a sunnier part of the Uk short of emigrating-try Jersey or even the south coast of England-Bournemouth for example.

The answer is as simple as I quoted some posts back. Being largely north of 49N and at the eastern end of a large ocean.

[AderynCoch]

Perhaps you should consider a sunnier part of the Uk short of emigrating-try Jersey or even the south coast of England-Bournemouth for example.

Good job he hasn't moved to Bournemouth this month - an abysmal 26.5 hours of sunshine so far.

[ZONE 51]

Because we have a temperate climate we are more prone to changes in air temperature, we are more likely to experience longer periods of mild air than cold or hot, and also wetter weather, this is because the airmasses meet up and mix creating low pressures/fronts in the Atlantic and sending them our way, the strong anticyclones we can get can last for weeks at a time and bring sunny weather for many, these seem to be less these days but are more likely in winter, cold blocks are stronger and more likely to stay put as far as i know, because of the cold and warm airmasses we are more likely to develop low pressures that push the high pressure ridges out of the way, in summer if the Jet Stream stays in an unseasonal pattern then we experience the wet conditions.

Thats my short take on this although not all the answer but an idea of what i think. And another thing, are we not seeing a more south movement of weather patterns over the last few years? it seems that something really has changed!

Edited June 18, 2012 by ElectricSnowStorm

[Interitus]

If you want somewhere really dull, try Campbell Island, south of New Zealand. Similar latitude to Birmingham, but only receives about 650 hours of sunshine a year. http://en.wikipedia....nd,_New_Zealand

Good call, half the sun of Shannon quoted in an earlier post and at the same distance from the equator.

Ok, maybe the Lima, Peru example was a special case of one particular type of climate with cold coastal currents creating persistent fogs and stratiform clouds, but also very stable air hence the dryness which further south is partly responsible for perhaps the driest place on earth in the Atacama desert.

So let's look at another country away from this cold sea and most people might expect tropical Colombia to be far sunnier than our neck of the woods.

However, the capital Bogota at only 4 degrees north of the equator receives around 1625 hrs sun per year at El Dorado airport.

And this is one of the sunnier parts of the area with 1452 hrs at Guaymaral airport, 1328 hrs at the Observatorio Meteorologico Nacional and 1085 hrs at Venado Oro.

The area is above 2500 metres in altitude and as such has something of an Andean cloud forest climate, but still these stations only have between 763-1111 mm precipitation per year. At the extreme, the town of Gabriel Lopez at 3065 metres receives 1104 mm of rain but only 637 hrs sunshine.

Fair enough, altitude may be another special case so how about the Pacific coastal region of Chocó? The cold Humboldt current affecting Lima doesn't reach this far and mean annual temperatures are in the 25-27C range, that's more like it!

No, the capital Quibdó gets around 1280 hours of sun and a fantastic 8000+ mm rain per year. Could be worse, it is 40 miles from the coast where Bahia Solano gets only 822 hrs - but at least only 5 metres of rain.

So tropical rainforest is another special case, is there anywhere else? Well Jaraguay in Cordoba province is at 70 metres asl, has 1233 mm of rain and 1651 hours of sun - just like being in Cornwall, except 16c warmer on average!

Of course there are plenty of areas which are very sunny, with some parts in the north bordering the Caribbean receiving 2500-3000 hours, but the essence is that though we live in a cloudy region there are lots of other places similarly affected.

[Interitus]

Perhaps you should consider a sunnier part of the Uk short of emigrating-try Jersey or even the south coast of England-Bournemouth for example.

That is a very good point, you don't need to venture far to experience dramatically different conditions.

For example a quick comparison shows that around 80% of years in Eastbourne are as sunny as Manchester's sunniest year on record (1995).

But it's summer time in particular where the sun is wanted, and out of 59 years only the memorable 1976 and 1995 acheived more than 700 hours of sun in Manchester - in Eastbourne this happens more than half the time - i.e. every other summer would be memorable with regards to sunshine.

Even the worst Eastbourne summer is in the top 20% for Manchester!