Sunny spells or sunny intervals?

[Stargazer]

A quick question for the more seasoned Netweather members - just something I've always wondered...

Is there a precise definition of sunny spells, sunny periods, sunny intervals, etc. when producing weather forecasts and reports? I tend to go with sunny intervals as being generally short, sunny periods as being of moderate or variable length and sunny spells as being long (so a day that is mostly sunny I would think of as one of sunny spells), but I've never been quite sure that I'm correct. I notice that the email NW forecasts (see picture) show a cloudier symbol against the text 'sunny spells' than 'sunny periods', so perhaps I've got these the wrong way round. Any takers?

[Backtrack]

A look at the cloud amount % should give you a good idea, but I always thought sunny periods were the best? Something I've always wondered too.

[Terminal Moraine]

A quick question for the more seasoned Netweather members - just something I've always wondered...

Is there a precise definition of sunny spells, sunny periods, sunny intervals, etc. when producing weather forecasts and reports? I tend to go with sunny intervals as being generally short, sunny periods as being of moderate or variable length and sunny spells as being long (so a day that is mostly sunny I would think of as one of sunny spells), but I've never been quite sure that I'm correct. I notice that the email NW forecasts (see picture) show a cloudier symbol against the text 'sunny spells' than 'sunny periods', so perhaps I've got these the wrong way round. Any takers?

I'm sure I read, many years ago, some guidance notes from the Met' Office on this.

From memory I think sunny intervals were spells of sunshine up to about half an hour and sunny periods were spells of continuous sunshine from about half an hour up to an hour and a half or so.

As far as I'm aware sunny spells is now used alongside, or instead of, sunny periods. Over the years a gradual looseness of terminology has crept into the weather forecasts whereas years ( decades! ) ago the regulations on descriptive terminology were strict.

This is particularly the case with regional forecasts where often the person delivering the forecast has no meteorological background and, in an attempt to make the forecast accessible to the casual listener, terminology is used which is at worst just plain wrong and at best misleading.

Perhaps John Holmes could shed more light on the sunny intervals/sunny periods discussion?

[Stargazer]

Thanks, TM - yes, I was wondering whether one of the old hands like John might know - I bet the MetO had a manual with just this kind of stuff in it!