West Cornwall - A major issue with visibility forecasts.

[Graham Easterling]

During these humid conditions with patches of low cloud & sea fog, the forecasts normally settle on M or G. As was the case for Penzance today, M most of the day with a couple of Gs thrown in for the sake of variation.

In practice it's normally E or P / VP.

Today being a good example. Much of the time the Lizard point has been visible from Penzance, meaning it's E, but along the cliff top along the Lizard, right up to Marazion, it's been VP.

So, from the Jubilee Pool around 14:45, looking across the pool in a SW direction, visibility certainly VG, quite possibly E.

At exactly the same time (well possibly 2 minutes later) looking towards Marazion.

Poor old Lord St. Leven in his castle on the Mount! 

In practice, these compromise visibility forecasts are almost always wrong, best to go for one extreme or the other, at least it's right for someone!

Maximum of 20.8C in Penzance (so far) back to normal at last! 

Graham

Penzance

[Graham Easterling]

Current visibilty forecast for Sennen is moderate. It's as good as it gets

The best visibility we ever get her tends not to be in a cold sector NW, but either just outside of sea fog, or just ahead of a warmer front. A bit counter intuitive, but it's a fact.

Graham

Penzance

[Graham Easterling]

Whilst, currently in Penzance, (11:15) the visibility is <400yards. The thickest fog here for a few years. You can't see across the harbour. It gradually came in >10am. Different story at Porthmeor St Ives, where the horizon is sharp.  

Mousehole on the south coast. Very limited vertical extent to the fog, so it's bright and the light is quite blue.

Graham

Penzance

[Len]

It is not at all surprising that NWP on the local scale cannot provide reliable forecasts on the hourly timescale.

They are, under the present conditions, very poor as you point out.

All that is needed is a general warning for poor visibility, but the models can give hourly forecasts and the computer does not lie.

LOL

Len

Wembury,  where the beach some of the time has been enveloped by fog,

while most of the time chez moi at 83 m asl has been in the clear.

[Graham Easterling]

You could barely see across the Jubilee pool around noon yesterday. Luckily, with little vertical extent, the warmth of the sun was still evident.

Graham

[jack.h...@gmail.com]

No fog up here, but not the sparkling visibility often associated with north Scotland.  I am far from sure as to the reasons, but in windy conditions it could be the salt spray lifted into the lower atmosphere.  It's not a common occurrence, but does happen from time to time.

Jack