uk.sci.weather (UK Weather) (uk.sci.weather) For the discussion of daily weather events, chiefly affecting the UK and adjacent parts of Europe, both past and predicted. The discussion is open to all, but contributions on a practical scientific level are encouraged.

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Old July 12th 18, 08:18 AM posted to uk.sci.weather
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Default Penzance - Back to cloudless

After a bright, dry but mainly cloudy day yesterday (though a different story on Scilly where it was very warm & sunny much of the day) not a cloud in the sky currently, a F3 N breeze, 20.1C @ 09:00.
https://www.aspects-holidays.co.uk/w...michaels-mount

Minimum temperature last night 16.7C.

Any thundery activity looks to be well to the east over the next 2 days, with the N wind probably remaining strong enough to see off a south coast sea breeze and associated convergence this far west.

I think I may have felt a rain drop yesterday afternoon, but probably an hallucination.

Graham
Penzance


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Old July 12th 18, 10:47 AM posted to uk.sci.weather
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Default Penzance - Back to cloudless

On Thursday, July 12, 2018 at 9:18:21 AM UTC+1, Graham Easterling wrote:
After a bright, dry but mainly cloudy day yesterday (though a different story on Scilly where it was very warm & sunny much of the day) not a cloud in the sky currently, a F3 N breeze, 20.1C @ 09:00.
https://www.aspects-holidays.co.uk/w...michaels-mount

Minimum temperature last night 16.7C.

Any thundery activity looks to be well to the east over the next 2 days, with the N wind probably remaining strong enough to see off a south coast sea breeze and associated convergence this far west.

I think I may have felt a rain drop yesterday afternoon, but probably an hallucination.

Graham
Penzance


The MetO has just lowered the forecast maximum temperature for Penzance to 20C.

Considering, that at 11:00 or so it was 21C at Bosullow on the moors, 22C at Lands End, 22C Culdrose & it's now 22C in Penzance, that's a strange change.
Even warmer on sheltered spots of the south coast just to the east.

The forecast temperatures have been consistently very low for places like Penzance & Plymouth of late, I seem to remember Len making a similar comment.

Even at Lands End, where it's really quite windy, the temperature has been over the forecast max for sheltered Penzance since 09:30.http://www.landsendweather.info/

With the open sea temperature now around 19C, https://www.ndbc.noaa.gov/station_pa...?station=62107
it's cooling affect is much reduced.

Graham
Penzance

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Old July 12th 18, 02:52 PM posted to uk.sci.weather
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Default Penzance - Back to cloudless

On Thursday, July 12, 2018 at 9:18:21 AM UTC+1, Graham Easterling wrote:
After a bright, dry but mainly cloudy day yesterday (though a different story on Scilly where it was very warm & sunny much of the day) not a cloud in the sky currently, a F3 N breeze, 20.1C @ 09:00.
https://www.aspects-holidays.co.uk/w...michaels-mount

Minimum temperature last night 16.7C.

Any thundery activity looks to be well to the east over the next 2 days, with the N wind probably remaining strong enough to see off a south coast sea breeze and associated convergence this far west.

I think I may have felt a rain drop yesterday afternoon, but probably an hallucination.

Graham
Penzance


A few small Cu developed, but with hardly any vertical extent. Mainly just inland as the sea breeze effect largely killed the N wind. Temp stuck around 22C much of the day. Dropping back a bit now (15:45).

Couple of pics from Pz Jubilee Pool taken 15:00 show the conditions. Visibility not as good as it has been. Lizard point not at all sharp.
http://www.turnstone-cottage.co.uk/JB.html

Graham
Penzance
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Old July 12th 18, 10:07 PM posted to uk.sci.weather
Len Len is offline
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Default Penzance - Back to cloudless

On Thursday, July 12, 2018 at 11:47:32 AM UTC+1, Graham Easterling wrote:
On Thursday, July 12, 2018 at 9:18:21 AM UTC+1, Graham Easterling wrote:
After a bright, dry but mainly cloudy day yesterday (though a different story on Scilly where it was very warm & sunny much of the day) not a cloud in the sky currently, a F3 N breeze, 20.1C @ 09:00.
https://www.aspects-holidays.co.uk/w...michaels-mount

Minimum temperature last night 16.7C.

Any thundery activity looks to be well to the east over the next 2 days, with the N wind probably remaining strong enough to see off a south coast sea breeze and associated convergence this far west.

I think I may have felt a rain drop yesterday afternoon, but probably an hallucination.

Graham
Penzance


The MetO has just lowered the forecast maximum temperature for Penzance to 20C.

Considering, that at 11:00 or so it was 21C at Bosullow on the moors, 22C at Lands End, 22C Culdrose & it's now 22C in Penzance, that's a strange change.
Even warmer on sheltered spots of the south coast just to the east.

The forecast temperatures have been consistently very low for places like Penzance & Plymouth of late, I seem to remember Len making a similar comment.

Even at Lands End, where it's really quite windy, the temperature has been over the forecast max for sheltered Penzance since 09:30.http://www.landsendweather.info/

With the open sea temperature now around 19C, https://www.ndbc.noaa.gov/station_pa...?station=62107
it's cooling affect is much reduced.

Graham
Penzance


Yes Graham.
Plymouth was the warmest in country today at 26C.
It was forecast to be 22C. But during the day today when the temp had already risen above that, they changed it on the website to 25C.

At least someone was monitoring the temp, but I thought the hourly output was just model output. In which case the model had been tweaked to be more realistic.

Len
Wembury
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Old July 12th 18, 11:15 PM posted to uk.sci.weather
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Default Penzance - Back to cloudless

On Thursday, 12 July 2018 23:07:36 UTC+1, Len wrote:
On Thursday, July 12, 2018 at 11:47:32 AM UTC+1, Graham Easterling wrote:
On Thursday, July 12, 2018 at 9:18:21 AM UTC+1, Graham Easterling wrote:

It was forecast to be 22C. But during the day today when the temp had already risen above that, they changed it on the website to 25C.

At least someone was monitoring the temp, but I thought the hourly output was just model output. In which case the model had been tweaked to be more realistic


This adjustment will be due to the current observed higher temperatures being assimilated into the latest model run. Completely automatic and no tweaks involved.

--
Freddie
Ystrad Rhondda



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Old July 13th 18, 08:14 AM posted to uk.sci.weather
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Default Penzance - Back to cloudless

On Friday, July 13, 2018 at 12:15:49 AM UTC+1, Freddie wrote:
On Thursday, 12 July 2018 23:07:36 UTC+1, Len wrote:
On Thursday, July 12, 2018 at 11:47:32 AM UTC+1, Graham Easterling wrote:
On Thursday, July 12, 2018 at 9:18:21 AM UTC+1, Graham Easterling wrote:

It was forecast to be 22C. But during the day today when the temp had already risen above that, they changed it on the website to 25C.

At least someone was monitoring the temp, but I thought the hourly output was just model output. In which case the model had been tweaked to be more realistic


This adjustment will be due to the current observed higher temperatures being assimilated into the latest model run. Completely automatic and no tweaks involved.

--
Freddie
Ystrad Rhondda


I've always assumed that was the case, despite a certain ex USW member telling me I was talking rubbish for suggesting so. I am pleased to have it confirmed.

The question is then why the Pz forecast was tweaked down when it was already warmer almost everywhere locally, away from the immediate north coast.

I suspect strongly that the tweaks are based on Camborne, which is always a very cool spot in a northerly. In fact it appears to be commonly the coolest spot in Cornwall in a situation where the wind's onshore in summer. (At 08:00 it was around 3C colder than even St Mary's airport, cooler than Newquay, Lands End etc.) I'm not saying it's wrong, there are aspects of the local geography which could explain it, as well as it being exceptionally cloud prone - it was about the only place a bit dull this morning.

However, using it to adjust forecasts for the south coast where there's unbroken sunshine & a gentle offshore wind, is clearly going to result in the big errors that have been typical of late. I can only assume that data from Culdrose, which tends to show a more similar temperature profile (though still rather different) during this sort of spell is not used.

If my assumptions are correct, it clearly shows how forecasts are suffering as there are no recording stations along the 100 miles of the Cornish south coast. Now in the old days . . .

Plymouth was corrected the right way because the correction was based on Plymouth.

Graham
Penzance So far the warmest July since before 1991.
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Old July 13th 18, 08:24 AM posted to uk.sci.weather
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Default Penzance - Back to cloudless

Sorry for using the word tweak, I should have said adjusted down. I was not having a dig, I appreciate your input Freddie.

Graham
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Old July 13th 18, 09:07 AM posted to uk.sci.weather
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Default Penzance - Back to cloudless

On Friday, 13 July 2018 09:14:30 UTC+1, Graham Easterling wrote:
On Friday, July 13, 2018 at 12:15:49 AM UTC+1, Freddie wrote:
On Thursday, 12 July 2018 23:07:36 UTC+1, Len wrote:
On Thursday, July 12, 2018 at 11:47:32 AM UTC+1, Graham Easterling wrote:
On Thursday, July 12, 2018 at 9:18:21 AM UTC+1, Graham Easterling wrote:
It was forecast to be 22C. But during the day today when the temp had already risen above that, they changed it on the website to 25C.

At least someone was monitoring the temp, but I thought the hourly output was just model output. In which case the model had been tweaked to be more realistic


This adjustment will be due to the current observed higher temperatures being assimilated into the latest model run. Completely automatic and no tweaks involved.

--
Freddie
Ystrad Rhondda


I've always assumed that was the case, despite a certain ex USW member telling me I was talking rubbish for suggesting so. I am pleased to have it confirmed.

The question is then why the Pz forecast was tweaked down when it was already warmer almost everywhere locally, away from the immediate north coast.

I suspect strongly that the tweaks are based on Camborne, which is always a very cool spot in a northerly. In fact it appears to be commonly the coolest spot in Cornwall in a situation where the wind's onshore in summer. (At 08:00 it was around 3C colder than even St Mary's airport, cooler than Newquay, Lands End etc.) I'm not saying it's wrong, there are aspects of the local geography which could explain it, as well as it being exceptionally cloud prone - it was about the only place a bit dull this morning.

However, using it to adjust forecasts for the south coast where there's unbroken sunshine & a gentle offshore wind, is clearly going to result in the big errors that have been typical of late. I can only assume that data from Culdrose, which tends to show a more similar temperature profile (though still rather different) during this sort of spell is not used.

If my assumptions are correct, it clearly shows how forecasts are suffering as there are no recording stations along the 100 miles of the Cornish south coast. Now in the old days . . .

Plymouth was corrected the right way because the correction was based on Plymouth.

You may be correct that the Penzance forecast is unduly affected by the Camborne observations. The way I understand it, each observation has a radius of influence (both at the time of observation and for a short time before and afterwards), so I assume that Culdrose does have some influence too. But Camborne also is an upper air station (i.e. they send up weather balloons a couple of times a day) and it is possible that (owing to the sparsity of upper air observations) it has a larger circle of influence than Culdrose.. I am speculating here, though.

Here are some links to useful articles describing aspects of data assimilation:
https://www.metoffice.gov.uk/researc...tion-uk-models
https://www.metoffice.gov.uk/researc...f-observations
Note the massive number of observations assimilated - and the fact that synop assimilation is only a small part!

--
Freddie
Ystrad
Rhondda
148m AMSL
http://www.hosiene.co.uk/weather/
https://twitter.com/YstradRhonddaWx for hourly reports (no wind measurement currently)

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Old July 13th 18, 09:08 AM posted to uk.sci.weather
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On Friday, 13 July 2018 09:24:51 UTC+1, Graham Easterling wrote:
Sorry for using the word tweak, I should have said adjusted down. I was not having a dig, I appreciate your input Freddie.

If I thought that was a dig, I wouldn't last very long on this newsgroup ;-)
I do believe the term that is used is "nudge".

--
Freddie
Ystrad
Rhondda
148m AMSL
http://www.hosiene.co.uk/weather/
https://twitter.com/YstradRhonddaWx for hourly reports (no wind measurement currently)
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Old July 13th 18, 09:20 AM posted to uk.sci.weather
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Default Penzance - Back to cloudless

On Friday, 13 July 2018 09:14:30 UTC+1, Graham Easterling wrote:
On Friday, July 13, 2018 at 12:15:49 AM UTC+1, Freddie wrote:
On Thursday, 12 July 2018 23:07:36 UTC+1, Len wrote:
On Thursday, July 12, 2018 at 11:47:32 AM UTC+1, Graham Easterling wrote:
On Thursday, July 12, 2018 at 9:18:21 AM UTC+1, Graham Easterling wrote:
It was forecast to be 22C. But during the day today when the temp had already risen above that, they changed it on the website to 25C.

At least someone was monitoring the temp, but I thought the hourly output was just model output. In which case the model had been tweaked to be more realistic


This adjustment will be due to the current observed higher temperatures being assimilated into the latest model run. Completely automatic and no tweaks involved.

--
Freddie
Ystrad Rhondda



I suspect strongly that the tweaks are based on Camborne, which is always a very cool spot in a northerly. In fact it appears to be commonly the coolest spot in Cornwall in a situation where the wind's onshore in summer. (At 08:00 it was around 3C colder than even St Mary's airport, cooler than Newquay, Lands End etc.) I'm not saying it's wrong, there are aspects of the local geography which could explain it, as well as it being exceptionally cloud prone - it was about the only place a bit dull this morning.

However, using it to adjust forecasts for the south coast where there's unbroken sunshine & a gentle offshore wind, is clearly going to result in the big errors that have been typical of late. I can only assume that data from Culdrose, which tends to show a more similar temperature profile (though still rather different) during this sort of spell is not used.

I've just looked on a map - Camborne looks closer to you than Culdrose, so I would expect it to have slightly more influence on the Penzance forecast. Note that the influence just depends on spatial difference, not geographical stuff as involved as distance from the coast where the wind is onshore.

--
Freddie
Ystrad
Rhondda
148m AMSL
http://www.hosiene.co.uk/weather/
https://twitter.com/YstradRhonddaWx for hourly reports (no wind measurement currently)



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