Apparent temperature

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xmetman

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Jul 10, 2019, 11:13:29 AM7/10/19
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The difference between yesterday, after the passage of the warm front, and today is like chalk and cheese.

Don't laugh but today's dewpoint in Strathpeffer feel like you're in a sauna, and even after a couple of very hefty monsoon like showers, it's very sultry here.

I don't know if I've got my apparent temperature calculation correct but the chart looks like this.

I reckon the temperature here is around 20°C and the dewpoint ~18°C or so.

Aboyne has an apparent temperature of 22.7 at 14 UTC.


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xmetman

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Jul 10, 2019, 11:35:28 AM7/10/19
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Some impressive totals from today's showers

xmetman

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Jul 10, 2019, 2:50:00 PM7/10/19
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Apart from Altnaharra, the sparse network of Met Office rainfall sites failed to catch any of today's larger totals. 

The estimated total for Strathpeffer of 12.9 mm looks far too conservative for the torrential rain that I witnessed. 


Brian Wakem

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Jul 10, 2019, 4:18:37 PM7/10/19
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On June 29th when we had that 1 hot day the dew point here peaked at 21.4C and the temp was 31.2C at the time.  Not sure what that scores on the apparent temperature scale but it was like being in the Canaries in mid-summer but without the wind.

-- 
Brian Wakem
Lower Bourne, Farnham, Surrey
Live obs @ 21:16:50 : 16.9C, DP 11.8C, RH 72%, 0.0 mm

xmetman

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Jul 10, 2019, 5:01:08 PM7/10/19
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I'll look up the algorithm and see...
Meanwhile the very heavy rain continues across our part of NE Scotland.
There may have been a couple of thunderstorm warnings issued by the UKMO but as far as I can see there was no thunder or lightning across anywhere in either Scotland or Northern Ireland today according to Blitzortung. Forecasting thunderstorms seems to be problematic with the models it would appear...

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xmetman

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Jul 11, 2019, 9:03:24 AM7/11/19
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Julian Mayes

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Jul 11, 2019, 10:06:22 AM7/11/19
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That's an excellent SEPA rainfall summary at the end of the post. Would be useful if the Envir. Agency could replicate it for England (some hope!).  And the Natural Resources Wales too.  Met Office perhaps?   (too informative for them!). 

Maybe we don't get enough rain down here any more to bother.

Julian     (increasingly mystified at the north / south split in the weather this summer - in the absence of strong air pressure developments).  

Jack Harrison

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Jul 11, 2019, 1:03:53 PM7/11/19
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Wednesday’s storms were extremely localised and in the absence of significant wind, stayed where they formed.  In a 7 mile drive, I passed through intense rain, dry roads and then more rain.

 

As I write this at 1745 Thursday, just had a transient 50 strong flock of swirling House Martins  Normally, I don’t see many House Martins here but a developing shower/storm brings them in chasing insects in the rising air currents. The flock has now moved away to the south east so I guess that is where the shower is most likely.  This is not the first time in the past couple of years that I have made this observation of bird behaviour.

 

But this does raise the possibility that insect-chasing birds (perhaps detectable on radar) could be used as shower forecasters.

 

And now 15 minutes later, cloud base is a mere 100 feet above ground,

 

Jack

xmetman

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Jul 12, 2019, 1:10:20 PM7/12/19
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Julian

The data from SEPA is easy to access. I've been putting together an application to download it today because I figure I'll need it now I live up in this part of the world.

It's disappointing that you can only download 7 days of hourly data, but I did manage to catch the 62.6 mm at Urquhart before it disappeared into a digital black hole and confirm (at least to myself) that it was the wettest place despite what the BBC presenter said in the news.

There seem to be around 275 stations in Scotland. 

I've also found the API to let me access the English data from the EA ~1000 stations apparently.


Bruce.

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Julian Mayes

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Jul 13, 2019, 12:37:51 PM7/13/19
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With apologies to those in the northern half of Scotland........changing the meaning of apparent to its general sense, I'm really surprised how warm today feels in the south. I was hoping for a fresher northerly flow today (albeit gentle) but my house is still stubbornly ~ 25C inside and when out driving the car recently I needed the aircon on - and I only use that when I need to. It has not been particularly sunny here either. 

Julian  
Molesey      Surrey    

xmetman

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Jul 13, 2019, 1:17:20 PM7/13/19
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Its gradually has got a bit fresher during today up here, but as you say it's still a bit sticky further south. 
Some big contrasts in the apparent temperature in places at 15 UTC which must be due to wind speed differences.

I use this formula for the apparent temperature:-
AT = Ta+0.33×e−0.7×ws−4

This is a better version which includes the effects of temperature, humidity, wind, and radiation:-
AT = Ta+0.348×e−0.7×ws+0.70×Q/(ws+10)−4.25
where:
Ta = Dry bulb temperature (°C)
e = Water vapour pressure (hPa) [humidity]
ws = Wind speed (m/s) at an elevation of 10 meters
Q = Net radiation absorbed per unit area of body surface (w/m2)

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