Probably a shortlived topic, but what the heck!

As often happens in a spring northerly, there are some impressively low humidities around this afternoon.

The lowest I've seen so far is 23% at Odiham at 1 PM today and as of right now Farnborough is the lowest I can see: 19C, dewpoint of -1C for a 26% relative humidity.

It's a good day for drying clothes in central southern England by the looks of it!

If out of the sun for more than a few minutes it's none to warm, about 16C

The lowest relative humidity which I can report for today so far has come at the botanic gardens in Edinburgh where the temperature at 3pm was 17.3°C with a dew point of 4.8°C. That in turn works out to a relative humidity of just 37.5% to the nearest 0.1%.

That is even lower than Bolty's above reported figure of 38% although his figure might just be rounded off to the nearest 1%, whereas my own figure is given to the nearest 0.1%.

Clear blue sky's with low humidity and dps which is nice for running in.

62% here now after an afternoon 'low' of 54%. 

I recorded 29% today and even now at 8:30 in the evening it is only 46%. That would explain why the air seemed a little chilly when I arrived home despite the temperatures being in excess of 18C. I was surprised how warm it was.

That must explain the almost gin clear air yesterday with great visibility, good laundry drying conditions and the ground drying out fast.

I wonder if we are entering a protracted dry spell?  or will it a blink and you miss it event and back to normal Atlantic service after the W/E.

Interestingly despite the low humidity at ground level (Farnborough and Odiham are both near me and it was indeed a good drying day!) there were some very impressive contrail displays overhead for much of the day - always a sure sign of high humidity aloft. A look at the GFS data confirms that up at 250mb it was close to 100% humidity in the SE corner of the country for much of the day, with much drier air further west.

Looking west from here you could see the almost ruler straight boundary between the drier air to the west and the humid air to the east: quite striking the way the contrails just stop dead!

So that's what has evaporated the cloud.

Brightened up smartly this morning and now blue sky and sunshine.

An excellent example of a marked change in humidity!

Incidentally, today's lowest that I can find is 29% at Coningsby at 4 PM.

http://www.weatheronline.co.uk/weather/maps/current?LANG=en&DATE=1526396400&CONT=euro&LAND=UK&KEY=UK&SORT=3&UD=0&INT=06&TYP=feuchte&ART=tabelle&RUBRIK=akt&R=310&CEL=C&SI=mph

Lowest  Humidity  29%    06-05-2018  @ 14:07 

For the neighbouring stations at the time in question, we had relative humidities of 45% at Edinburgh Airport (temperature = 13°C, dew point = 2°C) and 47% at the botanic gardens in Edinburgh (temperature = 12.2°C, dew point = 1.6°C).

Those are both a bit higher than the value for Edinburgh Gogarbank at that time (and I do agree that this seemed to be a bit low), but all of those values are still below 50% which confirms even more, that we are in quite a dry air mass just now.

Having said that though, the Sun could be contributing towards that quite a lot as well since the relative humidity has tended to be much lower during the day, before increasing at night as the actual temperature (which is known as the dry bulb value when it comes to measuring humidity) drops.

Some very low relative humidities are being observed once again this evening here in Edinburgh.

At Edinburgh Gogarbank, a relative humidity of 33.5% has once again just been observed as at 7pm this evening with a temperature of 15.5°C and a dew point of 2.2°C. That might seem a bit low and yet just an hour earlier on at 6pm, the relative humidity at the botanic gardens in Edinburgh was 34% with a temperature of 14.4°C and a dew point of 1.2°C.

However, neither of those measurements are as low as the relative humidity of just 19.5% which was reported at the botanic gardens in Edinburgh at 7pm this evening, with that coming from a temperature of 14.7°C and a dew point of -1.4°C.

Clearly, either something very strange is going on with the readings at both of those stations, or something very strange is going on with out atmosphere which has caused us to be in such a dry air mass just now.

EDIT:

As at 8pm this evening, those above values for the relative humidity have been beaten once again with the relative humidity down to 31.0% (temperature = 14.8°C, dew point = 1.0°C) at Edinburgh Gogarbank and just 14.0% (temperature = 14.3°C, dew point = -2.9°C) at the botanic gardens in Edinburgh.

Lowest   28%  rh.  15:14    on 17-05-2018.

Record Low of 2018  26% rh  10:56   05 - 04-2018 

On this occasion as well, we can't even say that this is down to the sunshine in any way as this afternoon is turning out to be be nowhere as sunny as what we have become used to recently (this is shown by the fact that just 12 minutes of sunshine have been recorded at Edinburgh Gogarbank over the course of the last two hours).

23% up in Edinburgh must be very unusual, I'd have thought?