Interesting drop in RH% and DP just before the arrival of the sea
breeze. No idea why - anyone?

Time; temp; RH; DP; direction; speed (mph). I don't now how the
following table will look when posted as a binary. Hope it makes sense.

13:05 26.7C 63% 19.1C NW 2
13:10 26.9C 60% 18.5C NW 3
13:15 27.1C 47% 14.8C WSW 3
13:20 27.2C 41% 13.4C WNW 4
13:25 27.2C 46% 14.6C NW 5
13:30 27.3C 46% 14.7C W 4
13:35 27.4C 52% 16.7C S 2
13:40 27.6C 58% 18.5C S 7
13:45 27.6C 54% 17.4C S 6
13:50 27.7C 61% 19.5C SSW 8
13:55 27.8C 60% 19.3C S 9
14:00 27.8C 60% 19.3C S 9
14:05 27.7C 61% 19.5C S 9
14:10 27.7C 62% 19.7C S 8

--
Nick Gardner
Otter Valley, Devon
20 m amsl
http://www.ottervalleyweather.me.uk

Either drier air arriving from the north west or local convection dispersing moisture upwards.

--
Freddie

On Monday, August 28, 2017 at 7:57:43 PM UTC+1, Nick Gardner wrote:
Interesting drop in RH% and DP just before the arrival of the sea
breeze. No idea why - anyone?

Time; temp; RH; DP; direction; speed (mph). I don't now how the
following table will look when posted as a binary. Hope it makes sense.

13:05 26.7C 63% 19.1C NW 2
13:10 26.9C 60% 18.5C NW 3
13:15 27.1C 47% 14.8C WSW 3
13:20 27.2C 41% 13.4C WNW 4
13:25 27.2C 46% 14.6C NW 5
13:30 27.3C 46% 14.7C W 4
13:35 27.4C 52% 16.7C S 2
13:40 27.6C 58% 18.5C S 7
13:45 27.6C 54% 17.4C S 6
13:50 27.7C 61% 19.5C SSW 8
13:55 27.8C 60% 19.3C S 9
14:00 27.8C 60% 19.3C S 9
14:05 27.7C 61% 19.5C S 9
14:10 27.7C 62% 19.7C S 8

--
Nick Gardner
Otter Valley, Devon
20 m amsl
http://www.ottervalleyweather.me.uk

Maybe brief entrainment of drier air from above boundary layer.
Incursion of sea breeze is seldom a smooth affair.

Len
Wembury, SW Devon

Assuming the wind data is correct, I find the sequence of temperature and dewpoint rather odd. For a start I can't understand why your dewpoint was as high as 19C not long before the sea breeze arrived. The air mass dewpoint was around 15 or 16C. And then why did the temperature not fall, even though the sea breeze had been blowing for more than half an hour.


Dick Lovett

On Monday, August 28, 2017 at 8:51:32 PM UTC+1, Freddie wrote:
Either drier air arriving from the north west or local convection dispersing moisture upwards.

--
Freddie

Local convection may have been associated with instability along the sea breeze front, which rarely moves in a regular fashion. It often moves inland in 'bursts' before dying slightly - then trying again.

Graham
Penzance

On Mon, 28 Aug 2017 14:19:09 -0700 (PDT)
wrote:

Assuming the wind data is correct, I find the sequence of temperature and
dewpoint rather odd. For a start I can't understand why your dewpoint was as
high as 19C not long before the sea breeze arrived. The air mass dewpoint was
around 15 or 16C. And then why did the temperature not fall, even though the
sea breeze had been blowing for more than half an hour.


Nick lives in a very strange place. Often very hot locally. Also I'm
not sure of his exposure, if it is a secluded garden then dewpoints
can easily be very locally high and not representative of the wider
area. Nevertheless almost certainly the decrease was due to convection. 90% of
sea breezes observable from my house at 10 miles distance are accompanied by
cumulus.

Will
--


---
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On 29/08/2017 10:01, Will Hand wrote:
Nick lives in a very strange place. Often very hot locally. Also I'm
not sure of his exposure, if it is a secluded garden then dewpoints
can easily be very locally high and not representative of the wider
area. Nevertheless almost certainly the decrease was due to convection. 90% of
sea breezes observable from my house at 10 miles distance are accompanied by
cumulus.

Moderate exposure to the north and east but hills in the distance,
sheltered to the west (other houses and Aylesbeare Common) and rather
exposed to the south (down the valley). Garden backs onto open fields to
the north, east and south with a wooden 5' fence around the perimeter of
a good sized garden.

There's another weather station about 1.5 miles away at the other end of
Newton Poppleford village and a little higher up. The DPs there are
similar but the temperature is nearly always a degree or so down by day
and up at night.

Sea breezes here often at this time of year do not effect the
temperature and DPs much, very different to the spring months when they
can have quite a dramatic effect. Being about 2 miles from the sea
itself, the sea breeze has to push a bit of already 'warmed' air through
before we get to the actual sea air itself meaning a delay in
temperature and humidity drop after the sea breeze has arrived (that's
my theory anyway!).

Thanks for the replies. I've looked at previous similar days and the
drop in humidity and then rise seems to be absent, so I guess it is
rather a rare event. I'll keep watching and see if it happens again.

--
Nick Gardner
Otter Valley, Devon
20 m amsl
http://www.ottervalleyweather.me.uk