"Dave" wrote in message
...
Could the high overnight temperature of 17.2c in Teignmouth be due to a
Foehn effect off Dartmoor?

https://en.m.wikipedia.org/wiki/Foehn_wind

No. Conditions wrong for that.

Will
--
http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------

On 17/12/2015 17:28, Dave wrote:
Could the high overnight temperature of 17.2c in Teignmouth be due to a Foehn effect off Dartmoor?
https://en.m.wikipedia.org/wiki/Foehn_wind

Last night's temperatures remained fairly constant at between 13.0C and
14.0C peaking at 14.2C at 08:30.

Maybe there was a Föhn effect at Teignmouth. The wind here was generally
southerly all night which meant it was blowing straight in off the sea.

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

Depending on the exact wind direction, Teignmouth does get some shelter from the hills of Shaldon/Ness in a SSW-WSW, as a rower we often make use of this shelter.

On 17/12/2015 19:34, Dave wrote:
Depending on the exact wind direction, Teignmouth does get some shelter from the hills of Shaldon/Ness in a SSW-WSW, as a rower we often make use of this shelter.

Well, if the wind had been blowing parallel (SSW direction) to the coast
then there are a lot of hills and valleys to create a Föhn effect.
Knowing the RH% and DPs would help to solve this.

The RH here remained pretty much constant at 90% for much of the night.

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

Graham, yes I did see the link Xmetman posted but, I was very busy at work & only briefly able to view on my iPhone & it's difficult to view the chart/graphs.

"Nick Gardner" wrote in message
...
On 17/12/2015 19:34, Dave wrote:
Depending on the exact wind direction, Teignmouth does get some shelter
from the hills of Shaldon/Ness in a SSW-WSW, as a rower we often make use
of this shelter.

Well, if the wind had been blowing parallel (SSW direction) to the coast
then there are a lot of hills and valleys to create a Föhn effect. Knowing
the RH% and DPs would help to solve this.

The RH here remained pretty much constant at 90% for much of the night.


Hi, at 0400 at Haytor we had T +12.4C RH 83% DP +9.6C Wind SW 9 knots (3m
corrected to 10m using method of Burt for a VP2).

Now the wind direction is incorrect but there where occasional veers to W.
Dry adiabatic lapse rate is g/cp = 9.81/1004 ~ 9.81C per kilometre.
My station is 306m above Den Gardens in Teignmouth. So DALR increase is 9.81
x 306/1000 = 3K
Thus a fohn from Haytor at most would deliver 15.4C given a starting RH of
83%.
I *could* understand circa 16C this way as some places round Haytor could
have been 0.5C higher. But not +17.4C.
So how do we get that extra heat low down. Hills round Teignmouth are lower
than Haytor so extra heat still needed for any fohn from those.

Now, I was watching weatherobs.com closely yesterday as records were in the
making. I dismissed it at the time, but IIRC I remember seeing a ship report
of air temperature of +17C in SW approaches south of circa 49N. This could
have been the pulse of warm air low down that Bruce has already mentioned?
But where did it go after wafting over Teignmouth? I suspect it went aloft
over Exeter way and not picked by Dunkeswell etc. We are not going to get to
the bottom of this without detailed upper air data, which we don't have. The
only other way to understand would be a super high resolution modelling
study, possible but somebody needs to be persuaded to carry it out. It
requires somebody to first write an observational paper, David? Bruce? I'm
too busy I'm afraid but I'd be willing to proof read etc. Given that the
figure of 17.4C is relatively very high I think that this case could be
immensely interesting and I have AWS data obviously for Haytor should it be
needed. Perhaps someone like Ant Veal would like to help?

Cheers,
Will
--
http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------

Eskimo Will wrote:


"Nick Gardner" wrote in message
...
On 17/12/2015 19:34, Dave wrote:
Depending on the exact wind direction, Teignmouth does get some
shelter from the hills of Shaldon/Ness in a SSW-WSW, as a rower
we often make use of this shelter.

Well, if the wind had been blowing parallel (SSW direction) to the
coast then there are a lot of hills and valleys to create a Föhn
effect. Knowing the RH% and DPs would help to solve this.

The RH here remained pretty much constant at 90% for much of the
night.


Hi, at 0400 at Haytor we had T +12.4C RH 83% DP +9.6C Wind SW 9 knots
(3m corrected to 10m using method of Burt for a VP2).

Now the wind direction is incorrect but there where occasional veers
to W. Dry adiabatic lapse rate is g/cp = 9.81/1004 ~ 9.81C per
kilometre. My station is 306m above Den Gardens in Teignmouth. So
DALR increase is 9.81 x 306/1000 = 3K Thus a fohn from Haytor at most
would deliver 15.4C given a starting RH of 83%. I could understand
circa 16C this way as some places round Haytor could have been 0.5C
higher. But not +17.4C. So how do we get that extra heat low down.
Hills round Teignmouth are lower than Haytor so extra heat still
needed for any fohn from those.

Now, I was watching weatherobs.com closely yesterday as records were
in the making. I dismissed it at the time, but IIRC I remember seeing
a ship report of air temperature of +17C in SW approaches south of
circa 49N. This could have been the pulse of warm air low down that
Bruce has already mentioned? But where did it go after wafting over
Teignmouth? I suspect it went aloft over Exeter way and not picked by
Dunkeswell etc. We are not going to get to the bottom of this without
detailed upper air data, which we don't have. The only other way to
understand would be a super high resolution modelling study, possible
but somebody needs to be persuaded to carry it out. It requires
somebody to first write an observational paper, David? Bruce? I'm too
busy I'm afraid but I'd be willing to proof read etc. Given that the
figure of 17.4C is relatively very high I think that this case could
be immensely interesting and I have AWS data obviously for Haytor
should it be needed. Perhaps someone like Ant Veal would like to help?

Cheers,
Will

I've had a look at the ship/buoy obs from yesterday. The warmest I
could find was 15.2 deg at Buoy 62163 at 47.5N 8.4W. There might, of
course, have been something that was not in the dataset that I looked
at.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
http://peakdistrictweather.org

"Norman Lynagh" wrote in message
...
Eskimo Will wrote:


"Nick Gardner" wrote in message
...
On 17/12/2015 19:34, Dave wrote:
Depending on the exact wind direction, Teignmouth does get some
shelter from the hills of Shaldon/Ness in a SSW-WSW, as a rower
we often make use of this shelter.

Well, if the wind had been blowing parallel (SSW direction) to the
coast then there are a lot of hills and valleys to create a Föhn
effect. Knowing the RH% and DPs would help to solve this.

The RH here remained pretty much constant at 90% for much of the
night.


Hi, at 0400 at Haytor we had T +12.4C RH 83% DP +9.6C Wind SW 9 knots
(3m corrected to 10m using method of Burt for a VP2).

Now the wind direction is incorrect but there where occasional veers
to W. Dry adiabatic lapse rate is g/cp = 9.81/1004 ~ 9.81C per
kilometre. My station is 306m above Den Gardens in Teignmouth. So
DALR increase is 9.81 x 306/1000 = 3K Thus a fohn from Haytor at most
would deliver 15.4C given a starting RH of 83%. I could understand
circa 16C this way as some places round Haytor could have been 0.5C
higher. But not +17.4C. So how do we get that extra heat low down.
Hills round Teignmouth are lower than Haytor so extra heat still
needed for any fohn from those.

Now, I was watching weatherobs.com closely yesterday as records were
in the making. I dismissed it at the time, but IIRC I remember seeing
a ship report of air temperature of +17C in SW approaches south of
circa 49N. This could have been the pulse of warm air low down that
Bruce has already mentioned? But where did it go after wafting over
Teignmouth? I suspect it went aloft over Exeter way and not picked by
Dunkeswell etc. We are not going to get to the bottom of this without
detailed upper air data, which we don't have. The only other way to
understand would be a super high resolution modelling study, possible
but somebody needs to be persuaded to carry it out. It requires
somebody to first write an observational paper, David? Bruce? I'm too
busy I'm afraid but I'd be willing to proof read etc. Given that the
figure of 17.4C is relatively very high I think that this case could
be immensely interesting and I have AWS data obviously for Haytor
should it be needed. Perhaps someone like Ant Veal would like to help?


I've had a look at the ship/buoy obs from yesterday. The warmest I
could find was 15.2 deg at Buoy 62163 at 47.5N 8.4W. There might, of
course, have been something that was not in the dataset that I looked
at.


Thanks Norman. As it was weatherobs.com it might have been a private vessel?
Or I may have been mistaken. Still like to understand this very high
temperature, where did it come from?

Will
--
http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------

On Friday, 18 December 2015 09:03:47 UTC, wrote:
Thanks Norman. As it was weatherobs.com it might have been a private vessel?
Or I may have been mistaken. Still like to understand this very high
temperature, where did it come from?


Will,
It wasn't read by Devon tourist board personnel, was it? (;0)
Ken

On Friday, 18 December 2015 09:03:47 UTC, wrote:


Thanks Norman. As it was weatherobs.com it might have been a private vessel?
Or I may have been mistaken. Still like to understand this very high
temperature, where did it come from?

Will
--
http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------

It's come from on high.
In other words, it's hot air from the UKMO in Exeter.
:-)

Len
Wembury
---------------------------------------------------