More AWS crap?
 

I noticed on xcweather about half-an-hour ago a report from Wattisham of
'heavy freezing unknown precipitation' with a temperature of PS01 and
dewpoint of zero. How come?

--
Graham P Davis, Bracknell, Berks. Web-site: http://www.scarlet-jade.com/
"Nobody can get the truth out of me because even I don't know what it is. I
keep myself in a constant state of utter confusion." [Col. Flagg]
OS: Linux [openSUSE Tumbleweed]

More AWS crap?
 

On Sunday, 10 December 2017 11:02:29 UTC, Graham P Davis wrote:
I noticed on xcweather about half-an-hour ago a report from Wattisham of
'heavy freezing unknown precipitation' with a temperature of PS01 and
dewpoint of zero. How come?

You can have freezing precipitation with a temperature above zero. I have no idea how an AWS works out whether it is freezing or not - perhaps some sort of ice accretion sensor?

--
Freddie
Fishpool Farm
Hyssington
Powys
296m AMSL
http://www.fishpoolfarmweather.co.uk/
https://twitter.com/FishpoolFarmWx for hourly reports

More AWS crap?
 

Graham P Davis wrote:

I noticed on xcweather about half-an-hour ago a report from Wattisham of
'heavy freezing unknown precipitation' with a temperature of PS01 and
dewpoint of zero. How come?


Maybe it has a ground temp sensor that is reading 0C ?


--
Brian Wakem
Lower Bourne, Farnham, Surrey
http://www.brianwakem.co.uk/weather
Live obs @ 18:46:03 : 1.1C, DP 0.4C, RH 95%, 12.0 mm

More AWS crap?
 

On 10/12/17 18:46, Brian Wakem wrote:
Graham P Davis wrote:

I noticed on xcweather about half-an-hour ago a report from Wattisham of
'heavy freezing unknown precipitation' with a temperature of PS01 and
dewpoint of zero. How come?


Maybe it has a ground temp sensor that is reading 0C ?


Could be, I suppose. I've heard many forecasts of freezing rain with air
temperatures (and wet-bulbs) above freezing when the ground is frozen
but I've never seen it happen.


--
Graham P Davis, Bracknell, Berks. Web-site: http://www.scarlet-jade.com/
"Nobody can get the truth out of me because even I don't know what it
is. I keep myself in a constant state of utter confusion." [Col. Flagg]
OS: Linux [openSUSE Tumbleweed]

More AWS crap?
 

On Sunday, 10 December 2017 19:21:41 UTC, Graham P Davis wrote:
On 10/12/17 18:46, Brian Wakem wrote:
Graham P Davis wrote:

I noticed on xcweather about half-an-hour ago a report from Wattisham of
'heavy freezing unknown precipitation' with a temperature of PS01 and
dewpoint of zero. How come?


Maybe it has a ground temp sensor that is reading 0C ?


Could be, I suppose. I've heard many forecasts of freezing rain with air
temperatures (and wet-bulbs) above freezing when the ground is frozen
but I've never seen it happen.
I've actually seen this more often than classic freezing precipitation. YMMV!!

--
Freddie
Fishpool Farm
Hyssington
Powys
296m AMSL
http://www.fishpoolfarmweather.co.uk/
https://twitter.com/FishpoolFarmWx for hourly reports

More AWS crap?
 

Graham P Davis wrote:

On 10/12/17 18:46, Brian Wakem wrote:
Graham P Davis wrote:

I noticed on xcweather about half-an-hour ago a report from
Wattisham of 'heavy freezing unknown precipitation' with a
temperature of PS01 and dewpoint of zero. How come?


Maybe it has a ground temp sensor that is reading 0C ?


Could be, I suppose. I've heard many forecasts of freezing rain with
air temperatures (and wet-bulbs) above freezing when the ground is
frozen but I've never seen it happen.


I had never seen it until we moved to Tideswell but it has happened on
a few occasions here, albeit with the air temp not very far above zero.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
https://peakdistrictweather.org
Twitter: @TideswellWeathr

More AWS crap?
 

On 10/12/17 19:31, Norman Lynagh wrote:
Graham P Davis wrote:

On 10/12/17 18:46, Brian Wakem wrote:
Graham P Davis wrote:

I noticed on xcweather about half-an-hour ago a report from
Wattisham of 'heavy freezing unknown precipitation' with a
temperature of PS01 and dewpoint of zero. How come?


Maybe it has a ground temp sensor that is reading 0C ?


Could be, I suppose. I've heard many forecasts of freezing rain with
air temperatures (and wet-bulbs) above freezing when the ground is
frozen but I've never seen it happen.


I had never seen it until we moved to Tideswell but it has happened on
a few occasions here, albeit with the air temp not very far above zero.


I've seen the reverse, where surfaces are above zero and the air is
sub-zero. First time was in the 61-2 winter over the New Year when a
cold front came in from the east, replacing the drizzly warm sector with
moderate rain and sub-zero air. Above-ground surfaces got coated with
ice first and then pavements after the rain cooled the surface.

In all forecasts I've witnessed of freezing pptn with non-super-cooled
rain, the surfaces warmed up before any chance of ice forming. Not
saying it can't happen but I would have thought there'd need to be a
pretty hard frost before the rain fell. Perhaps I'll have to move to
Tideswell. ;-)

--
Graham P Davis, Bracknell, Berks. Web-site: http://www.scarlet-jade.com/
"Nobody can get the truth out of me because even I don't know what it
is. I keep myself in a constant state of utter confusion." [Col. Flagg]
OS: Linux [openSUSE Tumbleweed]

More AWS crap?
 

Graham P Davis wrote:

On 10/12/17 18:46, Brian Wakem wrote:
Graham P Davis wrote:

I noticed on xcweather about half-an-hour ago a report from Wattisham of
'heavy freezing unknown precipitation' with a temperature of PS01 and
dewpoint of zero. How come?


Maybe it has a ground temp sensor that is reading 0C ?


Could be, I suppose. I've heard many forecasts of freezing rain with air
temperatures (and wet-bulbs) above freezing when the ground is frozen
but I've never seen it happen.


Light rain here for the last 20 minutes and the temp had stayed below zero.
Ground is still frozen from last night so it'll be freezing on contact.


--
Brian Wakem
Lower Bourne, Farnham, Surrey
http://www.brianwakem.co.uk/weather
Live obs @ 20:39:48 : -0.1C, DP -0.7C, RH 96%, 0.0 mm