I was wondering, given this current cold few days, how DAM thicknesses
were calculated. Just wondered given the Davis setup I have whether it
is possible?
--
Keith (Southend)
http://www.southendweather.net
e-mail: kreh at southendweather dot net

"Keith (Southend)" wrote in message
...
I was wondering, given this current cold few days, how DAM
thicknesses were calculated.

.... the total thickness (or Relative Topography for continental users)
is the given by the separation of the 500 hPa and 1000 hPa surfaces -
bigger numbers, warmer air, smaller numbers colder air. To keep an eye
on such, you need to know both the height of the 500 hPa surface and
that at 1000 hPa. The latter you could in fact compute from a
surface-based instrument, as is standard practice for radio-sondes
(using the mslp & screen temperature), but you can't ascertain the 500
hPa height from the surface - you need a radio-sonde (or satellite
sounding) for that.

To look at actuals from radio-sonde ascents, try this ...

http://weather.uwyo.edu/upperair/europe.html

leave the default ('Text List'), and then click on the station you
want to interrogate. Scroll down the list nearly to the bottom and you
will find the 1000 - 500 hPa thickness given (in metres).

Martin.

--
Martin Rowley
West Moors, East Dorset (UK): 17m (56ft) amsl
Lat: 50.82N Long: 01.88W
NGR: SU 082 023

Martin Rowley wrote:
"Keith (Southend)" wrote in message
...
I was wondering, given this current cold few days, how DAM
thicknesses were calculated.

... the total thickness (or Relative Topography for continental users)
is the given by the separation of the 500 hPa and 1000 hPa surfaces -
bigger numbers, warmer air, smaller numbers colder air. To keep an eye
on such, you need to know both the height of the 500 hPa surface and
that at 1000 hPa. The latter you could in fact compute from a
surface-based instrument, as is standard practice for radio-sondes
(using the mslp & screen temperature), but you can't ascertain the 500
hPa height from the surface - you need a radio-sonde (or satellite
sounding) for that.

To look at actuals from radio-sonde ascents, try this ...

http://weather.uwyo.edu/upperair/europe.html

leave the default ('Text List'), and then click on the station you
want to interrogate. Scroll down the list nearly to the bottom and you
will find the 1000 - 500 hPa thickness given (in metres).

Martin.


Thanks Martin,

I remember that link from before, but I never realised the thickness was
there.

Best regards

Keith (Southend)

--
Keith (Southend)
http://www.southendweather.net
e-mail: kreh at southendweather dot net

Martin Rowley wrote:
"Keith (Southend)" wrote in message
...
I was wondering, given this current cold few days, how DAM
thicknesses were calculated.

... the total thickness (or Relative Topography for continental users)
is the given by the separation of the 500 hPa and 1000 hPa surfaces -
bigger numbers, warmer air, smaller numbers colder air. To keep an eye
on such, you need to know both the height of the 500 hPa surface and
that at 1000 hPa. The latter you could in fact compute from a
surface-based instrument, as is standard practice for radio-sondes
(using the mslp & screen temperature), but you can't ascertain the 500
hPa height from the surface - you need a radio-sonde (or satellite
sounding) for that.

To look at actuals from radio-sonde ascents, try this ...

http://weather.uwyo.edu/upperair/europe.html

leave the default ('Text List'), and then click on the station you
want to interrogate. Scroll down the list nearly to the bottom and you
will find the 1000 - 500 hPa thickness given (in metres).

Martin.

Thanks Martin,

I remember that link from before, but I never realised the thickness was
there. I guess 5344 we would think as 534 DAM ?
03882 Herstmonceux Observations at 12Z 03 Mar 2009

Best regards

Keith (Southend)

--
Keith (Southend)
http://www.southendweather.net
e-mail: kreh at southendweather dot net

Keith (Southend) wrote:
Martin Rowley wrote:
"Keith (Southend)" wrote in message
...
I was wondering, given this current cold few days, how DAM
thicknesses were calculated.

... the total thickness (or Relative Topography for continental users)
is the given by the separation of the 500 hPa and 1000 hPa surfaces -
bigger numbers, warmer air, smaller numbers colder air. To keep an eye
on such, you need to know both the height of the 500 hPa surface and
that at 1000 hPa. The latter you could in fact compute from a
surface-based instrument, as is standard practice for radio-sondes
(using the mslp & screen temperature), but you can't ascertain the 500
hPa height from the surface - you need a radio-sonde (or satellite
sounding) for that.

To look at actuals from radio-sonde ascents, try this ...

http://weather.uwyo.edu/upperair/europe.html

leave the default ('Text List'), and then click on the station you
want to interrogate. Scroll down the list nearly to the bottom and you
will find the 1000 - 500 hPa thickness given (in metres).

Martin.

Thanks Martin,

I remember that link from before, but I never realised the thickness was
there. I guess 5344 we would think as 534 DAM ?
03882 Herstmonceux Observations at 12Z 03 Mar 2009

Best regards

Keith (Southend)


Yes, 5,344 metres is 534.4 decametres

http://en.wikipedia.org/wiki/Decametre

Your Davis weather station could roughly calculate this if you can
attach a probe a long way up a pole!

Joe

Joseph Hunt wrote:
Keith (Southend) wrote:
Martin Rowley wrote:
"Keith (Southend)" wrote in message
...
I was wondering, given this current cold few days, how DAM
thicknesses were calculated.

... the total thickness (or Relative Topography for continental
users) is the given by the separation of the 500 hPa and 1000 hPa
surfaces - bigger numbers, warmer air, smaller numbers colder air. To
keep an eye on such, you need to know both the height of the 500 hPa
surface and that at 1000 hPa. The latter you could in fact compute
from a surface-based instrument, as is standard practice for
radio-sondes (using the mslp & screen temperature), but you can't
ascertain the 500 hPa height from the surface - you need a
radio-sonde (or satellite sounding) for that.

To look at actuals from radio-sonde ascents, try this ...

http://weather.uwyo.edu/upperair/europe.html

leave the default ('Text List'), and then click on the station you
want to interrogate. Scroll down the list nearly to the bottom and
you will find the 1000 - 500 hPa thickness given (in metres).

Martin.

Thanks Martin,

I remember that link from before, but I never realised the thickness
was there. I guess 5344 we would think as 534 DAM ?
03882 Herstmonceux Observations at 12Z 03 Mar 2009

Best regards

Keith (Southend)


Yes, 5,344 metres is 534.4 decametres

http://en.wikipedia.org/wiki/Decametre

Your Davis weather station could roughly calculate this if you can
attach a probe a long way up a pole!

Joe

I'm planting the beans ;-)

--
Keith (Southend)
http://www.southendweather.net
e-mail: kreh at southendweather dot net

"Martin Rowley" wrote in message
...
| "Keith (Southend)" wrote in message
| ...
| I was wondering, given this current cold few days, how DAM
| thicknesses were calculated.
|
| ... the total thickness (or Relative Topography for continental users)
| is the given by the separation of the 500 hPa and 1000 hPa surfaces -
| bigger numbers, warmer air, smaller numbers colder air. To keep an eye
| on such, you need to know both the height of the 500 hPa surface and
| that at 1000 hPa. The latter you could in fact compute from a
| surface-based instrument, as is standard practice for radio-sondes
| (using the mslp & screen temperature), but you can't ascertain the 500
| hPa height from the surface - you need a radio-sonde (or satellite
| sounding) for that.
|
| To look at actuals from radio-sonde ascents, try this ...
|
| http://weather.uwyo.edu/upperair/europe.html
|
| leave the default ('Text List'), and then click on the station you
| want to interrogate. Scroll down the list nearly to the bottom and you
| will find the 1000 - 500 hPa thickness given (in metres).
|

Just as a matter of interest, can someone give the reason why the
"thickness" isopleths only appear on forecast charts 36 or more hours ahead,
and not on actual, +12 or +24 charts? If both 1000 hPa and 500 hPa fields
are produced for all these times, there seems no reason why those
potentially useful thickness contours do not appear on current and near
future charts.
--
- Yokel -

"Yokel" posts via a spam-trap account which is not read.

"Yokel" wrote ...
snip
Just as a matter of interest, can someone give the reason why the
"thickness" isopleths only appear on forecast charts 36 or more
hours ahead,
and not on actual, +12 or +24 charts? If both 1000 hPa and 500 hPa
fields
are produced for all these times, there seems no reason why those
potentially useful thickness contours do not appear on current and
near
future charts.

.... we had this discussion several years ago: find it at ...
http://tinyurl.com/a9ohu8

I don't think anything has changed in essence so I can't see TTHK
appearing on T+0/T+24, and in any case, there are so many other
diagnostic variables available that total thickness, whilst
undoubtedly still useful, has fallen somewhat out of fashion.

Martin.


--
Martin Rowley
West Moors, East Dorset (UK): 17m (56ft) amsl
Lat: 50.82N Long: 01.88W
NGR: SU 082 023