"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.