I have been tearing my hair out over this one but I think I have finally tracked it down…
I had ‘show cloud height in metres’ ticked in Units/other settings. I couldn’t work out why the software was showing a lower cloud base (in metres) than the figure that was logged to the MySQL database (after converting from feet). From my own calculations the MySQL database had the correct value. When I unticked the ‘show in metres’ all the figures matched up (WD and MySQL data).
Brian, I think there may be a conversion factor that is out somewhere when converting from feet to metres for cloud base. It seems like the cloud base conversion is using 3.5 feet per metre instead of 3.28 perhaps?
Of course, this may be something peculiar to my set-up and not a bug at all. I am at an altitude of around 1500 metres above sea level but that is set in the options. If anyone else can confirm what is described above I would be interested to know what you find (cloud base in feet = dew point depression x 412).
i think so to - but there is another problem i think
my programm says clouds are at 840 meters
METAR SAYS FEW240 and this means 24000ft
24000ft are 7315.2 meters i think
OR AM I WRONG
see attatched info
TAKEN FROM THIS SITE http://www.homepages.mcb.net/bones/01UKAV/METAR.htm
Cloud
Usually this is a six figure group and one that most of you will already recognise. The group consists of three letters that describe the cloud cover followed by three figures for cloud height ABOVE AERODROME LEVEL.
Cloud amount is given as;
FEW
Few. This indicates 1 or 2 oktas of cloud.
SCT
Scattered. This indicates 3 or 4 oktas of cloud.
BKN
Broken. This indicates 5 to 7 oktas of cloud.
OVC
Overcast. This indicates 8 oktas (solid cloud cover).
Cloud height is given by the next three figures which show the altitude in hundreds of feet. i.e. 040 is 4000 ft, 004 is 400 feet, 200 is 20,000 ft. Examples:
SCT020 - Scattered at 2000 ft.
BKN005 - Broken cloud at 500 feet.
OVC250 - Overcast at 25,000 feet.
WD calculates what the cloud base would be based on the way that dew point changes with altitude. The value it calculates is the height that the base of clouds would appear if there were to be any cloud. This doesn’t mean to say that there will always be cloud at that height. So in your case WD has calculated that the cloud base would be at approx 840m…if conditions are right for cloud formation.
METAR info is based on observations rather than calculations and so should always be correct. If there’s cloud they’ll report it, if there isn’t any cloud they’ll give CAVOK (or something similar).
In your case it’s not a metres/feet conversion miscalculation of cloud height…it’s just that the cloud is forming a lot higher than dew point calculations would suggest, which only means that the conditions aren’t suitable for cloud forming at a low level, but are higher in the atmosphere.