Outside temperature trend

[simonvfr]

I seem to be getting odd results in the Trend box for outside temperature. Today, with a rapidly declining temperature (down more than 2º in the last hour - see attached) the trend figure is showing as -0.5º per hour.

Error? Or have I not understood the basis for the calculation?

[steve]

It uses the difference between the temperature now and the temperature three hours ago (divided by three), which I understood was the 'standard' way to do it, or at least the way UKMO do it. But I can't find my reference for this at the moment. Pressure is done the same way.

[simonvfr]

Thanks for the explanation of the calculation.

I could understand using a three-hour average for pressure, which changes more slowly (and steadily), but it seems to hide some significant features of the weather when applied to temperature. In the example of my graph from today, the sudden drop in temperature was followed by a sharp shower - and yet the temperature change didn't show in the trend figure, because of the earlier sharp increase.

I had a quick search, but could not find any description of a 'standard' methodology, so I would be interested in a link if you can dig one out!

BTW - I am a very happy convert from another well known brand of software. Is there a way of importing data from antipodean software data files?

[steve]

I could understand using a three-hour average for pressure, which changes more slowly (and steadily), but it seems to hide some significant features of the weather when applied to temperature. In the example of my graph from today, the sudden drop in temperature was followed by a sharp shower - and yet the temperature change didn't show in the trend figure, because of the earlier sharp increase.

Yes, I know what you mean. I'll see if I can find my reference.

BTW - I am a very happy convert from another well known brand of software. Is there a way of importing data from antipodean software data files?

It's unlikely that I'd ever write an importer myself. I did actually spend a while once looking for the format of the data files, but failed. Even if I had that info now, I haven't really got the time. The format of Weatherlink files, for example, is well documented, but I just haven't had time to write an importer.