The meaning of <#temptrend>

[KarlS]

Cumulus in all its versions always offered a webtag called <#temptrend> and <#temptrendtext>. I never looked at the definition of those webtags and just assumed they reflect the current temperature trend. Then I looked at the temperature graph below:

Image1.jpg

Despite the temperature obviously going up after 6:00, the <#temptrend> tag insisted it was going down. At first I thought I had found a bug, but a look at the Wiki defined the webtag as "The average rate of change in temperature over the last three hours." Now, who would have thought?

I searched on and found <#TempChangeLastHour>. This is still not the information I am looking for. Maybe <#RecentOutsideTemp m=10> is the value I want? Well, not exactly, since it compares a single value to the averaged value of my 10 minutes reporting period. However, it is the best "current" temperature trend I can come up with.

Anyway, if you are using the <#temptrend> tag on your web page, be aware of what it represents!

[mcrossley]

I believe that is the standard way of measuring the temperature trend in meteorology, the same for pressure trend.
Maybe @freddie can share some more information or a link?

Anything shorter than an hour is going to be very erratic and possibly misleading due to short term fluctuations.

[freddie]

Temperature trend is not an especially useful measurement in meteorology - unlike 3-hourly pressure trend which can be directly related to equations of motion in the atmosphere and is very useful in practical meteorology. So to answer the question, there is no meteorological standard period I know of over which temperature change is measured.

[mcrossley]

Thanks, I guess Cumulus used three hours (with 1 hour change value also available) to match the pressure trend then.

[KarlS]

Thanks guys for the clarification. Being not a meteorologist I have used this webtag on my (custom) web site for years now and always assumed it was the current temperature trend. Shows you never to assusme!

[mcrossley]

Well, it *is* the current temperature trend for the last 3 hours expressed as a per hour value. The current trend is always going to be the value now compared against some value in the past, the question is how far into the past. MX provides values for 3 hours and 1 hour.