Monday, 11 May 2015

Blow, blow thou Winter Wynd

The bard can always be relied upon for a cliche when short of a title for a post: in this case from 'As you like it'.   As I would like it, if I had any say in the matter, is a whole lot less windy than it was yesterday!

The one good thing about yesterday is that we were at home, with a fire full of red box and stringybark and not out in the camper!  This was particularly so when we went to bed and could hear the wind howling.  So how windy was it?

This image from the BoM Doppler Wind radar site at 1100 on 10 May gives a hint!
The shading only occurs where there is rain for the radar signal to bounce off which is why it is restricted to the mountains.  (For most of the day the precipitation stayed up there, which did keep things tolerable here.)  Looking at the scale, that navy blue colour indicates 80 -90kmh.

By 1330 the precip. had broken up a bit and started to move out of the mountains.
The main reason I included that image was for a phenomenon shown at Gundaroo (halfway across the image about halfway between the top of the image and radar position).  The shading there is red: this happens when the gusts are >100kmh and the system starts in again from the far end of the scale!

The outside temperature wasn't too bad - between 8oC and 11oC - but I wondered what the wind chill was.  According to my weather station the minimum wind chill was 0.7 oC (but I know that understates the strength of the wind due to low positioning of the station).  That led me to wonder what my weather records had to say about wind chill.

This first chart shows the wind chill calculated by the station for April 2015, with readings every 30 minutes
The jagged nature of the original series clearly reflects the daily cycle of temperature, which should be removed if I showed a 48 (period (48 half-hours per day) moving average.  That gives the red line, which is far cleaner, suggesting an overall gradual drop across the month, with a big plunge around the 21st.

Going for my records since November 2013 enables me to plot these graphs of average and minimum wind chill by month: they are pretty consistent with a plot of minimum temperature for the same period.

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