Saturday, 19 January 2013

Canberra trails Robbo!

My friend (I originally typed 'fried', which is possibly apposite, given the topic) Denis posted yesterday that Robertson had its hottest day ever.  The Canberra ABC News announced last night that Canberra had had its second hottest day ever, so we must concede defeat.

Of course if I was a weaselly Canberra booster (sorry about the tautology) I'd point out that 'our' 40.2C kicked butt over their 38.3C.

There is nothing mustelidiferous about boosting Carwoola however.  We maxed out at 41.4C at 4 pm.  That is certainly the highest temperature recorded by my weather station in the 7 weeks it has been operating.  (I can recall one earlier day - perhaps 2009 - on which we got to >40C, but recorded neither the exact reading nor the date.)

It is interesting to compare the temperatures in Carwoola on this date with those of 10 days earlier.
The chart shows a more typical start to the day with temperature declining to about 0700, but then rocketing up to over 30 degrees by 1000.  It carried on rising and was warmer through until 2200.

Of particular interest to me was the impact of cloud cover.  During the day we had a couple of periods (marked with 1 and 2 red splots) when cloud came over and temporarily knocked the edge off the heat,  It was very noticeable the it stayed hot until well into the evening: about 2200 (3 red splots) I noticed that the temperature had dropped by 6 degrees in about 30 minutes: I don't believe it was a coincidence that the blanket of cloud had cleared.

Although hotter than the 8th, the fire danger on the 18th was more modest at 'Severe' rather than 'Catastrophic'.  This probably reflected the expected lower winds on the latter day.  That turned out to be the case: the "sum of gusts indicator" for the 8th was 230km while for the 18th it was 'only' 165km.  The peak gust was the same but was more of a spike, and occurred later in the day.
Apart from these data, it was good to see less actual fire activity in this area on the 18th.  What we need now is several mm of good soaking rain to knock down, and moisten, the grass.

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