Monday, 8 January 2018

Unpleasant weather

The weather forecast for the weekend  6-7 January was unpleasant indeed.  And the weather delivered thereon!  I spent most of the time cowering in the air-conditioned indoors.

The reason for the unpleasantness was the hot air being delivered from the centre.  This is demonstrated nicely by a clip from Meteye in the morning of the 7th showing wind coming from the NW at 25 -30 kph.
Another clip, the doppler Wind view from the Captains Flat radar, shows that stronger winds are yet to arrive.
By late afternoon matters were looking a little stormy out the window and on the Weatherzone presentation of the radar data.  We are at the red X and the system was moving as shown by the arrow.
It duly arrived.
I will return to this below but will conclude the clips with this one of the Weatherzone radar for Victoria, from about 2000 hrs showing a very intense line of storms.  (It was heading East rather than South East so went past us to the North.)
The first chart shows the hourly maximum and minimum temperatures for the two days (and a little bit of the 8th.
 This shows that we got pleasant minima on both days (but a nastily high one of 21 oC on the 8th).  As the 2 full days showed different profiles - particularly for the minimum temperatures I plotted a comparative chart.
The plummet in hourly minimum between 4pm and 5pm - 10oC - as a storm front passed through is, and was, most impressive.   While it kicked up a whisker thereafter its heart wasn't in it and the worst of the heat had gone.

I also looked at humidity.  The first chart is the equivalent of the preceding one.
 I noticed that the shape of the lines was almost a mirror image of the temperature chart.  looking at the correlation between the series confirmed this with a value of the correlation coefficient of -0.98 for the 6th and -0.94 for the 7th,/sup>.  That shows up rather interestingly if the rH is subtracted from 100!

We scored 1.2mm of rain in the squall then and a further 0.4mm before 5am on the 8th.  While not a drenching it laid the dust.  (Pro-rata expansion of the 1.6mm total gives an expected annual total of 52.2mm!)

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