Wednesday, 2 December 2015

November Weather report: a bipolar month

I have started to draft this early on the 26th as the weather has been unusual over night (and still is).  It was windy: here is the 6am Doppler radar image.
The blob of red around Tumut is a result of the palette 'cycling' when it goes past the end of the range (ie over 100kph).  That is unusual.  So is the appearance of red spots (some tinged with dark blue) in the East, indicating that winds are around or above 100kph out that way.

The other notable record is that the minimum temperature overnight was 21.8oC.  (The previous highest minimum I have recorded was 17.1oC in January 2015. ) The temperature has then stayed pretty constant as shown in my weather station.
I suspect that the day's minimum actually came at 23:59.  When I got up at 0530 on 27 November the temperature was 0.3oC: now that is cool.  Our tomatoes seemed to have survived!

Before getting to the normal commentary on the weather of the month I will deal out a brickbat to Microsoft for laying a gigantic update to Windows 10 on me.  They may say all my files are where I left them, but they had managed to trash the driver for my weather station which has taken me most of 24 hours to recover from.

On the other hand a huge bouquet to Davis Instruments Australia.  Despite it being 3 years since I bought the system and all the difficulties of trying to fix up an incompetent customer over the phone, they persevered and got m back on the road!

Rain

It really was a month of two halves.  We recorded 72.6mm in the first 15 days and then not a drop!
The upshot was a fair amount up on last year, but well down on average (although the average for November is itself schitzoid with well over 100mm for 4 of the years 2007- 11 with the remaining 4 years varying from about 50 to about 75mm).

Temperatures


The most interesting aspect of the chart is the period 25 to 27 November, covering the events described in the preamble.

  • The long red bar on the 25th shows that the temperature at 2330 was well above that at 0030 on that day.  
  • That is followed on the 26th by the longest blue bar I have seen, reflecting the massive drop in temperature between 0030 and 2330;
  • The 0030 temperature was very close to the day's maximum and that for 2330 close to the minimum.
  • The line on the 27th shows the minimum barely breaking above zero.

Overall for the month, while only 3 maxima were over 30oC 14 were above 25oC.  At the other end of the scale 14 days had a minimum above 10oC (including a run of 6 days from 2nd to  the 7th).

Looking at averages - with the usual warning about not having many values to average - the average maximum for November was effectively the same as the average for the last 3 years.

For minimum temperature November was way warmer than average.  Looking at actual values it appears that this is due to November 2013 being noticeably cooler than usual.

Humidity

The chart of daily humidity at 1500 Hrs repeats the theme of month of two halves.
 Before the 16th  only one day recorded an rH  below 40%.and most days were significantly above that value.  After the 15th only one day was above that value!

Comparing with my average suggests this year to be noticeably more humid than average.
To some extent that is a result of missing data from a rainy period in early November 2013.  Using the data for the equivalent period in 2015 in place of the blanks raises the average and thus reduces the difference.

Wind

The wind continues the demonstration of a month of opposite halves.
In this case the first half of the month was quite calm (an interesting comparison to our time in Robe SA where it was continually blowing hard) while the second seemed very windy, which is supported by the chart.  The wind speeds shown for the 26th are much lower than those suggested by the doppler image in the preamble reflecting the positioning of my anemometer in a relatively sheltered spot.  I think the relativities for the site are OK.

Comparing this month with the average shows it to be somewhat below average and definitely below some other months this year.

Summary

Basically the first half of the month was cool, calm and moist while the second half was hot, windy and dry. 

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