June Weather Report

There were stories in the media about torrential rain across Australia defying the forecast of El Nino.  

Not in Mallacoota they didn't.  Very dry (3rd lowest June rainfall) and mild.

Rainfall

I'll start by zooming the BoM map to Victoria.

The mid-green patch on the coast might be the legendary Drummer rain-shadow keeping us dry, but the dark blue area shows the Great Dividing Range blocking the flow from the NW.  Mt Hotham scored 172.8mm for the month, the 8th highest since 1994.

My weather station totalled 26.8 mm - BoM Airport 26.0mm, Gabo Island 19mm.  The manual Fools Haven station at Genoa has not yet been included in BoM output, but is probably responsible for the orange area to our North on the map.  It will come as no surprise that we are well below June 2022 and the median fall for the month.

The fall for June was 40% of the median for the month and resulted in the YTD fall dropping to 90% of the median fall YTD.

It will also not be surprising that the pro-rata estimate of the annual rainfall for 2023 had been dropping steadily since the first week of May.  The current estimate/guess is 808 mm.

Temperatures

The anomaly ended the month as +0.21C.   After the usual fluctuations in the first week the measure stabilised as a slightly positive value.

The time series of values of the anomaly fluctuates greatly.  

I have explored the uses of moving averages to smooth this out but the only value that is effective is a 12 month period.  That is interesting as implying a seasonal effect, but I need to think about it a little more before making a noise about it.

The chart of daily extremes shows, as usual, considerable variation around the average for the date.

Combining these two approaches, I also calculate the number of days for which both min and max are above the average, both below average, etc.  For June there were more than expected days in which the minimum was below average and the maximum was above average, suggesting that the range of temperatures was unusually high.  In fact the average daily range for the month was only 0.1C above the range of the long term values.  Examining the daily ranges shows that conclusion to be a balance, with 4 days with a range >12C but also 4 with a range <6C.

There were no runs of 3 days significantly above or below either extreme.  We came close to a heat wave (3 days above) on the 6th-7th both of which had significantly high values for both extremes.  Both values were significantly low on the 19th.

Minimum Temperatures

The average minimum was a little above 2022 and as noted above a trivial amount above the long term average.

A time series of average June minima shows as close to a flat trend line (ie not significantly different to zero) as could be imagined.

Restricting the data to that from my WS shows the monthly values fairly tightly bunched through the first 6 months.

There were two days with minima significantly (ie >1SD) above average (see above) and 2 with minima significantly below average.

Maximum temperatures

2023 was a fair amount above 2022 and a little above average.

The time series rose in the early years by since then it has flattened  out, varying around 16C in a tight band.  As before the 'trend' is very much below significance.

Looking at the 5 sets of data from my WS again shows a tight grouping with the June value getting back in the pack.

Humidity

There are a couple of interesting upwards spikes in the line of afternoon values ...

.. and a very noticeable downwards spike on 25 June.  On examining the latter it looks to be quite a reasonable record, but I can see nothing else in the records (no wind change or temperature drop) to explain it.

Nothing of great interest in the comparative charts for the two standard times.

Wind

A couple of slightly draughty periods ..

.. but nothing dramatic.  The two longest runs were 175km which is 200th of 1600 daily observations.  Overall the average run for the month was very close to the values for last year and the 5 year average.

TEMPEST data

In addition to the data from my weather station a friend, located in the town centre, has provided access to data from his weather station connected to the TEMPEST network.  This gives information of solar radiation and lightning strikes amongst other data.  As I only have a few months readings limited analysis is possible, but watch this space (or rather, future editions of this space).