June 2019 Weather Report

As well as the quantitative measures which form most of this report, it may be noteworthy that we have seen quite a few plant species in flower in June, which are described as Spring flowering.  Or it may be that there always a few plants that bloom out of season!

In what follows I make frequent use of data from the BoM site on Betka Rd near the airport.  The heath on the site has been slashed recently and I wonder what effect the change in albedo and the decomposing slashings will have on the readings there.

My overall summary is that the month was (again) quite dry with below average (BoM) to well below average (Angophora Drive) rainfall.  The afternoon humidity (BoM) was well below historical levels but the morning humidity was a bit higher than history.  Temperatures - especially the average maximum - were above average while the mean temperature worked out to a little above average.  Winds were not remarkable.

Rainfall

Rainfall this month shows interesting differences according to the weather station examined.  In the table below "Wunderground" refers to private weather stations on the Weather Underground network.  The 5 sites are marked (approximately) in this Google Earth clip.

• Angophora Drive  41.0 mm
• BoM Mallacoota  66.4 mm
• BoM Gabo Island  55.4 mm
• Wunderground Bellbird Creek 50.3 mm
• Wunderground Maramingo 37.1 mm

It is unusual, in the 4 months that we have been here, for my station at Angophora Drive to be lower than the BoM site, so a little maintenance would seem to be indicated.  (That has happened and all seemed OK with the rainfall cup.) For the time being I am taking the BoM Mallacoota reading (66.4 mm) as a better measure.  This is still well below last year and somewhat less than the median value.

In terms of year to date we have currently received 357 mm which is 92% of the median fall to this month.  We have usually received 49.7% of the years rain by end of June so extrapolating that for the year we are looking at an annual fall of 720 mm.

A similar pattern was seen with the number of rain days in the month.

In recent months the rainfall deficiency has eased for many parts of the country.  As a Victorian example the BoM site at Woodend - near Ballarat - has reported 324.6 mm for the year to end June, after being at 41.6 mm for the year to end April.  A doom-laden graphic is the BoM 14 month rainfall deficiency for Australia.

Updating to the 5 month deficiency shows that there is very little of Victoria or NSW (outside of the NE corner)  with a serious or worse deficiency.

Coming back to the local situation I have compiled series of rolling cumulative rainfall for 18 month and 12 month series for BoM Mallacoota.  Both show the series ticking up in the last few months.

Temperatures

Overall the month was close to average.  We finished with a calculated average 0.2^oC above the long term average and - unlike Europe - had no dramatic extremes.  

Maximum temperatures

The average maximum temperature was well above both the average and the value for 2018.

 Minimum temperatures

The average minimum temperature was a little above both last year and the average, but not significantly so.

Humidity

As is usually the case humidity varied considerably from day to day through the month.  The data in this overall chart are from my weather station: the 1500 values there are very similar to the BoM readings but my station recorded lower values at 0900 (some of the BoM values for 0900 are very low, such as 60% on the 30th - this seems to be due to a breeze blowing the humidity away from the BoM site while we were under a small inversion). The most notable reading from my WS was the very low 1500 hrs on the 30th.

Humidity 0900

For this comparative data I have used information from the BoM site.  The averages cited by BoM are from 1908 to 2010 - I have no idea why the series ends in 2010, although cost-cutting would be the usual suspect.

This year is above the average but below June 2018.

 Humidity 1500

In contrast to the morning readings the afternoon value for June 2019 is well down on the average, as well as the value for 2018.

Wind

The 1500 wind speed suggests the month was not unusually windy at Angophora Drive.

In terms of average daily wind run the month was lower than the past 4 months for which I have records at Angophora Drive which seems to be broadly similar to the historic data from BoM.

The strongest gusts over the month recorded at 3 local stations were:

• Angophora Drive 46.7kph on 4 May
• BoM Mallacoota 72 kph on 3 May
• BoM Gabo Island 81 on 3 May 

The relativities are pretty much as expected (the difference between 3 and 4 May is of no consequence as they were both windy at all three sites).

In terms of the direction of the wind as usual the majority of winds come from the Western half of the rose, with no "on the hour" recordings from ENE, E or SSE.  To some extent these may reflect items blocking the flow, but past research has shown a close match between my wind direction readings and the BoM site.  Also, some of the gust readings do contain records from the 'missing' directions so the blocking is not complete.

I have looked at the reading for the highest speed gust in each hourly interval to see how wind speed varies according to direction.  To give some context to this I have calculated the average speed for the hourly gusts in June and all readings since we moved here.

Although few in number the gusts from the SE quarter seem to have been particularly strong in June.  Looking at the period overall the average speed of gusts seems remarkably unaffected by the direction from which they come.