Weather Report April 2020

The month overall was fairly bland.  Rain somewhat below normal (again) and overall temperature slightly above normal.

Rain

We totaled 61.2 mm for the month, with three days of falls greater than 10 mm.  The total was 78% of median and brought year to date to 83% of the average.  On the positive side, at least the April fall was above last year although by the end of April the total year to date was almost identical to 2019

A pro-rata estimate of the annual rainfall is now 781 mm.  The values of that projection since the start of the year suggests it is plateauing around 800 mm.

Temperatures

The temperature anomaly finished the month at +0.3^oC.  Overall more minimums were above average than below, while maxima were  almost evenly split. 

	min above	min below	total
max above	9	5	14
max below	10	6	16
total	19	11

The pattern overall was not significantly different to that expected although eyeballing the daily values hints that for the first three weeks minima were high and maxima low while the reverse was the case for the rest of the month.

The daily extremes are reasonably stable with two warm days mid-month standing out.

Maximum Temperature

The average maximum from my weather station was above average which may reflect the average coming from the BoM site, which is typically cooler than my site due to a sea breeze cooling afternoons at the airport.   

A time series of average maxima - allowing for the difference due to siting, shows the maxima are all over the place between 18^oC and 23^oC.  The "trend" is not at all significant. 

Minimum temperatures

Again the average minimum for the month was above the long-term mean.  It was however below last year's value.

 Again the time series is all over the place and no significant trend is shown.  As the series appeared more stable from 2007 onwards I looked for a trend in that but it was not significant.

Humidity

The chart of daily humidity has a couple of unusual features.  Firstly it is unusual to see so many days where the 0900 value is below than for 1500.  Secondly the very low 0900 values for 16-18 April caused me to check with the BoM data for those periods: they were almost identical.

Despite the low values referred to above the monthly average for 0900 is above the longer term mean from the BoM site and above the value for 2019 (which was very dry.

 In contrast the 1500 humidity was somewhat lower than other periods.

Wind

The month was not very windy.  The three days with long runs all preceded fronts coming through with consequent rain.  The winds on 29 April were given much hyperbole in the media (I was mildly disappointed that no one actually coined the neologism "windmageddon").

 Overall the run was less than last year and below the benchmark of BoM values adjusted for that site being much more exposed than my site.

 In terms of the direction of wind it made the usual April switch back to NW-N, with 36% of wind recordings coming from that section of the compass.