March 2021 Weather Report

 The overall phrase for the month is WET with slightly cooler than average temperatures.  

Rainfall

The total fall for the month on my weather station (WS) was 199.8 mm.  The BoM site was relatively arid at 166.8  mm 😁.  A comparison of the two sites is made more complex than necessary by BoM presenting the falls on a day concluding at 0900 hrs on the following day 😠.  The difficulties posed by this are illustrated in a chart of daily rainfall.

On 13 March my WS recorded 20.4 mm in the hour to 1900.  The BoM monthly summary for Mallacoota (at the Airport) shows zero rain on that day.  Showing my paranoia about technology my first thought was that something was wrong with my WS (or my computer, or both).  Then I thought to look at BoM records for Gabo Island, which showed 24.4 mm recorded against 14 March, and daylight dawned.  The 8.0 mm recorded at the airport on the 14th didn't "jump out".   My post on Mallacoota Weather and Wildlife Facebook group on the 13th notes "Well that was fun! At home, 19.4mm in about 20 minutes. Maximum rain rate was 188mm per hour and maximum wind gust 48kph. And a few flangs as it dies down! "

Again the comparison of the major event on 23 March is complicated by BoM showing it against 24 March! No wonder climate change denialists attack BoM: not only do they make a rod for their own backs, but thrash themselves with it.

My usual comparison of this year with last year and median fall shows clearly the magnitude of the fall.

Looking at a time series of March falls this month was the 4th highest (deepest?) fall for March.

The rain rates in the major event were not remarkable, with peak rates late in the evening at just over 70 mm/hr. The peak rates for the events of 13 and 27 March at 188 mm/hr and 274 mm/hr respectively were more dramatic (although total accumulations on those days was much less). The rate on 27 March was the highest I have recorded in my 2+ years of observations here.

The final aspect of rain is my pro-rata extrapolation of rainfall to date.  As shown in the following chart this got a huge boost on the 23rd of March and has stayed at or above 1600mm for the year since that date.

Temperatures

My overall measure of temperature the monthly anomaly has ended the month at -0.34C.  The prgress of the measure through the month shows the convergence to the value.

In calculating the daily contributions to the anomaly, using BoM data I end up with a series of daily maxima and minima with can be compared with a series of daily averages for those metrics.  Having got series, one HAS to chart them.

I also have series of the daily extremes from my WS.  Very similar to the above.

Minimum Temperatures

The average minimum for the month was 14.6C, exactly the same as last year and a smidgin above average.  The was a series of above daily average minimum (if that makes sense) from 18 to 26 March, contributing to an overall result of half the minima being above average for the date.

Maximum Temperatures

The average daily maximum at my WS was 22.9C a little above the long term BoM average, but below the value for 2020.  This is influenced by a station difference with the BoM site having a March average of 21.8C which is slightly below the long term average for that site.

Humidity

Generally normal humidities apart from the period 20 -23 March, as the major storm brewed up.  I was surprised to see the values for 13 and 14 March so low, but they both correlate well with BoM values. I suspect this shows how a storm cell can generate in a few hours and dump a heap of rain.

In a slightly historical context, using only WS data - which now contains 3 years of readings for the first three months of the year - the 0900 value is above both last year and the average.

For 1500 hrs this year is almost exactly average and somewhat above the value for 2020.

Wind

A surprisingly calm month, in view of the number of storms recorded.

The direction of the wind was more focused than usual on the NE and W-WSW components of the compass.  While a good lot from NNW, relatively little from NW, N or NNE.