Mallacoota Weather event of 21- -25 May 2020

We had an unusual very damp spell from 21 May to 25 May.

It was mainly unusual because the dampness (90 mm to 100 mm around Mallacoota) seemed to be confined to quite a small area.  To our West, Orbost managed 37.4 mm and to the North, Merimbula had 1.2 mm and Bega 0 mm!  Of particular interest to Mallacoota was Bombala, at the head of the Genoa River catchment, scoring 3.8 mm: that won't do much to flush the Inlet.  From conversations with, and Facebook posts from, others in the area the amount of rain dropped off quickly with records of 55 to 70 mm from Gipsy Point and Wallagaraugh (only 13 km from the coast).

The first graph shows the rain in terms of the fall during each hour and the maximum rate during the hour.  The 5 boxes at the foot show the different days,    Note that the lines are on different scales: the chart shows the greater amounts of rain, at a very modest rate. on the 22nd/23rd with lesser amounts but at a relatively high rate on the other days.

The second chart shows wind speed as both average speed over an hour and maximum gust during the hour.  I have used a single scale in this chart to shown how, even with basically modest winds there can be quite high gusts.

The next chart uses the same data as the one above but plots on different axes.  The similarity of pattern between the 2 series is very obvious.

The next chart is rather tricky, and I wondered whether to include it.  

(Ignore this red bit if details of charts aren't your idea of heaven!) Plotting wind direction is always tricky since if compass degrees are used a small shift from North (0 degrees) to NNW (337.5 degrees) appears much larger than a shift from NNW to WSW (247.5 degrees) although the latter is a fair more significant shift.  To try to overcome this I have used an indicator based on the 16 quadrants of the compass with the count increasing by 1 as move East from North and decreasing by 1 as move West.  The same problem arises around South, but that is less commonly found.

What it shows is basically a steady flow from sector -5 (WSW) and -6 (SW) with occasionally records from sectors +5(ESE) and +6 (SE) particularly on the 24th and 25th.  Interestingly several of the Easterly switches coincide with the rainy squalls.

 

The final aspect of the weather is the average temperature for each hour.  After the event really kicks off late of the 21st the temperature is pretty stable, between ~10C and ~15C showing the insulating effect of clouds.