Weather event of 2 - 3 June 2024

The Bureau of Meteorology (B0M) forecast a rain event for Mallacoota over the second and third of June with 25% probability forecasts of up to 20mm for the 2nd, and 40mm for the third.  This has turned out to be very conservative with my weather station (WS) recording 33.2mm on calendar 2nd and 68.8mm up to 1300 hrs on the 3rd (totalling to 102mm).  I will update this as time goes by.  (For comparison the BoM station at the Airport has recorded 124mm to 1300.)  The chart shows the hourly falls at my WS.

These falls have had a noticeable impact on my pro-rata estimates of the annual fall: the current (0800) value of that guesstimate is 966mm compared to a median annual fall of 903mm.

Having just ticked over the 0900 reset the final record by BoM for the day from 0900 yesterday is 112mm.  This is the highest June rainfall recorded at the airport since records began there in 1975.  Looking at all months it is the 8th heaviest daily fall (the top step on the podium is 20 May 1978 with 192 mm.

The rain rate has varied quite a lot suggesting a lot of squalls have been embedded in the falls (see discussion of differences below).

To get an idea of the spread of rain I cover 4 sites as shown below.  The values are falls from 0000hrs on 2 June to 0500hrs on 3 June:

My WS             69.6mm

BoM Airport    79.4 mm

BoM Gabo       36.0 mm

Clarke St          70.4 mm

My initial thoughts were to have severe doubts about the value for Gabo, since it is only 17km from the airport station and both are equally exposed to the West wind currently blowing.  However on comparing the hourly recordings from Gabo, Airport and my WS it seems that the situation is more that the Airport station is right on the edge of the system and the squalls are having a reduced impact on the sites further East.  I have put the data - to 7am, it takes some fiddling to get the BoM data formatted as is needed - in a Google sheet.

It is always difficult to examine radar images for this area since Mallacoota is at the reliability limit of the Bairnsdale tower.  However the image from my laptop computer at 0738hrs tends to support the above theory.

A freeze-action attempt from my phone (also based on BoM data but I think from a slightly earlier time) gives a somewhat different look and feel, but does support the theory of Mallacoota being on the edge.  Further the blue areas embedded in the white - especially the rain area approaching from the South - indicate squally cells in the general murky drizzle.

The wind is also notable.  The highest gust on the 3rd - up to 0800hrs) is 49.9kph, while he Airport has registered 80kph and Gabo 95kph.  These are about the normal relativities.

A question arises as to how the BoM performed in this exercise.  At a simplistic level the forecasts were so much below the actual event that they could be given a "fail".  However some ameliorating issues need to be included in any assessment.

• When an event breaks records it is very difficult to forecast it as there is no equivalent history.
• As noted above Mallacoota was right on the edge of the event and exactly what was recorded where was to some extent random due to small squalls.
• The forecasts are probability based not lines in the same.

I am tempted to rate this a fail, but not an egregious fail.  However they did forecast an unusually high level of rain for the two days so warning signs were there.  My view ends up somewhere between "must try harder" and "could do better".  Another wet patch is due Thursday - Friday so lets see how that pans out.

Here are a few photos from a visit to Betka around 11am on the 3rd where the surf was UP..

The next two photos have a Hooded Plover as the target (two of them were present).

Lots of gulls.  Note also the 'kelp line' showing the height of the water before it broke out.

On getting home, the sun was out giving a nice rainbow.

As well as the rainfall bringing water down the rivers the wind from the South and West  has been push water into the Inlet.  This has raised the level of the Lake as shown by this image of the marsh next to Fisheries Jetty: normally there is no water visible in the vegetated area.