Recent heat

You may have noticed it has been somewhat hot recently.  That had led to the BoM issuing a heat wave warning over various days for most of Victoria with the warning lingering in the Mallacoota area.  

I have compiled a blogpost defining various terms that can be used as shorthand for periods of extreme weather.

Here are the temperature readings from my weather station so far in March 2023 (note this is a screengrab image not a table).

The period 2 - 4 March is close to a cool spell, but fails as it is only 3 consecutive days, with an above average maximum on the 5th (after a significantly cold morning)!

From 6 to 11 March is a hot spell, as all readings for 6 consecutive days are above the daily average, albeit 3 readings are less than 1SD above the monthly average.  Embedded in that period is a heat wave from 9 to 11 March, with three consecutive days with both readings more than 1SD above the monthly average (bold red numbers).  (Looking at BoM forecasts I am confident that the hot spell will extend over 12 March with a fair possibility that the heat wave may also extend since Meteye implies a temperature <17.3C is possible up to midnight.) 

Indeed the minimum on the 12th was above the 1SD criterion, and the maximum above the +2SD limit so the heat wave continued for a 4th day (and the hot spell for a seventh  day).  I suspect the 13th will be a warm day, so will extend the hot spell but not the heat wave.

I have used a yellow fill with orange dots to indicate the readings that are >2SD above the monthly average.  The boundary value for that criterion for minimum is 20.3C so the 11th missed out on that by 0.4C.  Had we ended with 3 days with both readings >2SD above average I think I would have added a term of "extreme heat wave".

It should be stressed that my Weather Station compiles data on calendar days and as a result can give different results to BoM which is based on a reset at 0900 hours.  Thus my WS is currently showing a minimum for 12 March of 19.4C but that may change as a change comes through later in the day.  For BoM the current low temperature (18.5C) is likely to be preserved by the 0900 reset. 

I really wish the BoM would change to a calendar day, but appreciate this would cause much turmoil where stations are still based on manual readings, some of which have very very long series (eg Timbillica has a rainfall series starting in 1909!)  While only 2 of the 96 stations shown in Latest Weather Observations for Victoria are manual, the equivalent report for Queensland lists 14 manual stations.