Here are some standout rain and flood statistics from the past fortnight in eastern Australia.
This was a VERY rare event for some areas, with an annual exceedance probability (AEP) of between 0.1 and 0.05%.
AEP = probability of exceeding a rain/flood level in a given year.🧵
This was a VERY rare event for some areas, with an annual exceedance probability (AEP) of between 0.1 and 0.05%.
AEP = probability of exceeding a rain/flood level in a given year.🧵
#Brisbane's 676.8 mm in 72 hours was a new three-day rain record for the city, with data going back to 1840. This 72-hour rain rate has an annual exceedance probability of 0.2 to 0.5% (1-in-200 to 1-in-500 year event) in Brisbane. 
Doon Doon in NSW copped 1040 mm in 48 hours. That's more than one metre of rain in two days! This rain rate, in this part of NSW, has an annual exceedance probability of between 0.1 and 0.05% (1-in-1000 to 1-in-2000 year event).
The Wilsons River at Woodlawn, just upstream from Lismore, peaked at 15 metres on Monday, February 28. This is 1.5 metres ABOVE the 1-in-500 year flood level for this location. The exact average exceedance probability is unknown, but likely 0.1% (1-in-1000 year event) or lower.
Dunoon in NSW, located north of Lismore, registered 775 mm in 24 hours. This was the highest 24-hour total observed during this event. It's also the 2nd heaviest daily rainfall ever officially recorded in NSW, beaten only by 809.2 mm at Dorrigo in February 1954.
#Sydney had 10 consecutive days with at least 13 mm of rain per day. This is a new record for the city, with data available back to 1858.
It's worth highlighting that annual exceedance probability is not a schedule, it's a probability. A 1-in-1000 year rain rate is not rain that occurs only once every 1000 years. It is, instead, a rain rate that has a 0.1% chance of occurring at that location in any given year.
It is possible to have 1-in-1000 year rain/floods in two consecutive years.
Climate change is also making extreme rain more frequent in some parts of the world. So, what was a 1-in-1000 year event in a past climate may now be a 1-in-100 year event, for some places.
Climate change is also making extreme rain more frequent in some parts of the world. So, what was a 1-in-1000 year event in a past climate may now be a 1-in-100 year event, for some places.
You can find more details about this historic rain and flooding event in this @weatherzone article: weatherzone.com.au/news/how-rare-…
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