(The Guardian) Rain, rain go away – please
We’ve all heard about a “threepeat” La Niña and many of us have got used to Indian Ocean dipoles* lifting the odds of above-average rainfall for most of Australia.
In the next week and more, we’ll see those odds being realised in the form of another bout of rain in the east. Swollen rivers across the eastern states are going to swell a bit more – with flooding likely in some areas.
Near Sydney, Warragamba Dam, easily the biggest in the city’s system, has started to spill again, as will most of the other dams. Whether that triggers flooding again in the benighted Hawkesbury-Nepean Valley seems a little unlikely on current forecasts. Still, Richmond on the Hawkesbury section of the river has a BoM prediction of 30mm or so for both Saturday and Sunday, so there will be some damp spells ahead.
As we noted the other day, September itself was another relatively wet month.
The average rainfall of 33.62mm across the country was less than September in 2010 and 2016, but before that you have to go back to 1917 to find a wetter September.
All that moisture in the soil and the cloud cover tends to moderate temperatures, as we saw last month....
But there was quite a difference between days and nights, with maximums relatively cool (even cold) in parts of the country. Minimums, though, were typically warmer than average. Global heating, of course, nudges the background temperatures higher so the chances of unusual warmth, versus historical levels, continue to climb.
*The Indian Ocean dipole measures how sea-surface temperatures on the west and eastern parts of the ocean basin compare with each other. The current spell is in its “negative phase”, with the east relatively warm, increasing the odds of more convection and north-west cloud bands forming, channeling more rain toward the nation’s south-east.
We’ve all heard about a “threepeat” La Niña and many of us have got used to Indian Ocean dipoles* lifting the odds of above-average rainfall for most of Australia.
In the next week and more, we’ll see those odds being realised in the form of another bout of rain in the east. Swollen rivers across the eastern states are going to swell a bit more – with flooding likely in some areas.
Near Sydney, Warragamba Dam, easily the biggest in the city’s system, has started to spill again, as will most of the other dams. Whether that triggers flooding again in the benighted Hawkesbury-Nepean Valley seems a little unlikely on current forecasts. Still, Richmond on the Hawkesbury section of the river has a BoM prediction of 30mm or so for both Saturday and Sunday, so there will be some damp spells ahead.
As we noted the other day, September itself was another relatively wet month.
The average rainfall of 33.62mm across the country was less than September in 2010 and 2016, but before that you have to go back to 1917 to find a wetter September.
All that moisture in the soil and the cloud cover tends to moderate temperatures, as we saw last month....
But there was quite a difference between days and nights, with maximums relatively cool (even cold) in parts of the country. Minimums, though, were typically warmer than average. Global heating, of course, nudges the background temperatures higher so the chances of unusual warmth, versus historical levels, continue to climb.
*The Indian Ocean dipole measures how sea-surface temperatures on the west and eastern parts of the ocean basin compare with each other. The current spell is in its “negative phase”, with the east relatively warm, increasing the odds of more convection and north-west cloud bands forming, channeling more rain toward the nation’s south-east.
