It’s been dry the last few weeks, which is typical for this time of year. Ongoing dry would rapidly increase bushfire risks…but the good news (as I’ve been, likely boringly, saying for a long time) is that wetter weather is on its way…eventually.
We need roughly 4 things to come together to get that ongoing wetter weather – so below is a summary of where they are sitting, and where they are heading:
To our west, The Indian Ocean – and it’s behaviour, called the Indian Ocean Dipole, or IOD . A negative IOD means warmer waters close to NW WA, and that typically brings above average spring rainfall to most of the eastern two thirds of Australia and to south-east Western Australia. The current forecast from the BoM:
…looking pretty good – nothing too extreme (a much stronger negative event in 2011 gave the big Queensland floods) but sitting in the negative, and likely to be there until early next year.
To our east – the massive Pacific Ocean, the largest climate influencer in the world (El Nino / La Nina). For a higher chance of rain we need a La Nina – cooler towards South America and warmer towards us. Here’s how that one is looking today:
Looking pretty good I reckon. A La Nina was declared by the BoM earlier in the week. Even better – the atmosphere has recognised what the ocean is doing and has coupled:
…No point have a La Nina in the ocean if the atmosphere doesn’t respond to it. And below us – we look south towards the flow around the South Pole. Negative means drier for us, positive wetter. Right now it’s looking like this:
Trying to make sense of that one? The surface is at the bottom of the graph. You can see the negatives from mid August through until now…and that ties in nicely with the drier weather. The good news – it’s looking a lot less negative moving forwards.
The fourth thing – we also need some luck…all the drivers do is weight the dice…we still need that dice to roll in our favour – and with every driver pointing towards wetter there is every chance that we’ll see that happen.
The latest weekly outlooks from CFSv2 reflect this. Here’s the forecast for this week coming – wet weather moving in to our south and west:
…Skip a few weeks ahead and look at the forecast:
The latest 46 day ECMWF forecast also reflects this. Check out this animation showing total forecast rain across our region over the next 6 weeks:
Don’t take the figures literally – this is an average of multiple model runs and is only intended to give an indication…but what it does show is the rain potential day after day right through the run…we’re not just looking at one potential event – instead what we’re likely to see is the increasing chance of rain week by week.
All of this is just words – and luck will still, as always, play a decent part in what happens, but the signs are as good as they can be. As we get closer to individual rain events I’ll post again with more information on what we’re likely to see.
Images: Bello Weather / Meteologix / Stratobserve / Tropical Tidbits BoM – many thanks to all of these sites.