Welcome to the Climate and Water Outlook for November to January.
A strong El Niño, coupled with other climate influences, mean the north of Australia may
see a delayed start to the wet season rains and fewer tropical cyclones.
In the south, there’s an increased risk of heatwaves and bushfires.
First, let's look at spring so far.
September was the third driest on record for Australia, and these dry conditions extended
into October.
But that hasn’t meant an absence of severe weather.
In mid-October storms and hail hit the southern wheat belt of Western Australia.
Areas with severe long-term rainfall deficiencies now extend across large parts of Queensland,
northern New South Wales, Victoria and into South Australia.
The first weeks of October saw temperatures up to 12 degrees above average, with early-season
records at a third of our reference stations.
This set the stage for one of our hottest Octobers on record, further drying crops and
other vegetation.
Tasmania and Victoria both declared total fire bans prior to their usual fire danger
periods, and bushfires have already occurred in all southern States.
Lower-layer soils have also been drier than average, contributing to low rainfall runoff,
and an early end to southern Australia’s water-storage filling season.
As a result, many water storages are now less than half full.
Virtually all of our major storages are now at lower levels than at this time last year.
So what's driving Australia’s climate at the moment?
There are several influences pulling moisture away from Australia:
In the Pacific Ocean, El Niño is still strengthening and remains our strongest since 1997–98.
In the tropical Indian Ocean, a positive dipole has also strengthened, to levels not seen
since 2006–07.
Around the northern coast of Australia, cool ocean temperatures are reinforcing these drying
patterns.
However, one driver has been pushing some moisture towards us: very warm waters in the
sub-tropical Indian Ocean.
So how might this tug-of-war play out over the coming months?
Most international climate models suggest El Niño won’t start to decline until early
2016.
However, the positive Indian Ocean Dipole—and its drying influence—will start to break
down during November.
Each year, winds swing from easterly, as we are seeing now, to westerly, and the dipole
collapses.
This change is linked to the annual movement of the monsoon trough in the tropics.
Likewise, sea surface temperatures to Australia’s north are likely to return to normal by the
end of the year.
While these drying influences may ease, the sub-tropical Indian Ocean is expected to remain
warm, potentially drawing some moisture towards Australia.
But we need to remain on alert for bad fire weather.
Historically, when we have a positive Indian Ocean Dipole before an El Niño summer—as
we have in this year— we’ve seen more fires.
With the drying influences on Australia due to ease, what's the outlook for November to
January?
In several areas, odds favour wetter-than-average conditions for this time of year.
Drier-than-average conditions are expected in the north, due to a later start to the
wet season rains, and in parts of the southeast.
Our rainfall outlook has moderate accuracy at this time of year.
A similar outlook is shown in the US and UK climate models, while the European model suggests
average rainfall.
Turning now to streamflow:
With below-average rainfall and dry soils, our October to December forecasts show low
flows at 98 locations.
Near-median flows are forecast at 13 locations, with high flows more likely at only seven.
Accuracy for our streamflow forecasts is high at this time of year.
In early October we released our Tropical Cyclone outlook.
The Australian region usually has around 11 cyclones each season, of which four cross
our coastline.
El Niño typically reduces cyclone activity in our region, meaning fewer tropical cyclones
than average are expected.
However, at least one cyclone has hit Australia every year since records began.
Turning to temperatures, warmer-than-average days are likely in southern Australia.
Nights are likely to be warmer than average across most of the country.
Accuracy for the temperature outlooks is high at this time of year.
So in summary:
We’ve been dominated by drying influences, but these should ease as we move into summer.
Odds favour above-average rainfall for some inland areas and the seasonally dry southwest,
but drier in the north and southeast.
Low streamflows are likely to continue in many areas, and the risk of bushfires and
heatwaves remains high.
For more details, head to our website at bom.gov.au/climate/ahead
You can also follow us on Facebook and Twitter.
Our next video will be released on Thursday 19 November.
For the Bureau of Meteorology, I’m Andrew Watkins.