INDIAN OCEAN INFLUENCE - WINTER 2022

The Indian Ocean is expected to influence the rainfall and temperature spread through the nation with many global agencies supporting a wetter phase developing, but not necessarily a cooler phase for Winter 2022.


The key to the Winter turning wetter is the aggressive pace as to how the Indian Ocean warms and we will start to get clues as to how aggressive that will be by mid May.


There is plenty of warmer water through the Indian Ocean and this is expected to increase looking at the latest data sets coming through, BUT, as we have seen in recent years, this has not always translated out in real time observation.


With that said, lets look at the latest forecast information and data sets and go from there, setting the base for what we may expect this Winter.


FORECAST

Indian Ocean Dipole Forecast - Curated Forecast - Mid April Spread.

The forecast for the Indian Ocean Dipole is to turn sharply negative through the second half of Winter with the event likely to peak during Spring. The impacts of the IOD will be felt during Spring more than Winter, however, this does not mean inland areas will not see above average rainfall and temperatures through tropical and northwest Australia will not remain elevated as a result. But the weather will certainly tend wetter as we go through Winter from July onwards through SA and into the eastern states. Spring looks very wet at this time, but the confidence on specifics for one given point is so low. But the trends, and this is what this forecast is about, is showing a trend towards another negative IOD. Can it change? Sure can and we have seen that happen in a heartbeat. So be aware that forecasts can move around quickly in this region.


June to August 2022

The Indian Ocean Dipole is forecast to shift warmer through June and more likely through July, when the impacts of the IOD is felt across the nation.

Above average temperatures over northern Australia with the chance of rainfall higher than normal (may be a poor dry season for the north.

Across the southern and eastern areas of the nation, we should see above average rainfall in most (not all) districts from southern WA through southern and eastern SA and into VIC and NSW (mainly over inland areas). This is likely to become more of a feature as we move into August.

August to October 2022

The data sets coming through in the past few days have strengthened the signal for a negative IOD for the Spring 2022. This would lead to above average temperatures and humidity values over northern Australia. The early onset of wet season rainfall/build up very much likely after a disrupted dry season.

Above average rainfall and cooler than normal weather for large parts of southern, central and eastern inland portions of the nation would be unfolding during this period on the current guidance. Note that this forecast will tighten and will likely soften a little too. But these signals are stronger than last year.


DATA - More information to come in the weeks ahead as this primarily preliminary data and analysis that I have been working on for a week.

MODELLING

International Model Spread - IOD - Tending Negative - June 2022

The BoM model last year went early with the negative phase developing through the Eastern Basin. I am leaning more with the Euro on this one.

International Model Spread - IOD - Tending Negative - July 2022

BoM too aggressive, leaning more with the Euro.

International Model Spread - IOD - Negative - August 2022

The IOD will likely increase in strength from August as per last year which is expected to then be reflected with higher rainfall rates for large parts of the nation and then indeed temperatures over northern Australia will be well above average (as I have been talking about since February when I was back in Darwin talking with the elders up there with their forecasts for the remainder of 2022/23.)

International Model Spread - IOD - Strong Negative - September 2022

I fully expect the IOD to bottom out lower than last year and this event could be more prolonged than last year too as we head into Spring 2022. This could lead to a moderate to major flood risk for areas of southeast and eastern Australia. This is something for the back of your mind and not in the front of your mind just yet, but something to track here every fortnight as we move through the cooler growing season.

SEA SURFACE TEMPERATURES

Euro Sea Surface Temperature Outlook - June through August 2022

Above average sea surface temperatures (something I have been talking about for months now) will clearly have major impacts on rainfall and humidity values throughout the nation. This will start to be observed more from July onwards I suspect.

Euro Sea Surface Temperature Outlook - July through September 2022

The warmer waters look to strengthen and expand near and to the south of Indonesia and extend throughout the classic region where we see extensive cloud bands and rainfall events emerge through the Winter across Australia. But, as per last year, we can have the warmer waters, we need other climate drivers to be in phase (negative SAM etc)

Euro Sea Surface Temperature Outlook - August through October 2022

The peak of the IOD is typically in September through October and the waters reflect that but note how the warmer waters extend way down the west coast of WA. This could send in very wet weather with onshore winds and frontal weather, away from cloud bands from the northwest, so this is an ominous look for a very wet period once again for western, southern and central/eastern inland parts of the nation.

RAINFALL

Euro Rainfall Outlook - June through August 2022

Note the rainfall coverage is excessive for large parts of the nation but looking at the broader data sets, this looks to kick in from July and August I suspect, so the devil is in the detail. Wetter as we go seems to be a good forecast on current data.

Euro Sea Surface Temperature Outlook - July through September 2022

Note the rainfall becomes very much above average for large areas of the nation, with many centres forecast to reach 70-90% values above the norm for this period and I want you to focus on Indonesia and offshore northern Australia which supports the IOD in negative phase, higher rainfall anomalies there signals the phase is rather strong.

Euro Sea Surface Temperature Outlook - August to October 2022

Early onset rainfall, widespread rainfall extending from the northwest as well and widespread rainfall via cold fronts and inland troughs. This is a very wet look at would rival 2016 standards for inland areas. So that is an analogue to consider when looking at this event at this time. But it will likely chop and change.

IRI Rainfall Outlook- June through August 2022

Also supporting a very wet look across the nation with the Indonesian Archipelago looking very wet which supports the negative IOD through Winter, more likely from July onwards.

IRI Rainfall Outlook- July through September 2022

Note the rainfall signals are strengthening for inland areas of QLD, NSW and into VIC and decent rainfall chances for SA through this time. The northwest also seeing early onset rainfall opportunities this next wet season.

TEMPERATURES

Euro Temperature Outlook- June through August 2022

Warmer than average conditions for large parts of the north reflects the above average SSTs through waters north of WA through the NT and into QLD. With the large amounts of moisture, this will lead to more cloudy skies and cooler than average temperatures are possible with the wetter signal for southern and central inland of the nation. Coastal areas would likely see seasonal conditions and warmer nights.

Euro Temperature Outlook- July through September 2022

The cooler signal through Winter and into early Spring indicates the negative IOD phase strengthening with the rainfall rates and frequency increasing as we track into August and September. So once again the higher impacts from the negative IOD phase will be found during the second half of Winter.

Euro Temperature Outlook- July through September 2022

Even stronger signals for classic temperature distribution through the nation. Warmer and more humid over the northern tropics with thick cloud cover for longer duration over central and southeast parts of the nation leading to widespread rainfall and cooler days. Nights will still be warmer generally (not devoid of frost).

IRI Temperature Outlook- June through August 2022

Noting the temperature anomalies running high over northern Australia with the higher moisture content thanks to the elevated SSTs throughout the region. Not seeing huge signals for colder weather developing over inland areas and that could be quite right, given the elevated SSTs across most waters surrounding Australia.

IRI Temperature Outlook- August to September 2022

Once again noting that the IOD phase strengthens through Winter and begins to peak through early Spring and you can see that reflected in the below average temperatures being forecast for this period. That is directly linked to larger rainfall spread.

So that is the general data sources that make most sense and are easy to consume but I will have a broader update on this after ANZAC Day as more data comes in and my rainfall and temperature forecasts for Winter will be refreshed for that update plus a look at Spring 2022 in greater detail too.









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