Strong signals for a wetter and colder June out west with persistent moisture building in the Indian Ocean being slung east.
A cooler than normal June over the southeast with persistent onshore southwest winds with ridging likely.
Drier over the QLD and NSW coasts with a westerly wind regime to persist for the month and ridging.
Heat levels will come down over northern Australia with perhaps a few dry season sprinkles.
June Temperature Outlook - % chance of exceeding the median June temperatures. Valid Friday May 28th 2021.
June Rainfall Outlook - % chance of exceeding the median June rainfall. Valid Friday May 28th 2021.
ENSO - Neutral
Indian Ocean - Neutral
Southern Annular Mode - Negative
Little movement in the signals coming from climate modelling. The drivers are essentially in neutral phase and likely to remain there for the coming month at least, especially the Indian Ocean Dipole and the ENSO. They will have little impact on rainfall for now across Australia and little impact on Temperatures.
The Southern Annular Mode is remaining negative for the last week of May as picked up a fortnight ago. We are seeing in response to that, major cold fronts on either side of the nation, with NZ being pummeled this weekend and the west of the nation experiencing more above average rainfall. The SAM should trend back towards neutral by this time next week, but some members do keep the SAM negative into June.
It must be said that the SAM is very tricky to forecast ahead of time, and so we have to continue to monitor this twice to three times weekly and then correlate that with the weather across our latitudes.
The SAM will oscillate through periods of negative and positive through winter, however this is the largest negative spike we have seen all year so we will see how that continues to impact the weather over the next week.
Southern Annular Mode - Two Week lead forecast showing the negative trend turning positive, but this transition may be a little bit more drawn out. When the SAM is negative, more rainfall is expected over southern parts of the nation and drier weather over eastern Australia.
The Indian Ocean currently remains at neutral values, with no warming or cooling bias in place. The moisture that is emanating out of the Indian Ocean out of a tropical disturbance well west of Indonesia, feeding the jet stream and dragging down into the northwest of Australia. Some locations could see a few months worth of rainfall over the coming week, leading into June with that moisture plume advancing towards the coast.
For the remainder of the nation, that moisture will only provide beneficial rainfall to northern and western parts of the nation, with some chance of light dry season rainfall over the NT and WA with large scale cloudbands. The risk remains low at this time, but next week will be telling as we kick start to the month in terms of how much of an impact that cloud has on temperatures throughout the month.
The Indian Ocean will have little influence on rainfall for southern and eastern Australia during June, with cold fronts within the westerly wind belt the main source of rainfall for southern Australia. That will leave eastern QLD and NSW relatively drier with a prevailing westerly wind regime and persistent ridging in place.
The Indian Ocean is still anticipated to trend negative through winter and spring by some of the climate models, but they are diverging in the time that this takes place. The BoM model wants to bring that negative pulse through mid winter where the impact wouldn't be as acute. The Euro and CanSIPS models have the negative phase more pronounced and prolonged later winter into spring which would be more beneficial for widespread rainfall through the back half of winter into spring, and also lead to average and below average temperatures. So something to watch for sure moving through June to see if these trends continue to strengthen and converge.
Indian Ocean Dipole Forecast - POAMA BoM Model for the remainder of the year. Warm neutral to negative phase would bring up rainfall chances for the remainder of the year.
Other global models have a negative IOD for the later part of winter into spring 2021. This would be better for rainfall lovers and those wanting the spring rainfall to be more productive this year. It would bring better rainfall odds to parts of SA, QLD, NSW, VIC and TAS. It could also invigorate an early season ignition for northern season rainfall too.
September IOD model spread.
October IOD model spread.
The ENSO (Pacific Ocean) region is expected to remain neutral for the remainder of 2021, that is the general consensus. However some of the longer term seasonal trends are shifting cooler and bringing up the chance of another La Nina developing during the later spring into summer.
The signals are mixed at the moment. I would not be shocked at a double La Nina which have occurred after a prolonged period of El Nino. Just be aware that a significant warming trend and an El Nino would be likely to follow next year if this was the case as a response to a double La Nina occurring.
Once again, I am not convinced of a La Nina but would not be shocked. But I will have more to say on this when the new numbers come out in the next fortnight.
ENSO Lead Seasonal Forecast - Remainder of 2021.
Some of the more reliable climate modelling agencies are tipping the balance back to a La Nina through the latter part of the year. Something to watch.
ENSEMBLE DATA ANALYSIS
The more reliable Euro ensemble has been correct on the wet May over WA and a drier trend over interior parts of the nation with the colder nights and days over much of eastern Australia. It continues with that trend into June and I am going to align with that based upon the coming 2 weeks of deterministic data. So confidence is rather high for that to verify to a good degree during June.
Euro Rainfall anomalies for June 2021.
Shows that strong bias early in the month and then again later in the month off the NW coast of Australia and that moisture running down through the southern and central inland of WA into western NT and SA. The west coast was wet this month and it verified where GFS was drier and that did not verify. East coast seeing a winter dry out which is very normal when the SAM is a negative phase and ridging then takes place over this region more often than not. So perhaps the dry spell that the east coast has been crying out for is coming. Mixed odds for rainfall west of the divide through the east, so lower confidence on rainfall numbers and whether we reach average totals here. And possibly some dry season rainfall for the NT and WA.
GFS Ensemble June Rainfall Anomalies - June 2021.
Like Euro, has the stronger signals for rainfall over the west and offshore the west coast. Probably a bit too dry across the nation as a whole and over the southwest of the nation, based off what the synoptic scale is looking like for next week. I think the values are way to dry for southern Australia as well with more frontal weather being analysed by this same model, bringing excessive rainfall to WA through to the southeast into June. I reckon that dry signal for the east coast is also fair under current guidance.
GFS Rainfall for the first week of June.
Heavy rainfall over the southwest does not line up with the climate outlook so in that case I throw that out. But for east and south, there could be a few more drier weeks on the way as the driver sort themselves out, particularly the Indian Ocean.
Euro Temperature anomalies for June 2021.
The warm bias is high chance of coming off over northern Australia in the absence of thick cloud cover developing from the moisture spreading through the jet stream. Also warmer through QLD with a prevailing westerly wind regime and with cold fronts at this time, sliding east rather than surging north. Cooler than normal weather for southeast and west with the frontal weather rolling through the west and cooler in the southeast with persisting southwest winds near ridging high pressure stuck in the BIght. So more gloomy days are on the way, not wet days for the east. More gloomy days, but not overcast for the west, with more rainfall.
GFS Temperature anomalies for June 2021.
Similar look for June as per the Euro. Probably more ridging in the east with onshore southwesterly winds and dry air for the southeast inland leading to colder cloudy days and more overnight frosty weather for the southeast inland regions away from the coast. Warmer weather over the north and west, that is probably not as likely, given the amount of moisture likely to spill over the nation in the form of thick cloud and potential patchy rainfall over the outback, which we are seeing right at this moment.
All it takes is a cloud band to move across northern Australia for a number of days and temperatures can plummet to 10-15C below normal for a few days, meaning that this can lop a few degrees off the monthly average. So something to watch as we go through early next week.
June 3rd 2021 - Temperature anomalies.
June 4th 2021 - Temperature anomalies
So no real change to the rainfall or temperature signals from the climate data and the next major update from all modelling will be during the second week of June for the next 4-6 weeks and seasonal outlooks.
Winter Temperature Outlook 2021.
Winter Rainfall Outlook - 2021.
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