CLIMATE UPDATE - JUNE OUTLOOK

Headlines


  • A drier month for many inland regions.

  • A warmer month for many inland regions.

  • Wetter over the southwest and southeast with frontal weather persisting.


We are heading into the first month of winter with a dry and warmth month overall, expected for large parts of inland Australia. For coastal areas, a fast flowing wave pattern is likely to establish as we enter June with the Southern Annular Mode turning negative and thus supporting wetter signals for these regions.


Starting with rainfall.


A drier trend is likely to unfold for many locations away from southern Australia, due to the negative SAM phase. This helps to propel dry air from west to east over inland Australia while frontal weather buffets southern coastal states. With the SAM remaining negative from late May, which will likely bring some good rainfall to some inland areas, the timing of this activity means that a lot of inland Australia will start out drier than normal.


Southern Annular Mode Forecast - Valid May 17th 2021. Note the red line goes negative into late May and into early June. This could be the first big burst of frontal weather for the southern winter season.



With onshore westerly winds expected for southwest WA, that will see days of showers and storms, with frontal weather becoming involved in that flow. Each front bringing bursts of heavy rainfall and strong winds. That seems a reasonable bet going off current signals from modelling, suggesting well above average rainfall for a good part of June.


The persistence in the negative trend in the SAM will keep the rainfall chances up as the frontal weather will expand further north from the Antarctic region, meaning a colder wetter month is more likely than drier and mild.


However for inland areas, the negative SAM has the opposite impact with mild, windy and dry weather to develop with the fast flow pattern.


Mean Sea Level Pressure anomalies for June 2021, shows no real signal of above or below average pressure for this time of year, suggesting a fast flow pattern may be established for a good part of the month over southern Australia with no blocking patterns nearby. Valid May 17th 2021.


The BoM are indicating that the Indian Ocean will go into a negative phase in June, influencing rainfall. I do not believe that will occur, with a neutral phase to continue. However with that said, some chance of tropical moisture being drawn into larger scale frontal weather can still bring rainfall over inland WA and for that reason, I have extended the rainfall chances being above average through that region. It doesn't take much rainfall however to produce above average rainfall.


Indian Ocean Dipole - May 17th 2021. Note, this is the only model suggesting a negative IOD from June onwards where the more reliable Euro has a negative IOD developing during our spring which could see very wet weather for QLD and NSW running into summer.


The east coast will turn dry with the westerly wind regime likely to be in place for a good part of the month. Some areas of western NSW and QLD run the chance of going rainfall free for the month of June on current guidance. But the confidence for these regions is low, in line with the climatic signals also low skill at this time.


The tropics will remain very dry in line with the seasonal shift to dry season. That we have higher confidence in.


June Rainfall Anomalies - Raw Data Euro Ensemble forecast. Valid May 13th 2021.


Rainfall Outlook - June 2021. Weather Matters %chance of exceeding the median rainfall for the month of June. Valid May 17th 2021.

Temperatures


The temperature outlook is largely unchanged from a fortnight ago with relatively mobile weather patterns over southern Australia, allowing cold air to rush in from time to time, into the southeast inland, producing well below average temperatures, even without the presence of higher rainfall.


We have seen this occur throughout May, with severe early season frosts after recording breaking cold mornings in April over inland NSW and QLD.


More of that is likely to occur, especially if cut off low pressure systems develop over the eastern inland, dragging in the colder drier airmass into the region.


However with the SAM going negative, the climatic impacts of this phase is felt more through the cold season, with the frontal weather moving north away from the Antarctic naturally but when the phase is negative, the fronts move further north.


The impact will be colder, wetter and windier weather for southern coastal areas of Australia. But that same windier weather associated with the fronts, brings in drier continental air in the westerly flow, keeping skies clear and sunny. The fohn wind phenomena also lends itself to warmer than normal weather in a general westerly flow lee of the divide in QLD and NSW in these setups.


The cooler than normal weather from mid May - which has been running well below average, will be normalised according to GFS by mid June - suggesting that temperatures will be above average for at least the first half of the month over the east while coming down over in the west with the pattern flip.

The Euro Model also shows the pattern flip from the well above average temperatures for the last week over WA being neutralised by colder weather forming in the burst of westerly winds over southern Australia through June. It may be persistently below average temperature values for southeast NSW and the ACT over the coming weeks.


With the Indian Ocean remaining neutral on my current forecast, little to modest moisture may get involved in some of the frontal passages, bringing patchy rainfall from time to time, but it won't be sufficient at this forecast, to have a large impact on temperatures over eastern and northern Australia.


Increased cloudy weather over southern and western Australia will lead to cooler than normal weather, and with the showery windy weather associated with the active frontal weather through the first week or so of June, it may be enough to keep the month cooler than normal overall.


Graziers should be advised that June could be a difficult month for stock with the increased windy, showery weather likely to unfold later in May and continue into June.


June Temperature Outlook - Valid May 17th 2021. %chance of exceeding median June temperatures.

This is a preliminary forecast for the month of June and major decisions should not be based off these forecasts. This is information as drawn by the models with my weather analysis overlay. The forecast confidence does improve through May and June as the winter season establishes and the climatic drivers that bring winter weather have bigger impact over southern Australia.


The Southern Annular Mode appears to be the major driver for the coming 2-3 weeks which leads into June 2021.


Need more tailored seasonal information with more focus on your region for your farming and agricultural needs? email me at karllijnders@weathermatters.org for more information about how I can help and what I can provide.

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