CLIMATE DRIVERS UPDATE - JUNE VALUES AND OUTLOOKS.

INDIAN OCEAN - TENDING NEGATIVE THIS MONTH AND PERSISTS TO DECEMBER.

The main influence on the nation's weather is the Indian Ocean Dipole and the negative phase is expected to be quite drawn out and deep through the latter part of the Winter into Spring with the chance of well above average rainfall spreading through the country via deep moisture in the jet stream from northern and western parts of WA and through to Central Australia, much of SA and into the southeast inland. The peak of the influence from the driver is expected from August through to November before conditions ease in December. Flooding is expected to be a significant issue as we move into Spring across large areas of the country with the highest risk expected to be located through inland QLD and NSW into northeast VIC. As we move into Summer, the IOD traditionally has less impacts on the country as we transition into the northern wet season.

SOUTHERN ANNULAR MODE - TENDING NEGATIVE FOR THE COMING FORTNIGHT.

The other main driver of greatest influence at this time of year is the Southern Annular Mode with the negative phase over the coming 2 weeks expected to fire up those westerly winds over Southern Australia leading to more cold fronts impacting the mainland, moisture being drawn in from the Indian Ocean and this seeing rainfall chances increasing as we move into the second half of June for southern WA through SA and into the southeast inland. The eastern inland could go quite dry for the next 2-3 weeks in the absence of cloud and moisture streaming in via the Indian Ocean along the jet stream. Northern Australia also looks to enjoy some drier air for the next 1-2 weeks before we see another surge of northeasterly winds moving into July. There is the chance the SAM turns back neutral during early July but then it is more likely to shift negative than positive on this current guidance (60%) during July. Negative SAM means more westerly wind dominance across the nation and increases rainfall in Winter over southern Australia but dries out the interior.

ENSO REGION - REMAINING COOL NEUTRAL WITH A REASONABLE CHANCE OF ANOTHER LA NINA DEVELOPING SUMMER 2022/23

The ENSO region is near resolving that La Nina phase with the influence waning for the nation, though noting that the elevated SSTs over northern Australia, especially north of the NT and north and east of QLD are a direct result to the prolonged La Nina and will likely remain in place through the Winter period. This may increase rainfall chances over northern and eastern Australia when upper troughs approach the region. But it is more likely that features heavily in Spring. The ENSO is likely to stay at COOL NEUTRAL for the season but there are signals that it may begin to shift back into weak LA NINA territory through Spring and into Summer increasing the chances of above average rainfall across northern and eastern Australia to the end of the year. If we see this occur, it will be working with the negative IOD, both working hand in hand to produce excessive rainfall and severe weather potential in the form of widespread flooding. With the ENSO at present, we are behind a predictability barrier that happens at this time of year, being a period of natural transition, and better guidance for this driver will become available from mid July onwards.

This will be updated again in 2 weeks, but the signals are largely unchanged for the coming 6 to 9 months.


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