It has been a very difficult time for forecasters making sense of what has been an unusual season which has bucked all the climate guidance (which is not uncommon for this time of year as most outlooks between July and September is of low confidence nationally), we have seen anomalous rainfall events in the past few weeks and below average temperatures for large chunks of the north where these areas were forecast to be drier and warmer under the climate drivers.
But with weather, it does not fit into a one size fits all box. This means the forecasts need to be agile (hence why I update them so often).
So, let's have a look at the guide for the remainder of the season to see where we stand.
FORECAST VIDEO - REMAINDER OF WINTER 2022 - ISSUED TUESDAY 19TH JULY 2022
REMAINDER OF WINTER (NEXT 6 WEEKS BUT THAT TAKES US TO THE END OF AUGUST)
%Chance of exceeding or not exceeding the median rainfall for the remainder of Winter 2022
The blip in conditions which has seen a wave of above average rainfall through northern and eastern areas of the nation and a wave of below average rainfall across the south and west of the nation about two weeks ago is being repeated again - does that mean that the blip is actually a trend we see in a time of prolonged La Nina? Something to talk about at another time. This weather has been in response to a very anomalous pattern that these models DO NOT see! Once we see the blocking pattern resolve once again over the next week, conditions will likely resume more seasonal values across the nation once we see a broad westerly flow develop, that is determined by the SAM tending more neutral to negative. This will start to be evident in the next week and at this time, the models are suggesting that it is likely the more traditional westerly wind regime will take over the nation and this then allows the influence from the Indian Ocean Dipole to return to the nation's northwest, central and southeastern areas of the country. So, on the current guidance (reviewing all the international data and local data sets over the past week) the wetter as we go through Winter remains the right call. Remember we are now on the downward slide to Spring, a long way to go through the season in terms of weather, and so further volatility in the forecast packages should be expected.
SOUTHEAST AUSTRALIA - FOOD BOWL
The southeast starting to see rainfall return through the coming week or two after we lose the blocking pattern over the east. That may still trigger widespread above average rainfall along the east coast in the coming 2 weeks but that starts to ease as the winds tend westerly through the end of July. As we move into August, the frontal weather looks to become more aggressive according to modelling with the wild card in the mix to increase rainfall totals, the Indian Ocean Influence. There is evidence that may start to take place in August but the other region of influence that created the huge rainfall over QLD is the warmer than normal waters north of the nation, which could also trigger larger rainfall events over QLD and into NSW through August as well ahead of the Indian Ocean influence peaks through Spring. Onshore winds over the east will provide showers, heavier than usual thanks to the warmer than normal waters there. Overall, the interior looks seasonal, but could easily swing wetter if rainfall sweeps southwards from QLD into NSW and becoming more seasonal over the southern parts of NSW and into VIC and SA throughout the remainder of August
There is still a drier bias over the coming week for areas that should record regular rainfall, and this looks unlikely to be overcome on the current guidance from the modelling so a weaker drier bias is the right call for southern and eastern VIC, southern SA and extending back into WA where some areas could see 50mm below what you would normally experience. The rainfall will return through the south of the nation, but the intensity is all dependent on the peak of the long wave trough through southern Australia and how much moisture is drawn into each of those systems. There is a lot of moisture sitting back over the Indian Ocean, dammed by the upper ridge over the eastern basin, it will be released into the jet stream at some stage, but more likely into August. Then a wetter Spring is still on the cards, and we are seeing that dam wall breaks with frontal weather approaching WA in the short term, that should play out further east into August.
A good chance of above average rainfall developing through this period as we see the door opening to widespread moisture surging south into frontal weather moving through the agricultural areas of the southwest inland. The frequency of fronts won't be above the average, the moisture associated with frontal is above the average and that will lead to more robust rainfall events. The moisture should start to pick up over parts of the outback as the moisture is allowed to surge more freely through the interior and into frontal weather passing through southern Australia.
A signal for above average rainfall continues for northern Australia with that related to the higher-than-normal SSTs surrounding northern WA, the Top End and Northern QLD. Values have come down in recent weeks with the persistent easterly flow but offshore, waters are warming still, slowly, which at this time of year is always a cause for concern for those wanting the dry season conditions to persist well into September. That looks unlikely this year and I do think we see moisture and rainfall chances coming up for the second half of August with the risk of 1 rain event before then sweeping through the region via an upper trough dragging moisture southwards over the region, similar to what we observed back in late June and early July.
The above average rainfall signals continue for the eastern parts of QLD and extends into the southern interior, that is connected to the anomalous weather conditions in the next 5 days and really, it sends most of the guidance above the average. Beyond that event, the persistence of easterly winds is expected to continue with coastal areas south from Mackay to the NSW looking to get further above average rainfall chances through what should be the dry season. The rest of the interior may start to see elevated rainfall throughout the second half of August with the jet stream spreading the moisture in from the northwest through to the southeast with the higher chance of rainfall then evolving on and west of the divide and that will be a theme into Spring creating the very soggy signals for harvest.
TEMPERATURES - REMAINDER OF WINTER NEXT 6 WEEKS BUT THAT TAKES US TO THE END OF AUGUST)
%Chance of exceeding or not exceeding the median temperatures for the remainder of Winter 2022
The cooler bias is beginning to ease over the northern areas of the nation and there is the expectation now that we have the coolest and driest part of the dry season up north, that conditions will begin to warm up and become more humid and the heat engine should also crank into gear. If the heat engine cranks quicker than forecast, this will lift the instability values ahead of systems ahead of frontal weather passing in from west to east. Some chance of cooler than normal weather continuing into the SWLD of the nation thanks to persistent cloud cover and frontal weather, but it is marginally cooler and that signal also exists along the east coast of QLD. Most areas should be near seasonal.
SOUTHEASTERN AUSTRALIA - FOOD BOWL
Generally seasonal weather conditions are forecast to continue for the Food Bowl. We could see some periods of above average temperatures and below average temperatures but overall, coming out seasonal. Note that the current pattern of easterly winds, while wet and cooler, overridden the cold freezing nights of last week and below average day time temperatures. So that fluctuation to continue. The westerly wind belt is forecast to increase its influence with warm northerly periods during August and as the heat engine continues to crank into gear, some warmer periods ahead of more general rainfall will be a feature through August.
Generally seasonal values for the southern states with the warmer air developing over the northern parts of the country being drawn south and southeast with frontal weather spreading from west to east. So periods of warmer days ahead of fronts and cooler periods under rainfall and westerly wind patterns. So very much seasonal weather.
The cooler bias continues for the west with the chance of widespread cloud cover, more frequent frontal weather and windy periods to see the overall temperatures come in about 0.5-1.5C below normal. The moisture via the Indian Ocean could also strengthen the cooler bias if it is allowed to pass through the jet stream and into frontal weather. Overall, the cooler signal has verified of late for the west and that remains unchanged with this current outlook.
Warmer weather is starting to emerge through the weeks ahead as the heat engine starts to wake up thanks to the elevated SSTs developing offshore the northern states. The warmer weather will then extend to the deserts across northern Australia. The hotter it gets and the quicker it gets hotter, the more instability to deal with at the end of August with buildup conditions developing early.
Seeing some of that warmer air developing over the northwest parts of the nation beginning to be transported south and southeast through the nation ahead of frontal weather, at this stage, in the absence of blocking high pressure, the weather should tend warmer than normal over the inland with the warmer air starting to become a feature for the back half of August. The east coast remains near seasonal for now but that is conditional upon the easterly winds not being dominant. The warmer it gets, the more volatile the weather will become through the remainder of August.
More information can be found in the video, and I will have more details on this tomorrow morning for each of the drivers and their potential impacts on the nation moving forward.
Refer to the video for further information on the latest data sets for the remainder of Winter
Remember to check back in on the short- and medium-term forecasts. It is imperative that you utlise that rather than looking for unrealistic forecast expectations for longer range forecasts,