The weather is set to turn more dynamic as we head into September. Lets take a look

Rainfall Outlook for September 2021

% chance of exceeding the median September Rainfall for 2021

Humidity has already started to increase over the northern tropics heralding a warmer period of weather and a chance of an early build up for the northern tropics. The moisture is expected to be drawn from the north and northwest through September with troughs moving out of the west of the nation and running into the moisture, lifting it into showers and thunderstorms. Now the rainfall over inland areas is deceiving, with a lot of green and blue on the board but it does not take much for inland areas to see above average rainfall, including the coastal areas of the NT and QLD. The east coast will still see seasonal conditions develop after a drier August. That humidity will increase for the east coast during the month of September, but the rule will be, wetter as we go through the month of September with the Indian Ocean the may driver for rainfall opportunity for the month of September.

Temperature Outlook for September 2021

% chance of exceeding the median temperatures September 2021

A much warmer month expected over northern Australia which is in line with the early onset of humidity and build up conditions throughout the month. We have seen that humidity increase in recent weeks with temperatures well above average. That should continue for northern areas, and will drift south at times during the month. The increasing rainfall chances for the second half of the month will offset the warmer bursts to kick off September for southern areas, and increasing rainfall and cloudiness will keep a lid on day time temperatures. It doesn't mean it will be cold! It will mean there are more wet and cloudy weather for the month than not. I will review this again in a fortnight.

The main driver for this month is the Indian Ocean Dipole which is expected to bring in large scale moisture pouring in from the northwest and north of the nation, coupled with the moisture in the trade winds over the east, it will be getting wetter as we go through the coming few weeks, with already some evidence of that playing out in the medium term modelling which I covered off this morning. The weather is expected to turn more humid over the north and this will come south through inland areas, if troughs develop during the coming month, then thunderstorm outbreaks may kick off an early storm season for QLD. Higher chances of rainfall more west of the divide at this time through QLD which could bring some relief for many throughout the region.

The risk of La Nina is increasing a bit in the latest data sets, with some global agencies pushing the risk up to 70% while the Australian data is unchanged, but areas along the east coast and indeed right through the region need to pay attention to forecasts in the coming 4-6 weeks which could see plenty of changes to the forecasts, with a stronger wetter signal developing.

I will have a look at the latest La Nina risk coming up on Tuesday to see where we stand moving through Summer.

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