SA - RAIN EASING IN THE WEST. DRY WEEKEND THEN SHOWERS RETURN NEXT WEEK WITH WARMER DAYS.

The weather is tending drier across the northwest today after what has been a wet night for remote northwest SA. The rainfall is set to ease and lift out of the state during today as the high pressure ridge over the Bight builds back over the state. The high will be the driving force for fine weather this weekend and into early next week with warmer northerly winds developing.


A strong cold front is expected to whip through southwest WA and then travel east into the Bight on Monday night and there could be some patchy rainfall crossing the Eucla into the Nullarbor but it could stop short of the Ag Areas, maybe some light rainfall for the Eyre Peninsula.


A cloud band is forecast to develop on Wednesday over the interior of WA ahead of the next front that will see a better chance of rainfall developing across the state. This will likely come through the Ag Areas from Wednesday and linger through the end of the week into next weekend.


Modelling has been all over the shop with how much rainfall one place can expect from one place to the another. So expect that to keep evolving. The forecasts will chop and change and the overall trend right now is for warmer days next week with rainfall developing from west to east through the state from mid next week at this time.


Let's take a look

FORECAST

Rainfall Next 10 Days

Rainfall is forecast to be somewhat confined to the west and northwest tonight as the system that brought the heavy rainfall in WA is weakened by the high pressure system over the Bight. As we move into the weekend it is essentially dry and mostly sunny with warmer days on the way. The northerly flow may bring in some moisture from QLD so most areas dry, warm and partly cloudy with the small chance of an afternoon shower here and there. Next week we will see a larger cold front approach from Monday with patchy rainfall sliding southeast from the state as the front slides away. The next system of note will be a stronger system moving in from the west with a larger band of rain developing as the moisture from the Indian Ocean comes into the frontal passage that should peak closer to the coast. This offers Ag areas a better chance of rainfall mid to late next week with a milder shift, then another strong cold front with showery periods and a colder shift over the next weekend into next week will end the month and kick off June.

I really want to increase rainfall totals further but that would be inappropriate given the poor signals across modelling in terms of consistency. While you will see higher rainfall totals across some of the data sets, for now, 10-20mm is a fair forecast for the Ag Areas, starting from mid next week to the end of the month, but with the higher rainfall totals sitting back in WA, this could and easily change for further heavier falls.

MEDIUM TERM

May 26th-June 10th 2022

Rainfall Anomalies

Rainfall anomalies are forecast to be quite elevated across the northwest of the nation and this spreading southeast via the jet stream in advance of an eastward moving long wave trough south of SA, this taking the wet weather throughout the southeast. Rainfall expectations at seasonal levels most elsewhere.

As we move into Winter, the rainfall should continue to evolve along the jet stream with the higher chance of above average rainfall through the northwest of the nation and extending southeast once again along the jet stream and into the southeast. Some well above average rainfall near the northwest coast of WA is likely. Some showery winds with above average falls for June over Cape York are possible.

Temperature Anomalies

The warm end to the month for the east and north extending to the east coast continue to strengthen on the signals. The colder bias over the northwest a very high chance of occurring under thick cloud and colder westerly winds and rainfall moving through. The amplification of the pattern representing the temperature spread across the nation, which could support severe weather across the country.

The cooler bias following the strong cold front and rainfall event moving through the southern third of the nation will send a large plume of southerly winds through the country during the first week of June, with further rainfall developing out west with another cold front, cooler than average weather continues for the western interior. Warmer weather with elevated humidity looks reasonable over the tropics.

DATA - Refer to the video for more context behind the forecasts and why models are all over the shop from run to run


00Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 2 Weeks

The major weather systems to watch will be out over the west with a few fronts in the coming week, the major rainfall event along the east coast of QLD could produce locally heavy falls and thunderstorms. The high pressure over the southeast dominating the weather across the country with the system determining the influence frontal weather will be having on the nation as we move through the short and medium term. The latest GFS showing more bias for rainfall over the east coast and out west, but this morning it had a freer flowing pattern of rainfall moving from west to east across the country. That in itself shows you that using the broader data sets for forecasting is key. So don't rely on those apps, look at all broader information here to help guide your understanding.

00Z GFS - Precipitable Water Values - Next 2 Weeks

Moisture spread like this morning is largely unchanged compared to this morning, but as mentioned this morning, the placement of low pressure in relationship to that moisture determines where the rainfall evolves and becomes heavy. The higher moisture levels sit over the western parts of the nation and also across the east coast at the moment but I am not so sure on the deeper rainfall event along the east coast just yet and that moisture may end up staying further offshore with ridging holding out on that moisture being lifted into widespread falls. Moisture is still expected to spread across the country from west to east at this time.

00Z GFS - Rainfall Accumulation - Next 10 Days

Refer to the video for more context and analysis

00Z CMC - Rainfall Accumulation - Next 10 Days

Refer to the video for more context and analysis

00Z Euro - Rainfall Accumulation - Next 10 Days

Refer to the video for more context and analysis

00Z GFS - Rainfall Accumulation - Next 2 Weeks

Refer to the video for more context and analysis

A closer look in - make sure you catch the rainfall update tonight to see the broader data sets. They offer more reliable information related to rainfall events and I can assure you this WILL CHANGE from the next run and tomorrow morning again. More clarity on rainfall will be found from Sunday. So, patience is required.

More coming up from 8pm EST with a look at the models and rainfall.

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