COLD AND SHOWERY THROUGH THE SOUTHWEST - BUT A MORE WIDESPREAD RAINFALL EVENT LURKS ON SUNDAY.

A cold and blustery change moving through the southwest this morning with a wet start to the day for many over coastal areas of the SWLD. Light and drizzly rainfall will make it through to inland areas today, but probably not as heavy as what was being modelled last night for inland areas.


Showers will continue today with a gusty west to southwesterly flow in the wake of the cold front, will keep the light to moderate showers going over the southwest coastal areas.


The front itself, likely to collapse the further east it travels at it encounters drier air and the upper high that is over SA. So rainfall for the coast east of Esperance likely to be light and patchy, less than 5mm.


Rainfall for the coming 36hrs - Valid Tuesday 29th of June 2021.

Front has not been as vigorous as forecast with rainfall a little less than forecast by most models, so I have brought the rainfall down even though some models have higher falls than this.

Following this front high pressure moves in for the remainder of the week, with only a glancing front coming through the southern coastal areas during Thursday bringing a few light showers as that passes onto the east, where the bulk of the wet weather should be.


GFS 12z run - Surface pressure pattern with precipitation for the coming 4 days.

High pressure moves in from the west with clearing conditions from Wednesday through to Saturday. Note a front that eventually brings a cold outbreak to the southeast of the nation may bring showers to the south coastal areas during Thursday afternoon. Then the next major wave arrives on Sunday.

GFS 12z run - Surface pressure pattern with precipitation for Sunday through early next week.

A major change does develop for the southwest and west coastal areas. This next system may also interact with moisture from the Indian Ocean, seeing another large cloud band develop with more widespread inland rainfall forming. Models not handling the scope of this system well, due to the nature of the weather over the east moving slowly, so it will come down to whether the door will be opened up enough to allow the system to come through at peak strength, or whether the system is slower and moves through in a weakening phase. That becomes clearer by Friday as better data is established around the weather systems around Australia as they will be occurring in real time.

Lets look at the Euro model to compare the weekend system against the GFS,


Euro 12z run - Surface pressure pattern with precipitation for the next 10 days

Note the similarities in the timing of the system moving in from Sunday. The depth of moisture over the Indian Ocean is also similar. The system moves through at the same speed, it is the placement of the low pressure system off the southwest which is different and that will determine the heavier falls and severe weather potential for the southwest coastal areas. Note both models do continue the follow up rainfall signals with more fronts to develop after this.

Rainfall data from the models


GFS Rainfall - Next 16 days - Valid 18z Tuesday 29th of June 2021.

Supporting the onslaught of fronts during next week and that pattern continuing, I think it is too light on with rainfall through the inland areas connected to the Indian Ocean moisture supply so numbers will increase for inland areas of southern and central WA.

Euro Rainfall - Next 10 days - Valid 12z Tuesday 29th of June 2021.

More aggressive with the lead system coming in on Sunday contrasting that with GFS and note the moisture sitting offshore over the Indian Ocean. Likely that will be pulled into the cold fronts at some stage next week.

KMA Rainfall - Next 12 days - Valid 12z Tuesday 29th of June 2021.

This model has picked most of the cloud bands ahead of time with again showing the influence of the jet stream ahead of fronts dragging the moisture south and east into the fast flow pattern over southern Australia. That makes sense to me based off what we have seen so far this season.

So it may be easing over the coming days, but a reminder today there is a high risk to stock through the south of the state which will ease by tomorrow.


Farmers and Graziers Forecast for Tuesday. Conditions ease later today.

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