A WET SHIFT FOR WA CONTINUES TO STRENGTHEN IN MODELLING

Not much change in the overall trends for rainfall to become widespread over southern and western WA from Sunday with a strong cold front introducing an unstable and gusty westerly flow that will take us through most of next week.


GFS 18z run - 500mb flow pattern at 18000ft above our heads.

Note the fast flow patter that establishes with 2-3 large long waves to pass through during the coming 2 weeks. High pressure becoming hard to find for the southwest of the nation as we move into mid July. So the trend for a wet and windy period is looking probable, in line with the wettest time of the year for this region.

The moisture content looks good for every front that passes through with sizeable rain band likely on each event. The two events of the greatest potential to bring the widespread rainfall through to inland areas include Sunday, next Wednesday and again later next week into the weekend. For example Sunday's front could drop 40mm in some locations along the west and southwest coasts. This could be repeated 2-3 times and there you can already see many areas exceed 100mm of rainfall for the week.


GFS 18z run - Precipitable Water Values for the coming 2 weeks.

Significant moisture running into lifting mechanisms means widespread rainfall with heavy falls for coastal communities. The question will remain, how far north and how far inland does each front bring the rainfall? We will have to take it one system at a time but as you can see there is plenty on the board.

Over the Indian Ocean, there is significant moisture pooling, and today that continues to be the case as the front due in on Sunday starts to move further north and drag in the upper level jet stream helping to transport that moisture south and southeast towards Australia.


Satellite Imagery - Valid Friday 2nd of July 2021.

Note the moisture surging into the fronts sitting well offshore, this helping to bring up the rainfall totals once the fronts arrive, and modelling may have to factor this in to their rainfall forecasts as they are sitting a little bit light for Sunday afternoon for the west coast.

Rainfall from the Euro data set this morning has started to finally pick up on the moisture infeed from the northwest, but not for the lead system, for the third system in the sequence, I do anticipate better rainfall odds with this first feature judging by satellite imagery over the Indian Ocean and will continue to monitor trends.


Euro 12z run - Rainfall for the coming 10 days - Valid Friday 2nd of July 2021.

Note the heavier rainfall shield coming in at the end of the run, I do think that will be replicated for the first system coming in this Sunday and Monday.

Putting it all together, it is all about the rainfall from Sunday so make the most of the fine and warm weather today and tomorrow as things turn wet from Sunday afternoon through next week. I may have to introduce a rainfall chart for northern areas later today based off the model guidance.


Rainfall for the coming 10 days - Valid Friday 2nd of July 2021.

Need more tailored weather information? Email me at karllijnders@weathermatters.org for more information.



14 views0 comments