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Driest 12 months on record for big chunk of WA

Source Weatherzone Tue 07 May 2024

If you're wondering why the long overdue rain that fell in parched southwest WA last week was so welcome, take a look at the chart below. The chart shows rainfall deficiencies Australia-wide in the 12 months from the beginning of May 2023 to the end of April 2024. Source: BoM. As you can see, small parts of NSW, SA, and Vic all experienced serious deficiencies or worse, while a significant portion of Tasmania – including the area in the southeast around Hobart – was also very dry. But the eye is immediately drawn to Western Australia, where a huge area of the state's west endured significant rainfall deficiencies over the last 12 months. The BoM issued its monthly drought statement this week, and rainfall was again below average for western, southern and central parts of Australia in April. One of the charts that illustrates the ongoing situation in the west is the soil moisture map. When you see that some areas have seen the lowest soil moisture on record, it explains why even hardy native species like WA’s iconic Jarrah trees have begun to die off in some areas. Source: BoM. The next chart below shows the WA rain that fell in the week up to May 6, which included the heaviest May falls in 82 years in the town of Wandering, about 120 km southeast of Perth. As mentioned, that rainfall event was welcomed by locals but much more will be needed over the traditionally wet winter period. Source: BoM. Here's one more chart that should give reason for hope for residents of the southwest. It shows sea surface temperature anomalies in the waters off the coast. Source: BoM. With warmer than usual waters, there's a greater chance of storms and heavy downpours when moisture-laden winter cold fronts start sweeping northward from southern waters. The positive IOD isn't all bad news for the southwest either. While it tends to point towards a drier winter (and worse snow season) for the southeast, the southwest can see more rain than average.   Image: How the positive IOD affects rainfall in Australia. - Weatherzone © Weatherzone 2024