Are we getting rain this winter?

My title came from a search someone did and ended up at my blog. I’m not sure where “we” lives, but if they live in Perth, on 29 July when they did the search I thought Perth’s rain was over for the winter. I was wrong, but we did have 11 days of no rain from 26 July to 5 August. Temperatures hovered around 20°C and it felt like summer had arrived.

In July rain fell on only 16 days, half a month of no rain when July is Perth’s wettest month. I can’t believe I had to water some of my garden!? It was from the rainwater tank so it’s been replaced since then, but one morning I spent too long watering, missed my bus and had to wait half an hour for the next one. Despite so many fine days we still received 149.6mm of rain, only slightly below July’s average rainfall of 152.9mm. In June we received 20mm above the average, so for the two months rainfall was higher than average.

satellite image of cloud cover 15/08/09 09:30 The past week the rain fell in earnest, with high winds to make for real winter weather. At 9:30 yesterday morning there was quite a bit of cloud cover over Perth, the southwest and the wheatbelt, which has been dumping the downpours on us. Today there were lots of sun showers and fine periods. When I was a kid my family called a sun shower a Monkey’s Picnic. I thought this was what everyone called them. It was only a few years ago that I discovered my family are the only people in the universe who call them that, but I still say Monkey’s Picnic whenever it rains when the sun’s shining.

JR the weatherman chats on RTRfm on Thursday mornings and in the middle of the 11 day summer interlude he said the record for a dry spell in winter was 28 days in 1902. That year had Perth’s warmest and driest August on record. We didn’t quite make the record this year and Perth is far from having rainfall deficiencies this winter, although other places are not faring so well.

For the 24-month period from August 2007 to July 2009, serious to severe rainfall deficiencies remain evident across much of southeast Australia and parts of central Australia. These regions experienced some average to above average rainfall during the final months of both 2007 and 2008, as well as through the most recent autumn. However, most months through the period were drier than the long-term mean, especially during the growing seasons. Both 2007 and 2008 were classified as positive Indian Ocean Dipole (IOD) years, which is likely to have contributed partly to the low winter and spring rainfall recorded across parts of southern Australia during both these years.

Rainfall deficiencies for 24 months from 1 August 2007 to 31 July 2009

The news isn’t so good for very long term rainfall patterns in the southwest of WA and other areas.

Very long-term rainfall deficiencies outside of the drought periods discussed above persist across parts of southern and eastern Australia. Most notably, rainfall has been below average across much of southwest and southeast Australia since 1997, while the Murray-Darling Basin has experienced below average rainfall since 2002.


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