Region enjoys a wet April

May 12, 2017

Benalla recorded its first frost of the season on Wednesday, May3.

This was a little later than normal, but much earlier than last year when the first frost was on May 31.

The latest chart shows severe tropical cyclone Donna approaching the Queensland coast, passing through Vanuatu on the way.

It has deepened to a very low pressure of 963 mbs, which is most unusual for May as no other cyclones have had central pressures lower than this after March in the past 125 years.

In the past tropical cyclones have occurred in May in 1916, 1941, 1948, 1963, 1969, 1989 and 1991 in the South Pacific Ocean and Timor Seas, but none of these had central pressures lower than 985 mbs.

The years of occurrence of past May cyclones listed above were not dry years in north east Victoria.

The sea surface temperatures east of Tasmania right up to the Timor Seas have continued well above normal this week and this no doubt contributed to the very late development of cyclone Donna.

The mean maximum temperature for April was 22°C and the mean minimum temperature was 8°C.

Both these recordings were a small fraction below the long-term normal for April in Benalla.

The rainfall of 71.7mm was 22mm above average.

The highest temperature was 26.6°C on April 7 and the lowest temperature was 24.4°C on April15.

April last year was nearly three degrees higher at 24.8°C and the rainfall much less.

Perth had no rain during last month only for the fourth time for April in 140 years.

The other three occasions were in 1920, 1977 and 1982.

In April of 1890 there was only 1.3mm rainfall in Perth.

Hopefully the rest of this year does not follow the very dry 1982.

But fortunately April 1982 was a dry month in Victoria and NSW, whereas last month was notably very wet at some centres.

It was the wettest April in 138 years of records at Echuca with 136mm rainfall.

For some time I have found a cycle running at 127 years and in view of Perth’s very low rainfall in April of 1890 it does put the rest of this year in line with 1890, which did see rainfalls above average most months from April 1890 to January 1891.

The well-above sea surface temperatures in the Tasman Sea close to Tasmania north up to Byron Bay, which has persisted for a long time since mid December, is one main factor to enhance rainfall in our regions.

— Peter Nelson, retired CSIRO weather officer, Benalla

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