Unseasonable warmth in WA

By Peter Nelson on May 10, 2017

The first week of this month has seen unseasonably high temperatures for May along the western areas of WA. Last weekend Perth recorded 31 degrees, Geraldton, 34 degrees , and Carnarvon recorded 35.3 degrees . These places had their hottest May temperatures since 2003. It was interesting to note that Perth's rainless Aprils were not followed by high temperatures during the following May in 1920, 1977 and 1982. Perth's very low April rainfall in 1890 was actually followed by a 30 degree temperature in the following May.

Such unseasonable warmth this time of year in WA very often leads to above normal warmth in our regions within the next fortnight and this previously happened in 1907, 1953, 1962,1972, 1978, 1980 and 1991. Three of these 1907, 1962 and 1991 did lead to above normal warmth in June in our regions. Except for 1972 which was a dry year, the other cases had significant rainfalls either in May or June. 

A most interesting feature on the synoptic charts was severe tropical cyclone Donna with the lowest reading of 963 mbs which is extraordinary low for May . There has not been a deeper cyclone than Donna in the South Pacific Ocean in the last 187 years dating back to 1830. There were a few May cyclones in 1916, 1963, 1969, 1989 and 1991 in the South Pacific Ocean but none of these had central pressures lower than 995 mbs. 

I do have an old BOM publication of Hurricanes in the South Pacific dated February 1925 which I got in 1958 and this one lists all the Hurricanes and tropical Storms dating back to 1830 and before that a report of a tropical cyclone in February 1789.

By Peter Nelson on May 10, 2017

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