Re: La ~ Nina and her effect on the Australian storm season / General weather

La Nina rainfall my my local area

As suggested, I would need to compare other La Nina's for my local area to see what has happened. I have managed to locate old rainfall data going back to 1950 for the Collins Street Weather Station at Seven Hills. Data started here on 1 January 1950. There is nothing before that. I have used that to compile some rainfall for the period September to March but only for the known La Nina years since 1950 that I am aware of. Prior to that, I cannot find anything.

However the Prospect Weather Station has rainfall records going back to January 1877. I found some rainfall records for the 1917/18 La Nina period as well for that station.

I also found daily temperature records for Prospect going back to about 1976.

I cannot find records of the number of thunderstorms.

I have presented 3 tables. One is for rainfall during La Nina periods September to March for my nearest weather station since 1950 being Collins Street, Seven Hills. This is for the La Nina's that I am aware of. One is for rainfall for the La Nina periods of 1910 and 1916/18 from the Prospect Weather Station. There appears to have been a La Nina around about 1917/18 and the third one is for the number of 30C days for the La Nina years 1983/84, 1989/90 as well as the most recent ones. I have used the Prospect station for this so there are minor variations.

I have discovered that a dry January and February has occurred before during a La Nina year for Blacktown (January and February 1965). I have discovered that La Nina's can bring very wet summers but also drier summers (The comparison of the wet summer of 1955/56 to the dry summer of 1964/65 is amazing). It appears on the whole that a La Nina does bring a wetter spring / summer period overall but occasionally, it can be drier. So far the rainfall for this La Nina 2010/11 is much lower than that of recent and previous La Nina's (September to March period).

When comparing the number of 30C days during La Nina periods (September to March) at least from 1983/84, there seems to be a reduction in number of very hot days although I have found that it reached 42C on 3/1/1990. It reached 40C three times this summer just gone at Blacktown.

It seems that this summer 2010/2011 for Blacktown has been quite reasonable and not too wet.

I found the data from the Bureau of Meteorology site "Water and the Land" in climate data. The tables referred to are provided below.

Harley Pearman

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