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

February weather conditions for Blacktown 2011

February 2011 was unusually dry and warmer than normal. The weather conditions for February is in stark contrast to what the models were suggesting and is in stark contrast to that experienced in recent years. Blacktown has had a run of wet February's but February 2011 saw the second driest February I have seen since 1998 with just 14.8 mm of rain falling on 3 days. When looking at rainfall for January and February 2011, just 52.8 mm has fallen. The mean for the period is 215.2 mm and the median for the period is 174.7 mm at the nearby Collins Street weather station.

It seems that this La Nina episode has disturbed our January and February normal rainfall patterns in which it has been drier than normal. This is unexpected considering that many other regions are experiencing heavier than normal rainfall.

While I was out of Sydney for 7 days during the month, I am only aware of one thunderstorm occurring being the 28/2/11. This was not significant in nature and only 1 mm of rain fell where I live.

It reached 30C on 13 days taking the total number to 50 days so far for the season till 28/2/11. The average maximum temperature for the month at Blacktown was 30.2C which was above average. The average minimum temperature was 19.4C which was also above average. The start of March has been warm with the maximum temperature reaching 30C on 3 out of 4 days. It has reached 30C on 53 days at Blacktown to 4/3/11.

On a monthly basis, the number of thunderstorms show no trends but for the season, it is becoming apparent that the number of thunderstorms is much less. I have counted just 14 thunderstorms on 10 days with many of these being minor in nature and having little impact. 

It seems that when comparing the La Nina of 2007/2008 and 1998/1999 to that of 2010/2011, they seem to be all different with different weather conditions and different impacts. For example, I expected a wet February but instead a dry February occurred. The February of 1999 and 2008 (La Nina years) were wet in comparison.
 
The table for February is provided below.

Harley Pearman

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