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Friday, 1 March 2002
MONTHLY CLIMATE SUMMARY - NSW REGIONAL OFFICE
Monsoon trough adds to February rains in NSW
February rainfall: A dramatic change in the rainfall pattern for February compared with January hints ill-advisedly at an oddness in weather patterns. February rainfall in New South Wales this year was augmented by the rapid development early in the month of a monsoon trough in Australia's tropics. It was a striking contrast to the blocking pattern that minimised the effect of rain-bearing fronts in January.
Rainfall in most districts was generally above average (map 1), but falls in parts of the western and northern districts were close to average for February. Nevertheless, these areas recorded substantial falls towards the end of the month. Districts along the eastern seaboard received decent rain early in the month and again towards the latter part of the month. On 5 February, many Sydney suburbs and coastal regions of the Hunter and Illawarra received their normal February rainfall in just one day. The downpour was preceded by good falls in the first few days of February. In the Sydney basin - the area with the most rainfall for the month - total rainfall was 300-400 millimetres.
Rainfall, summer 2001-02 (December to February): NSW recorded below-average rainfall for summer (map 2). Northern and western borders of the State fared worst, with totals in the lowest 10-30 per cent of all recorded summers. Rainfall was generally below-average in December and January.
February temperatures: Mean maximum temperatures across the State were below average. The coldest regions were in the southern tablelands and south-west slopes and plains (map 3). Mean minimum temperatures were near average overall, with a warmer region in the north-east and cooler regions in the southwest (map 4).
A note about deciles: Deciles are used to give an element (in this case rainfall) a ranking. Deciles are calculated by arranging the totals in ascending order (from lowest to highest), then splitting them into 10 equal groups (thus the groups are called deciles). The first group would be in decile range one, the second group in decile range two, etc, up to the highest annual totals (highest 10 per cent) being in decile range 10. See this website for more information: http://www.bom.gov.au/climate/glossary/deciles.shtml
A note about temperature anomalies: The monthly mean maximum or minimum temperature anomaly is the difference, point by point across the State, of the long-term monthly mean temperature (maximum or minimum) with the current month's mean. Deciles are not used for maximum or minimum, but a direct difference in degrees.
Further information:
The latest rainfall and temperature maps: http://www.bom.gov.au/climate/austmaps/
A directory of Bureau services is available on poll fax: 1800 630 100
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