Sydney's offshore Sea Surface Temperatures (SST's) have remained above 21 degrees for the last four days. SST's are currently 22.5 degrees off Sydney beaches. The May SST average for Sydney is 20.3 degrees, while SST's reached up to 23.2 degrees on the 15th May.
Heat lingering after a record hot summer and a lack of strong cold fronts so far this season have contributed to the warmer than average sea surface temperatures recently. Adding to this, the East Australian Current, which brings warm tropical water into the Tasman Sea, has recently strengthened and extended further south.
SST's generally have a lag time of three months compared to atmospheric temperatures. This corresponds to the warmer than average SST's recorded off Sydney recently and the record hot summer.
Warmer than normal SST's can combine with a cold atmosphere to produce ideal conditions for the development of East Coast Lows (ECL's). ECL's are intense low pressure systems which occur a few times each year off the eastern seaboard of Australia and can generate heavy rain, rough seas and damaging winds.
This weekend, a low pressure trough will form over Western Australia, before moving east over the coming days. By mid-week it should have reached the east coast, with indications that an ECL will form off New South Wales or southern Queensland.
If an ECL does form, characteristically it will generate heavy rain, strong winds and large seas along parts of the eastern seaboard.
To keep abreast of the situation, keep an eye on weatherzone.com.au for updates over the coming days.
© Weatherzone 2013
09:12 EST Weather forecasters say some parts of the Hunter have received more than half of their annual rainfall average since April.