UPDATE
The SES is preparing for a "wind swing" which will see strong westerly winds experienced over recent days replaced by southerly winds from Tasmania hitting Sydney about midday Thursday.
The system will likely bring wind speeds of 60km/h with gusts of up to 95km/h to the city.
Gusts of 61km/h were record at Sydney Airport at 12.30pm while a gust of 65km/h was registered at Lucas Heights at noon.
At 12.15pm Sutherland Shire SES warned that a major tree operation was underway in Prince Edward Park Road in Woronora where the road has been blocked.
Police and NSW SES crews are working to restore access and motorists are asked to please avoid the area.
Waves are predicted to double in height, with wild winds and surf posing an erosion risk to the entire NSW coastline.
A NSW RFS hazard reduction burn near Helensburgh (adjacent to the Garrawarra Centre) that was scheduled to commence tomorrow has been postponed due to forecast wind gusts on Saturday.
EARLIER
Sydney's coast will be pummelled this week by unusually powerful swells generated by a deep low in the Tasman Sea.
The Bureau of Meteorology has issued a warning for hazardous surf and swell and damaging waves from tomorrow for the Illawarra, Sydney and Hunter coasts.
"Surf and swell conditions developing in the afternoon and evening are expected to be hazardous for coastal activities such as rock fishing, boating, and swimming in the following areas," the Bureau warned.
Bureau forecaster Jordan Notara said the combination of the deep low and a high pressure system is the source of the big swells.
"Wave heights for offshore Sydney will approach six metres on Thursday. It's quite a rare event, particularly for August", Mr Notara said.
The record wave recorded for offshore Sydney in August stands at 6.41 metres.
The current forecast is a moderation compared with predictions last week that pointed to waves of eight metres or higher during the coming event.
Waves are likely to reach three to four metres on Wednesday, producing hazardous conditions for those on the water, and rough rides for those on Sydney Harbour.
Sutherland Shire Lifeguards posted on social media on Wednesday: "SWELL ALERT: Huge South swell looms for southern exposed beaches here at Cronulla for Thursday & Friday. Extremely hazardous surf 10-12ft + following the development of an intense, slow-moving low pressure system over the southern Tasman Sea."
NSW Maritime advises skippers and owners of small crafts to be on high alert and check the conditions before considering crossing a coastal bar or heading offshore.
Rock fishers should also check weather forecasts before heading out, avoid fishing near dangerous surf and wear a lifejacket.
Every skipper is responsible for the safety of their vessel and all on board.
Safety Advice *
- People should consider staying out of the water and avoid walking near surf-exposed areas.
- Rock fishers should avoid coastal rock platforms exposed to the ocean and seek a safe location that is sheltered from the surf.
- Boaters planning to cross shallow water and ocean bars should consider changing or delaying their voyage.
- Boaters already on the water should carry the appropriate safety equipment and wear a lifejacket.
- Boaters should remember to log on with their local Marine Rescue radio base, via VHF Radio or the Marine Rescue APP, and consider their safety management plan.
*NSW Police Force, Marine Area Command