Whether or not the storm gets bad enough to be defined as a “bomb”, meteorologists agree it will be a wet and windy few days for people on the coast.

Towering waves, storm-force winds and nearly 10cm of rain can be expected in parts of NSW over Tuesday and Wednesday.

“Sydney and the adjacent Central Coast and Illawarra regions can expect the worst of the weather from this system,” Sky News Australia chief meteorologist Tom Saunders said.

He said meteorologists were watching the system to see if it develops into a bomb, which is when a low-pressure system deepens rapidly over a short period of time.

The approaching system is “an extremely fast rate of development and is very rare near the NSW coast”, Mr Saunders said.

“This particular low has the possibility of becoming a bombing low, but regardless is will be an east coast low which will bring heavy rain, gales and huge waves to the NSW coast later on Tuesday,” he said.

Mr Saunders said the waves could get whipped up more than eight metres tall, while the Bureau of Meteorology predicted waves bigger than five metres.

“Significant wave heights could reach in excess of five metres for much of the southern and central NSW coast, including Sydney,” BOM meteorologist Miriam Bradbury said.

She said there was a risk the swell could cause “significant” coastal erosion.

The Bureau has watched the weather system as it moved across Victoria on Sunday night and into central and eastern NSW.

Monday evening would see gusty showers and storms in those areas, before the system is predicted to move out over the ocean where it would stall and “deepen into a low”, Ms Bradbury said.

“(It will direct) significant winds, rain and swell across the southern and central NSW coasts,” she said.

“Strong and gusty winds will wrap around the deepening low.”

By Monday evening, the situation had deteriorated to the point that the BOM issued a severe weather warning for Sydney, the Illawarra and the south coast, urging people to stay away from the surf and to move their parked cars out from under trees.

By Tuesday afternoon, it is forecast winds will blow nearly 100 km/h – faster than a Learner driver is allowed to drive – and the gustiest part of the coast will be between Newcastle and Moruya near Batemans Bay.

In the 48 hours between Tuesday morning and Wednesday night, between 30 and 50mm of rain is expected to fall on the Hunter, Sydney and Illawarra coasts, as well as the nearby inland areas.

Parts of that area could get up to 90mm, the BOM said. Sydney is expected to get between 50 and 70mm of rain.

While Monday was a relatively warm day with temperatures of up to 27C, those are set to plummet by as much as 12 degrees as the bad weather hits.

The weather system should move along by the end of Wednesday.