NSW flood explainer: When is it going to stop raining in NSW and why has it been raining so much?

Multiple severe weather events back to back have residents across south-east New South Wales wondering if, and when, the rain will stop.

NSW SES has received 585 storm and flood related jobs over the last 24 hours and is urging people to stay home where possible.

Dover Heights and Diamond Bay looking south from Vaucluse. Storm water is blown back by strong winds that are battering Sydney’s coastline. Thursday 7 April, 2022 (Peter Rae)

Here’s a breakdown of the upcoming forecasts.

When is it going to stop raining in Sydney?

Sydney has been lashed with 114mm of heavy rainfall in the space of a day, with 125mm recorded at Sydney Airport, causing widespread flooding and devastation.

A strong upper level trough is amplifying over central NSW.

In response, a coastal trough has deepened near the central coast and is likely to drift inland, producing areas of heavy rainfall on the east coast.

This coastal trough is forecast to weaken on Thursday evening, with less rainfall predicted by the Bureau of Meteorology (BoM).

In recent weeks, much of Sydney’s north experienced significant flash flooding, catching commuters off guard and rendering them trapped as floodwaters swept their cars off the road.

Cars were beginning to float on the Roseville Bridge, which was closed, cutting off parts of the Northern Beaches from the rest of Sydney.
Cars were beginning to float on the Roseville Bridge, which was closed, cutting off parts of the Northern Beaches from the rest of Sydney. (9News)
Sydney NSW floods
Flash flooding in Balgowlah are , Manly Photo Nick Moir 7 April 2022 (Nick Moir)

When is the rain going to stop in Lismore and the Northern Rivers?

While residents continue to grapple with the damage left by recent extreme flooding in Lismore and its surrounds, the BoM is forecasting more showers and thunderstorms for the region.

Residents in Lismore are exhausted and calling for more help as the impact of floods becomes clear.
Residents in Lismore are exhausted and calling for more help as the impact of floods becomes clear. (9News)

Today showers are increasing across Lismore, most likely during this afternoon and evening. The region is set to experience some light winds of 15 to 20 km/h in the early afternoon then becoming light in the late afternoon.

Tomorrow, the BoM said the area could see the “chance of a thunderstorm, with possible heavy falls in the afternoon and evening”.

Why is it raining so much?

A strong upper level trough is moving through the coast, bringing a burst of dangerous weather to parts of eastern NSW as it moves towards the coast.

Intense rainfall rates are not expected, however there is a small chance of locally intense rainfall developing around coastal areas north of Wollongong, associated with thunderstorm activity.

Severe thunderstorm warnings will be issued if this activity eventuates.

How much rain is Sydney expecting over the weekend?

Conditions are expected to ease during Thursday evening.

Several flood warnings and a flood watch are current for parts of southern and central New South Wales.

Locations which may be affected include Bega, Batemans Bay, Nowra, Goulburn, Wollongong, Sydney, Katoomba and Gosford.

Recent rainfall observations include –

Cronulla South Bowls Club: 107 mm in 3 hours to 1:10 am

Little Bay: 107 mm in 6 hours to 2:30 am

Lucas Heights: 57 mm in 2 hours to 2:40 am.

Darkes Forest: 67 mm in 2 hours to 4:50 am.

Reverse waterfall created as Sydney lashed by rain

How long does La Nina last?

According to the Bureau of Meteorology, La Nina is likely to last until mid-autumn.

The 2021-22 La Nina is past its peak, with outlooks indicating it will return to a neutral El Nino-Southern Oscillation level during the southern hemisphere autumn.

“As La Nina weakens, it will continue to influence global weather and climate,” the BoM said.

Reference-www.9news.com.au

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