East coast low caused the flooding rains

THE torrential rain and strong wind that ravaged the eastern coastline last week was caused by an east coast low (ECL).

The Australian Bureau of Meteorology defines an ECL as, “an intense low-pressure system that occurs on average, several times a year off the eastern coast of Australia”.

ECLs form in different ways depending on a variety of weather conditions, even the seasons can influence the way in which they are created.

In summer they usually form from the remnants of ex-tropical cyclones.

At other times of the year they generally develop a short distance offshore within a pre-existing trough of low pressure.

This occurs because of the presence of favourable conditions in the upper atmosphere.

There are generally 10 significant ECLs per year in Australia, with only one of them being labelled as severe.

According to the bureau’s records between 1973 and 2004, there is no trend in the occurrence of east coast lows.

There is also no apparent increase or decrease in the frequency or severity of ECLs.

However there seems to be a rise in the spread of days where Ulladulla has received 100mm plus millimetres of rain.

Since the Ulladulla Weather Station was established in 1994, the town has only had 10 days in which it has received 100 plus millimetres of rain, though not all of these days were correlated with ECLs.

Four of these days have occurred within the last 12 months.

The wettest was October 12, 2012, when 233 millimetres of rain fell on the town.

This day also happens to be the wettest ever recorded in Ulladulla, as well as being caused by an ECL. 

The most common features of an ECL are gale force winds, heavy rain, flash flooding, prolonged large swells and rough seas.

“It was very important that we were prepared, as it let us disperse warnings about the dangerous seas as well as prepare two boats in the case of someone needing to be rescued,” said radio operator at Ulladulla’s Marine Rescue, Doug Musker.

When people do not take notice of warnings, accidents can occur, as is obvious by the death of a fisherman from Tuross during the wild weather.

“People need to heed warnings; otherwise it becomes very dangerous for them,” Mr Musker said.

There are many differences between ECLs and tropical cyclones, even though the results of their carnage are quite similar.

While tropical cyclones form over warm waters close to the equator, east coast lows develop over the low temperature waters and cold winds which are prevalent in the Tasman Sea, and ocean surrounding it.

Tropical cyclones also have a larger life span than ECLs, which usually only function for three to four days before disbanding.

In the past 12 months Ulladulla has been hit by three east coast lows on October 12, April 20 and June 24, and ex-tropical cyclone Oswald on January 29.

Smartphone
Tablet - Narrow
Tablet - Wide
Desktop