Freak of nature: An anatomy of an East Coast Low
IT’S the weather event half the population of Australia who lives on the East Coast from Fraser Island to Hobart dreads, and it’s coming soon to a sky near you.
With yet another East Coast Low forecast to form this Sunday, bringing heavy rain and dangerous winds and waves, we thought we’d take a deeper look at this awesome natural phenomenon.
The East Coast Low is a storm which as its name suggests is unique to Australia’s East Coast, particularly the southern stretch sitting on the Tasman Sea.
It’s a weather event that occurs mainly in late summer, autumn, and early winter - but its most common month is June.
Characteristic elements of an ECL, as it is known in weather circles, are damaging winds, heavy, intense rainfall, and storm surges along the coast.
Their formation is driven by the temperature difference between the warmer Tasman Sea air and colder air in the high levels of the atmosphere over the continent.
A warmer autumn, such as the one we just had, may be likely to result in more severe ECL formation in winter, as the sea surface temperatures are warmer, and hence the air temperature difference between the Tasman Sea surface and the continent are more extreme.
Unlike the troughy, extended rainfall events that commonly generate longer running flood events on the Northern Rivers - ECLs move quickly, generating transient but intense rain more likely to result in flash flooding.
An ECL is more likely to damage coastal areas than inland regions, thanks to the huge short-range swells they generate and storm force coastal winds.
Such characteristics make it one of most dangerous weather patterns to grace our skies, sitting alongside the ex-tropical cyclone that more frequently strikes north of Fraser Island in summer.
Ex-tropical cyclones can also become ECLs at times.
As the Bureau of Meteorology points out in their page on the subject, they can be deadly: “Falling trees and flash flooding have caused fatalities on the land, many small craft have been lost off the coast and larger vessels have run aground during these events”.
ECLs are also of particular concern to homeowners on delicate stretches of coastline such as Belongil Beach.
One might comment that ECLs make a mockery of Australia’s obsession with beachfront coastal development.
The Bureau of Meteorology has a detailed database of ECLs from 1973.
“Each year there are about ten “significant impact” maritime lows,” it says.
“Generally, only once per year do we see “ ‘explosive’ development.”
“The gales and heavy rain occur on and near the coast south of the low centre, while to the north of the low there can be clear skies. The challenge for forecasters is to accurately predict the location and movement of the centre of the low.”
“Looking at all the lows between 1973 - 2004, there is no evidence of a trend.”
ECLs can generate one or more of:
- Gale or storm force winds along the coast and adjacent waters
- Heavy widespread rainfall leading to flash and/or major river flooding,
- Very rough seas and prolonged heavy swells over coastal and ocean waters which can cause damage to the coastline.