The monumental waterspout which sent boaties’ heads spinning and put Batemans Bay in a whirl on the weekend has also swept up professional weather-watchers.
“Impressive,” was the response of Michael Logan, a severe weather forecaster at the Bureau of Meteorology, to the 100km per hour spin-out.
Don't miss our online gallery of photos residents captured of the event.
“It was an incredibly strong one,” he said of the ocean tornado that held coastwatchers spellbound for about 20 minutes on Sunday afternoon and could be seen from vantage points kilometres inland.
“It is one of the most impressive I have seen footage of, off the NSW coast, in the past 10 years I have been forecasting,” he said. “We get lots of photos in of waterspouts, but not of that strength. It would have been pretty nasty inside it.”
Mr Logan said the spout formed when two opposing winds met at water level, creating instability.
“As that instability is released, an updraft goes up in the middle and it catches it, pulls it altogether and it starts to spin.
“Most of the waterspouts we see are quite weak and almost have a ropy look as they work their way up to the cloud.
“(This) was incredibly strong and well organised and that is why it was so impressive.”
Mr Logan said waterspouts were usually associated with light showers and were short-lived, but Sunday’s thunderstorm explained this one’s intensity.
He said the phenomenon was a column of cloud, rather than of water, as surface water was condensed under centrifugal force in a low-pressure zone inside its funnel.
“The winds are rotating at 100km per hour or more and inside that funnel of air, it causes the pressure to drop dramatically, which causes all of the water to condense into cloud,” he said.
Mr Logan said spouts travelled with the cloud system above them, and rarely came ashore.
“You do hear these anecdotes of fish ending up in backyards and random things like that, but most waterspouts are too weak to do that,” he said.
“But occasionally, they have come ashore and torn a roof off a very unlucky house.”
Mr Logan likened the spout to a spinning ice skater.
“As the updraft goes up through the middle, it is the same for the atmosphere as when an ice skater brings their arms in; it causes it to spin much, much faster.”