Saturday, December 11, 2010

Why is the Surf SO Cold?

It's almost mid December.
It's summer.
Daytime temperatures are getting up into the high 20s.
Then why is the ocean so cold? Jumping into 15-16 degree water is no fun.
This is winter stuff.
Finally we had an explanation from my surf report web site today. report that "The coldest water is pretty much isolated between the mid north coast (around Port Macquarie) and the south coast (Eden/Bateman’s Bay) anomalous to what we expect for summer and a La Nina season.
This summer is not living up to its reputation. We have just endured the wettest spring on record, the wettest start to summer, and sea surface temperatures have been fluctuating around 16-17 degrees(DECC, MHL) during the last week of November and the first few weeks of December, the lowest recorded temperature was below 15 degrees. The East Australian Current travels south down the east coast sending warm water down to Tasmanian waters from QLD, however BOM sea surface maps show the current is flicking offshore just south of Port Macquarie transporting warm water offshore.
During La Nina cycles the east coast of Australia is expected to experience warmer wetter conditions and persistent onshore winds. Relentless ENE and NE winds blowing at a parallel angle to the coast drive ocean currents south and offshore, due to the Coriolis Force. The centrifugal motion of the Coriolis effect causes water to move to counter-clockwise in the southern hemisphere i.e. away from the coast.
Persistent onshore wind conditions result in Ekman transport, the term for when surface water is pushed away at the ocean surface and is then replaced by colder water from the depths offshore."
So there you have it.
We can only wait and hope.
Meanwhile it's fun to watch the newly arrived tourists running down the beach for their first plunge of their holiday....and then obviously wishing they hadn't.

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