ECL Forming Next Week?

[thermalben]

No probs oldman - that's a completely valid question. However, I meant what I wrote - an ECL is both a particular type of low and an abbreviation for East Coast Low.

An ECL is a low that deepens very rapidly off the East Coast.. also known as a "bomb". For a low to be classified an ECL, we need a 1hPa drop every hour for at least 24 hours. This typically happens under the influence of an upper level trough and a sharp thermal gradient. Night time tends to be the period when we see the most "explosive" developments occur, as radiative cooling creates a sharp drop in temperatures (with ascending height), increasing atmospheric instability.

As they tend to be located close to the coast, we typically see large waves, strong winds and heavy rainfall whenever there's one present.

[2nd Reef]

Mr Matson!

While class is in can you help me with this;

Is an ECL the same as a cut-off low? Or an occulated low?

If not, what is the difference?

Cheers Ben.

[barstardos]

you mean occluded (in other words 'cut off')

[2nd Reef]

Yeah, I guess I do mean occluded.

What do you know Barstardos? Are they the same thing as an ECL?

I've always thought that cut-off lows were associated with fronts that move off the coast, and a low lingers behind as the front moves east and out into the Tasman. They do seem to be an east coast phenomenen, so are they ECL's?

Perhaps they can be ECL's by way of Ben's explanation of dropping pressure for a certain period of time.

I've also noticed that the term (cut-off low) is often used by South African surfers, especially around Durban, where they get swell generated by similar weather patterns as Sydney.

[thermalben]

A cut-off low is exactly that - a low that has been "cut-off" from the westerly flow further south. An ECL is a cut-off low, but it's given a seperate name (ECL) due to the stronger dynamics. There are no requirements for a low to be called "cut-off", other than the obvious.

I wasn't sure if you were referring to an occluded front, rather than an occluded low (both of which are rare in the Australian region). An occlusion is when a cold front overtakes a warm front, usually resulting in a bout of pretty ordinary weather. For more reading on synoptic features in the Australian, check out this page.

[thermalben]

cut-off lows ... seem to be an east coast phenomenen

Not at all. There's a weak cut-off low in the Bight at the moment, and current guidance suggests a reasonably intense cut-off low will develop SW of Margaret River on Sunday.

[2nd Reef]

Hey Ben, thanks for taking the time to answer that.

Now I'm praying for some ECL's so I can see the theory in action!

Much appreciated...

[oldman]

Thanks Ben,

I remember a classic example of a 'bomb' that developed just off the coast around Port Mac to Coffs Harbour and moved down the coast, sending in some of the biggest swell, and in initial east nor east direction for Sydney. It was quite spectacular, about 3 or 4 years ago I would say, although I lose all track of time in these things.

The weather bureau used the term 'bomb' and I understood the dynamics of what happened, however I wasn't aware they had given official parameters of 1 hpa per hour for 24 hours, so I am now the wiser.

This swell seems to have dropped off a bit from yesterday, but I saw some earlier forecasts suggesting it will build again for the weekend. I should visit that website run by that guy, you know, Ben something or other. What was that website name and url again?

[Da Duke]

Here's an example of a pair of cut-off low's that results in a intense swell increase south of my belt buckle!

[One Mile Point]

Here's an example of a pair of cut-off low's that results in a intense swell increase south of my belt buckle!

wouldnt that sheila be a bit old now?

[chucknorris]

Many a fine tune's been played on an old fiddle.