Swellnet over calling wave heights

Thanks for the feedback Zane. From my vantage point I watched the D'Bah cam early morning for a while and saw plenty of 2-3ft waves but perhaps that was just a brief pulse of activity (buoy data shows the trend was downwards all day.. not sure what time you were there?).

Anyway, surf reports are useful as a snapshot in time from one location - but as we all know the surf can change rapidly. With the new site we'll be overhauling the surf reports and hope to be able to improve on the service in a major way.

Gee, this has nipped the head off an old sore. There was a former local SN swell reporter who was infamous for overstating conditions. Gave everyone the total shits. He has long gone thank Christ. Things have improved drastically since which is good. Over time you get to know how the local reporters call it but some incidental variations do occur as Ben points out.

The day to day calls are therefore pretty good in my book but when those "once in 10 year swells man, it will be cord to the horizon" are called the over-frothing here and elsewhere is plain humorous. Some of the SN boys need to be let out away from their computer modelling and get some fresh air into their lungs from time to time. Craig, you listening or has Ben still have you chained to the basement desk?

Don't worry about me Floyd, I get plenty of sunshine and salt to wash away the computer model froth!

I've found the calls on here pretty good in recent times at least. If anything I find that CW (dare I mention that here!?) tends to overcall compared to SN.

Which coast are you on, ird?

There is nothing so frustrating as SN and CW overcalling the forecasts on the surf coast. The last 2 weeks have been the absolute pits. These swell "gurus" have been calling 3-5ft and 4-6ft virtually every day for the last 10 days and are still forecasting this for the next few days. Hello fools, when the swell is west, we don't get it. The surf has been 1-3ft and packed for days.
I will give you a tip. When the lows form up high under WA and then travel SE under tassie (while weakening) we get very inconsistent and small swells, no matter how impressive the lows look. The same storm pattern has happened for 2 weeks and you've constantly overcalled it. Today was a classic example. It was 1-3ft with one wave 4ft sets every 45 minutes. Are you lot paying attention? Swell direction is absolutely crucial and your forecaster simply doesn't get it. Maybe if this craig bloke lived in Victoria (rather than NSW) and saw how many flappers came down to Bells to surf his "4-6 footers", he might understand how annoying his forecasts are.

Good news Craig see if you can release the the 2 monkeys developing the new webpage sometime also :)

Carpetman, you are spot on and SN reporters can be guilty of that when and where stuff. Dumbs down everything it does.

Vic-local, yep it happens, but, if you know how it works why does it frustrate you? If enough flappers (your term) get pissed off they mightn't bother and its less crowds for you.

Although SN do take steps to keep things general my only true gripe about SN and CW etc is when guys get on the forums and spill their guts about things that could and should remain on the down-low.

e wrote:

Vic-local, yep it happens, but, if you know how it works why does it frustrate you?

It's frustrating because you have so-called experts making the same mistakes week in week out. I live on the coast and know how to pick a swell. It's the Melbourne based surfers who see a great forecast and flock to the coast. When it's half the predicted size and really inconsistent, they are still going to surf because they've invested half a tank of petrol and 90 minutes of time to get to the waves. Instant crowd where nobody wins. Not the locals and not the punters who have taken days off work, filled the car, and wasted their time, effort and money.
And as for 4-6 foot surf forecasts meaning less crowds, do you seriously believe that?

Vic-local the last 2 months have been really tricky regarding these west swells and some have come in better than expected and then others seemed to have passed by.

It's a tough call which I have to make every day and just a slight change in track or positioning makes or breaks the size on the Surf Coast.

At least the next few swells are a bit easier to get a grip on.

For the last few months, SN have been spot on where I live, absolutely to the foot, even half a foot, bang on.

Yeah. And even though the last few weeks may have been slightly out for vic SN were still WAY closer to the mark then other sites.

e wrote:

Vic-local the last 2 months have been really tricky

Sorry Craig, the last two months have been very predictable, you just need to know what to look for.
Here is a brief list to help you.
1. Storm track. The conveyor belt of lows we've had this winter has been very stable. The lows obviously travel in an easterly direction but they do vary slightly. This is crucial. If a storm comes up from the south it's going to produce way more swell than a NW-SE swell track.
2. Low behaviour. Do they intensify or dissipate under SA? This is crucial to size and it's been very predictable this year with storm after storm doing exactly the same thing for weeks on end.
3. Local winds. If it's flat or small and we are getting 50+km/h northerlies on the leading edge of the low, it's not going to build.
4. How fast are the storms travelling. To get days of swell we really need a big low to set up under TAS-SA for days at a time. The last few weeks they have been travelling pretty quickly.
5. A good way to forecast down here is to pay attention to what the current low has delivered and make a judgement whether the next low will produce a similar/smaller/ or larger swell.

The biggest issue I have with the SN forecasts is the lack of understanding of our swell window. It's not under WA. On some occasions SN have been calling for swell from storms to the West of WA. These swells never get to the west coast of vic.
For every one day you've under-called it, there would be 10 days of overcalling it. The days you and CW undercall it are bliss. Crowds are way down.

Sure I haven't used technical terms here, but common sense, observing current surf conditions, and understanding patterns goes a long way.

Good luck with your predictions in the future.

I live on the coast and know how to pick a swell.

By: "vic-local"

Well, the problem here is that everyone's an expert. No matter what we forecast (undercall, spot on, or overcall), there's always a handful of people putting their hand up after the fact saying "I could have done that better".

The biggest issue I have with the SN forecasts is the lack of understanding of our swell window. It's not under WA. On some occasions SN have been calling for swell from storms to the West of WA. These swells never get to the west coast of vic.

By: "vic-local"

That's simply not true, and I'll be happy to point out many examples of quality Victorian swells every year that originate from low pressure systems below WA.

For what it's worth, Craig works alongside me VL - literally - and we discuss the finer complexities of surf forecasting all day, every day. And, the Victorian swell window has been an ongoing personal project of mine ever since I started. For every 'ideal synoptic setup' you list, there are many small aberrations that challenge the likely surf outcome.

Remember, we do this day in, day out. Sure, we make errors: no-one is perfect all the time. But we're always the first to admit when we get it wrong, so that we learn form our mistakes. Craig writes detailed synoptic notes three times a week which go into the reasoning behind each and every forecast - you don't even get that kind of insight from the BOM.

Ok VL, I think we all understand your position.
But I think the SN guys do a better job than other sites.
I think swell direction is very important in Vic as it is here in SA.
You guys have Tassie blocking and we have Kangaroo island.
Any way the next 4-5 days look awesome (but I'm no expert) with a big red blob hitting SA, which is a little unusual as they normally drop away to the south.
Yorkes will be PUMPING me thinks!!

It's a forecast off...

VL what are you calling for the coming weekend?

Living on the Mornington Peninsula, i marvel at how close Craig's forecasts are, almost to the minute. From the tone of vic-local's complaints, he just wants Craig to down call every forecast to keep the crowds away from HIS breaks.

It amazes me that these guys who are lucky enough to live near the surf figure that they have more rights than guys that have been living closer to the city for work but drive down whenever possible. I have been surfing the same breaks on the peninsula for 45 years and surf at every possible chance so i consider myself a local even though i have to drive 35 minutes to get there.

Keep up the good work Craig, your forecasts keep me in the water and that keeps an old fella like me alive.

Thanks for the kind words OOB, glad you're still getting wet as much as possible, great to hear!

I think we all want the exact same thing.

Perfect forecasting, that only we find out about. No use finding out its pumping if four hundred other people know and the surf is absolutely chock full, so you can't get a wave.

If this is the only advice you take (Swellnet's), then of course there will be times when its wrong (slightly out / different to what you thought etc) but if you use other sites then you should be all good.

I also use the Manly Hydraulics Lab site, bloody wonderful, and with Swellnet and a look at the weather charts been pretty lucky with catching swell. Work full time too though so I miss a lot. Work sure gets in the way of surfing sometimes.

ood, 35 mins isn't too long a drive to consider yourself a local.

Getting the occasional forecast wrong is entirely forgivable. We don't live in a perfect world. But when there is consistent over-forcasting it's time to re-evaluate.
Yes we do get the very occasional swell from a low under WA, but it has to be a very big low, it has to be way way south of WA, and it has to be slow moving/or working over an already rough ocean. And even then it's going to be incredibly inconsistent. When swell periods bump out to the 16 seconds + range (typical of this kind of storm) the "pro" forecasters get too excited. Especially with fast moving storms.
The last few weeks have seen impressive lows set up just under WA and then drop down while weakening in the Surf Coast swell window. Surf Coast has been 1-3 ft. East Coast 6-8ft.
As for my prediction. The next few days are way too westerly for real quality. Friday morning will be leftover junk swell but cleaning up during the day. Sat morning smaller but building to 2-4ft. Sunday slightly bigger but this will be one of those incredibly inconsistent swells. Forecast is showing onshores Sunday midday onwards.
There will probably be great waves saturday afternoon and Sunday Morning. But it's going to be packed, high tides won't help.

Nice one Vic, five days of forecast and you gave the wave heights for one afternoon!

How does anyone know if you're overcalling/undercalling if you don't give heights?

So without committing to a size for Wednesday, Thursday or Friday, we can only go by your Saturday forecast, which is: "Sat morning smaller (than Friday) but building to 2-4ft."

Which is almost identical to Craig's forecast issued yesterday: "Building W/SW swell from 2-3ft in Torquay to 3ft+ during the late a'noon. Fresh N/NW winds."

Hey Ben how about giving VL a job, he is obviously eminently qualified for the job and he has no problem with swell forecasting on public forums like this.

e wrote:

It's a forecast off...

VL what are you calling for the coming weekend?

I was answering Carpetman people. The request was for the weekend forecast, which I gave. Having a crack at me for not giving heights on Wednesday-Friday is a bit rich.
And top to bottom bells , do you want me to do the maths for you for sunday? "2-4ft sat and slightly bigger sunday". That would be 3-4ft.
I totally stand by all my comments. You guys want to get out from office and away from the computer modelling, and do some more on the ground observing. I've given you some much needed advice. Whether you choose to take it is up to you. Maybe you should have a genuine look at the synoptic charts for the last three weeks and did some cross referencing with actual wave heights at Bells. It might be an illuminating exercise.

So out of curiosity, what was the forecast for yesterday afternoon, Monday Sept. 30?

That;s for the surfcoast

Thanks for the forecast VL.

I was hoping there'd be a significant difference between yours and SN's so by next monday we could crown a new champion forecaster!

Winner gets one of Edwin Maher's famous pointers... youtube.com/watch?v=WikKCWaOCbA skip 2mins in for the action!

Its Torquay... each spot, reef or beach differs in size from each other everyday there so how can you say they are over or under forecasting. If the forecast is 3-4 foot, i bet you will find 3-4 footers somewhere near torquay.. Ive always found it obvious winki picks up more swell than say juc... so if one of those spots is 3-4 foot is the forecast not accurate? regardless of consistency.

relly you never truly know the quality until you get there anyways, forecast sites are a good gauge to whether or not you may wanna drive, say 90 mins from the city. I used to live in the city and would drive down for any kind of waves so long as it wasnt completely un surfable.

e wrote:

So out of curiosity, what was the forecast for yesterday afternoon, Monday Sept. 30?

Not exactly sure Shaun. Maybe 4-5ft. Ben, Craig can you help out with that question?
The surf was 2-3 ft very inconsistent. Packed.

VL ,

Quit whinging will ya .....
You obviously don't need to forecast coz you clearly look out the window in the morning .....
If the swells been so shit , and your clearly an experienced Surf hunter , look elsewhere , ( let the hordes have their " 3 ft " shit ) ....

Why O' why whinge , you clearly Know your stuff !?! , put it use and get yourself to where its epic each day !

i Agree with Oldman , its been SA's year ......
End rant ......

Which coast are you on, ird?

By: "thermalben"

I'm on the East coast Ben, Sydney area mostly but been heading a little north lately too to escape the flat spells.

Glad I don't live in your world vl, cause it's nowhere near the surf haha

e wrote:

So out of curiosity, what was the forecast for yesterday afternoon, Monday Sept. 30?

By: "vic-local"

Not exactly sure Shaun. Maybe 4-5ft. Ben, Craig can you help out with that question?
The surf was 2-3 ft very inconsistent. Packed.

We had reports of solid but inconsistent 4ft+ waves on the reefs. Which seems to fit in well with the new swell that arrived at at Cape Sorell at around 10am (peak swell periods of 18 seconds)and filled in through Bass Strait during the afternoon.

Hsig at CS built from around 4m in the morning to 7m around 4pm or thereabouts, which is probably within the top 10% of historical Hsig data at Cape Sorell (Hmax topping out at 11m Monday afternoon, and 12m overnight).

Tz at CS also reached 12 seconds which is very impressive - we only see these values a couple of times a year. This is a very good sign of an exceptionally strong and focused swell event.

Local winds at Cape Sorell were relatively light on Monday (~15kts until mid a'noon, then 10kts or less for the rest of the day), which mean that the majority of the swell recorded at the CS buoy was groundswell, and not local windswell (usually, there is a high windswell loading at the CS buoy during significant swell events).

If the swell was straight SW in direction, a rough estimate based on this data would have been for a peak in the 8ft to maybe 10ft range at Bells/Winki late afternoon or early evening.

However, because the swell direction had a stronger west component, this shaved off size on the Surf Coast, so 4ft+ is a reasonable figure for set waves. Which is in line with Craig's forecast of "building to 4-5ft late afternoon".

So what was it again, did you under call it this time.

This VL sounds more grumpy and skeptical than me, I'll have to lift my game.

Has anyone tried the salty caramel, chocolate mousse yet?

I missed out monday arvo , I was in a business meeting with Claw.

shaun, Craig wrote (off the top of my head), small surf for most of the day ahead of a late afternoon kick to 4-5ft. This was a forecast issued the Friday prior.

And this is a classic illustration of one of the endearing problems of our surf forecast routine, which has been ongoing for the last twelve years (for me anyway).

Monday afternoon's forecast pulse was issued on Friday morning - more than eighty hours prior. However, Craig was working morning shifts on Monday and therefore had to issue his forecast that day mid-morning - before the swell had even registered at the Cape Sorell buoy, and therefore well in advance of the swell reaching the Surf Coast (and therefore well before receiving any kind of local verification from Torquay).

As such, the 'next' forecast timestep issued by Craig - for Tuesday morning - was for the backside of the swell event still bearing down on the Surf Coast.

Therefore Craig's forecast on Monday contained a MAJOR assumption that the Friday forecast (for a 'late kick Monday') was in fact correct. Along with another assumption that the swell phase would then play out as the models had previously anticipated three and a half days ago - and not ease more rapidly than expected overnight, leading to smaller-than-expected size on Tuesday morning.

But hey! That's just another day in the life of a surf forecaster. Besides, Craig had another fifteen Australian coasts to forecast for that day anyway.

Shaun, You didn't miss out.
It was another overcall. Winki was 2-3ft very inconsistent yesterday.
Ben has just given his reasons for the 4ft+ forecast. It's obvious these guys pour over figures, maps, readings all day.
My point is, when their forecasts routinely over reach, it's time to re-evaluate how the final wave heights are estimated.
Southey: The surf hasn't been "shit". It just hasn't been pumping like the forecasts predicted. Yes I'm whinging, but I have good reason to. Forecasts of great surf simply brings in the crowds. Who wins when it's small inconsistent and crowded? I'd love to have the time to duck off to quieter spots but there is thing called work.
I simply ask SN forecasters to have a look at their recent forecasts, cross reference with actually wave heights, look back over the charts buoys, and have a genuine re-evaluation of their methods.

So you haven't tried the mousse yet?

No, I didn't miss out.

VL, what's your preferred chart source? Just want to see what you think of a few hindcast images.

Ben,
4ft + on Monday? Whatever.
Nobody should get upset with the occasional inaccurate forecast, (it's not an exact science) but seriously "4ft+" and you stand by that?
If you put your hand up and said, "yep, we got it wrong" all would be forgiven. Claiming it was 4ft+ from your desk in Sydney when all we see from the cliff tops are very inconsistent 2-3 foot sets tends to reduce your cred.
Still haven't tried the moose shaun. No animal hostilities here man!

VL, we had first hand reports from the Surf Coast of a late pulse in the few hours before dusk of 4ft+ sets. This ties in with the buoy observations too. We also observe the surf all day via our surfcams.

We're not really going out on a limb here - the 6-7m Hsig values recorded at Cape Sorell on Monday afternoon are very high (as I said previously, had the swell been SW in direction it'd have translated to 8ft+ Bells).

Don't worry, I've put my hand up many times over the last 12 years to say I got it wrong. Also done it on camera too.

So back to my question - what charts do you use? Standard BOM sea level pressure? 10m winds? From which source?

Hi Ben
I'm a big fan of the 7 day interactive BOM charts with the greater australia and southern hem outlook. These give me a great indication of how storms behave. It's not unusual to see the same patterns for weeks at a time. I also use magic seaweed buoys, not so much for wave heights but for primary swell direction. The readings in degrees really helps. Anything over 240 degrees, you need to put a big ? mark on the forecasts. This is especially the case with long swell periods.
When swell direction changes from 240s+ down to the low 230s or 220s that's when the consistency and size kicks in. I also pay attention to local winds. Strong NW and Northerlies can really delay a swell. SE winds knocks down size incredibly.(and not just for the day it blows).
These three sources give me a very good indication of whether the next few days will be bigger, smaller or about the same size, and in combination with on the ground observations, I get a pretty accurate forecast. When in doubt, I will have a look at a few other charts, and readings.
I can also get a pretty good idea of what the following 2 weeks are going to be like from the charts, not that I'd put numbers or dates on any of the incoming swells.
Personally, I think you guys put too much weight on the CS buoy, and underestimate the effect of direction. And then the tides throw in another wildcard. Big highs can kill a swell, delay a swell, or have little effect if it's a quality SSW swell.
So you and I use the same variables, I just think your weightings need reassessing.

Just to pick up a few of your points here VL.

I also pay attention to local winds. Strong NW and Northerlies can really delay a swell.

By: "vic-local"

No they don't. Once a swell is generated, there's very little that can stop it.

What you're probably seeing is that the wave models are over-calling ocean wave heights due to the additional component of local windswell in the mix (with the groundswell trailing some distance behind). It's very common with pre-frontal synoptic winds in WA, SA, Vic and Tas.

SE winds knocks down size incredibly.(and not just for the day it blows).

By: "vic-local"

Not quite sure what you mean by that, as the general premise doesn't make much sense. Sure, SE winds will significantly reduce the quality of a pre-existing groundswell by creating a cross-wobble in the lineup (which the TQ reefs hate, as they're primed for long period W/SW thru' S/SW swells). And short range SE swells will always be low in quality by nature. But SE winds don't simply 'knock down size' on the Surf Coast.

I also use magic seaweed buoys, not so much for wave heights but for primary swell direction. The readings in degrees really helps. Anything over 240 degrees, you need to put a big ? mark on the forecasts.

By: "vic-local"

You do realise that the MSW direction data (like most surf forecast sites, including our new website yet to be launched) is computer generated?

In my experience, computer model forecasts of swell direction across the southern states are not always accurate because there is usually a mixture of swells in the water. The models are unable to discern the finer details between individual swell trains from swells exhibiting similar characteristics (period, direction). So, they lump them in all together with one direction.

We use different techniques to confirm and qualify the likely swell direction. However without a directional buoy in the region (and also due to the alignment of the Vic coast) there's no way to confirm what actually arrives at the coast.

In any case - sure, the more west in the swell direction the less size we see in Torquay. That's hardly a revelation.

And for what it's worth, there have been a number of acute west swells that have punched well above their weight in Torquay in recent years.

Personally, I think you guys put too much weight on the CS buoy, and underestimate the effect of direction.

By: "vic-local"

No, that's not correct. In fact we could often go on at length about the effects of direction relating to the CS buoy but there's simply not enough time every day.

We don't simply look at the CS buoy on its own - it's used on conjunction with a number of other buoys as well as local wind observations and satellite data to fine tune the model forecasts (see my comments on the previous page re: percentage of ground/windswell at the CS buoy on Monday, relative to the concurrent strength of the wind at the Cape Sorell AWS. Ever seen anyone else reference that kind of information to justify the buoy readings?)

And then the tides throw in another wildcard. Big highs can kill a swell, delay a swell, or have little effect if it's a quality SSW swell.

By: "vic-local"

Sure, tides play a factor at all locations. Although not every 'big high' will kill a swell, and the term 'delay' a swell is not technically correct either (where do the swells wait during this delay? Circumnavigate King Island for a few hours until they get clearance from the Surf Coast?)

So you and I use the same variables, I just think your weightings need reassessing.

By: "vic-local"

Well, thanks for your in-depth (assumed) critique of our forecasting techniques. Glad to know these last twelve years have been well spent.

vl, take that .

The report for south arm (tas) the other day said 2-3ft. I rocked up about 30 minutes after the report was updated. It was 0.5-1ft all day. It never got over 1.5ft.

What day was that MD? Hard to really know otherwise. However our surf reporters upload accompanying photos most days to verify their reports - were there any photos with the report?

Last Saturday or Sunday?? Can't remember for sure. Yeah there were photos, Maybe it was just the particular place I went to on south arm..
Otherwise most days it's pretty good and accurate :)

Just gone through the Sunday archive report and there are five attached images, all taken at South Clifton which look somewhere in the 2ft+ range (so North Cliffy would have been a little bigger). However the swell had a lot of west in it (not a great direction for the South Arm) which means that some locations probably dipped out.

Jeez though, the South Arm is a complex place to get your head around forecasting-wise!

VL ,

I'm with you on the effects of Wind on swell in Bass Strait . Not sure if we are on the same tram with why , but I put it down to a Combo of Wind and Tidal flow .
tb & Craig are yet to convince me otherwise that what i see happen is not attibutal to what i think is causing it .

A prime example which is easier to correlate , is Strong NW winds redirecting SW - W groundswells into a WNW direction and making places in Nth coast of Tassie work for a few hours , before the SSW-SW wind post frontal re corrects it .
The other is with little or no wind a Swell inside and outside Bass Strait will have less difference in strength and size . But put a thirty kt Northerly - Easterly on the same Swell and it'll disappear in a few hours ( obviously dependant on coastal facing direction.)
Still to be corrected on why that happens and why its even more visible the further east you head into Bass Strait even when comparing beaches/coast that face identical directions ..... Answers pls .

A prime example which is easier to correlate , is Strong NW winds redirecting SW - W groundswells into a WNW direction and making places in Nth coast of Tassie work for a few hours , before the SSW-SW wind post frontal re corrects it .

By: "southey"

How about this: Tassie North Coast sees a combination of refracted W/SW swell and NW windswell at the same time.

And rather than the post-frontal S/SW wind 'correcting' the 'redirected' swell, you're really just seeing a rapidly dying short range NW windswell fade into nothing, while the underlying long period W/SW swell continue to motor along (showing very small surf heights on the Tassie North Coast, due to the high refraction).

Surface winds don't 'redirect' swells. Rather, local bathymetry will steer swells to particular locations depending on their size, period and direction. And if there is an opposing wind to the swell direction (ie NW wind over a W/SW swell), well then it'll generate an additional swell on top.

BTW, I'm not saying that winds and tides don't affect the surf. They certainly can, and do have an effect.

I am however trying to correct broad, sweeping statements that are at glaring odds with meteorological and oceanographic convention.