How to Read the Charts

So, so you think you can tell; Heaven from hell? Blue skies from pain?

With apologies to Pink Floyd, so you’re a savvy 21st century human, all hipstered up with trimmed facial hair and blithe coolness, but does your 100mb/s fibre line, Netflix account and a plethora of surf forecasting apps prove you worthy?

Your main Whats App group is called Barrel Brus or the Surfragettes, but you’re on a bunch of others, such as South Coast Fish Heads, Dungeons Keepers, the Hot Curls, Pier Pressure, Grannies Who Shred, and the Wave Pool Wannabes.

However, as a keen surfer (apologies for the hipster remark) obsessed with good waves, you find your hit rate lower than desired, despite the digital candy store at your fingertips. The skunk factor - exacerbated by the randomness spewed out by climate change - can be high. Remember when Rocky Road, for want of a random generic surf spot, was rated five stars by a forecast website but when you got there, it wasn’t even one?

I  stood at Long Beach watching Sunset Reef thunder at 25 feet, while a galeforce southeaster tore the tops off giant peaks to turn them into 100 foot spumes of spray, whiplashed backwards.

I saw a salt-caked surfer stagger past wide eyed, trying to control his board as it bucked like a bronco in the wind, which must have been 45kts. I am sure they’ve changed their internal algorithm now. Too much of a good thing is not necessarily good.

Rule #2 Always check for the existence of other swells in the ocean. The models give credence to the primary swell. This is significant wave height: the average height of the biggest one third of the waves. Other swells are not shown. WW3 outputs secondary swell data but few take notice. Besides, this information can be sketchy. Often a localised windswell will be given priority over a smaller groundswell. This often happens with northeast winds on the East Coast and the southeaster in Cape Town.

When I give my swell courses, I also tell people to be wary of the final figures spat out by the model. The data can be accurate, especially a couple of days before, but the glitch is what arrives with your primary swell. How do find this out? Read on McDuff.

Rule #3 Skunkage is inevitable, but reduce it by widening your sources and types of information. Calling an epic day is not easy. Surf forecasting tools don’t give you parameters like “quality” or “consistency”. And of course they don’t say: at 9.30am a six metre Great White will brush against your leg.

There are so many variables to compute, particularly from a week out, that you might as well throw bones and burn incense. Fortunately, there are other tools. For me, the most valuable tool (especially for spots with funny angles of approach like Durban) is the good old synoptic chart. Yes, the original contour map of air pressure on the surface of the sea. It was first published as a gray-scaled one dimensional image in newspapers - one frame in the animation - that is now published as three-hourly animated, colour-coded forecast charts going up to at least seven days.

These charts come directly from the Global Forecast System (GFS), which provides the raw data for WW3, so you’re in effect skipping the middle man when you study this chart. The GFS surface pressure charts provide a graphic rendition of where and when certain winds will blow at what velocities for how long. I only look at the end data on forecasting apps to “prove” what I calculated in the first place.

By looking at the root, the source of the end data, I feel I have a head start. By having the focal point of winds in a storm in front of me, I am able to form a much clearer picture of those hard-to-know variables like direction, quality and consistency, but that is not easily learned. A few decades obviously helps.