August 29th, 2016

Part 2 Understanding the weather.

“The weather forecast here always says rain and its always wrong!,” I’ve heard many a front desk staff person explain to customers. This isn’t completely untrue, it’s just that the weather is always changing here because we are exposed to uninhibited weather systems of the pacific ocean.

However with a little better understanding of how the weather works, specifically weather patterns things can be quite predictable. Understanding these patterns and how to decipher what weather forecasts are telling us can make the difference between good and poor decisions making on the water. Three factors that affect our paddling are wind direction, wind speed, and sea state.

What makes wind.

Let’s start by actually taking a look at what makes wind. Wind is the way the earth distributes the sun’s warming energy. The equator is closer to the sun then the poles, hot air at the equator rises, cools in the higher atmosphere and sinks back down towards the earth. I’m keeping it relatively simple here but this movement of warm and cool air creates areas of high pressure (more air particles)  and low pressure (less air particles). The pattern of how air particles move from areas of high pressure to low pressure is driven by the earth’s rotation.

paddleboard weather

In the northern hemisphere air fills in areas of low pressure in a counter clockwise direction. Low pressure is associated with rain. Hmmm. So there’s a big clue here. Counter clockwise winds (South East winds), mean approaching low pressure which also often means rain especially if the low pressure system is large or moves directly over Vancouver Islands.  But sometimes there’s a weaker low that sits far offshore and doesn’t approach, giving us warm weather associated with the light south winds without the moisture. Just looking at the weather channel online will show rain, but understanding what the system is doing allows us not to be thrown off by this simple prediction.

In the opposite direction, North West winds mean approaching high pressure, associated with clear skies but also cool air. Think afternoon sea breeze and crisp clear nights.

wind patterns

So by looking at the forecast wind direction we see how we can predict weather conditions. Now let’s take a look at wind speed.

Weather-Wind-Speed-strong-windWeather-Wind-Speed-light-winds

Wind Speed.

We can think of areas of high and low pressure in the atmosphere as peaks and valleys where air particles creating more weight in the high pressure ridges (like peaks of a mountain) want to move toward and fill in the low pressure troughs (like the valley below). The steeper the difference between these peaks and valleys, the faster the air flows (stronger wind). The steepness in between the highs and lows can be read by isobars on a weather chart. Isobars are lines connecting points of equal atmospheric pressure, similar to topographic lines on a map.
Isobars

Steeper gradient means stronger winds. And its these winds that create the sea state we paddle in. So an approaching low with big gradient different from the surrounding high pressure shown by isobars that are closely positioned means you can expect more wind and rougher seas.

Sea State.

Paddling in wind and a developing sea state can be tricky. You should know your limits based on your ability and your craft. For example when paddleboarding you have a higher center of gravity and standing up rather than sitting means the wind has a greater affect on you. Often times 10 knots of wind can create quite a challenge.

Here’s some basics of the sea state you can expect, 7 to 10 knots of wind creates chop on the water. 11 to 16 knots creates small white caps. 17 to 21 knots creates moderate waves.

tofino swell

Swell.

This leads us one more factor that we need to consider on the west coast, swell. We can see here that as the wind moves across the surface of the water it creates waves. If the wind blows long enough and hard enough the waves eventually make their way away from this wind source. This is called a ground swell.  The further the swell travels away from the storm (the low pressure system) that created it , the space in between the peak and the trough of the swell widens.  There’s a lot more details to talk about when it comes to swell, but I’ll save surf forecasting for next month. Within our scope here, we can sum things up by noting that a swell travels further away from its source will be more spaced out and therefore be calmer to paddle in. Where as if the storm that created the swell is close we can expect a choppier and messier sea state. Heads up though, even though ground swell may mean calm paddling it doesn’t necessarily mean you’ll have an easy time making it through the surf. Ground swell translates to more powerful surf.

So there you have it, even though each of the factors I’ve talked about can be elaborated on quite extensively, I hope I’ve demonstrated some basic concepts that will help you understand the weather and paddling conditions just a little better. So next time you check the forecast, why not take a look at the marine weather forecast for Vancouver Island South found at weather.gc.ca or even check out some weather charts on a site like stormsurf.com to get an idea of what’s happening on a larger scale. Get out there,  have fun and be safe.

Emre doesn’t expect you to really nerd out on the weather like him, but you can always track him down at tofinopaddle.com to see what the weather is really doing.