The power of weather stations

Entrance Island weather conditions

I thought I'd take a moment to focus on one of the least used tools at the disposal of paddlers: the recent weather history of weather stations.

To be clear, I'd like to draw attention to the recent weather history, not the current weather. There's a reason for the distinction, that being the trend the weather stations can portray. And that trend can save a life.

The image to accompany this article is of the Entrance Island weather record this particular evening. It was a wild day today -- thunder, rain, sun, wind, calm. A day to be extremely careful.

The forecast was this: "Wind westerly 5 to 15 knots increasing to northwest 15 to 25 early this evening with gusts to 30 and becoming northwest 15 to 20 late this evening. Wind diminishing to northwest 5 to 15 early Friday morning then becoming light Friday afternoon." That's pretty specific. Moreover, it was accurate. But what if it wasn't? What if the only tools you had to work with was the current situation and what came before?

This isn't hypothetical. This forecast is for the Strait of Georgia south of Nanaimo. This forecast takes in a huge region: Howe Sound, Tsawwassen, the Gulf Islands, Victoria, Nanaimo... and the weather is anything but uniform across this vast distance. It will be different -- strong winds at Tsawwassen, for instance, when far more calm elsewhere. But it will also progress differently. Vancouver may get the oncoming weather first, but more than likely it will get it last. Consider a storm front, which circles counter-clockwise. The initial winds will be southerly as the front moves in from the west. If it stalls offshore, you will get southerlies possibly for days as the mass rotates counter-clockwise to drive the wind up the B.C. coast. 

But when the front moves inland, the tail end will pass, so the low pressure system will still bring stormy conditions, but from the north. 

This particular evening shown in the weather report was dramatic, and a reason to stay off the water no matter what, but here was the trap. At about 6 p.m., in Nanaimo the weather was just about dead calm. In Vancouver at that time, the wind was blowing hard. From that information, you could well deduce the storm had passed west, and the worst was over.

Witness what was happening at Entrance Island, though, at this time. Entrance Island is a more exposed location on the outer water of Nanaimo off the northeast extent of Gabriola Island. The weather had gone from four knots to 10 knots in the two hours between 4 and 6 p.m. 

That's a disturbing trend, but one not evident in the more sheltered water closer to Nanaimo. And it was going to get worse -- far worse. in another two hours, the wind would more than double again to a nasty 25 knots. You would not want to be on the water at that time. But if you weren't to know that when you made the decision to head out...

This situation happens all the time on the coast. Experienced mariners know to read the clues. For instance, tugs waiting to cross Cape Caution above the northern end of Vancouver Island will pay particular attention to conditions at West Sea Otter, the offshore weather buoy to the distant northwest. The tug captains will take note as to whether West Sea Otter is calm or descending. If so, no matter the conditions at Cape Caution at that time, they will know the condition at Cape Caution is almost certainly going to improve.

And more importantly, the reverse is true. If Cape Caution is calm, but winds are strong and/or the condition is deteriorating at West Sea Otter, captains will likely stay put and not chance the crossing.

It's a bit more complex than that, but the basic truth is the weather stations can presage local conditions if you know what to look for. One factor will be the direction of the prevailing front, not the direction of the wind. Wind can come from the north or south, but the front could be coming from the west. So beware of that trap.

From there build in known factors. For instance, if the normal weather for the summer is calm mornings followed by afternoon northwesterlies, an offshore weather station reporting a trend of rising southerly winds from 3 a.m. to 6 a.m. will be a sure indication something is amiss. Even if the forecast isn't reporting that possibility.

Worse yet, maybe the forecast is by and large correct. But you're in the region of West Coast Vancouver Island South, which covers from Nootka to Port Renfrew, a ridiculously large and varied coastline. You may be within the portion not conforming to the overall trend. 

Where to look for weather station information? Start here, click the applicable weather station to take you to that station, then click the "Past 24 Hour Conditions" tab in the menu bar near the top of the page. 

This, the forecast and your own examination of the weather for clues should give a clearer picture of the outlook for the near future. 

And the bottom line: if you're not sure, wait it out. Many disasters are the result of rushing to meet an artificial deadline. Sitting it out may not be ideal, but it won't cost a Coast Guard rescue or, worse yet, a fatality. 

At the very least, it's worth knowing you're not alone out there. There's a weather buoy bobbing around out there somewhere working hard to keep you informed. Be sure to use it! 

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