Since this post has now become completely hijacked, and since, as Dave has surmised, I am completely bored...
Tim brings up an interesting point - "Assuming this was measured with the same windmeter..."
In reality, a wind meter doesn't measure wind speed at all. It measures the force, or pressure of the wind. The force of the wind is proportional to the the air density and actual
speed, which is unknown. In fact, if you took a wind meter that was properly calibrated for standard conditions on Earth, and used it to measure the wind speed on Mars, you might find that it also reads 20mph, when the actual wind speed might be several hundred miles per hour (not that uncommon for Mars). This is because the atmosphere is so much thinner on Mars.
The important thing about this thought experiment is that a land sailor on Mars with a 200mph wind measuring 20mph on a given wind meter would feel similarly powered to a land sailor on the playa at Burning Man when the same wind meter was indicating 20mph with an actual wind speed of essentially 20mph. The bottom line is that the important factor is the force of the wind, not the actual wind speed.
To Ollie's point: "All I know I that during the regular season, 20 on the coast seems more powerful than 20 at the delta...". If it were the same wind meter reading 20mph, and in the actual location of the riding (i.e. on the water in the riding zone and not somewhere on land), then a rider should feel equally powered, even if the actual wind speeds, due to differences in temperature and humidity, are a couple of mph off from 20mph, even in opposite directions. I've heard a lot of people echo Ollie's observation. And I've noticed myself that I can feel overpowered at Waddell on a 10m kite when the wind graph shows a steady 20mph, yet at the delta I'm more likely to be comfortably powered on a 12m when the graph says 20mph. But I believe that is more likely attributable to differences in calibration between the 2 sensors, or their locations relative to their respective riding zones, and not to the temperature and humidity characteristics of the air at their sites.
OK, I'm going to go for a bike ride now in this beautiful weather, and try to convince myself that it is as much fun as kiting.
Oh, and yeah Dave, I do want to go to Costa Rica. I just can't.