As shown below, the Olympic rainshadow is normally on the northeast side of the Olympics, while heavy precipitation is found on the south and southwest side of the barrier.
But something unexpected happened on Tuesday morning.
The weather radar indicated precipitation in the rainshadow area, with nothing apparent on the southwest side (see below, there is some ground clutter on the SW side from the radar beam hitting some peaks).
Rain gauges picked up modest rainfall north of the Olympics, with precipitation on the dry-sky lovers in Sequim and vicinity. Surely unwelcome for those hitting the links that morning.
The origin of this backwards situation? The low-level winds had reversed, with northerly wind approaching the Olympics from the north (see surface wind below).
This situation was associated with high pressure to the north and low pressure to the south (see below), with the wind blowing from high to low pressure.
We will be dry until the middle of next week, after which the atmospheric spigot turns on in a major way.
Thanks for the clear explanation.
ReplyDeleteHope the coming spigot brings snow. Low snowpack in Oregon and the SW US is really bad news
ReplyDeleteThank you for explaining this interesting scenario. Its been a dry, pleasant week along the Grays Harbor coast after Sunday's unexpected rounds of thunder moved through. I had no idea that an Olympic rainshadow could actually develop out here. It so often develops over Sequim that it seemed like that was the one and only place it could happen.
ReplyDeleteI used to escape to Sequim in the fall for golf and long hikes—trading Seattle’s steady drizzle for blue sky and dry air. There’s something magical about playing a round with low clouds drifting overhead and not a drop of rain falling.
ReplyDeleteOnce, though, I glanced up and saw what looked like a solid wall of rain moving straight toward me off the mountains—so dense it seemed almost theatrical. I took shelter for about an hour. A rare exception, perhaps, that proved the rule.