Weather Blog

Maybe the best Convergence Zone video ever?

Maybe the best Convergence Zone video ever?

March 2 marked the third weekend in a row that a Puget Sound Convergence Zone has made news.

(It's true! Here are my CZ-related blogs from Feb. 16 & Feb. 23)

But I'd say none have put on quite the show that this latest one did, only because there were two HD cameras rolling right in the heart of the wind battleground this time around.

Greg Johnson's SkunyBayWeather.com provided a fantastic illustration of how a zone forms then rages.

First, here is the video -- I suggest setting it to 720 HD quality for full effect:



As the video begins, note the south winds at the time and the wall of clouds forming off to the north (the camera looks to the north from Hansville -- that has Whidbey Island on the right side in the distance). Also note it's 55 degrees.

Through the first 30 seconds of the movie, the south winds continue to collide with west/northwest winds coming down the Strait of Juan de Fuca and through Admiralty Inlet.

But watch as but as the zone intensifies, the north wind begins to assert itself and push the zone south.

At 36 seconds into the movie a very important radical shift in wind occurs from the south at 25 mph to the north. The north wind will continue to assert itself and push the zone south to where it will eventually roost in its usual south Snohomish County area.

To those who live in the Convergence Zone, that shift in the wind to the north is a sign you're about to get very wet soon, as the rain typically follows shortly after.

Also note the intense drop in temperature with the wind shift. At 1:17 pm the actual day's time stamp, it's 57.6 degrees. By 2 p.m, it's dropped to 46 degrees and now the north wind is raging at 28 mph -- it would eventually peak at 40 mph. Watch the sky and you can see the battle raging between northerly flow and southerly flow.

At about 3:18, it finally begins to rain there as we're at 45 degrees and north wind at 23 mph. Remember, just two hours ago, we were nearing 60.

Hansville would get 0.06" of rain over the next two hours as the main, intense part of the zone shifts to the east to Snohomish County-- Everett's Paine Field had nearly a quarter inch of rain (0.22").

By 5:30 p.m. in video time, the zone's antics are just about done for Hansville (still going strong in King County late Saturday night though) -- just in time for one spectacular sunset!