Weather Blog

It's a bird. It's a plane. It's a... Super Convergence Zone!

It's a bird. It's a plane. It's a... Super Convergence Zone!

OK, not a true weather term, and it wasn't really "super" if you were caught driving in the heavy rain overnight and this morning. Paul Deanno says his wife probably wouldn't call it "super" since the rain pounded so hard on their roof that she couldn't sleep last night. But it certainly was a supercharged Convergence Zone.

The heavy rains Tuesday night were a combination of a batch of rain that moved up from a low in California, combining with the colliding winds of a Puget Sound Convergence Zone to add some extra oomph.

And by "extra oomph", we mean incredible downpours. So much so that Seattle set their daily rainfall record (which was admittedly a paltry 0.28") -- before the sun even came up Tuesday. They were at 0.88" as of late Wednesday morning (and counting.)

A typical Puget Sound Convergence Zone involves winds meeting up (or converging) after going around the Olympic Mountains. That's enough to get some rain going after a front has moved through (like Tuesday. But this Convergence Zone wasn't alone; there's a strong area of low pressure spinning over Northern California.

That low sent a significant amount of moisture our way, which also converged right over King and Snohomish counties. We basically had winds coming from the north, south *and* east colliding at different levels over the Puget Sound area.

(That California rain was wrapping around from the east, which is why some of you saw the rain moving in the rare east-to-west direction.)

The result: Several hours of moderate to heavy rainfall overnight. Well over an inch of rain fell in many Eastside communities, with a spotter in Issaquah reporting 2.55".

Here are some of the other big rain winners, most of these according to the CocoRahs community rainfall network, totals from overnight through about 7 a.m.:

  • North Bend: 1.58"
  • Snoqualmie: 1.53"
  • Fall City: 1.53"
  • Kirkland: 1.21"
  • Maple Valley: 1.16"
  • Auburn: 1.12"
  • Covington: 1.00"
  • Renton: 0.98"
  • Bellevue: 0.96"
  • Kent: 0.93"
  • Woodinville: 0.90"
  • Federal Way: 0.89"
  • Seattle (Sea-Tac): 0.88"
  • Mercer Island: 0.84"
  • Redmond: 0.81"
  • Sammamish: 0.76"
  • Everett (Paine Field): 0.75"
  • Tacoma: 0.33"
  • Olympia: 0.00" (Yep, they got squat.)
  • Forks: 0.00" (They got squat too. When was the last time Seattle was nearly an inch wetter than Forks?)

The heavy rains and saturated ground knocked over a few trees on the Eastside, with reports of a few tree-related problems on Mercer Island and Capitol Hill, and power was knocked out to just under 3,000 people in West Seattle.

(For the record, the forecast models did have part of this equation, only the California moisture was supposed to only reach the mountains and Cascade foothills. And it wasn't supposed to be anywhere near that heavy, but the convergence zone really set it off.)

The rain is set to taper off later today as the zone fizzles, but in the meantime, hopefully you can wring out a bit.