Windstorm in 24 hours!

December 13, 2006

Okay here are my thoughts on wind tomorrow night:

1.  Models all seem to like a landfall somewhere between C. Vancouver Island and NW Washington Coastline.
2.  Taking the GFS/NAM at face value, I would figure maybe gusts to 50-55 mph at PDX and in metro area…hardly a major windstorm, but a nice little winter windstorm.

But once again the MM5-GFS is very insistent on a strong bent-back occlusion swinging through in the late evening or midnight.  The new 00z version even seems to develop a 2nd surface low that skirts around the south side of the Olympics, almost like a "dumbelling" around the initial low.  That really tightens the gradient.  I counted 15 mb PDX-OLM and 23 EUG-OLM.  This is major windstorm material, especially considering the 1000-2000′ wind is forecast to be 60-70 kts.  IF that wind surfaces gusts to 70 mph are likely from PDX north.  I say PDX north because of the tightest gradient up north.  That’s why I leaned heavily on that during the 10pm weathercast.
For those of you on the coast, the southwest wind that comes surging in behind the occlusion is amazing.  MM5 once again shows 60kts sustained surface wind slamming the coastline.  Wow…One other reason is that the whole surface low/bent-back occlusion is moving at 50 mph, which is great for a quick hit of strong wind.
On the negative side, I am worried a bit by the weak surface wind forecast on the same MM5.  Only 20-30kts in the valley even though it’s far stronger just a couple thousand feet above.  Hopefully the model doesn’t know something I don’t.  I’d hate to see gusts to only 45 mph after such a big anticipation of the event.

As for snow, I pretty much covered that at 10:45.  Not real impressed with precip on MM5 for Saturday or Sunday.   Earlier runs had a surface low moving up to mouth of the Columbia, but 00z models a bit sketchy on that.  I feel it’s going to be a pretty quiet weather weekend with snow showers mainly in the hills on Saturday only.  My high temps at PDX may even be 2-4 degrees too cold if we get much sunshine.
Back to mild rain next week..Mark