Christmas Morning Surprise (Wind)

December 25, 2005

I should have paid closer attention…2 of gifts from my wife last night included:  a storm survival kit for the house and a nightlight/emergency flashlight combo for power outages.  Hmm….funny that I wake up at 4am to electricity buzzing off/on/halfway on etc…also flashes in the sky and then it was pretty obvious.  A very warm wind blowing from the southwest means some sort of surprise windstorm.

The low pressure center that travelled just offshore last night ended up stronger than expected, and when the cold front moved through early this morning, strong winds above mixed down to here on the ground.  I’ve scanned all sorts of observations, including Forest Service sensors in the mountains and ODOT sensors.  I can’t find a single gust above 50 mph anywhere below 4,000′ here in Northwest Oregon.  Hard to believe that peak southwest wind gusts from 45-50 mph dropped dozens of trees and put 30,000 PGE customers out of power for Christmas Morning.  That’s the largest outage since the ice storm 2 years ago!  Just about all damage was confined to an area east of I-205/99E and west of the Cascades, and between I-84 on the north and Marion County on the south.  Clackamas and E. Multnomah County seemed to get the brunt of the outages.

Pressure gradients (actually observed, not forecast by models) seemed to barely even support winds that strong.  And even more interesting is that 50-60 mph easterly winds in some spots such as Gresham last week downed fewer trees than 40-50 mph southerly winds today.  I suppose it could be related to the fact that it’s been 6 years since PDX has seen a southerly wind gust over 50 mph.  Our trees have had it easy lately.  Maybe many of those would have gone down over the last few winters.   

The weather pattern stays very active through the first few days of 2006, so we’ll be watching closely for any strong areas of low pressure approaching the coastline.  There should be 5 good "waves" or chunks of energy moving through between Sunday evening (now) and Saturday Evening (New Year’s Eve).

By the way…the high of 63 degrees is the warmest Christmas Day since the 1980.  If you were here then, you may remember lots of flooding.  That’s the event where part of Mt. Hood washed down and washed out a good chunk of Highway 35 and several bridges in Hood River county.