Keeping a Close Watch

November 20, 2009

Oh, that doesn’t look so good in miniature form.  Click on the image to see the 45 hour sea level pressure map from the UW’s WRF-GFS.  It shows a relatively deep low moving from about Tillamook to Yakima late Saturday night.  It’s a wave on the trailing end of  tomorrow’s very wet cold front.  On this model it deepens to about 989 mb.  This setup HAS, in the past, produced a windstorm in the north Willamette Valley.  It’s been a very fast event too.  A sudden surge of SW wind, maybe 2-3 hours maximum, then that’s it.  Wolf Read has the most amazing collection of data for Pacific Northwest windstorms.  He has a good writeup on the January 1990 storms.  Keep in mind there were a series of storms and the one similar to what I am thinking is the night of January 7th-8th 1990.  That produced gusts 60-70 mph here in the Portland Metro area and damaging westerly wind gusts in the Gorge.

Now that’s one model…the 18z NAM and our 12z/18z RPM both show the low either over us or slightly to the south.  The NAM has it passing over Salem, which is a good windstorm for the south Valley but nothing here.

So this could be nothing for us here in the Metro area or a great quick windstorm coming up tomorrow night.  Ahhh, the anticipation of the 00z models! 

11pm Update:

00z models seem to have come together a little bit, but not enough to say with confidence that we do OR do not have a strong wind event on the way.  Our RPM model and the NAM are the southern models with a track from Tillamook to Yakima.  The NAM is pretty much right over Portland and weakening as it moves by; not good for a strong southerly wind here.  The RPM only gives 8 millibars EUG to PDX.  Gusts 40-50 at best with that.  The 00z GFS is the stronger one and has the track farther north, maybe AST to North Central Washington.  This one gives us 10-16 millibars gradient from Eugene to Olympia.  That’s more significant, especially the WRF-GFS version.

So this means we are still up in the air and must say “can’t wait for the 12z models!”.  Hopefully they’ll have more agreement.  My gut feeling is that this may just be a non-event since we didnt’ see any dramatic strengthening in the 00z runs…but we’ll see.

Chief Meteorologist Mark Nelsen