10pm: Stormy Weather Update

December 10, 2014


Evening models are in and just about all of them show the same thing now; a surface low tracking up the coastline just offshore.  Nice to see them finally agree 18-24 hours out.  Here are the quick highlights:

  • Strong wind arrives at the central coastline midday to early afternoon, moving north it’ll reach the Columbia River (Astoria) around 4pm.
  • In the valleys this WILL NOT be a HUGE windstorm like Dec. 1995, but it’ll probably be a bit stronger than what we saw in October.  Strong wind arrives sometime after 3pm.  Most action will be during the evening commute.
  • There will be plenty of power outages and trees down by this time tomorrow evening.
  • Peak gusts at metro area airport locations will likely be in the 45-55 mph range.  Somebody somewhere in the metro area will probably record a gust 60-65 mph on a hill-top.

For some reason I’ve been having trouble forecast-wise with this storm the past 24 hours.  All in my head of course.  I think I figured it out this evening.  The forecast train a couple of days ago started out with the possibility of a BIG storm.  But models have ever so gradually weakened things a bit so now we’re back to a “normal” strong winter storm instead of something possibly “epic”. Here is my forecast I’m using at 10pm:



Note I lowered my forecast for the valleys slightly, down to speeds similar to October’s storm.  There are two reasons for that:

1. All models are showing the low pressure system filling significantly after it reaches the southern Oregon Coast.  The ECMWF fills it a full 10 millibars from 10am to 10pm!   That would reduce the pressure gradient from south to north.

ecm_10am ecm_10pm

2.  The strong WRF-GFS has gradually been lowering its gradients the past 4 runs too.  Yesterday morning it showed a peak Eugene to Portland gradient of 8mb, now it’s 6.  The change from North Bend to Astoria is more significant.  It had shown 19mb, now just 13!  That makes me think the 70-90 mph gust forecast out there could be too high.  65-80 seems more likely.

I see there are schools cancelling on the northern Oregon and southern Washington coast.  Most likely those locations won’t see gusty wind until AFTER school gets out anyway, but I guess they are being extra cautious.

There is actually one more run of models tomorrow morning, so I’ll post once more around 10am.  As of 11:30pm I’ve turned off comments for the night.  I’ll turn them back on tomorrow morning after I post again.  Good time to go to bed anyway!

Chief Meteorologist Mark Nelsen

High Wind Warning Issued

December 10, 2014

1pm Wednesday…

Portland NWS just issued a High Wind Warning for all areas west of the Cascades in NW Oregon and SW Washington at midday.  This if for storm #3 of our current round of wet/windy systems.  Here is the latest:

  • Confidence is very high that the Oregon Coast will see a major windstorm Thursday midday-afternoon.  Gusts 75-90 mph look likely out there.  Today’s storm turned out a bit weaker than expected, but don’t let that lull you into a false sense of security if you live out there, tomorrow’s system is different.
  • Confidence is also high that there will be gusty south wind late tomorrow afternoon and evening in the western valleys too.  I’m confident that we’ll see gusts at least 35-50 mph.  This is a pretty typical winter wind event here.  Not a huge storm in that case, but enough to cause some trouble.
  • Much lower confidence that we have a “big” windstorm coming to the inland valleys.  There IS a high enough chance that the NWS pulled the trigger on a High Wind Warning.  That means gusts 58+ mph.  That would be a big deal and the strongest we’ve seen here since December 2006.
  • Wind will be from the normal easterly direction much of the day tomorrow…nothing interesting will happen until after 2-3pm.
  • Based on available info as of noon:  In the valley, from Eugene to Longview, I’m forecasting a sudden increase in south wind during the mid-late afternoon hours in the valley.  Southerly gusts 45-55mph.  This is similar to what we saw in late October.  Because of the leaves on the trees and the very wet ground at that time, PGE had 80,000 customers out at one time!  I think the same speed right now wouldn’t do as much damage with no leaves, but still a pretty decent southerly windstorm.

MarkWarnings_High Wind

The big question is whether the wind ramps up beyond that into “Big Windstorm” category.  Models seem to have back-pedaled just a bit and some have turned a bit weaker in the past 12 hours.

All the morning model runs are in with a few changes.

1. The GFS is farther offshore, which would put 50mph gusts almost out of range for the metro area.

2. The ECMWF is also ever so slightly farther offshore, but not enough to make much of a forecast difference.  It’s also SLIGHTLY weaker with inland wind.

3. The GEM has a perfect track with the low heading north to around Olympia…quite a pressure rise, but it’s also the slowest.

4.  All models are filling the low after it passes the central Oregon coastline.  Not a big deal, but I noticed it.

5.  Timing is slower all around…by about 6 hours compared to 24 hours ago.

6.  The 12z and 18z NAM still say gusts 30-35 mph at best.  I ignored it.  Our RPM is very weak as well.  Strange since it’s based on the GFS.

In general the trend looks a bit weaker to me and I’m not sold that we have any sort of major windstorm coming for the valleys, thus the wide range in the peak gust forecast (45-60 mph).  There are still 2 more main model runs before the event, including one before I’m on at 10pm tonight for our “big show”.

So the big story for right now is “wait and see” what changes in models for the next 12 hours, and GET READY FOR A BIG STORM on the Oregon Coast!

Chief Meteorologist Mark Nelsen