Big Coastal Storm Late Wednesday

March 8, 2016

11pm Tuesday…

January, February, and this first week of March have been very quiet weatherwise.  But one very strong storm is developing to our southwest.  It’s going to be a classic “southwester” as the deepening surface low races almost straight north along the 130 west longitude line.  Typically for a widespread windstorm in our area we need a deep low to move along this track EAST of that line, so this one will be pretty far out.  But it’ll bottom out down around 970 millibars as it moves towards Haida Gwaii or the northern tip of Vancouver Island.  That’s a strong storm and one capable of giving widespread 65-75 mph gusts at the coast.  I wouldn’t be  surprised to see an isolated spot or two (not Mt. Hebo or Meares Hill) around 80-90 mph.MarkWarnings_Wind_Coast_Valleys

After a strong easterly Gorge wind in the morning (gorge and east metro), a southerly pressure gradient will set up in the Willamette Valley in the late afternoon and evening.  That’s when wind will pick up in the Valley.  I sure don’t expect a damaging wind in the valley, but breezy and rainy for the evening

MarkWarnings_Wind_Coast_Valleys2

One would think that we could get a decent windstorm with the extremely strong wind overhead tomorrow night.  The WRF-GFS cross section shows 90 mph wind over Portland around 10pm-1am tomorrow night; one of the only times I’ve seen an 80 kt. wind barb overhead.

wrf_sounding

But the isobar orientation is not lined up correctly down here at the surface since the low is way offshore.  Thus the wind won’t get too strong.  It would be a totally different story tomorrow night if we had a strong south to north pressure gradient in the western valleys.

Chief Meteorologist Mark Nelsen


ECMWF Upgrade Today

March 8, 2016

The best numerical weather prediction model on the planet just got a bit better this morning.  As of this morning’s run the ECMWF global model has been upgraded to an ~9 kilometer resolution.  That’s a higher resolution than the GFS (I think 12 or 13km?).  Resolution refers to grid point spacing in the model.  Generally the closer together the grid points the more features the model can see.  Of course that’s assuming the initialization is correct…a big assumption at times.  You can see how ECMWF regularly beats the American model (GFS) in skill scores; I found this on Ryan Maue’s Twitter page:

0Capture

Note the comparison is for 500mb height in the mid-latitudes.  A score of “1” would be perfect, so the higher the better.  See the parallel (new) model run for the past few months has been slightly better than the operational (regular ECMWF) run.  Today the parallel run IS the operational run with the slightly higher resolution.

But what does it mean????  Well, it’s not quite as remarkable as that famous double rainbow video and I don’t want to spend 3 minutes on it, but…

The model will just tend to do slightly better as it catches a few more details.  Also, with slightly better terrain you may see a bit more detail.  Here is an example with two images:

  1. Last night’s ECMWF run for peak wind gusts with Wednesday night storm
  2. This morning’s higher-res ECMWF run for the same time

ecmwf_oldecmwf_uv10g_portland_8

You can see a little more detail in the 2nd image in the Coast Range and maybe in the Cascades.  It’s going to be a crazy windstorm at the Coast tomorrow evening!  Could see gusts in the 65-80 mph range!  Both runs show that.

Check out estimated snowdepth for next Monday; same timing with last night’s run and then this morning’s upgraded run…

ecmwf_snowdepth_oldecmwf_snowdepth_portland_25

Notice less “overspill” of contours into the valleys east and west of the Cascades?  Similar totals in the mountains but you don’t see as much down below.  Especially obvious in Jefferson and Wasco counties in north-central Oregon.

This is all minor stuff, but the point is that global models keep improving at a slow pace.  Compare this to 10-15 years ago and it’s a huge improvement!

By the way, I don’t generally show these images on the blog because they are not supposed to be redistributed.  They are available through a paid service…WeatherBELL.  About $185/year.  I think a one-time showing for the purposes of the model upgrade is alright though.  You can always give WeatherBELL a try…I think they have a free 7 day trial.

Chief Meteorologist Mark Nelsen