Snow Storm ’09 Wrapup…What Happened?

December 30, 2009

I woke up with a headache today (really, no drinks after the shows yesterday)…must have been lots of that stress hormone running through me yesterday afternoon and evening.  What a depressing day for forecasters here in Portland.  It’s time to break it down and see how things panned out.

First, let’s get this out of the way:  We (I) really screwed up this forecast!  We apologize to those of you stuck in the worst Metro area commute in my 18 years forecasting here.

See, that wasn’t so hard…the air feels more clear now.  Let’s answer a few questions.

WHY WAS THE STORM & TRAFFIC SO BAD WITH ONLY 2-4″ SNOW?

1.  It wasn’t forecast: 1-4″ of snow was widespread across the metro area with no one forecasting more than “maybe it could start as snow”.  No TV weather people or the NWS.

2. Because of that no one had alternate plans or drove their “snow cars”:  I normally drive a crappy (in the snow) two wheel drive that gets great mileage.  I only drove the 4 wheel drive because I expected something frozen at my home in the western Gorge.  Otherwise it would have happened to me too.

3.  Timing was the worst it could be:  The beginning of the afternoon commute when thousands of us were at work.  If it was 6-9am most would have stayed home.  If it was at 8pm everyone would have made alternate plans for the next morning.  We were trapped at our workplaces.

 

WHY CAN’T YOU PEOPLE EVER GET IT RIGHT, YOU’RE WRONG AGAIN!

I have received 2 emails about this and seen harsh criticism on the Oregon Media Central site plus a few on this blog as well.

I am keenly aware (being in the TV business) that often “perception IS reality”.  For years there will be residents that remember the big storm “they” screwed up…”see, they never get it right!”  I could have 100 correct forecasts, screw up one big one and people will only remember that one.  That’s human nature; so it goes, I’d be the same way sitting on the other side of the TV tube.  But let’s get rid of all emotion and look at the reality.  We’ve hit almost every major weather event the last few years.  Here’s a list:  1. Last year’s major cold wave forecast 7-9 days ahead of time. 2. Snow arrival with cold wave forecast several days ahead of time.  3. Biggest snowstorm in decades forecast 3-4 days ahead of time last December (20th). 4. Worst heat wave in decades forecast 5-7 days ahead of time last summer. 5. Severe thunderstorms on June 4th.  We knew, and mentioned, that good chance for afternoon storms moving into the Valleys.  6. Major cold spell this December forecast 5-7 days ahead of time by most of us.

The last time we really screwed things up was January 2007 (almost 3 years ago), remember the trace or so of snow that turned into 3-5″?  So I think we’ve done pretty well the last 5 years.

 

WHY WAS THE FORECAST SO BAD?

Yesterday was definitely NOT one of those situations where we say “wow, where did THAT come from?”  We knew all along that it was going to be close (see my blog posting the night before)…and by yesterday morning it was a marginal situation forecast-wise.  We probably should have said (via TV, blog, Twitter, etc…) that it could start out as snow or even get some sticking snow.  Here’s a good example…using the 4km WRF-GFS sounding.  It’s the highest resolution model we have access to here in the Metro Area.  This is the forecast sounding at 4pm yesterday from the 00z model the night before to the left. Notice the model shows temps above freezing in the lowest part of the atmosphere after the precipitation starts.  Looks like rain, with snowflakes possibly reaching down to the ground mixed in…that’s the forecast I went with at 10/11pm.  Now check out the 12z run (comes out around 8am) on the right side. Notice it shows it slightly colder…at most it’s +1 deg C. in the warmest part of the atmosphere.  This is pretty much a snow scenario…maybe some mixed too.  Now keep in mind we have easterly flow as well.  And keep in mind too that the 4km WRF sees the Columbia River Gorge as a 1,500′ pass through the Cascades, so it usually doesn’t show the fine details of the lowest chunk of a cold airmass.  But you have to admit this model actually did quite well…within a a degree or two of what actually happened yesterday.  We should have hit this harder…forecasting “all snow most areas with a Trace to 2″ snow” .  We did get the cold pooling and best uplift on the westside of the Valley, so higher snow totals there.  Models did show this and I think I mentioned that in the previous post.  By the way, check out the Meteogram for PDX from the same 12z model:
It clearly shows the evaporative cooling around 4pm as the precipitation starts, lowing the temp to 34-35 at PDX.  Not so bad eh?
 
So in the end, the weather system came in on schedule, precipitation started out and ended on schedule, but the temperature was a few degrees too warm.  Some won’t like that answer, but that’s the truth.  Drew Jackson has a perfect comment on this here.
 
Chief Meteorologist Mark Nelsen