Strong Sound Breeze and Tragedy

Last night's 11 PM news and today's Seattle Times related a story about the tragic death of a young man near Seward Park who had been using a Yamaha personal water craft.  The ST article is found here.  In this article there was a brief mention of a sudden increase in wind and choppiness of Lake Washington.

Was there a meteorological origin to this terrible incident?  If so, could it have been predicted?

I think I caught a piece of whatever happened while bicycling home around 6:30 PM from the UW-- not far from NOAA Sand Point I was impressed by the strength of  the head wind out of the north.  It was really strong.  Now on warm sunny days a northerly wind often develops north of Seattle and is called the Sound Breeze.  But this time it came up fast and hard.

Probably the best observation for the boating incident was from the wind sensors at the central part of the Evergreen Floating Bridge.  As shown in the map below  the bridge was upwind of the accident site (X for the incident location and O for the wind sensor).  The winds were from the north so the Evergreen Point wind sensor was in the perfect location.

Here is the wind speed record on the Evergreen Bridge.  Wow.  Around 6 PM there was a very sudden ramp up of wind speed to over 20 mph from roughly 3-5 mph.  That wind, plus a good water fetch north of Seward Park meant rapid growth of waves.

Strong winds also developed down Puget Sound.

The high resolution computer models had a good idea that strong winds would push into the Strait of Juan of Fuca and down into Puget Sound.  Here is a forecast for 8 PM of surface winds from the UW's ultra high resolution model prediction (1.3 km grid spacing!):

Even the UW system did not have enough resolution to handle Lake Washington, which is too narrow to properly resolve.  But it was clear that strong northerlies would hit around dinner time (you can see all these graphics for every hour on my department web site).

But why were the winds so strong and why did they come up so suddenly on Wednesday?  I suspect the answer was the passage of an upper level disturbance that afternoon which really revved up the pressure differences between the coast and inland yesterday. Here is an upper level map showing you the heights of the 500hPa pressure surface at 5 PM--can you see the trough over us?  I think that is the culprit.

So we start with the normal Sound Breeze--essentially a large regional sea breeze.  As the western Washington interior heat up relative to the Pacific and Strait, westerly winds develop in the Strait each afternoon and then push southward into Puget Sound.  But this time the Sound Breeze was supercharged as the passing trough causes an enhanced east-west pressure difference that drove even stronger flow through the Strait and then down into Puget Sound.

My hope is that in a few years we can combine our observations and improved models with modern communications (e.g., smartphones and the like) to allow us to provide highly useful and timely warnings of such events.  We won't stop all such tragedies, but hopefully many injuries and deaths can be avoided.

Bogus Arguments of Some Global Warming "Skeptics"

During the past week I have gotten several emails from folks who said they had absolute proof that human-induced global warming is nonsense.

The argument they offer:  volcanoes put out way more CO2 than human activities. So it doesn't matter what we do!

Since I have heard this claim at least a dozen times during the past few months, I thought I should just give the facts:  HUMANS EJECT WAY MORE CO2 INTO THE ATMOSPHERE EVEN DURING MAJOR VOLCANO YEARS.

A number of studies have shown that global volcanic activity injects about 0.15 to 0.26 gigatons per year of CO2.  Anthropogenic CO2 emissions produced by mankind provide about 35 gigatons of CO2 in 2010.   Way more.

To put it another way:  current volcanic activity puts out about as much annually as our states of Florida, Michigan, and Ohio.  We have a lot more states and then there is the rest of the world!

The following figure (from a very nice article in EOS by Terry Gerlach of the Cascades Volcanic Observatory in Vancouver, 14 June 2011, volume 92, No. 24, pg 201-202): shows the ratio (the ACM) between human and volcanic CO2 emissions (shown by the dots).  The range of uncertainty (based on the uncertainty in volcanic emissions) is show by the brackets.  What one should conclude is that  human emissions dwarf volcanoes and the ratio is increasing.  Today we put out well OVER A HUNDRED TIMES more than volcanoes.

 

So please!  Lets move on with this.  Volcanoes today are minor players in the CO2 world compared to us.  

In a future blog I will deal with another argument by the denier set--that human impacts will be dwarfed by the variability of the sun.   As I will show in that blog, this is simply not true either.  I will leave to others to deal with conspiracy theories dealing with Al Gore.

Now don't get me wrong.   Some groups on the "pro" side of global warming are sometimes fast and loose with the facts too, particularly in their claims of C02 induced extreme weather and huge losses of Cascade snowpack.  We can't have a rational discussion of the threat of anthropogenic global warming--and it is a serious threat-- if clearly wrong information is used as bases for arguments.

The Upcoming Week AND What Have We Been Missing?

I just took a look at the latest model output and it appears that we have a fairly decent week ahead.  In fact, the Climate Prediction Center's 6-10 day forecasts have a different look than we are accustomed to:

Higher odds for warmer than normal in the West (including us), near normal over the middle of the U.S., and cooler in the East.

The persistent West Coast troughing has weakened and we have fairly normal weather for the entire week.  That means dry and temps getting up into the mid-70s.  Just perfect for painting your house (which I just did).

But something has been missing this year.  Something that many of us miss: some good warm spells, with substantially above normal temperatures (like the 80s!! and dare I say it?...the 90s).

Here is the plot of temps versus normal for the last four weeks at Sea Tac:

We got to 80F only twice and never got to 85F.  Most days we  fell short of the normal max.  So why have we been plagued with lack of warm spells?

The answer is that we simply are not getting the right set up--big upper ridge over the west side of the Cascades, surface high pressure to the east, and a thermal trough at low levels moving up the Oregon and Washington coasts.  This is particularly ironic for me, because my student Matt Brewer and I have a project, funded by the U.S. Forest Service to study thermal troughs and to learn how to predict them better.  Thermal troughs are often associated with wildfires.

Want to see what a good thermal trough looks like?  Here is a forecast of one from almost exactly a year ago.  The solid lines are isobars (lines of constant pressure) and the shading denote lower-atmosphere temperatures.  You see the low pressure extending to the WA coast?  Starting over Nevada?  That is it.  And high pressure to the northwest of us over southwestern BC.

We haven't seen such a pattern this year.  Want to see a super thermal trough?  Here is the one with our big heatwave during July 2009:

The low pressure area extended to Vancouver Island!

Thermal troughs, or thermally induces pressure troughs, typically extend up the coast from CA during our heat waves.  They are inevitably associated with offshore flow that keeps the cool marine air away from us.  They are the tail of about a big dog...the dog being large scale high pressure that sets up the offshore flow.

Anyway, lets hope we get a nice thermal trough before the summer is out.  Warm when one wakes up, perfect at night for an outdoor bbq or an evening stroll.