September 25, 2011

The New Radar Documents A Frontal Passage

Monday Morning Update:

Here is the storm total precipitation ending 10:30 AM on Monday from the new radar....notice the enhanced precipitation on the windward (SW) slopes of the Olympics:

In science, major advances in understanding often come with a new instrument, one that casts light on a previously unobserved phenomena.  Certainly, that is true of meteorology; through new understanding and additional data from new sensors, the skill of prediction increases.

The frontal system that passed through during last night and today was observed from beginning to end by the new Langley Hill radar---lets take a look at only one viewpoint:  the reflectivity at the lowest elevation angle (.5 degrees).   As we have talked about many times in this blog, such reflectivity is closely related to precipitation intensity.

First, consider the image at 5:34 PM yesterday.  Note the precipitation intensity (reflectivity) is given in dbz and yellow is very heavy stuff, green a lot lighter, etc.  Looking offshore we could see the approach of the Pacific frontal system (something we could not do before).   During the day yesterday (Saturday) the skies over Puget Sound clouded up and some light showers formed as the air over the western interior destabilized at midlevels--producing lots of altocumulus castelanus.   You can see the light showers in the radar, indicated by the north-south linear features.   Not forecast well.   This was not frontal precipitation, but rather the instability was initiated by the approach of the upper level trough associated with the front.

Four hours later around 8 PM the offshore precipitation was approaching rapidly and some light showers remained over the western slopes of the Cascades,

As the evening progressed the band reached the coast, as shown by this image at 1:44 AM.  Look how nicely the radar shows the band from Vancouver Island to south of Tillamook, Oregon.  The location of this radar was chosen very, very carefully to allow such a comprehensive view.  Behind the band the precipitation is spottier and more intense, indicative of convective precipitation.

And now the great disappearing trick!  The Camano Island radar had a blind spot west and south of the Olympics.  Of course, our new radar has a blind spot too--NW of the Olympics!   Here is a view of few hours later that shows this.  Believe me, the band extended north of Everett.  And look can see instability showers over the Pacific, with some with red colors---very, very heavy rain.  Interestingly the surface front (with the lowest pressure and windshift) was NOT with the continuous precipitation band over Puget Sound, but was still offshore at this time.

In fact, there was another band of precipitation, fairly convective looking, that come in with the front around 9 AM Sunday (see below).

 Around 12:38 PM there were lots of showers over the western slopes of the Olympics and coastal mountains.   You see the regular streakiness in the convection?  That is associated with convective roll circulations.  And see the bluish colors just off of Gray's Harbor?  That is the radar seeing the surface of the ocean.

And finally the situation after the front around 5 PM on Sunday...a few convective showers over the Pacific.  Showers and sunbreaks.

This radar is going to teach us a great deal about Northwest meteorology.  Knowledge that will both aid my colleagues in the National Weather Service and help us gain a better understanding of the interactions of incoming weather systems with our coastal terrain.

 Seattle School Board Candidate Events

There are two important gatherings to listen and talk to Seattle School Board candidates:

Wednesday, Sept 28th-7:30pm
The Stranger's School Board Candidate Debate
Town Hall - 1119 8th Avenue, Seattle
NOTE:  The event is FREE but tickets are required.
Click here for ticket information.

Friday, September 30th 6-8pm
West Seattle Meet & Greet Happy Hour with Candidates Marty McLaren & Sharon Peaslee (and I will be there too!).   Refreshments, of course.
TOPIC: Improving Math, Science and STEM in SPS
7020 18th SW (north of SW Myrtle)
Donations appreciated. - all are welcome


  1. The disappearing trick -- that seems to leave out Whatcom and Skagit Counties, and near-border BC too. If the new radar were to supplant the Camano Island radar currently on the UW site, I would be somewhat disappointed (I'm in southern BC, and prefer the UW radar to what Environment Canada provides).

    In any case, fan mail: I enjoy your blog and have learned a lot from it.

  2. Is the radar "seeing the surface of the ocean" likely to be a greater problem at the zero degree elevation angle, when that feature is operational?

  3. Hugh..don't worry---you will have BOTH Camano Island and new Langley Hill radar. Camano is down now for upgrade.

    Yes...see clutter will be a greater issue for the zero degree---some of it we can remove and in any case it will cover only a small portion of the domain


  4. Very nice, Cliff.

    As importantly, I stood outside in the deep, moonless darkness, and listened to a flight of waterfowl talk to each other high above until, moving north to south, their conversation trailed off in the distance.

    Haunting. As haunting as the first time I heard it when I was a child growing up on a small farm on what was then a largely wooded and farm covered Sammamish Plateau.

    I suspect that as sophisticated as our technology is, those geese and ducks and other birds that make their vast migrations, learned and mastered what we know, and have yet to learn, eons ago. Maybe more than we'll ever know.

    Winter is on its way. It lurks just north of us where it chases the sun south. Look closely behind the V formations of those birds and you can imagine it as it gathers itself where they left it behind.

    Good luck with the radar.

  5. Is it possible to combine the Camano and Langley Hill radars in the same image? Will there be a URL for this? Thanks.

  6. John McBride, you sent chills up my spine.

  7. Dave -

  8. Cliff,
    I could not get the NWS radar national selector map to link me to the LGX station; just a matter of time for them to list it, I suspect. This blog would have benefited from a link to the new LGX station,especially since ATX is currently down. Blog edit possible? Anyway, I find its loop at

    I use the radars very much like you say you do for bicycling, as in frequently for planning outdoor activities. As such, they live on my browser toolbar. To use that bar space efficiently, labels have been shortened to NWS ATX and NWS LGX. Do you have a short moniker for your wonderful UW atmos composite loop? I would like to identify it with your acronym, if you have one for it.

    And thanks again for the time and effort you donate to educating us out here.

  9. Wow. Just saw the radar at 9:55am and it is beautiful. I have never seen my home area (Grays Harbor) covered like this...cant wait for the first huge storm. Also, Cliff, I was on the NWS menu of radars and noticed that many in urban areas have quite a bit of 'noise' immediately surrounding the core this pollution it's seeing? Thanks!

  10. Cliff...I'm wondering if the edge of the visible region (that the radar "sees" can be shown with a dotted line. It is hard to interpret at the outer edge - there may no precip, or they may be no signal...hard to tell...Chris in Victoria...

  11. Is the stalled system that was visible yesterday and visible today between Lopez Island and Port Townsend and west of those points a particular phenomenon or a result of Camano radar being down?

  12. I was out sailing Saturday and Sunday. Sunday morning, I got hit by that front in the Strait of Juan de Fuca. It was very exciting and a bit scary! And earlier, Sunday morning around 5 AM, I was hit by an unusual strong EAST wind while anchored near Dungeness Spit. I thought this stuff comes from the SW and enters the Strait from the West. That had me running scared too. Can you explain?


  13. I think you meant the blind spot was NE of the olympics.

  14. Are the ocean surface echos correlated with wave heights? Could they change with the tides?

  15. Would this little guy ( be your lost hound?

  16. No..that is not the dog..but thanks for asking!..cliff


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