September 29, 2009

An Active Convergence Zone

There was lightning and heavy rain in central Puget Sound tonight due to a strong Puget Sound convergence zone--the radar says it all (see image, yellow is heavy rain).

I watched the zone late this afternoon at the UW. Dark ominous clouds moved in from the north and a particularly dark line--associated with a shift from southerly to northerly winds--approached. Beyond the shift pouring rain was evident. Take a look at the dramatic passage at the UW (image)--large wind shift, a plummeting of the temperature, a jump in pressure as the line reached the instruments. And over a third of an inch of rain.
The high-resolution computer model (the WRF model) ran at the UW earlier in the day predicted the convergence zone formation (see image). Not perfect, but an indication of how far we have come in the last ten years or so. Certainly, meteorologists have bragging rights over their economist friends.


  1. A good forecast indeed. While it wasn't pouring most of the evening, we did have fairly persistent rain with big fat raindrops here 3 miles NNE of Monroe.

    A buddy of mine even reported seeing what looked like snow on his windshield in Lynnwood this afternoon. I've seen snow falling (briefly after a hailstorm) in June a few years back so I guess I shouldn't be surprised!

  2. Once again I'm seeing more T-storm activity south of Bellingham and nothing here. Is this due to the convergence zone?

  3. Here at our Fremont perch, we watched the convergence zone approach slowly last evening during supper. Looking west, we watched the higher clouds moving from the south. At the surface, we saw the winds push down from the north, wedging up the first layer of clouds. The wind went calm and the rain began, with some lightening for exclamations. It all slowly drifted south through desert and sunset. What a fine show for the dinner's entertainment.

  4. professor Mass -
    today on the radio (BBC) I heard them say that in Beijing they have airplanes ready to "seed clouds to prevent it from raining" for their huge upcoming parade. Can you explain what this means? Thanks so very much.

  5. I am not one to post but I recently read this in the New York Times and it pertains to east woodinville's comment.

    I would guess spraying chemical catalysts into clouds is harmful to the environment but do such strategies even work? And, has anything similar ever been tried in the US?

  6. It's cloud seeding and the Chinese seem to be the most interested in it these days (firing silver iodide shells into the skies as well as seeding from aircraft).

    The US did a lot of research (for military and civilian use) in the 1950s and 60s. The British too with Project Cumulus. It didn't come to much although it left a trail of conspiracy theories (Lynmouth disaster and Woodstock).

    See the wikipedia article for a good overview

  7. Over the Keynesian economists perhaps, but the Austrian Economists have predicted every disaster of the past 2 years and more.


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