Bye Bye Dry Streak

Saturday, September 8, 2012
9:07 P.M.

As I write this blog, I'm listening to Miles Davis' and John Coltrane's famous rendition of "Bye Bye Blackbird." It's a wonderful song, but as I listen to Miles' soulful tone, I can't help but feel a bittersweet sentiment in my soul. Because for me, the "Blackbird" is not only this dry streak, but this summer mindset in general. It's time to say goodbye to the lazy, long days of summer and it's time to think about school. I have to say though, I'm definitely looking forward to my sophomore year at the University of Washington and the experience of surrounding yourself with a seemingly unlimited supply of wonderful people, enlightening schoolwork, and drugs/sex/rock&roll. Just kidding about that last one. Kinda ;).

But in all seriousness, this front symbolizes summer's departure and autumn's arrival. It's Mother Nature's way of refreshing our minds and helping prepare us for the changes we will all experience as the nights become longer, the leaves become redder, the temperatures become cooler, and the days become rainier.

What's responsible for ending such a long dry spell? Let's look at some satellite photos to find out! I'm gonna go back in time a little for you, so you can see how the front that will bring us the first rain we have had in 48 days has come about.

03:30 pm PDT Fri 07 Sep 2012 - Eastern Pacific Infrared Satellite

The temperature at Sea-Tac Airport reached 90 degrees on Friday, which was the first time it has done so in 22 years. If you look at the satellite photo above, you can see a HUGE ridge of high pressure over the area with clear skies over all of Washington and much of the Pacific Northwest.

Today, the temperature only reached 77 degrees. Why?

09:30 am PDT Sat 08 Sep 2012 - Eastern Pacific Infrared Satellite

It's tough to make out, but there are some high clouds over the Pacific Northwest, and the flow transitioned from strongly offshore to slightly onshore. Our once strong ridge weakened considerably today.

Take a look at the latest satellite picture. The ridge has broken down even more, but more importantly, look at the Gulf of Alaska, and look at the center of low pressure that is beginning to form there. This, my friends, is the low pressure system that will give us the first rains we have seen in a very long time.

09:30 pm PDT Sat 08 Sep 2012 - Eastern Pacific Infrared Satellite

Obviously, you can't take satellite pictures in the future, but we do have a wonderful assortment of weather models that can do just that. Let's see what my favorite one, the UW WRF-GFS, says what the ultimate fate of this low pressure system will be.

Valid 11:00 pm PDT Sat, 08 Sep 2012 - 6hr Fcst - UW 36km WRF-GFS 3 hour precip

As of right now, there is a weak area of low pressure and some associated precipitation stretching from the Gulf of Alaska to the Queen Charlotte Islands.

But take a look at what is expected to happen a mere 12 hours later.

Valid 11:00 am PDT Sun, 09 Sep 2012 - 18hr Fcst - UW 36km WRF-GFS 3 hour precip

See that front? That's what's gonna bring the demise of our dry spell.

Here's a higher resolution model picture that shows you the 24-hour precipitation expected over our area from Sunday evening to Monday evening as the front brushes Washington.

Valid 05:00 pm PDT Mon, 10 Sep 2012 - 48hr Fcst - UW 4km WRF-GFS 24 hour precip

You can see that there is a little bit of precipitation over the Sea-Tac airport, and much more to the north, where a convergence zone is expected to form.

And, our dry spell will end.

Or will it?

Sorry, I couldn't help myself. :)

Charlie