October 06, 2012

Summer is Over on Friday

This is the blog I knew I would have to write eventually, and I suspect some of you will welcome it.

Our supernaturally dry, warm period is going to end on Friday.  We are close enough now and the agreement of the models are sufficient to suggest substantial confidence in this forecast (yes, there is a small probability it could be wrong).

Much of the region has had probably the finest late summer/early fall weather of the past half century, with the only downside being the fires, smoke, and our water bills.

Right now the atmosphere is locked in a very stable blocking pattern, one called a Rex Block (after Mr. Rex, not some king, although many of us might consider this royal weather).  In a Rex Block there is a ridge to the north and a closed low to the south in the upper level maps.  Here is the forecast map aloft (500 hPa) for 2 PM today to illustrate.  With a ridge over us, there is naturally a trough over the eastern U.S., where some folks are getting record cold and snow.

To illustrate what will happen this week, consider the sequence from the latest National Weather Service GFS model prediction (the European Center forecasts are very similar).

First, Monday.  Generally similar pattern and our warmth and lack of rain will continue.

 Thursday at 5 PM.  The block is weakening and you see flow coming in on the western boundary.  (this is when the Jaws music of impending doom should be played).  Still dry over us at this time, but with the closed low moving into southern CA, residents of LA will be cloudy and moistened a bit.  They can always retreat to their hot tubs.

 On Friday afternoon, the ridge is movingeastward, we are getting moderate westerly flow, and are weather is deteriorating, with clouds and perhaps some light rain on the coast.

 And here is Sunday afternoon. A strong trough moving just to our north and I suspect some light rain spreading to the NW interior.  No big storm, but coastal Vancouver Island could be quite wet.

Let me show you some fun graphics, never before shown on this blog...the cumulative rainfall from the NWS GFS model.  Here is the total rainfall falling between 5 PM this morning (Saturday) and Thursday at 11 PM.  Almost everyone get precipitation except us!  Even southern CA gets wet. 

And here is the same cumulative rainfall, but ending on Sunday at 5 AM.  Finally, some light rain spreads over the region.  Sorry.

Basically, our protective block is gone by next weekend and we will be vulnerable to passing storms in a progressive pattern.  Will the ridge come back?  Some models are hinting at it, so stay tuned.


  1. NooooooooooO!!!! I guess my coffee shop days are returning soon !

  2. "Much of the region has had probably the finest late summer/early fall weather of the past half century, with the only downside being the fires, smoke, and our water bills."

    Maybe down there.. Here on Vancouver Island there is a picture on the front page of the Victoria Times Colonist this morning showing the Thasis River (a major river on the northend of the island) completely bone dry with 1000s of young salmon dead in the riverbed.

    On the south end the Cowichan river is too low for spawning salmon to swim up, they are netting salmon in the estuary and trucking them further up the river.

    It's a crisis up here. The rain can't come soon enough. And we need a lot of it.

    I did some digging into the records in the Alberni Valley going back to 1894 we need 140mm of rain in October to avoid setting an all time dry record for July through October that was set in 1896.

  3. I can hardly wait! I might host a Rain Party!

  4. I've been watching the long range models for the last few days and I've been waiting for the moment when they were finally showing that chance of rain persist under 180 hours out.

    I was going to talk about this very possibility today in my own blog, you beat me to it. But that is ok because I'm positive you explained it in a much clearer and succinct way than I could.

    I probably wouldn't have even mentioned the Rex Block, even though I noticed it and could have.

    Personally, I'm looking forward to the return of rain.

  5. I'm delighted the rain is returning! Raking bone-dry leaves has been a very uncanny and un-Seattle experience. Thanks for the good news, Cliff!

  6. Finally! I do have to say I have thoroughly enjoyed this weather. I am not a fan of really hot weather and the perfect, sunny days with cool, crisp nights and morings has been amazing. But, I am ready for the storminess of October and fall to return. Can't wait for the first good wind storm to blow all the leaves around! And....sounds like I'll be able to have a fire soon. Yay! I love fall!

  7. Interesting comment by chrisale because dry weather is relative to normal climatology.

    You had multiple posts expressing its not rare to receive any rain in July, Aug., or Sept., but you head further north into B.C., and September and October is their peak rainy season. Then it sags south (November for us) to Northern California in January.

    All the while, Alaska is being pummeled by heavy rain. Just like how they got the heavy snow when we were high and dry early last winter. That location is our bizarro opposite weather wise.

  8. I have had a record tomato harvest this year. Giant Brandywines, Old Germans, and Fantastics. And to think I had contemplated pulling the plants up in Mid-July...amazing.

  9. oh crisale that is terrible news about the returning salmon.

    Thanks you Dr Mass for giving a bit more solid info on this pending change. Looks like the 0.1 band extends into the fire area, though have to imaging much of it with just get evaprotated way.

  10. Does anyone know what is burning up near Mt. Vernon? I could see the smoke plume from the Kingston Ferry last night.

    The wildfire risk is extreme. As much as I like these California-like endless sunny days, I'm feeling the increasingly vulnerability to wildfire risk. Especially along the Hwy 104 corridor west of the ferry, where smokers light up, and the flick their ashes and their still burning cigarette butts out of their cars onto the highways. Smokers need to use their ashtrays but unfortunately many of them feel like its their god-given right to fling their cigarette butts out the car window. That is, until they get pulled over and ticketed. The fine is over $1000 and if a wildfire ensues, potentially much higher with legal costs, etc.

    I've enjoyed not having to mow my two acres. My tomatoes are about done from the frigid nights though, and my hot peppers are all ripening fast. I've had a huge fig crop this year and I'm battling with the squirrels and jays over my nut trees. I picked the filberts early, they got all but one of my walnuts (and the tree was loaded) and the chestnuts still have a few weeks. Am borrowing a Have-a-heart trap to relocate the squirrels. They also like the bark on my maples!


  11. I'm curious, of all the past really dry summers we've had in the past few decades, how has the weather pattern been for the following fall and winters?

  12. Having lived in this area most of my life, I have to admit I am ready for the rain. I have almost become depressed from so much sunshine. Weird I know!

  13. I'm planning a trip to Mexico near Xmas time. My two departure options are Seattle and Denver. Any thought on which city is more likely to have the greatest chance of heavy snowfall?

  14. John..that is easy...Denver has a much better chance of being snowed in...they also have much more snow clearing capability...cliff

  15. I wish we had these kind of dry mild late summer/early fall *every* year. It would make soggy, wet, cold November through June weather much easier to deal with.

    Thank God for this fantastic Indian summer!!

  16. I have loved every single moment of this extended *dry* late summer/early fall. I wish every year were like this. I wouldn't find the 7+ months of wet and grey weather so challenging if we had a slice of seasonal heaven like this on a regular cycle

  17. Fine with me...

    One observation with the overcast weather today is from my home about 1/3 and 1.5 miles from HWY 99and I5 respectively, the traffic noise is minimal. Seems like clear days are much louder. I assume this is weather (cloud/humidity) related?


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