August 04, 2015

August will be a very different month

June and July together represented the warmest start of summer in Seattle history.

But history is not destiny and it appears August will be far cooler.

Let's start by looking at the latest forecast by for the first two weeks of the month (see below).   Most of the days only get into the mid-70s:  about as average as you can get.

The NOAA 6-10 day forecast concurs, with close to normal temps over our region/

The 6-10 day precipitation forecast is for ABOVE-NORMAL precipitation over our region (see below)

What about the next week?   Here is the total precipitation forecast over the next 7 days from the National Weather Service GFS model:  the Northwest gets some modest rain and only southern CA and Texas are dry.

 Why the change?   

The persistent high pressure (ridging) over the western U.S. has been replaced by troughing (low pressure).     Here are the ensemble (many model) forecasts of the difference of the upper level (500 hPa) heights from normal (the anomaly).  Blue indicates below normal heights, while higher than normal height (pressure) by green and reds.

The 72h shows several troughs over our region.

At 168 hr (next Monday) there is a trough right over us.

 Bottom line:  no heat wave the first half of the month, as the atmosphere stays in a very different configuration.  Thus, there is little chance that August will be a record warm month over the Northwest.


  1. Finally! Enough of this madness!

  2. That sound you hear is a huge collective gasp of relief.

  3. Now the questions is how much "troughing" do we need to changed the warm blob's future to "destined for failure"?

    Thanks Cliff

  4. How much precip to beat normal for Aug 10-14?

  5. Cliff: Interested in your thoughts as it relates to the longer term impacts to the broader eco-system as a consequence of our unprecedented summer.By my eye the "browning" and death of evergreen trees is very significant this year. I can't help but also notice many deciduous trees "turning" already; presumably drought-stricken.

  6. Rain here in Redmond right now! Good times.

  7. Yeah, but....for the entire month:

    Warmest spot in the whole USA is Seattle

  8. I'm a little confused about the comment from Benjamin: "Warmest spot in the whole USA is Seattle".

    So, you're saying hotter than the desert SW, with its 110+ degrees. Hotter than Death Valley at 115 or so. I'm skeptical.

    I think your confusion is that your link references temperature deltas to long-term norms. Average Seattle high temp in August is 76. The climate chart says we may average above that. Like maybe 78 or 80. But given the first two weeks are going to be average or below, I think the climate guys are off on this one.

    I think we're likely going to have the best weather in the country... just like every August. Once we get through the coolness and rain of this weekend.

  9. So, what about about the blob? Much previous verbiage about importance and persistence. Do not doubt your veracity (yet), but there is no explanation for why a major oceanic feature, which you have repeatedly posted about, is no longer a factor.

    What I am concerned about is that it might reappear in future posts, supporting your current opinion, with no continuity. Various political factions might well seize on this, to no good end.

  10. Come on John Marshall, dont be a troll. Obviously it was implied that Northwest has the best projection to be warmer than normal in August, based on latest CPC map. I was just pointing out that Cliff was generalizing the whole month by the first week of weather, specifically using The Weather Channel 10 day outlook, which we all know is garbage.

    cliff was in direct opposition to the CPC. I was just curious why he took that route.

    I have a 2 Atmospheric Science degrees, but dont live in Northwest. I just enjoy Cliffs posts!

  11. Actually, the Weather Channel extended forecasts have been better than any of the local weather channels which have been absolutely atrocious this summer. Now the temps are headed upward yet AGAIN which makes me wonder whether August will be ant cooler at all!!!

  12. So after a few nice cool days at the start of August, it seems that August now is not such a different month after all. Observed high yesterday and highs now forecast by the weather channel forecast for the next few days (thru Wed.) are from 8 to 10 degrees (F) higher than those forecast last week by for the same days.

    Aside from my disappointment (I like the cooler temps), I'm wondering what accounts for such a disparity? Has "the blob" returned?


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