August 11, 2010

Finally...Extended Sun and Warmth

There have been a lot of complaints about the weather lately.

Sure, there has been practically no sun along the coast. Yes, Seattle has had a record-breaking stretch of morning clouds. Sure, most days have not come close to the normal afternoon highs.

But things are going to change, so stock up on ice cream, get some ice ready, and put away those sweaters.

Heat is on the way.

The reason for the change? A substantial change in the large-scale organization of the atmosphere over the eastern Pacific. Earlier in the week am upper-level trough of low pressure was over the Northwest (see graphic) and ridging (high pressure) was well offshore.
The new situation is for the ridge to amplify and move eastward, with no trough dampening our days (next map).

With the amplifying upper level ridge, we will see increased offshore flow and the northward development of the west coast thermally induced trough (TINT). (I have a student working on this feature and we struggled to find a good acronym that was suitable for a family friendly web site).

Want to see the development of the thermal trough? Here is a series of maps with surface winds, sea level pressure, and lower atmospheric temperatures.

Thursday at 5 PM-thermal trough extending into southern Oregon!

Friday at 5 PM thermal trough into southern WA. Note the easterly offshore flow on the WA cascades

Saturday at 5 PM. Thermal trough into NW Washington. Offshore flow moving offshore. No clouds on the WA coast! AMAZING!
Sunday at 5 PM. Thermal trough even stronger and temps warmer still!

Tomorrow will be beautiful and near 80F, Friday in the mid 80s, Saturday and Sunday can see upper 80s to lower 90s. The Willamette Valley will be much warmer. Why? Far less influence of marine air in that enclosed valley.


  1. Cliff- after a few days in Northern Michigan, which normally has weather similar to ours in the summer, am enjoying our cool, foggy mornings and 75 F afternoons. It was 85-90 F and very humid many days in MI, and that is of course the good news compared to further south and east. We should also remmber all those warm, 55-60 F days in February when we could bike in shorts. People have such short memories! Enjoy each day as it comes. I'm loving sitting in fleece vest in my office each morning, listening to Classical Minnesota Public Radio (streaming) and chuckling at their 95 F heat and massive t-storms (5 inches rain there the other day in some parts of MSP).

  2. Nice work on the acronym. Although it would not be grammatically accurate, I'd like to suggest dropping the "I" and going with TNT! Sounds more exciting that way. :)

    Thanks for the good weather news.

  3. OK, 10:30 am on thurs sitting w/ the space heater on and clouds sitting in the sky. Are you sure the cool, foggy mornings are finally going away?

  4. This morning I noticed that a dense marine layer (or what I've always thought as a marine layer) kept the temperatures cool for quite a while. In an earlier post (9 Feb 2010) you mentioned that foggy mornings were indicative of sunny days.

    I have argued that a marine layer is not fog, but friends disagree with me. Could you perhaps clarify the difference between a marine layer and fog, and what they represent for Seattle/Puget Sound weather?


    Looks like our neighbors in NW MT are in for the first snow of the year? Sounds refreshing!

  6. What's the prognosis for next weekend? I'm getting married on Orcas on the 21st and getting a little nervous about the weather. Just our luck to have the summer leave again on Friday. This weekend is going to be glorious, however!

  7. Shoot, I think they already revised that Montana link and no snow is mentioned. Maybe upper elevations? That would be fun to see - all this great weather makes me itch for a roadtrip.

  8. Cliff:

    I noticed the smoke plume from a small fire in the Olympics is streaming to the SW, clearly showing the NE flow. I looked on "Modis" but cannot see the image for today is available.


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