September 28, 2015

A Perfect Autumn Week

I know many of you are looking forward to rain and clouds, but they will come soon enough.

In the meantime, enjoy an extraordinary fall week, with temperatures getting around 70F, no rain, and lots of sun.  And the bite of crisp temperatures in the morning to ensure you feel invigorated and alive.

The temperatures during the past four weeks have been very close to normal, as shown by the plot below (red and blue lines are average highs and lows)
Precipitation has been a bit below normal during the same period (blue is normal, red observed), by roughly .7 inches.
Want to see something amazing?  Here is the total precipitation predicted though Saturday at 5 AM (from the GFS model)  Nothing along the U.S. West Coast-:  WA is entirely dry.   But the  East Coast gets washed away.  SE Alaska gets torrential rain as well.

The pattern producing this weather is really not exceptional (see upper level map below for tomorrow afternoon).  A deep trough over the Gulf of Alaska is trenching Alaska, while a weak ridge is stationed over the western U.S. and Canada.  A weak trough is off of our coast.

The National Weather Service forecast for the next four days is  as close to ideal as imaginable (see below), with highs around 70 and lows near 50 (colder away from water). Sun.  No rain.

Last night some of the cooler suburbs southeast of Seattle dropped into the mid-30s...and that was at 2-m above the surface.  Some folks surely had frost.  In contrast, the temperatures only dropped to the mid-50s at some locations near the water. (the 92 was probably a thermometer near someones grill).  I am always amazed by our local contrast on cold, clear nights.  20F differences is not unusual...can get to 30-35F in the right situations.

This good weather won't last forever.  The latest NAEFS North American ensemble forecast of many model predictions indicates more clouds and some rain by the second week of October (see below).   So enjoy this pattern while you can.


  1. As delightful as this is, clear skies and sunshine have not exactly been lacking around here. Is it normal for the trees to be turning already? In some areas of the city, the trees have fully changed and are even dropping their leaves. Is this caused by the months of relentless sunshine and no rain, or is this normal? If the latter is true, then the trees here would be completely bare by mid-late October (which is earlier than Chicago!)

  2. Hi Cliff,
    Great September weather!

    I have a question that I have been unable to find an answer.

    When the Sea level rises by 10 centimeters will the King Tide rise only by 10 centimeters?


    Since the tide has more water with which to work, will the King Tide increase by more than 10 centimeters?

    Enjoy the sunshine

  3. There is one tree in the neighbor's yard that has completely turned like a week ago, it's quite strange. I'm in north Seattle near Shoreline, none of the trees here are looking like they are turning yet. im wondering if some trees start to turn early if there is water stress, But that is speculation.

  4. The leaves have usually turned and gone by Haloween

  5. I think the trees turned earlier than normal this year. I was assuming this was because it was hot and dry so much earlier this summer than most years.


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