January 26, 2010

The January Record

Will this month be the warmest January on record at Seattle Tacoma Airport? It is going to be a nail-biter but it appears we will make it.

A recap. The warmest January month until now was January 2006, when the average monthly temperature was 46.55 F. Where are we right now? Averaging all the days this month, including today, gives 47.1. Still above.

We have five days left.

Using the current NWS forecasts, the mean temperature of those days will be 45.9F.
Properly averaging this with the rest of the month gives a monthly-mean temperature of 46.9F. We make it with .35F to spare! Ok, I would like more of a margin, but it looks like the record will fall.

The east side is really cooking too! The monthly average temperature for Spokane so far is 35.2F which is 8.3F above their normal January temperature (26.9F). We are not going to beat 1953 (37.2F), but this January will come in second or third. A very respectable showing. What is missing in eastern Washington? The normal cloudy cold pool.

But what will really go down in the record books is the broad area of very, very low pressure over the western U.S. this month. Here is an amazing figure provided to me by Nate Mantua of the UW Climate Impact Group. It shows the pressure anomaly, the difference between the actual and climatological pressures, for January 15 through 23. An extraordinary anomaly reaching 21 mb (this is a large number for such things) over a huge area. I have never seen anything like it and probably won't see again for decades. There is reason that half the western U.S. set their ALL TIME low pressure records...records than have stood for 50-100+ years at these locations.


  1. It seems like a common weather pattern in Seattle area to have a dreary December, a relatively sunny and dry mid-late January, and a return to overcast and damp for several months.

    Would you agree, or is this just me?

  2. Cliff, I'm confused. The number (21) seems impossible. The normal range for the PNW is, I believe, 29.70 to 30.20 inches of mercury. Is this a different metric? You call it a "large" number. ??? Guess I need to read meteorology 101.

  3. You know if a computer model would have predicted those pressure values a month ago, I would have thought it would be one wet, wild, crazy week.

    But besides some coastal winds and little rain, it was actually a pretty benign week some places.

    It was like low pressure within low pressure, so it cancelled out the pressure gradiant, if that makes sense.

  4. MaryAnn K said "Cliff, I'm confused. The number (21) seems impossible."

    Cliff said: "An extraordinary anomaly reaching 21 mb (this is a large number for such things)"

    The mB is important! That's 21 milliBar

    The milliBar the standard unit of pressure in meteorology (but not quite an SI unit (that's Pascals) but close with 1mb == 100Pa).


    Not inches. Only the US uses inches (and Fahrenheit) for their public communications.


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