A Warm September, But Not a Record

I did some good old style number crunching this evening:  The average temperature at PDX through today is 67.98 degrees.  That is warmer than the warmest September on record (67.6 in 1994).

So then I took our forecast for the next 3 days, out of the 7 Day forecast, and recalculated the average temperature for the month.  If our forecast is correct, the average temperature should end up at 67.5 degrees.  That would just barely edge out 1991 for the 2nd warmest September here in Portland.  We’ll see how that works out, but it’ll be close.

As for weather forecasting the next few days; two items of interest.

One is the gusty east wind coming in tomorrow.  High pressure develops east of the Cascades and the pressure gradient through the Gorge ramps up from about zero at daybreak to 6 millibars by 8pm according to the WRF-GFS.  It shows 45 kt (50+ mph) wind up around 2,000′ exiting the Gorge.  That should easily give gusts 40-50 mph at the west end of the Gorge and 25-30 mph across a good chunk of the metro area after sunset.  I bet we get our first 60-70 mph gust at Vista House this season between 7-10pm tomorrow.

The wind dies off quickly Thursday afternoon, then it’s dullsville weatherwise through Sunday.

Models then show item of interest #2 for early and middle next week.  A strong westerly jet punches right into the West Coast for the first time this season.  Both the GFS and ECMWF show widespread significant rainfall from SW British Columbia all the way down to about San Francisco.  This will likely be the “season-ending” rainfall that extinguishes the fire season here in the Pacific Northwest.   Confidence is high in the big change next week, for example check out the 12z ECMWF Ensemble plot: 

The green line is the average 850mb temp the next 16 days.  The thick blue line is the actual operational ECMWF run the next 10 days.  The ensemble average is red.  You can see that beginning Sunday the 2nd 850mb temps go below average not only on the operational run but almost all the ensemble members too.  That continues through at least the 12 day mark.  If you’re looking for warm and sunny early October weather I sure don’t see it here.

The brand new 00z GFS version is similar:

Below average upper-level temps from later this weekend through at least the following 8 days or so.

Chief Meteorologist Mark Nelsen

41 Responses to A Warm September, But Not a Record

  1. Karl Bonner says:

    At DLS the running average for the first 27 days of September is 70.8 F, the averaged high is 85.7 and the averaged low 55.9. I entered 45/74 for today, 42/81 for tomorrow and 46/79 for Friday – and the final result is 84.9 high, 54.7 low and 69.8 mean. I think that’s about 4 1/2 degrees F warmer than a normal September for both highs and lows – the diurnal swings this month have been very near the norm of 30 degrees!

  2. Ken says:

    Sleepy Blog. Everyone must be out enjoying the last two days of Sunshine!!

    • Austin (Cornelius) says:

      No, I was just busy because I had my firefighting class. I don’t enjoy the weather right now. When there is winds up to 50-65 mph I will be saying today is a nice day. But no. I’m not satisfied at all right now.

  3. Timmy_Supercell (Klamath Falls @ 4200') says:

    Not exactly on the topic of temp records…. But still weather related.

    Not too long back I was searching around for information about Doppler Radars and discovered that some time in 2002 or 2003-ish, they were testing a radar system somewhere along the coast of Oregon. I forgot what exactly they were doing this for but what I want to know is how come they currently do not have one along our coast now? Since they were testing one about 8-9 years ago I figured we would have an extra one to use.

    • Timmy_Supercell (Klamath Falls @ 4200') says:

      It was something like this:

      It was an S-Pol Radar, not sure what ‘S’ stands for though.

    • Mark Nelsen says:

      I think it was a project to study precipitation and clouds within wintertime frontal systems passing over the Cascades.

    • Timmy_Supercell (Klamath Falls @ 4200') says:

      Would there perhaps be any archived imagery from this S-pol radar? This one does look interesting, and I heard that this radar already had dual-polarization installed to it. Which is surprising to me.

  4. Anthony Bertolo - Hillsboro says:

    I can’t tell if I’m ready for Fall weather or not.

    • Punxsutawney (aka HIOPHIL) at work by Sunset High elev ~280' says:

      Well ready or not the 12z GFS says fall is coming.

      Enjoy the next few days. Per the 12z GFS; after Friday, or possibly Saturday (east metro) we may not see 70’s again until sometime in 2012.

    • PaulB/Eugene says:

      After this week, next time that it is clear and sunny there will be frost

      Some suggestion that trough next week may split toward California…hope that is not the trend this winter otherwise San Fran would get much more rain than expected and we would mild and dry with cold bottled up E of Rockies

    • Punxsutawney (aka HIOPHIL) at work by Sunset High elev ~280' says:

      Ughh…in a few weeks any extended split flow around the northwest would leave us in the dreaded fogversion situation. Not what I would call winter.

    • Jesse-Orchards says:

      PaulB, the pattern you describe would be more reminiscent of an El Nino than a La Nina, which we’re heading into. I wouldn’t worry too much about it.

    • Joshua in Lake Oswego says:

      I am not only ready for fall, but winter as well. No more 70s would be awesome! Lots of rain- awesome! Freezing low temps- awesome!

      No split flows please. Just keep the hose pointed at us and bring in some artic air!

    • Karl Bonner says:

      Paul, I don’t think we’d get frost in the 2nd week of October after a heavy rain setup. Far more likely would be a pattern where fog doesn’t break until midday and high temps only make the low 60s, maybe even a semi-fogversion scenario with highs in the mid to upper 50s in places like Corvallis and Eugene.

      East of the Cascades frost would be likely above the Columbia lowlands, but The Dalles probably just gets lows in the 38-45 range. The more rainwater in the soil, the foggier and warmer the nights will be in mid-October.

  5. bgb41 says:

    Top 4 Warmest Septembers @ PDX:
    1st – 1994 with 4055 total degrees
    2nd – 1991 with 4041 total degrees <<<<2011 could tie this
    3rd – 1974 with 4038 total degrees
    4th – 1990 with 4021 total degrees

    Sept 2011 needs 377 degrees these last three days to tie the 2nd place record set in 1991 of 4041 degrees. 48/74/49/80/51/75 the last 6 periods here would equal that number.

  6. cgavic says:

    Sunshine and 58 degrees in sandy oregon

  7. SnowedIn - North Plains says:

    38.2 here in North Plains this morning…

    • Thejory says:

      Wow, that was a quick turnaround. Although the West wind was nearly non-exsistent there at the end.

  8. Punxsutawney (aka HIOPHIL) at work by Sunset High elev ~280' says:

    At 65.2 Hillsboro is tied with 1952 for the third warmest September since 1929. Like Mark, I expect the final number to be a bit lower when the month ends Friday.

  9. 38.3 for the low with a little bit of fog now the temp is up to 39.

    I see just the smallest of dustings of snow on MSH this AM.


    • Punxsutawney (aka HIOPHIL) at work by Sunset High elev ~280' says:

      39 at KHIO at 6:19am. Clear skies out here.

      Needed to put on gloves and a light jacket for the ride to work for the first time in quite a while. Fall is here!

  10. bgb41 says:

    9/27/2011 Oregon (All) Temperature Summary

    High:88 at MCDERMITT 26N(4464 ft)
    Low: 59 at Heppner Jct.(312 ft) & Blalock(280 ft) & DW2345 Toledo(43 ft) & CW1075 Boardman(322 ft) & John Day River B(305 ft)

    High:40 at Timberline Lodge(7001 ft)
    Low: 29 at Mazama (4590 ft )

    Largest Diurnal Change: 47 degrees
    Baker City Munic (83/36 ) (3373 ft )
    HEREFORD (81/34) (3599 ft)

    Heaviest Rainfall:
    1.80″ at NORTH FORK(3120ft)
    1.40″ at MUD RIDGE(3800ft)
    1.20″ at LOG CREEK(2800ft)
    0.88″ at YACHTS Yachats(74ft)
    0.83″ at DW7564 Estacada(1079ft)
    0.82″ at DW4118 Sandy(1250ft)

  11. Karl Bonner says:

    What I find most fascinating is how rapidly the Gorge winds are going to make a sharp U-turn. As of early evening The Dalles was still seeing sustained westeries at 15-20 mph. You’d think that, after today’s moderately strong west wind, tomorrow would simply see the west wind fizzle out with the east wind holding off until Thursday.

    And I bet Thursday morning is very chilly in the East Gorge, as in 40-45 most places!

  12. Boydo3 N. Albany 500' says:

    Smoothed? Probably won’t be THAT heavy.

  13. Mike near Clackamas Town Center says:

    Once the first storm rolls in early next week they’ll just keep coming with no end in sight.

  14. bgb41 says:

    00Z GFS @ KTTD — Extremely heavy rain for later next week

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