2nd 100 Degree Day

August 15, 2008

Snapshot A short post tonight, because I got behind making graphics for an extra segment.

We really lost the surface easterly flow today, in fact when I drove through Corbett, at the west end of the Gorge, it was calm around 11am.

So I think it's somewhat amazing that we still made it into the low 100s in the middle of August with no east wind in the metro area.  That's a really hot airmass!  I see Timberline Lodge made it to 82 degrees, that's the warmest I think I've ever seen on that sensor.

No significant changes for tomorrow.  Obviously the marine seepage is pumping humidity into our hot airmass; dewpoints have been rising this evening.  But the large-scale easterly flow continues through the day tomorrow, so I don't expect any major cooling push tomorrow until after peak heating time.

Models have come together on a strong shortwave swinging northeast through the region Sunday night and Monday AM.  This might be a great setup for a quick thunderstorm outbreak…something to keep an eye on for the next day or so.  This type of a shortwave moving through Eastern Oregon has brought a severe weather outbreak several times in my forecasting life here in Portland.

Okay, time to go…I'll be on vacation, one last time, Monday-Wednesday.  Next post will be Thursday…unless it gets really exciting Sunday night…Mark Nelsen


Hottest August Day in 6 Years!

August 14, 2008

Snapshot Whew!  That was getting stressful about noon when PDX was only 82 degrees.  I had a weak moment when I doubted my forecasting, but now at least we all know the temp CAN rise 20 degrees from noon to 5pm in Portland.  A nice even number to keep in our memory banks.  And we did this with easterly wind only surfacing east of I-205.  It has been a bit weaker than expected, and only a few isolated hills outside of the Gorge will continue to see the breeze overnight.  If you've lost the wind this evening, you probably won't see it again until midday tomorrow.

There is no significant change to the atmospheric temperature or windflow over the next 36 hours.  Easterly flow from near the surface to 5000' continues until midday Saturday.  I don't see any good reason that the wind will move any farther into the metro area tomorrow, so I figure just a notch or two of warming due to a slightly warmer atmosphere.  So I bumped the 103 up to a 104.  I hope we don't get a surprise 106…that would be really weird since I don't think we've ever hit that before (105 and 107, but no 106).

Looking at our RPM model and the WRF-GFS it looks like we don't even get any seepage of marine air until AFTER peak heating Saturday.  So I subtracted 4 degrees from Friday's high due to the easterly flow ending.  Either way we may actually have 3 days at/above 100 degrees…that's very rare at PDX.

Quite a push Sunday…I've got 84, although 00z models show quite a bit more digging of the approaching upper trough offshore than they showed 12 hours ago.  That COULD delay the cooling a bit, or at least weaken the push so that we still get around 90 on Sunday. 

If we hit 103 or higher tomorrow, it'll be our warmest August day since the great heat wave of 1981.  And, as Steve Pierce pointed out (the data master), we haven't had 3 days at/above 100 degrees since that July heat wave in 1994…Mark Nelsen