Fresh Podcast: End of Summer and Weather Guys in Hot Tubs

September 19, 2011

We just finished another podcast folks…Steph says this was one of the most entertaining, so listen up here:

Warm Week Ahead

September 19, 2011

After some very gray weather (my wife claims her SAD was already kicking in), we have a really nice week ahead.  Upper level ridging gradually builds over us, briefly gets squashed around Thursday, then the ridge rebounds quite strong, but slightly farther east over the upcoming weekend.  Check out this nifty little piece of weather geekery:

The future (and present too) of numerical modeling of weather patterns is in running “ensembles”, or many versions of one model.  In this case it’s the ECMWF model, run by the Europeans.  It’s the overnight run/runs.  What you see is a plot of 850mb. temps for the next 16 days.  850mb. is about 5,000′, or near Cascade Pass elevation.  The location is directly over Portland, Oregon.  Last night at 5pm is the far left side and Monday night the 3rd of October is on the right.  You can glean more information from this plot than you might initially think.  MY first thought would be…what a mess!  Click on the image for a larger view.

Note the thick lines: green is the average temperature for the next 16 days.  About +11 right now down to +9 or +8 in early October.  The blue is the OPERATIONAL run, which is the actual ECMWF run we would all look at in map form.    The red is the “ensemble mean”, which we all learned in 4th grade math means the average. 

I get this info out of the chart:

1. The next week is just about guaranteed to be above average, by just about all ensemble members.

2. The operational run peaks out around +24 on Friday afternoon, but the ensemble average is around +20.  Watch out about getting too crazy with forecast highs, the operational run is at the high-end that day.  But the following day (Saturday) the operational run is in the “middle of the pack”. 

3.  8 days from now, next Tuesday, the operational run is near the bottom of the pack, so the sharp trough shown then may be incorrect.

4.  Note how the model runs diverge over time into a spaghetti-ish mess?  By this Sunday afternoon (only 6 days away!), all of these runs indicate either an 850mb temp somewhere between +5 or +24.  Clearly a lot of variability.  Sometimes you don’t see such a huge spread and the forecast has more confidence.

5.  There is no late September snow coming to the Cascade Passes.  No run has 850mb temps below zero through the first day or so of October…the generally mild/warm pattern will continue.

Now remember this is all gleaned just from ONE numerical weather prediction model.  You can get the same info from the GFS or GEM (Canadian) model.  Whew! 

This is when someone walks up to the weather center and says…will it be sunny and how warm this coming Sunday?

Chief Meteorologist Mark Nelsen

It Rained!

September 15, 2011

Only in late summer or early Fall could it possibly be a headline; it rained in Portland today.  It appears we got all of .02″ at PDX, but that’s enough to break the 22 day dry spell.

No rain fell at Hillsboro Airport this evening (same farther south too).  That makes today the 52nd day without rain there.

Oregon AMS Meeting Next Saturday

September 14, 2011

Hey bloggers!

We have a Oregon AMS (American Meteorological Society) “fall kickoff” meeting coming up in just about 9 days.  This will be similar to last November’s meeting at Stark Street Pizza.  It’s a “joint meeting” again, functioning as a KPTV Weather Blogger get-together as well.  I’ll be there for at least the first hour or so…since I’ll be working the 5pm show that day.  Maybe I’ll get to meet a few more of you.

We hope to see you all there Saturday, September 24th at 1pm. There will be a social hour from 12 noon to 1pm. This is going to be a well attended event, so please arrive early for the best seating (although everyone just walks around chatting anyway!). Come have some of the best pizza in town. We will be raffling off some really great weather stuff along with some KPTV swag too!  Raffle tickets will be $1 each and all proceeds go to the Oregon AMS treasury. Also, let me know if you have something to present at the meeting and we will work it into the agenda. Of course this meeting is also open to the general public and new members (many of you???) are welcome to come sign up. Current members can also pay their dues for the current season underway now.

The annual WHAT WILL THE WINTER BE LIKE meeting is all set for OMSI in October.  This is by far the largest event our chapter organizes.  Last year it was in mid October, this year we move to Saturday, October 29th at 10:00am.  Mark it down on your calendars.

You can find out much more about the Oregon AMS at their website here:

Chief Meteorologist Mark Nelsen

Sharp Marine Inversion

September 13, 2011

A great picture from Scott Withers showed up on our Facebook page (fox12weather…”like” it!) today.  The location is Lookout Mountain is on the east side of Mt. Hood.  You can clearly see the inversion over the lower valleys; cooler nighttime air drains down into the lowest elevations while warm air remains above.  What you see here is not the marine inversion west of the mountains, but just overnight cooling.  Nonetheless, it shows the cooler/denser air down below trapping the smoke.

Check out the westside temps:  70 here in Portland, 61 at 1,100′ or so at Brightwood, but 71 up at Timberline Lodge at 6,000′!  Timberline has dropped less than 10 degrees since Sunday, while down in the valley it’s dropped 26 degrees (Brightwood).  The layer of cool air was about 3,000′ thick today, and will probably thin slightly tomorrow.  The marine inversion goes away Thursday and Friday with much cooler air moving in at the higher elevations.

Speaking of cooler, both the GFS and ECMWF show some sort of “real” rain arriving over the Pacific Northwest Saturday night or Sunday.  If so, it’ll be the first significant rain since late July.  It will have been exactly two months since the big soaking on the 17th of July.

Chief Meteorologist Mark Nelsen

Back to Normal; Fall Arrives

September 12, 2011


Today is like the “hangover” day weatherwise after our 9 day stretch of temperatures in th 80s and 90s.  We had 5 days at/above 90 degrees here in Portland, which gives us a summer total of 7, still well below our average of 13, but we’ve seen lots of 88-89 degree days (close calls).  A good chunk of the time we had hazy or smoky skies too, adding to that “end of summer” feel.

But look at the change…yesterday morning at 7am it was 84 degrees at the top of the KPTV transmission tower (1,900′), this morning it’s 52!!!  That’s a huge change; all due to marine air surging inland overnight.  For the first time in a week and a half a thick marine layer is overhead.  We’ll be lucky to hit 80 today. 

Get used to 60’s and 70’s for highs this week; I think part of our 7 Day forecast is probably too warm for mid-September onshore flow too.  Oh, and if you don’t start closing your windows at night, it’s going to be really chilly by morning inside. 

Fall is Here.

Chief Meteorologist Mark Nelsen

Hot Summer Across the USA; Not Here

September 8, 2011

The official 3 month numbers are in; this summer (June-August) was the 2nd warmest on record when the entire contiguous USA is averaged together.  Obviously our chilly June and July made for a different result here; in fact Oregon and Washington were the only two states with a below average summer temperature.

Here in the Pacific Northwest, it was the 2nd cool summer in a row.

You can click on either image for a better view of course.  The general trend is uphill, but lots of ups and downs; check out all those cool summers from around 1940 to 1960.  And you can clearly see did NOT end up a “green tomato summer” like 1993 and 1954-1955.

In other “warm” news, the race is on up in the arctic to see if it’ll be the lowest or 2nd lowest summer minimum sea ice extent.  The minimum usually occurs within the next week or two as it starts to freeze up again in the arctic.  Here’s the graph; you can see the clear downward trend since the satellites first started recording sea ice area in 1979.  Always keep that in mind when you hear “lowest ice extent ever”.

You can read more about it at the National Snow & Ice Data Center website.

We cooled down a few notches today, taking the edge off the heat, BUT we did hit a record!  It was a record warm overnight low…only 62 degrees here in Portland; highly unusual for September.

Chief Meteorologist Mark Nelsen