Weather Calms Down After Three Wet & Stormy Days

September 10, 2019

7pm Tuesday…

For the first time since Saturday we’re seeing a mellow evening in the metro area with respect to weather.  A chance for meteorologists to enjoy their dinner without a tornado warning showing up (twice).

It’s been a fun or crazy or annoying three days; depending on your viewpoint.

First, on Sunday we saw thunderstorms pop up quite late in the day.  One produced a tornado near Cornelius Pass, then as it passed through Vancouver a funnel cloud was seen by many;  but no touchdown in this case.  The NWS issued two separate tornado warnings for that storm

Tornado Today Stats

That tornado was the 2nd we’ve seen in our viewing area for 2019.  Remember the other was in NE Portland on July 1st.  Once again it was a very weak tornado.

Tornado How Many Each Category

The stats include all counties west of the Cascades from Centralia/Chehalis down to Lane county (Eugene).  Notice this tornado comes right during the autumn “tornado season” in our area.  Very loosely defined, but you get the idea.  There’s one other “season” in our area…May and June.  Still, twisters are rare in the Pacific Northwest.

Tornado Season Stats

That was Sunday, then yesterday lots more showers popped up in the afternoon.  There were two spots with unusually heavy downpours; east side of Hillsboro and Salmon Creek area in Clark County.  Check out these totals!  Most of these stations picked up all that rain within 2 hours (or less!).  I checked one home weather station near Westview High School: 1.88″ in one hour.  Amazing.

Rain Totals Metro Area.png

You might be wondering about the timing of the big downpours;  why not in the wet season?  It’s because warmer air can hold far more moisture than a chilly winter airmass.  So when it rains around here in the warm season it CAN really dump if the weather pattern is right.   In fact when I think of our big street flooding issues the past 20 years, typically it has been between May and October.

Today was day #3 with thunderstorms.  It did get quite intense during the early afternoon.  I see Lake Oswego picked up .80″ around 2pm.  As showers died down after 4pm in the metro area, the main lifting seemed to move south.  There were dozens of lightning strikes in the mid Willamette Valley.  Salem you had quite a storm during the evening commute.  In just a 30 minute period ending around 5pm, lightning detection picked up 44 cloud-ground strikes around Salem

KPTV 2017 Default Earth

The airport at Salem picked up .96″ in about 90 minutes.  Finally at 6:45pm I see most of the thunderstorms have dissipated.  It appears the official Portland observing location at the airport has avoided the big storms/downpours through these three days.  Still, we’re above average for rain this month.

Rain PDX Last 10 Days

A very brief look ahead says fall weather is here to stay.  There’s no sign of a significant warm & dry spell through at least the middle of NEXT week.  Here are the ECMWF ensemble hi/low temps for Portland the next two weeks (ignore the last day)

ecmwf-KPDX-daily_tmin_tmax_ecmwf-8116800

and ensemble rain forecast.  Good chance we get into the downpours/thunder action again this coming Sunday/Monday.  Maybe a bit drier around 20th or so, but then we’ll be deeper into the fall season.

ecmwf-KPDX-indiv_qpf_24-8116800 (1)

It’s quite possible that “summer ended” on September 6th this year.  We may not see any long stretches of upper 70s and 80s again.

High Temp Last 13 Days

By the way, a quick glimpse of Mt. Hood this evening shows snow stuck down to around 9,000′ on the mountain during our cool/wet spell

Cam Skibowl

Chief Meteorologist Mark Nelsen


That Tornado Warning in Portland Metro Area This Evening? UPDATED WITH 2ND WARNING

September 8, 2019

7:30pm Sunday…

Updated at 10pm Sunday…

Immediately after I published this post at 7:40 pm a 2nd tornado warning was issued for parts of Vancouver from the same strong cell.    Here’s a quick summary of the entire evening:

  • A heavy shower/thundershower moved from about Hillsboro to east Vancouver from 6:45 to 8:15pm
  • It prompted two separate tornado warnings (around Cornelius Pass and then central/east Vancouver)
  • It’s likely a tornado touched down around Cornelius Pass at a Pumpkin Patch (christened a “Gourd-Nado” by Brian MacMillan)

This pic from Jim Kessinger

DCIM101MEDIADJI_0149.JPG

  • As of this moment there are no reports a tornado actually touched down in Vancouver.  Apparently the “confirmed tornado on the ground” wording in the 2nd warning was because the funnel cloud appeared to just about touch the treetops.  So in reality a tornado was never observed on the ground, but very close.

ORIGINAL POST:

Well that was exciting…for about 10 minutes.  If you have a weather app, or the FOX12 app, you probably noticed a TORNADO WARNING appeared for a small part of the metro area around 6:50pm this evening.  That’ll get your attention!

As far as we are aware, there wasn’t a tornado on the ground.  If it happened, it would have been right around Cornelius Pass & Skyline Road in extreme NW Multnomah County.

Here’s the sequence of events:

  1. Weather spotter (and local weather geek) sent pic and called in funnel cloud report.  It was seen north of Hillsboro Stadium over the West Hills.
  2. At the same time radar did indicate very weak rotation, although that alone typically wouldn’t lead to the Portland office of The National Weather Service issuing a tornado warning in my experience.
  3. So Portland NWS issued a tornado warning for about 13 minutes from 6:47pm-7pm.  Then the warning expired.
  4. No tornado was seen on the ground and no funnel cloud was seen over NW Portland as it moved off the West Hills and into the flatlands as far as I’m aware.

Radar looked like this when the warning was issued.  Nothing out of the ordinary

TornadoWarning

But checking out the Storm Relative Velocity shows there was some weak rotation almost right over Cornelius Pass at 6:45pm.  We get a real clear view since it’s only about 5 miles from the Dixie Mtn. radar site.

KPTV 2017 Default Earth

Green colors indicated movement TOWARD the radar site and red is movement AWAY from the radar.  So you’ve got some counter-clockwise rotation going on in that spot.  I’ve seen weaker rotation than this produce a weak tornado in our region.

Within a few minutes most of that “wind shear” or weak rotation disappeared.

That wraps up your funnel cloud story for this evening kids!  Here’s a pic of the funnel cloud from Mitch Etter, taken from Hwy 26 on the west side of the metro area

photo mitch etter

Chief Meteorologist Mark Nelsen


Summer 2019 Is Over; Should Feel Like Early October Next Three Days

September 7, 2019

7pm Saturday…

What a change today! A thick marine layer kept us cloudy & gloomy west of the Cascades and then a cold front has passed over the top of that marine layer.  Instead of the 81 we saw Friday, today we only hit 69 in Portland.  A nearly two week period of very warm weather ended today.

High Temp Last 13 Days

 

Taking a look at the weather maps today it’s obvious that “summer is over”.

What does that statement mean?

  1. The seemingly endless & dependable days of (mainly) dry weather and warm sunshine are finished for this season.  That’s perfectly normal for early-mid September.
  2. The chance of hitting 85-90 again is slim, but still possible
  3. The very warm nights we’ve seen much of this summer will soon be coming to an end.
  4. Expect at least 1″ rain for most of us in the lowlands by the time we get to Tuesday evening, with up to 3″ in some Cascade and Coast Range spots.  Fire Season 2019 will continue to limp along on life support; good news!
  5. Temperatures at pass elevations and Cascade mountain lakes go from 70s yesterday/today to 50s the next few days…that’s chilly camping!

What could we still see?

  1. A briefly hot afternoon.  We can hit 90 even in early October, although it’s rare
  2. Several nice periods of sunny & warm weather; remember those two weeks of sunshine the middle of last October?  Lows in the 40s and highs in 70s were wonderful.

By the way, officially summer ends August 31st according to NOAA; meteorologists consider summer the three month period June-August.  Traditionally of course summer ends at the equinox the third week of September.

The next three days will feature a cool upper-level trough moving over the Pacific Northwest.  This is a classic setup for showers, downpours, thunderstorms, and maybe a funnel cloud or two as well.  All models are showing an unstable atmosphere each of the next three afternoons as the “warm” air bubbles up into the colder airmass overhead.  Ready for some lightning numbers?  Here’s a neat chart showing lightning strike frequency in the metro area for each hour of the day and each week of the year.  You can see two maximums in frequency; late spring & early summer and again in September or very early October (now).  In this situation it’s rare to see it anytime other than afternoons/evenings.  I think it’s interesting that for fall lightning it has a quicker cutoff in the evening, likely due to much earlier sunset than May/June.

multnomah-county-or-week

That upper-level low is right over us Tuesday on the ECMWF ensemble 500mb height chart:

ecm_tues_10th

Then east of here Thursday; that may be the best day of the week weatherwise.

ecm_thurs_12th

Next weekend another upper-level low moves by, but may stay just far enough north to spare us a wet weekend; tough call at this point.

ecm_sun_15th

There are strong hints that we return to drier/warmer weather next week.  See the ridging over the western USA in 10 days?

ecm_wed_18th

As for rain, check out the ECMWF ensembles again for Salem.  Just about every member puts down 1″ of rain, with most of that in the next few days.

ecmwf-KSLE-indiv_qpf-7857600

So hopefully everything you want to stay dry is now indoors or under cover.  Your yard/garden and our woods will get a much-needed soaking!  This growing season has been drier than average across the NW corner of Oregon and SW Washington.  The six month precipitation anomaly:

anomimage

Chief Meteorologist Mark Nelsen