Bird Migration On Radar Tonight

March 31, 2016

10pm Thursday…

It happens once a year; the huge nocturnal (night) migration of ducks, geese, swallows and all those other birds from warmer regions on our planet to northern/cooler areas.  Think about this; there are probably birds flying right over your home tonight that will end up spending the warm season in the Yukon or even near the Arctic Ocean!  Oh, and they may have spent the winter in Mexico or Costa Rica too.  That part doesn’t sound too bad does it?


Because birds are large compared to precipitation (rain/hail/snow) they show up quite well on radar and it doesn’t take that many to trigger an “echo” on the radar screen.  Of course you might be wondering like me why we don’t see birds on the radar screen all through the warm season?  We usually don’t because those birds don’t have any reason to move high up into radar range (more than a thousand feet or so).  But when migrating they go high to avoid low level wind fields, instability, and denser surface air.

Tonight they are quite visible on the “VAD” wind display.  Check out the current wind field over us, from the Troutdale Wind Profiler:


The area in yellow is the latest info (9pm) showing light west wind (less than 10mph) from the surface up to around 3,000′.  Then a light north or northwest wind from there up to 8,000′.

Now take a look at the wind profile from the Portland radar.  The radar is located up around the 2,000′ elevation just west of Scappoose.


Time goes from left to right.  The first column labelled “0228” means 2:28z or 7:28pm.  The last column is then 9:05pm.  Until about 30 minutes after sunset you see that light west wind the Troutdale profiler shows.  Then look at the 8-9pm hour…the echoes turn to straight southerly “wind” at 15-25 kts.  That’s all bird action.  It’s also fascinating that the highest echoes (birds) gradually increase in altitude…those guys are working hard to get up to their “crusing altitude”.  Ducks have been known to fly up around 30-50 mph!

This is what it looks like on the “regular” radar screen as the birds take off, from an earlier blog post:

By the way, there is a movie called WINGED MIGRATION (a documentary) produced about 10 years ago using hand-raised birds. They follow the birds (usually geese) while flying and migrating using some sort of very light aircraft. Or, actually I suppose the birds follow the aircraft since they imprinted on humans at hatching.  That means they think humans are part of their family. Now, believe me, this is no “party movie”, actually it’s REALLY slow, but great visuals for little kids to watch. Filming was done all over the planet. Here’s a clip for a little mid-day relaxation:


Chief Meteorologist Mark Nelsen


First 70 Degree Day in Portland Today

March 30, 2016

4pm Wednesday

Feels like May!  Low 70s this hour at PDX, first time this year!


How convenient…today IS the average date for the first 70 degree temperature in the Rose City


This has been a well-advertised warm spell with a big upper-level ridge developing just to our west and then sliding overhead mid/late week.  We’ll probably end up around 72-73 today, and tomorrow we should add a couple degrees…maybe hitting 74-76.  Same thing Friday.  So enjoy the warm March/April sunshine…it’s time after a VERY wet winter.

Looking ahead, in general the pattern is warmer than normal for the first week to 10 days of April.  Check out the GEFS (GFS ensembles) from the 12z run showing 6 hourly temperature anomaly.  Most of the time between now and the 2nd week of April it’s above normal.  No huge “heat wave” forecast, but you can spot the current warm period and another one around Wednesday-Friday next week.


The ECMWF also shows the 2nd warm period next week, although it doesn’t last very long.  See the spike in 850mb temps on the ensembles next Wednesday/Thursday:


As for rain, models have slowly backed off on shower chances for this upcoming weekend.  Here’s another cool graphic from the WeatherBELL site:


It shows the last 15 runs of the GFS model…newest at the bottom.  That’s 3.5 days worth of model runs.  Each horizontal row is one run of the model.  Take a look up/down on Saturday/Sunday.  Note that a weak system was trying to come through the Pacific Northwest as of about two days ago.  But now it’s totally gone, thus no rain forecast for our area until Monday.  You can also see that 2nd dry/warm period showing up now next Wednesday-Friday (7-9 days from now).   You can also glean from this chart that the GFS has been very consistent showing showers in the Monday/Tuesday time frame.

To summarize:

  • Unusually warm/dry weather continues through the weekend, but the solid sunshine disappears after Friday
  • For gardeners:  an excellent chance for our soils to dry out through Sunday
  • Finish up those activities by Sunday afternoon/evening, rain of some sort is definitely back Monday/Tuesday
  • The next 10 days look pleasant and a bit warmer than normal as we head into April

Chief Meteorologist Mark Nelsen


Vacation Time

March 20, 2016

I’ll be on vacation through Monday, March 28th looking for a sunnier/warmer place part of the time.

No blog posts unless we get a: Tsunami, Hurricane, Snowstorm (lowlands), or Volcanic Eruption.  Yes, I’ll be “offline” until Tuesday the 29th.

I might occasionally post on Twitter (@MarkNelsenKPTV) or my personal Facebook page (MarkNelsen)…maybe.

Chief Meteorologist Mark Nelsen

Spring Break 2016: The Usual Mix of Sun/Showers/Warm/Cool

March 18, 2016

9pm Friday…


Oregon’s spring break is here and lots of people are traveling today, tomorrow, or Sunday.  Often in search of sun, snow, or sand!  How does the weather look?  Surprise, quite a mixed bag.  That’s common in late March because we are in spring now, the transition between winter and summer.  And here in the Pacific Northwest spring goes on a LONG time since we don’t have real cold winters or scorching hot summers.


Today was warm of course, although very windy.  Peak gust was 41 mph at PDX.  That east wind dies down and we’ll barely notice it in the metro area tomorrow.  At the same time a dying front drags onto the coastlline.  So expect lots of clouds at the beaches and a few light showers.  Inland we’re ahead of the system so still a mix of warm sun and clouds…pretty nice for March 19th.

But this changes Sunday through Thursday this coming week; we will be under wet westerly flow much of the time.  So back to showers and cool weather.  Expect snow in the mountains at times too.  There IS still hope for the very end of spring break though…models are trying to pop up some sort of ridging along with the attending drier/warmer weather.  Take a look at the GEFS ensemble temperature chart, showing surface temperature departure from average.  You see the near normal to slightly below normal temps next week, then a real obvious warm spell around 3-12 degrees above normal.



The 10 day ECMWF 500mb height anomaly shows that upper-level ridging for Easter Saturday, or at least just offshore.


Wouldn’t that be nice to have sunny/warm for Easter weekend?  Of course that would probably be asking too much.  That said, the 12z ECMWF ensemble 850mb chart lends some moderate confidence to a warm spell in the 7-14 day period:


By the way, if you want to ski the next few days, choose tomorrow (Saturday) or Monday, not Sunday.  A warm system swings up out of California so likely a wet day at the ski areas:


Also for you social media folks, I finally broke down and created a Twitter page:

I have always had a Facebook page too, it’s here:

Chief Meteorologist Mark Nelsen

Unusually Strong East Wind Ahead

March 16, 2016

6pm Wednesday…

March & April are the months where we see the seasonal shift of wind in the Columbia River Gorge.

Easterly wind dominates in the cool season (November-early March) because the land is colder than the ocean.  Colder land, longer nights, and weak sun angle mean colder air can more easily pool over the land.  That means high pressure.  Air moves from high pressure to low pressure, so we get easterly wind far more often in that cool season.

Westerly wind dominates in the warm season (April through early October) because the land turns warmer than the ocean.  High pressure develops more often over the eastern Pacific and intense heating of the lower elevations east of the Cascades often causes an area of surface low pressure to form (mainly in the hottest 3 months) out there in the Columbia Basin.

The transition time is mid-March to mid-April.  At this time we can get strong wind from either direction, but we don’t get long periods with the wind stuck in one direction or the other.

But tomorrow and Friday we’ll see an unusually strong east wind develop at the west end of the Gorge due to strong high pressure dropping down over the Rockies.


This “event” is somewhat similar to the Veteran’s Day windstorm we saw 16 months ago.  Pressure gradients are not as strong though so it shouldn’t get quite that wild.  Still, the WRF-GFS has 50-60 kt wind just a couple thousand feet over our heads tomorrow night and Friday morning


Note the similarities to that event in November 2014 except 10+ degrees warmer:


That same model also shows 15-18 millibars gradient from Spokane to North Bend early Friday.  In the storm last year it was up around 21 mb.  But, we also saw 10s of thousands of power outages, some trees down, and a few gusts over 50 mph!  I don’t think it’ll get quite that crazy, but the WRF-GFS is painting gusts of 40-50 mph across the metro area during the overnight and morning hours Friday.  Very strong for March!  Our RPM is also showing spots of 50-60 mph gusts along the favored east wind spots east of Hockinson and Battle Ground.  I think that is way overdone.  The screaming message here is that along with our sunshine we’re going to see a very strong east wind event for about 24 hours starting Thursday afternoon.

Chief Meteorologist Mark Nelsen

Best Ski/Snow Conditions Since Christmas!

March 14, 2016

This was an El Nino winter, which true to form, was full of mild days and relatively uneventful weather once we moved past the first few days of January.  Last fall I mentioned that no El Nino winter since 1970 has produced an above-normal snowfall winter and so far that is still the case.  Government Camp seasonal snow is still well below normal, even with today’s snow.  The only way it would end up normal is if 120″ fell between now and May.  Pretty unlikely unless it’s going to be a VERY ugly late March/April in the lowlands!


But far better than last year eh?  Once you go higher on the mountain things are more what we’d see in a typical March.  Notice Mt. Hood Meadows has just about reached their average yearly total…it’s been a wet season!


That said, look at the storm totals so far…these are numbers since Saturday morning.


Wow, we haven’t seen this since early December!  And this time we have a nice deep base to start so even better reason to take those jumps now…

By the way, this could be a preview of next season.  We assume next year will be either neutral or a La Nina winter.  If we have a La Nina that’s great for skiing: lower elevation snow more often, heavier totals in general, and more periods of powdery snow.

I expect snow showers to taper off tomorrow evening and then a few days of dry weather commences.  Should be some real spring conditions Thursday and Friday.

Chief Meteorologist Mark Nelsen


2pm: A “Regular” Minor Wind Event & Wrapup

March 13, 2016

That was a bit underwhelming, should have stuck with original thoughts last night.  I never saw more than 8,000 PGE customers out of power at one time.

While not a total bust (we still had “Wind Advisory Level” gusts, just barely)…most of the metro area has only seen gusts in the 35-45 mph range.  Not a single 50 mph gust in the lower elevations.  We’ll see these gusty winds die down over the next few hours.  Peak pressure gradient from Eugene to Olympia was only 11 millibars, barely a windstorm event and as weak as the WRF-GFS showed this morning (it forecast about 10).

Seattle is getting nailed at this hour, SEA went from light east so southerly gust 56 mph in a short period of time!

Peak Gusts as of 2pm:

PDX: 38
Hillsboro: 38
Troutdale: 40
Aurora: 44
Salem: 41
McMinnville: 55
Chehalem Mt: 57
The surface low is making landfall right about now at Forks, Washington as a sub- 980mb pressure.  Here is a map from the pre-dawn hours from the NWS showing the model forecasts as of the 6z runs.


Winners:  GFS/RGEM/GEM  These models generally did well with track, with the usual minor flip-flopping on low location around in the final runs beforehand.

Winner: HRRR low pressure track.  It did quite well, but it did over-forecast the inland wind speeds.

Winners:  In general ALL models did well with low pressure intensity…within 5 millibars or so of reality through the past 48 hours.

Loser:  NAM and NAM-MM5  It was far too south on more than one run.  In fact at one point yesterday the low was almost over Portland!

Loser:  ECMWF  (This one hurts!) While not a disaster, the ECMWF was too far offshore on the track a couple days ahead of time, then over-compensated and pushed it slightly too far south in the end.

On tap…tons of mountain snow and then warm spring sunshine for a few days later this week…

Chief Meteorologist Mark Nelsen