Weather Radar Shows Spring Bird Migration

Reposted from The Cliff Mass Weather Blog

Weather Radar Shows Spring Bird Migration

Every day I have been checking the weather radar for signs of the northward migration of our feathered friends, and Wednesday night I finally saw it.
Ornithologists and those tracking the seasonal migration of birds have used weather radar for decades.  The radar signal of a target goes up rapidly with the size of the object (with the sixth power of the diameter) and thus a bird provides an immensely bigger signal than a raindrop.

Many birds like to migrate at night, so a good sign of birds is a large area of radar return that starts around sunset and fades at sunrise.  Meteorological signals don’t do that.
And the birds prefer to stay over land–precipitation does not care much about the shoreline.
So let me show you the birds… first at Portland.
At 5:40 PM Wednesday, right before sunset, nothing much was apparent.

By 6:41 PM, within an hour of sunset, echoes were appearing (reddish color), particularly NE of the city.

In the middle of the night at 11:49 PM birds were all over the place!

202003050749

Right before sunrise 5:57 AM, the echoes were declining

And gone by 6:59 AM Thursday morning, after sunrise.

National Weather Service radars have Doppler capabilities, which means they can determine the speed of the target towards or away from the radar.  Let’s check out the velocities of the birdies (see below). Blue/green means approaching and red/orange means moving away.
The radar targets are moving to the north—exactly what we would expect for birds migrating northward.

The Hoquiam (Langley Hill) radar showed the birds as well– here are the radar returns (called reflectivity) at 9:32 PM Wednesday night.  The light blue are birds.  They are not going very far offshore.

So why did the birds decide on Wednesday night to begin moving northward.  Yes, it was the right time of the year…but there is something else.  The meteorology was nearly perfect.
A warm front had moved through the region, followed by strong winds from the south, providing an easy ride!  Plus, the front had virtually no rain. 
To show you this bird conveyor belt, here are the winds above SeaTac Airport for the 24 hours ending 10 AM Thursday.  Time increases to the left and the Y-axis is height in pressure (700-hPa– is around 10,000 ft). Right after 7 PM Wednesday (05/03), the winds turned strongly southerly (from the south) and stated that way.  Literally, a strong tailwind!

These are meteorologically very smart birds.

38 thoughts on “Weather Radar Shows Spring Bird Migration

  1. I just love this article… I can’t help but wonder how many wind turbines are in those areas and if the kill has risen significantly.

    • No wind turbines in NW Oregon and SW Washington that I know of so the birds were safe. There’s wind farms east of the Cascade mountains where there’s a lot more wind.

    • And are these real birds with real wings or are they modeled birds in a super computer model?

      • Exactly and to use technical and scientific terms, it could be more worser than we thought because we didn’t know how much worser than we thought it was before it got worser.

        (Great article BTW).

  2. Wonder where the word “tailwind” came from?

    My favorite migratory bird is the Bufflehead. These little guys are like the hummingbirds of the ducks.. small and flap their wings at a very rapid rate. They fly fast and low over the water. How they get from very northern Canada and back every year is a testament to nature. Unlike the Canada Goose which stopped migrating in a lot of areas, the entire flock packs up and leaves every spring to head north to make more Buffleheads. https://en.wikipedia.org/wiki/Bufflehead

  3. I don’t think he’s seeing what he thinks he is seeing on those radar images.
    More likely it’s relative humidity (at the base reflectivity angle altitude )with near saturated air (Water vapor) as the radar operation turns up its gain in the cooling night.
    And the 932 pm ( 20200305_0532 UTC) is rain coming in. without knowing what is happening to gain adjustments on the radar, it is easy to get fooled.

    And one can go look at 3-day surface observations for many Locations, such as:

    SalemMcNary Field:
    https://www.wrh.noaa.gov/mesowest/getobext.php?wfo=pqr&sid=KSLE&num=72&raw=0

    Port Angeles-Fairchild Airport, Wa:
    https://www.wrh.noaa.gov/mesowest/getobext.php?wfo=pqr&sid=KSLE&num=72&raw=0

    These modern WSR-88D also operate around 3GHz (S band) whereas many of the older were at 5.5 GHz (C-band) and inherently better at seeing very low RCS birds.

    • re: “whereas many of the older were at 5.5 GHz (C-band) ”

      The old WSR-57 series were also S band (~ 2.7 GHz). The program in the 1970’s that resulted in the ‘gap filler’ WSR-74 series were in some installations C band, and the remaining balance were S band, based on the results of the research I’ve done on this subject over the past decade and half or more … Also the S band antenna on the WSR-57 was about half the diameter of the present WSR-88S (“NEXRAD”) series.

      Note also the present “TDWR” series of FAA RADARs are C band.

    • Can you explain what the Doppler radar shows? Would the relative humidity appear to be a cluster moving to the north at 25 knots?

      • The TDR-88D was likely in VCP mode 31 (or less likely mode 32).

        see: https://en.m.wikipedia.org/wiki/NEXRAD
        for a complete listing of VCP descriptions.

        VCP 31 -Long-pulse clear air mode designed for maximum sensitivity. Excellent for detecting light snow or subtle boundaries. Prone to detecting ground clutter. May be prone to detecting virga.

    • Anthony was similarly fooled in 2014 by a fast moving dust storm across central-eastern New Mexico. He thought it was a large flock of birds.

      https://wattsupwiththat.com/2014/03/19/mystery-plume-radar-image-near-nuclear-waste-site-solved/

      When that 2014 New Mexico radar return moved across Clovis-Cannon AFB, this was the local airfield met observation:
      18 / 1900 MST – 2300 MST (0200Z – 0500Z) blowing dust & low clouds (1500′ to 3000′) rolling through. w/probably virga showers.

      It was simply simply dust with a small isolated convection event.

      And here, Cliff’s “birds not going very far off shore (light blue)” is simply condensing water vapor from the onshore wind hitting the coast p, getting lifted and cooling, i.e. clouds, probably low level stratus and the further offshore rain is appraoching from NW of Olympic Peninsula.

      Now there are well documented bird migrations and insect plumes on weather radars. I just don’t think either the 2014 -New Mexico radar image nor this one from 5/6 March over Portland Oregon are birds.

      • Examples of coastal and inland orographic lift of moisture laden air.
        in the 20200305_0532 UTC radar shot of NW Washington, you can also clearly see the orographic lifting and resulting clouds around Mt Rainer to the SouthEast of Tacoma, WA. The coastal range of Washington forces the inflowing marine air up, stratus clouds… maybe some drizzle, after an otherwise clear day on the coast.

        All that light blue is simply water vapor condensing to clouds under orographic lift from the onshore winds bringing moisture laden air.

  4. re: ” so a good sign of birds is a large area of radar return that starts around sunset and fades at sunrise. Meteorological signals don’t do that.”

    What we hams call “tropo”, short for “tropospheric ducting” can occur though, and is seen as the sun sets and cooling of the boundary layer air occurs (and disappearing the next morning into daylight hours) … I wonder how many of these events that are sometimes perhaps mis-attributed are actually ‘tropo’ seen at 2.7 GHz (NWS WSR-88D operating frequency range) …

    I’ve got a good example of this from a local business park area that repeatedly (day after day) had showed anomalous, non-precipitation ‘returns’; the paved, built-up industrial area cools/warms at a different rate than the residential areas surrounding it with the many trees/yards and residential structures vs parking lots and industrial/business buildings/structures. An inspection aerially using Google earth shows up this industrial area quite well, and a match for the anomalous non-precip WSR-88D weather RADAR ‘returns’.

  5. Reference: “The Hoquiam (Langley Hill) radar showed the birds as well– here are the radar returns (called reflectivity) at 9:32 PM Wednesday night.”

    LGX RADAR site time/date-stamped: 20200305 0532z

    This link gives a 2 hr RADAR loop from 0400 GMT to 0600 GMT:

    http://weather.rap.ucar.edu/radar/displayRad.php?icao=KLGX&prod=bref1&bkgr=black&endDate=20200305&endTime=6&duration=2

    This link gives 0200 – 0600 GMT (4 hr) loop:

    http://weather.rap.ucar.edu/radar/displayRad.php?icao=KLGX&prod=bref1&bkgr=black&endDate=20200305&endTime=6&duration=4

    0500z Infrared satellite image:

    http://weather.rap.ucar.edu/satellite/displaySat.php?region=US&itype=03&size=large&endDate=20200305&endTime=5&duration=0

    Note: Targets observed at 124 nmi on a WSR-88D are at (give or take depending on prop conditions, etc) ~10,000 ft altitude, not sea level (or even the elevation of the RADAR site itself.)

    Conclusion: Precip (rain) was being observed on the LGX RADAR site.

    Nota Bene: I have no idea how long those links above will remain operable.

    Open for cross-checks, did I make any errors?

    • I agree.
      I think Cliff’s “migrating birds” is condensing moisture moving with the wind flows with the WS-88D operating in a high sensitivity (high gain mode).

  6. Excellent! Beginning last week, I heard the birds that overwinter here in California beginning to sing just before they start migrating northward. Once those migratory birds begin singing , they invariably leave here within 2 weeks, not to be heard again in these parts until they return in the fall. Great to see radar confirmation.

  7. The Doppler plots shows unambiguously that these are moving targets in a south to north direction (at a speed of approximately 35 knots). Ducting of clutter returns from the ground does not do that 😉

    Thank you for a most interesting article on an amazing behavior of our feathered friends. Mother Nature at its best.

    • re: ” Ducting of clutter returns from the ground does not do that ”

      A moving, differing (as to moisture content, temperature) tropospheric (lower atmosphere, such as the boundary layer, the layer nearest the ground) airmass (such as a front) though could be contributing … evening radiative cooling can create such air masses, and we observe ‘fronts’ coming through the DFW area of Tejas all the time with *no* visible cloud formation.

      If you’ve only ‘checked’ one sensor, RADAR in this case, that is insufficient to draw substantive, definite conclusions.

      THAT’S WHY we still go out as storm spotters to assist the NWS with what is called “ground truth” in reporting tornadoes and precursor conditions (such as wall clouds); ground truth is a cross-check on the RADAR observation with a pair of actual eyeballs …

  8. Spent an hour the other night, bundled up on the deck, listening to owls calling for mates and establishing their ‘territories’ for nesting. Imitating their “Who Whoo!, Who… who…” calls can sometimes entice them right into the trees near my house (SE of Seattle WA), as they try to identify the interloper in their world. Gives me ‘chills’, when they are that close!

  9. Cranes (Gru) flew over my house yesterday in SW france. They seemed a little confused though. They were heading NW to SE. Normally they would fly direct N to S

  10. Don’t encourage them as they’re typing up grant applications as we speak-
    The effect of weather radar on migrating birds….

    I might be getting paranoid but if the weather worriers can get rid of the radar they can completely control the message with the tree rings.

  11. I kind of have to agree that this is not a migratory bird example; that was my first inclination upon seeing the attached imagery. Although, I would agree that the situation appears favorable for it. Coastal radars are frequently plagued by all sorts of atmospheric discontinuities which can cause clutter, especially at night with inversions developing, even if there are algorithms employed to suppress it. More frequently, the staff is either too lazy or otherwise engaged in “research” or other non-meteorological duties to have the optimum clutter suppression program at work.

    I often recall seeing WSR-88D detecting waterfowl taking off from our service area’s estuaries and bays at sunrise during the transition seasons, pretty much spreading out in all directions for a few scans.

    I heard a lone geese two night ago…I felt badly for him, thinking he was separated from his flock.

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