Reposted from The Cliff Mass Climate Weblog
Climate Radar Exhibits Spring Chook Migration
Daily I’ve been checking the climate radar for indicators of the northward migration of our feathered mates, and Wednesday night time I lastly noticed it.
Ornithologists and people monitoring the seasonal migration of birds have used climate radar for many years. The radar sign of a goal goes up quickly with the scale of the article (with the sixth energy of the diameter) and thus a hen supplies an immensely larger sign than a raindrop.
Many birds prefer to migrate at night time, so signal of birds is a big space of radar return that begins round sundown and fades at dawn. Meteorological alerts don’t try this.
And the birds favor to remain over land–precipitation doesn’t care a lot in regards to the shoreline.
So let me present you the birds… first at Portland.
At 5:40 PM Wednesday, proper earlier than sundown, nothing a lot was obvious.
By 6:41 PM, inside an hour of sundown, echoes had been showing (reddish coloration), notably NE of the town.
In the midst of the night time at 11:49 PM birds had been in all places!
Proper earlier than dawn 5:57 AM, the echoes had been declining
And passed by 6:59 AM Thursday morning, after dawn.
Nationwide Climate Service radars have Doppler capabilities, which suggests they will decide the velocity of the goal in direction of or away from the radar. Let’s try the velocities of the birdies (see under). Blue/inexperienced means approaching and purple/orange means transferring away.
The radar targets are transferring to the north—precisely what we’d count on for birds migrating northward.
The Hoquiam (Langley Hill) radar confirmed the birds as nicely– listed here are the radar returns (known as reflectivity) at 9:32 PM Wednesday night time. The sunshine blue are birds. They don’t seem to be going very far offshore.
So why did the birds resolve on Wednesday night time to start transferring northward. Sure, it was the correct time of the yr…however there’s something else. The meteorology was almost excellent.
A heat entrance had moved via the area, adopted by sturdy winds from the south, offering a straightforward experience! Plus, the entrance had just about no rain.
To indicate you this hen conveyor belt, listed here are the winds above SeaTac Airport for the 24 hours ending 10 AM Thursday. Time will increase to the left and the Y-axis is peak in stress (700-hPa– is round 10,000 ft). Proper after 7 PM Wednesday (05/03), the winds turned strongly southerly (from the south) and said that approach. Actually, a powerful tailwind!
These are meteorologically very sensible birds.