COBirds,
It's been a while since I have made one of these posts, but it looks like it is finally time to post again. Monday and Tuesday of this week look like they will include generalized pushes of birds into CO and WY from the Southwest US. Southeastern CO may see some Gulf migrants from the SE direction.
If you hit the "earth" button in the bottom left of the linked pages for more options you can add your location to the map to help with map referencing: compass arrow on the "Control" row of buttons. You can also switch times if you want to control that for yourself.
At noon on Monday
https://earth.nullschool.net/#2022/04/11/1800Z/wind/isobaric/850hPa/orthographic=-105.12,40.19,2136/loc=-105.120,40.191 (green circle is Longmont, CO)
- West of the Divide: The connection of the SW winds to the Southwest US should mean a nice push of migrants with no specific convergent end point. Expect to see more migrants, not necessarily anything particularly rare, just the usual migrants making a nice run at covering some distance.
- East of the Divide: The connection to long-distance migrants just isn't there on the eastern portion of the state at this time. Expect short-distance migrants and probably some raptor movement.
12 hours later (Tuesday at midnight)
https://earth.nullschool.net/#2022/04/12/0600Z/wind/isobaric/850hPa/orthographic=-105.12,40.19,2136/loc=-107.210,40.763 (Best convergence pattern in CO at the Green Circle)
- West of the Divide: The pattern on the West Slope hasn't changed much except for adding some convergence on a line from Grand Junction through Craig, up to the CO/WY border. This looks like the best area for bird convergence and thus increased diversity and numbers around the state at this time.
- East of the Divide: The connection to long-distance migration has now been made. There are multiple weak convergence lines on the Eastern Plains that will cause some increases in bird density, but the final destination for those birds is likely into WY as there is nothing to stop them from continuing on that path.
6 hours later (Tuesday morning at 6am)
https://earth.nullschool.net/#2022/04/12/1200Z/wind/isobaric/850hPa/orthographic=-105.12,40.19,2136/loc=-108.364,37.407 (Best west slope convergence in CO at the Green Circle near slightly east of Cortez).
- West of the Divide: The northwest corner of the state has been cut-off from migration at this time, so the migrant convergence was short-lived but there may be some new birds in the northwest of the state. The rest of the west slope is still open for business though so expect a nice push throughout the morning and into day. The above map is around sun-up, so this is likely the time that the night migrants will put down and the best convergence is near Cortez, CO. There may be a weak frontal passage at the time as well which is a good indication for birds stopping their migration at this location.
- East of the Divide: At this time, the entire eastern Plains and Foothills of CO are open for general movement of birds, with no particular convergence within CO. Expect the Southwestern US migrants at this point.
6 hours later (Tuesday at noon)
https://earth.nullschool.net/#2022/04/12/1800Z/wind/isobaric/850hPa/orthographic=-105.12,40.19,2136/loc=-105.120,40.191 (Green circle back in Longmont)
- West of the Divide: Now the entire west slope is cut off from migration as the winds are now entirely out of the NW.
- East of the Divide: The green circle of Longmont is right at the cold frontal passage on the eastern Plains/Foothills. The winds to the south and east of the front are running parallel to the front, so the convergence isn't enhanced much for making a specific migrant trap better than any other.
6 hours later (Tuesday 6pm)
- All of CO: We're all cut off from migrants at this point since the winds are either westerly or northwesterly for the majority of the state and the backward trajectories don't point to good migrant source regions for this time of year.
So the message overall is, if you are in SW CO near Cortez/Durango on Tuesday morning, keep your eyes peeled for more diversity and increased numbers. If you are on the east slope, you have as good a chance as anyone else in getting migrants on Tuesday morning. Nowhere specific will be favored by the weather. Remember Dave Leatherman's mantra though, "find the food and find the birds."
Hope this helps you net some good birds over the next couple days. Keep me honest by reporting new birds and nothing new and no changes. All data is useful in that regard.
Bryan
Bryan Guarente
Meteorologist/Instructional Designer
UCAR/The COMET Program
Boulder, CO
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