Wednesday, November 13, 2013

Another CA Monarch Sighting - Blowin' in the Wind!

Photo by Paul Cherubini 11-12-13 Pismo Beach (Used with permission)

Photo by Paul Cherubini
Yesterday I heard the news. JB called and left a message with my husband, Bob, that a monarch tagged with Southwest Monarch Study Tag #AD183 was spotted yesterday at 2 p.m. at Pismo Beach by Paul Cherubini. Turns out it was one of the monarchs I had tagged at the Canelo Forest Service Administration Area (permit required) on September 14 at 10 a.m. while nectaring on a thistle. Exciting news!

You've likely seen the migration maps - monarchs from Arizona fly mainly to Mexico and a few fly to California. Yet those California sightings come in clusters. In 2008, five Southwest Monarch Study tags were spotted: Three in San Diego and two in Ellwood Main in Goleta. The photos of the tags from San Diego were fuzzy and the numbers unreadable. At first we thought there was only one in Ellwood Main but when we finally had a photo of the tagged monarch with the number clearly identified we realized the tag was in a different place on the wing than the earlier photo. In 2009 there was one spotted by Monarch Alert. Then none.

Canelo Monarchs 10-15-13
But 2013 felt different. In the field this fall and in all my workshop presentations I described our persistent and insistent monsoon this year - and how it was a good possibility it would cause California recoveries. Turns out I was right. So far we've had three sightings and with the Thanksgiving Counts right around the corner we may hear of more. So recently I took our Southwest Monarch Study recovery data to Darcy Anderson, M.S. Meteorology, to see if she could confirm what our Citizen Science Storm Spotters eyes were seeing in the weather maps - or not.

I met with Darcy on Monday. Briefly, she explained how every summer the jet stream retreats north. When this happens the winds shift in the extreme southerly portions of the United States. For example, instead of the prevailing Westerlies, during the summer months Florida will have Easterly winds. Eventually our summer monsoon creates the same scenario in Arizona bringing moisture from Mexico into the state from the South and Southeast. Monsoon is simply a change of wind direction.

One of the weather charts Darcy shared
This summer into late September the monsoon was exceptionally entrenched setting up deep Southeast to Northwest winds regularly and on some days intensely. During the week of tagging the three monarchs that were recovered in California this year, the air was often extremely unstable and even at 7 a.m. sustained winds were blowing at the surface  at 30 to 35 miles per hour from the Southeast to Northwest to above 10,000 feet on some days. This doesn't include gusts. Above that level there was a strong wind sheer with winds blowing from the Northwest to the Southeast. This is what Darcy Anderson, M.S. Meteorology, said about our recent California recoveries:

"Basically what I've found from the Tucson upper air soundings is that there were southeast winds during the September 15 - 20 time frame, at a relatively low atmospheric level, that could have "propelled" the two (now three) monarchs retrieved in CA. During the same time period, there were winds at slightly higher atmospheric levels from the NW and N that could have resulted in monarchs being propelled to Mexico from the same AZ area. It would all depend on the altitude of their flight. I think that will be the case for most CA sightings."

As we talked, Darcy shared copies of the Atmospheric Soundings for the time period to explain her findings. We realized that so far, every California recovery had strong lower level winds so we can not rule out wind as a driving factor in migration destination. Keep in mind if a monarch can ride a thermal high into an unstable air mass and punch through the atmospheric lid of the wind sheer layer above it is conceivable that we could tag two monarchs on the same day, and have one recovered in California and one in Mexico.
By late September and early October, the time of our peak migration in Arizona, winds tend to settle into a more typical Westerly direction. So far all of our recoveries from that period are in Mexico.

Darcy offered to keep daily weather maps every September, the time our monsoon season is likely the most unstable, to track weather phenomena in relation to the monarch migration in Arizona. Eventually we will publish this information after more data are available to see if this pattern persists. Amazing how our love affair with monarch butterflies and their fascinating migration could help us uncover and learn so many new things!

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