Looks like one of NASA’s two WB-57’s, NASA926, has been operating out of Miramar most of March. Conducting racetrack patterns at altitude…likely as a radar target of some sort?
Could be practicing for hurricane season, used them a lot last year.
http://silverplate1945.smugmug.com/photos/60938880-S.gif
You could always ask them: jsc-aircraft-ops.jsc.nasa.gov/wb57/contact.html 8)
I don’t think the Canberras are used as ‘targets’ by the military, the Phoenix Air Group are the main contractors for that. The flightpath looks like it was circling over the San Gabriel mountains and FL570 is a bit high for hurricanes. Could be some kind of weather-related study though - been a bit wet down there this year I understand 
Could be some kind of weather-related study…
That’s why there’s a “W” in WB-57 - it’s a bomber that has a secondary mission of weather.
Err yes, I think we all realise that. Question was what’s it doing at Miramar - not normally a NASA base. Not all missions flown by W- types are directly weather-related, it’s just an equipment/fit indicator.