Coastal vagrant weather

I believe that changes in offshore weather correlates with with the occurrence of vagrant land birds at Point Reyes and on the Farallons, California. The normal weather pattern here in June consists of a high pressure ridge situated about 1,000 miles west of the coast and a thermal trough in the interior deserts. This pattern results in strong Northwest wind flow along the coast.

But small pockets of low pressure periodically arise over the near shore ocean resulting in a temporary abatement of those strong Northwest winds and a shift in their direction. Based on anecdotal data I believe these wind shifts tend to produce landfalls of vagrants along the coast, at least in Spring.

The best conditions are when offshore winds are light (under 10 knots). If winds are from the south or southeast, even better. A high marine layer is usually preferable to clear skies. Dense low fog or clear skies with strong NW winds are the worst.

I use this site:

Arrow vectors immediately show current offshore wind speed and direction. In general we hope for short arrows and arrows pointing towards the north Click on the buoy for your area. For Point Reyes it is the Bodega Buoy:

Each buoy station offers detailed wind direction and speed charts for the past five days. Notice if the plots show any dips in wind direction. Those are switches from prevailing NW winds to more southerly flow. If these dips are also accompanied by drops in wind speed, there will likely be vagrants. If favorable conditions persist for multiple days, along with a stable marine layer, conditions will likely be excellent.

However, the most important factor in predicting vagrants regardless of weather is the time of year. Fall vagrant season peaks in late September and early October. Spring vagrant season peaks from late May to mid June.

Good vagrant finding!

--Joe Morlan
28 May 2009