Where do Cut-Off Low go when they die?
by Mike Godsey
Every summer several Cut-Off Lows approach the west coast shaking up our forecasting of the California wind patterns. Then after a few days or even a week we suddenly stop
mentioning the Cut-Off Low. The current Cut-Off Low was perfectly located to help funnel a combo of SW winds just aloft and NW winds at the surface bringing strong wind to many sites for almost a week.
So where where do these fickle counter-clockwise spinning low pressure go when they drop out of the forecast? Cut-Off Lows are formed when they pinch off one of the southward extending loops in the upper level wind. Once a Cut-Off Low pinches off it no longer is attached to the normal eastward flow of the upper level winds. So it just meanders about out in the pacific and impacts our wind when it wobbles towards the coast
. But after a few day to a week or more a larger than average upper trough passes by and the Cut-Off Low is swept up into the upper trough and is carried eastward across the west coast.
In this satellite video you can see this happening to the current Catalina Eddy. Notice it sweeping over the Gorge and notice the rain and thunderstorms it produces as it hits the mountains. Also notice all the SW flow over the Bay Area. Now can you see why Sherman Island has been so windy.