Cut-Off Low returns to its birth location.

by Mike Godsey, mike@iwindsurf.com

Way back on Aug. 18 I posted this unusual satellite video of an upper trough at ≈ 18,000 ft. turning into a Cut-Off Low just west of the Bay Area and deepening the marine layer clouds and creating SW flow just aloft:

https://blog.weatherflow.com/?p=14413

Since then the Cut-Off Low has wobbled about off the California but this morning, Aug. 21 it is back to its birth location just west of the Bay Area as you can see in the video below. Hence the East Bay and Sherman Island winds today.

Now look at the second image. Find the Cut-Off Low and California. Now look out at the pacific just north of Hawaii and find the inbound upper trough at 18,000 ft. If Benjamin’s extended forecast for Thursday is right that upper trough will suck up the Cut-Off Low and bring an end to our SW flow.

But remember Cut-Off Lows are disconnected from the upper level winds so they are pretty unpredictable so don’t be surprised if the forecast changes overnight.

The Weatherflow forecast team has already been burnt by this Cut-Off Low. My extended Southern California last Sunday night was for Southern California to have weak winds Mon.-Wed since some models had the Cut-Off Low dropping towards Southern California. Instead it stayed near the Bay Area so Southern California kept its wind.

Other models had the Cut-Off Low rejoining an upper trough and slide towards the Gorge bringing mid to upper 20’s to The Wall etc. Instead it lingered near the Bay and each day the forecasters had to back pedal on the wind strength as the Gorge saw mild winds.