By WeatherFlow Forecaster

Goooooood morning Rio Vista!!!

 After 4 days of Ben and I issuing marine surge alerts for Sunday I pulled the final trigger Saturday night:

Forecast 7PM Saturday: “Marine Surge Alert! Sherman will absolutely RAGE all day tomorrow.”


These images below, really layout the basic anatomy of a marine surge. 10 years ago marine surges always caught us by surprise. In a short few hours our forecast of hot and calm conditions would be blasted apart by a surge of deep fog and roaring chilly winds. These days we almost always forecast these events several days in advance. And Ben and I forecast these marine surges 4 days in advance.  If you have never seen a marine surge personally this link will take you to an amazing time lapse video: 18 hour time lapse video of a marine surge

But these two marine surges were different. The 2 animations just below of the Sherman Island winds Monday June 2 and Sunday June 9 show marine surges that were much stronger than typical.

Monday, June 2

Marine surgeShermanWindsANIM

Sunday, June 9


Carnage at Sherman Island



In the model imagery below you can see something that never happened until a few years ago…. the WRAMS actually forecast the marine surge BEFORE it happened.

But it did not get the impact of the Cut-Off Low or eddy until after the fact.


In the satellite image animation below first note the strong NNW winds from the North Pacific High shooting down the offshore waters and ripping at the fog.

The note the marine surge fog and southerly winds creeping up the coast.

Once they come near a gap in the coast range they accelerate and curve into the bay reaching Sherman Island about 4-5PM


 Meanwhile in the animation zone below you can see that in the transition zone between the North Pacific High’s NW winds and the marine surge

southerly winds a surface eddy spins up adding some power to the southerly flow curving into the Golden Gate.

Marine surgeEddyANIM

And in this last image below you can see the impact of the upper level Cut-Off Low in the clouds from 10,000 feet up. As the Cut-Off Low moves towards the Bay Area:

  • It induced a surface circulation off Central California augmenting the marine surge. (see bottom image)
  •  It increases the heights allowing the marine layer to thicken and pour through even the higher gaps in the coast range.
  • It transfers some momentum to the lower level wind and stirs up southerly flow in to 20-40 knot range on Bay Area hilltops adding a gust factor to the surface winds.