Why do the forecasts sometimes look almost exactly the same from day to day?

by Mike Godsey, mike@iwindsurf.com

You know all that geek talk about upper troughs and upper ridges? And how upper trough bring cooling, SW flow and a deeper marine layer while upper ridges bring warming and weaker winds?ZonalFlowNew

It is sort of confusing until you can visualize it.  So you might want to sneak a quick look at the 2nd video below before you continue.

Now Think of the upper ridges as being northward extending loops in the upper level winds while upper troughs are southward extending loops. Now imagine that there were almost no loops near us in the upper level winds. That is the upper winds were just from the west. That is called zonal flow which we will have aloft until <b>Wednesday</b> so there will be only minor changes in the wind pattern until mid week.

Or it could be that forecasters just get lazy at times or just are in a rush to get on the water so they don’t want to bother changing the forecast.

But for those who trust the weatherman this video shows the weather pattern that should persist from June 19 through June 24. Note the  upper level clouds stream
ZonalFlowBigPicturestraight from the near west across the west coast. There is no hint of the typical upper level ridges or troughs west of California. And it is these upper level ridges and troughs that bring changes in our wind pattern.

However this Wednesday night or maybe Thursday a chilly upper trough will bring a real cool down and increasing SW flow aloft while bumping the North Pacific High’s surface NW winds away from the Bay Area.

But the fact that we have zonal flow west of California does not mean that there are not upper level ridges and troughs out in the pacific. Let’s zoom out in the next video and you can see the zonal flow over California this week in fact is caused by upper level ridges and troughs that are way to the north and way to the south.  And that upper trough you see in the top of the 2nd video will actually drop over California by Thursday June 26 and bring a real shake up in the weather.