by Mike Godsey
You know the routine. First one to two day of strong El Norte winds. Then 1 or 2 days of mild El Norte + mild local sea breezes. So today you would expect at least upper-teens northerly wind. But…..no. Why, let’s examine the images below.
First look at the surface isobars for yesterday. Note the high pressure in the Great Basin and how isobars over the Sea of Cortez are creating northerly wind.
Now, look at the Today image. There is still high pressure but it is centered more to the north which, by itself, would mean weaker Baja winds. But the big news is that low-pressure area over the entire Sea of Cortez. As you can see this causes isobars to cluster over Nevada. So “our” wind is focused in that area.
So where did this area come from?
Look at the bottom image which shows the surface isobars AND the winds at ≈ 18,000 ft. Notice the southward dip in these winds. This is known as an upper trough and brings clouds and cooler air to our region. Also not the counter-clockwise spinning area within the upper trough. This is a near Cut-Off Low. Together these events have induced the surface low pressure you see in the isobars. Hence the weak winds likely today.