The Marine Layer


I took Doppler out for a quick walk this morning at 3:30 AM. She looks down. I look up.

The stars were mainly gone. A low gray cloud deck had moved in. Nothing unusual. I went to bed.

By the time I woke up the clouds were gone. It’s like this a lot in SoCal–sunny days/cloudy nights.

There is a reason. It’s called the marine layer. Let me explain.

May Gray, June Gloom

Every area has its own weather quirks. They all follow the laws of physics, often through interaction too complex for humans to fully understand. Take this afternoons clouds.


Even Californians complain about the weather. We should be ashamed of ourselves!

We have one of those potential kvetch times on-the-way. It’s the seasonal California May gray and June gloom. We’ll be waking to cloudy skies for most of the next week. They disappear by noon. This type of weather happens sporadically through summer.

In the case of coastal California, the offshore marine layer is typically propelled inland by a pressure gradient which develops as a result of intense heating inland, blanketing coastal communities in cooler air which, if saturated, also contains fog. The fog lingers until the heat of the sun becomes strong enough to evaporate it, often lasting into the afternoon during the “May gray” or “June gloom” period – Wikipedia

We’re over 10 miles inland. It’s not as bad as for coastal dwellers. Of course, they live on the California Coast. They’d better not complain. Ever. About anything.

This weather scenario wasn’t something we were looking for in Connecticut. Here, it shows up nicely on the forecast models. At the top is a BUFKIT readout from tonight’s 00Z GFS for KSNA, John Wayne Airport in nearby Santa Ana (Clicking the image will give you a much larger, much more readable look).

BUFKIT is an amazing program for visualizing weather data. It was developed at NOAA and is free, as is the data it uses.

With maps you see a large area for one specific time. With BUFKIT you see one specific place over a period of time. Go ahead–reread that.

There’s a lot going on, but what I’m looking at is at the bottom of the image. The lines are isohumes–lines of equal humidity. The cloud producing marine layer isn’t thick. On most days it only goes up 2,000 feet. It produces low, dense overcast. Sometimes there’s drizzle.

The marine layer forms in the evening and fades through the morning.

Every area has its own weather quirks. They all follow the laws of physics, often through interaction too complex for humans to fully understand. Take this afternoons clouds.

Perseids Meteor Shower Versus The Marine Layer

Tonight should be the best viewing for the Perseids meteor shower. I’ll be out with my camera to try and catch a few burning up as they descend toward Earth. Originally I was going to head to the beach, figuring an unobstructed ocean view would be great. Bad planning on my part!

I’ve reassessed. Cousin Michael and I will head inland instead.

As a meteorologist I’m used to factoring large bodies of water into the forecast. In Connecticut the influence of Long Island Sound often meant the difference between snow and rain on the shoreline.

Here in California our nearby body of water is the Pacific Ocean. Mo water. Mo problems.

Chilly water cools air near the surface making it more dense than the atmosphere above. In meteo terms, it’s an inversion.

Practically speaking this ‘marine layer’ acts as an atmospheric cap helping form low overcast. Sometimes it’s low enough and thick enough to form fog. Sometimes it produces drizzle.

As the day goes on, the Sun’s warmth breaks the cap and the clouds disappear.

The cloudy influence of the marine layer is pretty dependable during our warm weather season. Say the words “June gloom” and locals understand immediately, even in August.

Our home is 12 miles from the water. Since our late June arrival, marine layer overcast has rolled in nearly every night. If I went to the beach to see Perseids, I’d see nothing!

The first mountains east of us should block the clouds. They’re not very far. That’s where we’ll head.

I’m writing this at 9:20 AM. The Sun is beginning to break through after another overcast night. The marine layer cycle continues.