Tag: Convection

Let’s Look At Clouds From Both Sides Now

If it looks like the clouds are boiling, just like a pot of water on the stove, it’s because the dynamics are very similar. Heat is being transferred upward through convection.

NWS EDD

We seldom get the big picture of what’s on the radar by just looking at the sky. Not today. Today is different in SoCal.

The atmosphere is unstable on the the other side of the Santa Ana Mountains, around 30 miles east of me. That’s where the radar (at the top of this entry) shows strong thunderstorms.

What’s striking in the time lapse below are the mid and upper levels of the clouds producing the storms. There are no clouds in the way blocking my view.

If it looks like the clouds are boiling, just like a pot of water on the stove, it’s because the dynamics are very similar. Heat is being transferred upward through convection.

The heavy rain and lightning bolts are out-of-sight behind the mountains. Here, I only see the signs. Everything is moving north and will soon be gone.

Things You Can Learn From Clouds

clouds

I’m going to put on my science teacher hat for a moment. I saw something cool. You might enjoy understanding what’s going on.

An hour ago I propped my tablet against the bathroom window to take a timelapse movie of the clouds&#185. The sky was filled with beautiful puffy cumulus clouds. On a realtime basis they were majestic and seemed to hover in place.

Not so when sped up by a factor of 150 (that’s one shot every five seconds). Now the sky is turbulent. Roiling!

Gil Simmons, who I used to work with at Channel 8, calls these COW clouds. COW for “cold-over-warm.” I’ve also heard the effect called “self defeating sunshine.”

There’s a larger than normal vertical temperature gradient over SoCal today. Earlier this afternoon the temperature dropped almost 10&#176 Fahrenheit between 5,000 and 7,000 feet. That’s the cause for the clouds–the cold-over-warm.

Later tonight you’ll have to climb from 4,500 to 11,000 feet for that same drop.

Since warm air is more buoyant than cold, it rises and condenses forming clouds. This warm air moving toward the cold is called convection. It’s how heat moves when you put a pot of water on the stove.

If you look carefully at the very top of some of the lower clouds in my timelapse you’ll see the convection in action. The clouds grow upward looking very much like the bubbles of water rising in that hot pot of water!

If it looks like the clouds are moving multiple directions at once, you’re right.

There is wind shear overhead. As the clouds gain altitude they move from a southwesterly flow to northwesterly. It was even more pronounced earlier today. That shear adds to the convective cloud buildup. In fact wind shear is a major factor we look at when predicting severe storms.

Too much for one day? I’ll stop now.

The atmosphere is amazing when you watch it up close. There is so much going on and explanations within the laws of physics for all of it.

&#185 – Try as I might I can’t figure out how to keep the Nexus 7 camera from refocusing from time-to-time. That’s why the shot goes out-of-focus a few times.