Squall line

[JohnHuth]

Yesterday I had an interesting lesson from mother nature.

My wife and I were walking on the beach, she looked up in the sky and said "look at the mare's tails and mackerel scales....doesn't that mean rain?" "Sure enough," I said, looking up at the clouds.

I looked at the newspaper when I got home and there was no hint of a storm coming through. But, I decided to not go out for a long paddle I'd been planning. Instead, I took some photos of the clouds, which thickened more and more. Pretty soon we could hear thunder and saw a squall line approaching - photo attached.

Squall lines are more or less a linked up line of thunderstorms. The dark front is called an "outflow boundary" by some, and that's where huge winds in downdrafts occur. Sometimes it's called a gust front. This is often associated with major league wind-shear and microbursts. As the dark line of clouds passed over us, the water got very whipped up and lightning was flashing all over.

I think NOAA weather finally got on the stick and issued the storm warnings, but there was very little that would make you guess it was coming except for reading the signs in the clouds.

It would've been a tough time on the water.

[EEL]

Squall lines are more or less a linked up line of thunderstorms. ... Sometimes it's called a gust front.

I think NOAA weather finally got on the stick and issued the storm warnings, but there was very little that would make you guess it was coming except for reading the signs in the clouds.

John:

Do the clouds specifically portend a squall line before it forms and would you describe those clouds. Or do some clouds portend the potential for a squall line, but it is only when the squall line forms that you know one is coming? Do they tend to move in any particular direction as in from onshore to offshore or easterly/northerly?

Thanks for any info.

Ed Lawson

[JohnHuth]

Ed -

If you mean mackerel scales (cirrocumulus) and mare's tails (cirrus) clouds, then no, they don't specifically portend a squall line - just an approaching front. There is a sequence of lowering clouds and the cirrus is the highest in the sequence. There were also altocumulus clouds and the general lowering indicated a front coming.

What other things could've tipped me off to the squall line? It was beastly hot and humid with little wind in the morning. I was remarking to my wife that we were due for a serious thunderstorm, and I didn't understand why one didn't hit. The day before, I *was* out paddling and saw an anvil head form and then dissipate with no action, so there was something building.

In the morning, I saw a slow breeze build from the east, which I'm guessing was some inflow that fed the storm front.

The cloud sequence went by fairly quickly. Normally when you see that kind of cloud sequence happening fast, it means a strong storm I'd seen something quite similar when a tropical storm raced through a few years ago - the cirrus, followed by cirrocumulus followed by altocumulus (rollers) followed by a lowering cloud base, all happening within an hour or so.

In my case, the decision to not go on a long paddle was a "let's wait and see what happens to the weather" delay, and as the clouds built, it became more and more evident. The speed of the approach was another tip-off.

NOAA said that the storm itself was moving at 30 miles per hour - which is pretty consistent with what I saw on the ground.

I'm attaching a photo I took a little while later after the gust front ran by. You can see a patch of clear sky in the far distance, where the front was advancing, and then the disturbed region of the gust front behind that, followed by the general grey of the rain, and even a lightning bolt hitting the water.

John

[bazzert]

Here's one I took from Thacher Island, we made it back to Rockport with about 10 minutes to spare.

Barry.

[jdkilroy]

Hence the sailor's wisdom:

"Mares tails and mackerel scales make lofty ships carry low sails..."

Jon