Billows before the storm

Its not something a weather-centric sailor would say, but its what happened yesterday before today’s certain storm.   Maybe sailors should consider it…but with no cussing,  though.

The Weatherunderground weather site forecast for Catalina has 0.58 inches predicted for our storm. Such forecasts, I have to say, are “objective” and are based are model outputs that yo-yo forecasts every time a new model output  comes in.

To educate you on how bad this is, why just yesterday, based on the SAME model but a different set of global data, the model said we would have, 0.59 inches.   So, its already changing our forecast, diminishing it!  How bad is that?

The problem with those forecasts is that they are heavy with “objectivity”; there is no human intervention.  Its the work of a robot of sorts.   And we know what robots are doing to the economy and jobs.

Here, straight from a human heart,  we had a forecast of 0.33 inches total from this storm,  one laden with emotion and often based on wishful thinking when large amounts are forecast.  They’re often, based, too,  on pattern recognition (“looks like that storm that brought us that much last time, or look where the core of the jet stream is!”)1

That forecast of 0.33 inches in the gauges right here in Sutherland Heights is not going to change just because some new data came in!

So, which one do you want?  A forecast that yo-yos every few hours as demonstrated by the Weather Underground one?  Or one that stands tall against new data?

I think the answer is obvious.

OK, enough about “robots” and weather; on to yesterday’s afternoon billows:

12:49 PM. Layer of Altocumulus opacus moved in during the mid-day hours. Looked a lot like “Altostratus” to some, I am sure. But if you looked carefully as I always do, you’d have seen the sun’s disk in the brief thin spots. You can’t see the sun’s disk in Altostratus because its full of cloud and precipitation-sized ice crystals, which cause enough interference with the incoming sunlight to prevent the outline from being seen due to diffraction.   So if labeled it even momentariy as “Altostratus” you will get a demerit at the next meeting of Cloud Maven Junior club when your cloud diary is inspected by the other members.
1:59 PM. Showed signs of devolving into a Altocumulus opacus perlucidus layer as small cloudlets began to show up. No billows here, but let’s look over there next, but an hour an a half later.
4:06 PM. A very billowy sight! Or, as we cloud technicians would say, Altocumulus or Stratocumulus undulatus. The individual elements are a bit large for true Altocu, yet the layer is still quite high off the ground, about 7,000 feet above Catalina, or about 1,000 feet above the top of Lemmon. (This from the TUS sounding.)
3:07 PM. Billows galore!
3:07 PM, but a little more over there.
3:10. Billows to the north!
3:35 PM. Just going on and on!
3:38 PM. The billows (undulatus) structure was fading quickly, here almost two perpendicular waves are interacting with this cloud cutting it up into square elements resembling waffles.
3:38 PM. The billows (undulatus) structure was fading quickly, here almost two perpendicular waves are interacting with this cloud cutting it up into square elements resembling waffles.
3:38 PM. The billows were pretty much gone, and the sky cleared spectacularly after this.

Well, there you have it, another tediuous contribution from the CMP.

The End here,  but the beginning of the next storm!

1Analogs to previous weather patterns are also part of the forecasting arsenal used by computers and other forecasters these days.

By Art Rangno

Retiree from a group specializing in airborne measurements of clouds and aerosols at the University of Washington (Cloud and Aerosol Research Group). The projects in which I participated were in many countries; from the Arctic to Brazil, from the Marshall Islands to South Africa.


  1. Very entertaining post. Also, to add to the sailor lingo: “Red sky at night..”

    Guess we’ll see that happens on THIS night.

    1. You got it, Aumua, red sky in full glory just now! However, it was normally thought, due to a clearing to the west, to lead to fair weather, as you likely know, But not here. We often get cirriform decks like the one overhead now that are completely separate from those lower storm clouds.
      I once had a post about it, the clearing before the storm. Well, this isn’t quite the clearing, but it is something like that pattern.

      Thanks for you comment. Mostly I figure I’m entertaining myself…


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