What’s that?

Posted April 6th, 2011 by kcorliss. Comment (1).

It was a first for calendar year 2011 for me. Others may have seen such a phenomenon already but I was out of town for the “warm” week we had back in March. Last Friday, though, the sky north of town looked like this.

Recognize anything different? Look in the upper right corner. It’s a cloud with vertical development. Not all that dramatic but it’s there. It’s a scene which evokes yawns in the summer but is virtually absent for months during our northern plains winters.

Daryl and the good folks in WDAY’s weather room might have to weigh in on this and correct me, but as a professional aviator I know just enough about K-index to be dangerous. According to a NOAA site I found the definition of K-index is: a measure of the thunderstorm potential based on vertical temperature lapse rate, moisture content of the lower atmosphere, and the vertical extent of the moist layer.

Not sure why “K-index” popped into my head when I saw this cloud but it did. Granted we are some days away from our likely first thunderstorm, but it was somehow refreshing to see a cloud trying to ascend. It’s a sign of changing seasons for me.

(Again, feel free to correct me Mr. Ritchison). I understand most vertical development in clouds come from either thermal convection (heating) or frontal lifting. There was no weather front this day so I can only assume the sun is finally reaching the angle by which it has enough oomph to heat up the ground.

One response to “What’s that?”

  1. Daryl Ritchison

    You’re right Keith. Now that the soil is “black” again, we’re getting thermals each day. Upper level temps are cold enough to allow convective currents to develop. The main reason why I forecasted “isolated showers” today, probably not much more than sprinkles, but the air is “unstable” today. Good to see and a true sign of spring. :-)