Raindrops fall on Catalina ending rainless October

A trace of rain was officially recorded in Catalina at this site ending prospects of a rainless October.  It fell from high-based Cumulonimbus clouds in a band, partially lining the NW horizon that could be seen as the sun rose yesterday.  Some ants were injured by the falling drops, ones that reached millimeter sizes and fell at 5-8 mph, though in some areas, winds of 10-15 mph added to drop impacts.  Flying insects, while  obliged to avoid the watery missiles, were able to do so with ease due to the appreciable spacing between the drops of several feet.

Due to the short-lived hydrometeor events, many humans were unaware that rain had fallen in Catalina on more than one occasion yesterday.  That’s why we blog here.  Weather and cloud news you can rely on.

How high were the bases of those precipitating clouds spewing snow virga that melted to rain?  Higher than the freezing level! Haha..  The balloon sounding profile started with the Altocumulus perlucidus layer at 18,000 feet above sea level, 15,000 feet above Catalina, bases at -11°C.  By evening the lowest moist level had lowered to 14,000 feet ASL (11,000 feet AGL) and -3°C.  However, that last moist level had to be a bit lower than those snowy cloud bases IMO–we know that the moist level almost always lowers.

So cloud maven person will make the definitive call that the rainy (well, sprinkly) cloud bases were at 16,000 ASL (13,000 feet AGL) when they passed over, if that makes any sense or is anything you really care about.

Yesterday’s clouds

6:42 AM. Altocumulus perlucidus at -11°C (12°F). No ice evident.
6:43 AM. High-based Cumulonimbus erupts to the distant NW. Altocumulus castellanus layer from which it erupted can also be seen. The snow falling from cloud base is also evident, melting to rain just above the horizon.
6:54 AM. By this time the full band to the NW whose tail was to pass over us about mid-day is evident. Plenty of snow can be seen falling from these modest, high-based Cumulonimbus clouds.


As rain fell……this sky, 12:30 to 1 PM:

Kind of pathetic really; no shafting whatsoever, much less virga than on the horizon yesterday morning.  So our end of that band was so weak it was just barely able to get some drops to the ground.

Looks like this is it for rain in October 2017.  However, November 2017 appears to look much brighter for substantial, dust-removing rains in Catalina beginning in the first 10 days!

The End (I missed the sunset due to a social engagement–hope you saw it wherever you were).  Probably was pretty nice.

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. hi Art! Good to see you’re back. Well, we’re far from being rainless up here, I can tell you; 6.64 inches for the month so far, although little expected this week. Still, we are above normal for this month.

    1. Wow, that’s quite a change, Roland. And thanks for the comment. Not sure I will continue since this WP ad thing started.
      Once music erupted as I checked my page out! Very obnoxious.
      I guess they have to make money, must be going under.

      Kind of ruins the pristine web experience. Been too busy to check it out more thoroughly, see what I can do about it.


  2. Hi Art: the first snow of the season fell here last night. That’s my earliest observable snow on the ground since Oct.29, 1991.

Comments are closed.