Rain 0.22"; 9.11" season total - not a real sign of a heavy season

Tuesday's storm brought me 0.22" of rain in my back yard, bringing the season total to 9.11". That amount is just over the 3rd quartile of rain, for this point in the season.

Reposted from a comment I made on another blog:

Let's be clear on the statistical significance of our monthly and season-to-date rainfall figures taking this month as an example. You might think that we've had a lot of rain recently, but I'm here to tell you not so fast.

Data from the last several decades shows that in January we have a 50% probability of receiving between 3/4 and 4 inches of rain (in round numbers.) In terms of cumulative rainfall we have a 50% chance of having between 1 and 9 inches (again, round numbers) at the end of January.

We’re close to the top of that range of cumulative rainfall by my accounting. (I typically measure less rainfall than the official LA weather report).

The point here is that there’s huge variation in “normal” and indeed, there is nothing to suggest yet that we have had or will have an exceptionally high rainfall year. With about a 50-50 chance of being where we are right now, we’re sitting at “typical” in my book.

As an aside, mean rainfall figures (I have mean total seasonal rainfall at 12″ for LA) aren’t really as insightful as median rainfall figures (LA median total rainfall is about 7″). This is because rainfall is not symmetric about the mean. Bad Mom pointed this out to me some time ago, and she is correct.


  1. Did you read Bill Patzert's outlook? He doesn't see any signs of an El Nino.

    I looked at the SST anomaly analyses at NOAA and FNMOC (Navy) and I don't see an El Nino, either.

    Plus, a dome of high pressure set up residence above us, steering storms to the north. We might be lucky just to eke out a normal rain year in SoCal.

  2. I don't follow Patzert regulary, but he seems to have been routinely on target. We both seem to have the same outlook as well.

    I think we need to look for this El Nino to be a moderating influence and not another reprieve from drought.