We're on Storm Watch here in Southern California, which means that more than three drops were forecast to fall. If you live here, you may have been mystified by something that I'd like to try and explain if I can. (And the reason I think I can is that I once had a devout and bizarre interest in the field of weather prediction…not so much about how they arrive at the forecast but just what it all means.)
The National Weather Service was predicting a 90% chance (i.e., near-certainty) of rain between Friday evening and Saturday — between .75" and 1.25" in the Coastal and Valley areas with the bulk of it falling between late morning and mid-afternoon. Indeed, as late as 9 AM this morning, they said there'd be about four hours of moderate to heavy rain between 10 AM and 1 PM…and I guess somewhere near me there was. But where I am, we got about a quarter-inch overnight and just a few sprinkles between 10 and 1.
You see, the problem with projecting the weather in Southern California is that it can be pouring here and be fair and warmer downtown. This storm dropped a bit less than a half-inch wherever they measure that kind of thing in Beverly Hills and it dropped .04" in Downtown Los Angeles, which is not all that far away. When storms are very cold, they have a special tendency to do that…to come in as streams of soaking-wet clouds that dump a lot of rain in one spot but miss another right nearby. Partly as a spectator sport — and partly because I was trying to decide what kind of climate we'd be braving to go see Sid and Marty Krofft — I was monitoring the online radar images all day and I kept telling Carolyn, "This next wave just took a left turn on the 405 and it's heading for Oxnard." Oxnard got about a half-inch. The forecast was right some places. It just wasn't right everywhere.
Meteorologists are working on computer models that will largely do away with the whole concept of a weather forecast for someplace as large as Southern California. Though there will be one-size-fits-all cases where most locales here will get roughly the same, there will be enough variance where you'll have to get your forecast by going to a computer and entering your street address. There are already some places where you can do that but it's largely illusory. You enter where you are in Southern California, the computer checks to see where that is…and if you're in, say, Glendale they give you the forecast for Glendale and everything else in a fifty-mile radius that's at roughly the same elevation. That leaves you with a forecast that's much more general and approximate than you're led to believe…but we will see the day when you will get a specific forecast for your area. Some private weather services are already hyping that that's what they're giving you when it's really more general. But as so often happens, the technology will soon catch up with the hype. It usually does.