Friday, November 30, 2007

The Rains Have Come

The NOAA weather service has been unusually confused recently.

For several days they have been forecasting “rain showers” followed by a “red flag” warning. The latter is severe fire danger due to extremely low humidity and Santa Ana winds and the oddity is not that those conditions would follow rain showers, but that severe fire danger would do so. Following a very light rain things would dry out in a matter of hours, granted, but what they have been forecasting has been a system with a really good connection to tropical moisture.

They were saying that most of it would bypass us and go into Arizona, but that we would get showers and some steady rain for 24-36 hours. Amounts, they said, would only be about a tenth of an inch in San Diego, although they admitted that there was uncertainty in the forecast.

Well, the “showers” that were supposed to be arriving later this evening have been pounding on my roof since about 4AM, pretty much without a break. I don’t have a rain gauge any more, but I’d estimate we’ve had at least an inch so far.

The problem lies in forecasting the activity of a "cut off low," a low pressure system over the Pacific that is not connected to the jet stream. These things can sit motionless for days, and when they do move their direction and speed are pretty much random since there is no "steering current" of air to direct them.

What’s interesting is that the “Current conditions” on the NOAA site say that showers are moving through the area now and that the best chance for significant rain is late this afternoon and tonight. So, what is this that we are getting now? Well, according to them, “showers.” All I can tell you is that at times I’m finding it difficult to hear the radio because the “showers” are making so much noise on my roof. We may need an ark when the heavy rain gets here.

This may go from being one of the driest Novembers on record to one of the wettest, in the space of one day. If it keeps up it could become one of the wettest Decembers as well.

All kidding aside, this is much needed stuff; more than welcome. The only problem is that it is coming down hard enough that it may very well cause serious flooding problems in the recently burned areas of the county. Some prevention work has been done, but not anywhere near enough and some of this rain is quite heavy. The people who suffered through the fires do not really need to have more problems added on.

Keep them in your prayers.

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