That Wasn’t Really Rain, It Just Seemed That Way

If it looks like rain--water drops falling from the sky--and it feels like rain--wetness on the head--then it must be rain, right?

Not necessarily.

“It’s not really rain,” corrected John Sherwin, a meteorologist at WeatherData Inc., which provides weather forecasts for The Times. “What you’re feeling is drizzle.”

Regardless of what you call it, the moisture that fell over parts of Orange County on Monday night--don’t expect a repeat today--was caused by a mix of the usual marine layer and some upper atmospheric pressure from a cold front that moved southward over the county around dinner time.

“It’s the typical fog and low clouds that normally develop in the night and morning,” Sherwin said. “With the cold front approaching Southern California, the marine layer has been allowed to thicken ahead of that. And with the deep marine layer, you tend to find patchy drizzle developing.

“It can come down hard enough so that it looks like rain.”

But it doesn’t measure like rain. Sherwin said that as of 6 p.m. no measurable rain had fallen in the county, and that no more than .02 of an inch would fall during the night.

And while the cold front gave, the cold front also took away. Sherwin said the cooler air behind the frontal system would likely dissipate the marine layer tonight. The layer needs warmer air aloft to develop, and the front pushed the warmer air out of the area.

“Once you start seeing cooler air aloft, that helps kick out the marine layer,” Sherwin said. “So it should be partly cloudy [today], and [tonight should be] partly cloudy to clear with temperatures from the mid-50s inland to around 60 on the coast.

“The marine layer will be pretty much nonexistent.”

As will the rain. Or the drizzle.