It Might Rain, Might Pour--It Might Not

If the rain last week was your kind of weather, you’re in luck. Forecasters say there’s more on the way. Maybe a lot more.

Mike Smith, a meteorologist for WeatherData Inc., which provides forecasts for The Times, said it all depends on which weather system wins the race to the coast.

Smith explained it this way:

There’s a warm, damp, low-pressure weather mass that’s been sitting at sea about 400 miles west of Point Conception for the last few days. It’s been responsible for the humid weather and occasional light showers that have fallen here since the weekend.

Pushed Toward Coast

There’s another low-pressure mass, about 1,200 miles north of Hawaii, that’s begun to head this way, crowding the first one. As this new mass continues to move east, it’s begun to “kick out” the older mass, pushing it in toward the Southern California coast.

“That means some showers--damp weather--for a couple of days,” Smith said.

But there’s more.

“It’s something we’ve been watching, a tropical depression about 1,400 miles south of Los Angeles,” Smith said. “If it moves north fast enough, it could get caught up in that circulation off the coast.”

If the tropical depression--dubbed Selma by the National Weather Service--gets here first, the counter-clockwise circulation around the low-pressure mass moving onshore would pull the warm, moist air from the south right into the Los Angeles Basin.

“That could cause the rain to be fairly extensive, perhaps fairly heavy, by Thursday,” Smith said.

He said there might be as much rain as last week, when up to 3.5 inches fell at some points in the San Fernando and San Gabriel valleys, knocking out electrical power and triggering floods and mud slides that, in one case, blocked lanes of the Golden State Freeway for more than 24 hours.

On the other hand, Smith said, the low-pressure system may get here first. If that happens, the winds will push the tropical moisture around us to the south and east, and showers will be all we’ll get, today and Thursday, with clearing expected by late Friday.

“It all depends on which one wins the race,” he said.

Since all the contesting weather systems have originated in the warmer areas of the Pacific--unlike the winter storms, which frequently start out in the Arctic--it’s been uncomfortably muggy here for the last few days, with high temperatures in the 90s on Monday and only slightly cooler on Tuesday.

Afternoon High of 91

The Los Angeles Civic Center high reached 91 degrees Tuesday afternoon before the cloud cover moved in and readings dropped sharply into the 70s. Relative humidity ranged from 64% to 27%.

El Toro and Santa Ana shared a high of 86 degrees Tuesday; San Juan Capistrano reached 80 degrees and Newport Beach 75.

Smith said it should be a little cooler and a lot more comfortable today, with highs in the mid to upper 70s. He said the increasing cloud cover is causing the temperatures to drop.

Highs of 81 degrees were predicted for today in El Toro and Santa Ana, and in the low 70s along the Orange County coast.

Smith theorized--”but it’s only a guess”--that the warm rains this fall could be due to higher-than-usual ocean temperatures in the eastern equatorial Pacific, where readings are running about 5 degrees above normal.

“The higher temperatures could increase evaporation rates, and that could mean more moisture from there and more thunderstorms,” he said.

Times staff writer Jeffrey A. Perlman contributed to this story.