TRADITIONAL JUNE GLOOM MAY LINGER THROUGH SUMMER.

Byline: Steve Carney Daily News Staff Writer

Summertime, and the breathing is wheezy. Thanks a bunch, La Nina.

Forecasters say the global weather phenomenon will leave Los Angeles cooler than normal this summer, with the fog of June gloom extending summer-long and increasing smog.

``We're having a very volatile end to the 1990s. The bottom line is, anything can happen here,'' said Bill Patzert, a satellite oceanographer for the Jet Propulsion Laboratory in Pasadena and a watchdog over El Nino and La Nina.

``The one thing that isn't going to happen is normal conditions,'' he said.

Exactly.

Of the first 27 days in May, 18 have been unusually cool, according to the National Weather Service.

``The normal this time of year is around 74. Basically our daytime highs have been in the mid- to upper 60s,'' said Stuart Seto, weather specialist with the weather service.

Get used to it, starting this Memorial Day weekend.

Today will be cloudy with highs in the mid- to upper 70s in the San Fernando Valley. Sunday and Monday mornings will bring a chance for light sprinkles as the marine layer thickens, said National Weather Service meteorologist Gary Ryan.

Temperatures will be slightly cooler - 60s along the coast and low 70s inland - but the clouds will begin to dissipate.

``I think by Monday afternoon people will be happy with the weather,'' Ryan said.

It seems in New York, it's already summer in the city - the highs for the holiday weekend will be around 90, with partly cloudy skies, Ryan said.

``It sounds like beach weather there, but it's 91 and humid,'' he said. ``I'd rather take the Valley weather.''

The reason for our wacky weather simply is the one-two punch of El Nino in 1998 followed by La Nina, which has thrown Pacific Ocean temperatures into havoc. Unusually cool water has pooled off the coast and is creating the ingredients for a thick, long-lasting marine layer that typically hangs around in June but will likely linger through the summer, forecasters said.

``The very cold water along the coast intensifies the marine layer. And a thicker marine layer means it's going to be smoggier,'' Patzert said. ``Even if the May-June gloom doesn't last through the whole summer, probably the more serious problem is the extended smog levels.''

The marine layer forms because, as the day begins, the land warms up faster than the ocean. Lower air pressure above the warming land draws in cool, moist air from over the water. Like a wedge, that cool air pushes the warm, landlocked air higher, in effect creating a ceiling of hot air, Patzert said.

The meeting of warm and cool air also forms clouds, creating gloomy, overcast skies. But Patzert said even when the afternoon sun burns off those clouds, the ceiling remains.

And that traps the smog.

Not all forecasters agree La Nina will leave us with a smoggy summer, however.

Early morning clouds during June gloom tend to keep smog down, said Sam Atwood, spokesman for the South Coast Air Quality Management District. He said the worst smog days are those that are clear from sunrise on.

``That gives more time for the pollutants to be cooked into smog,'' he said.

Last summer saw a disturbing 12 days with Stage 1 smog alerts, compared to only one day in 1997, and AQMD forecasters predict this year will fall somewhere in between.

``Our meteorologist feels we'll be having a more normal summer, weatherwise,'' Atwood said.

Los Angeles' cool air and water temperatures this summer are from La Nina pushing the jet stream southward.

Patzert said coastal waters will be 2 to 4 degrees cooler than the normal low 60s this summer. That contrasts with the summer of 1997, after El Nino, when the water was about 6 degrees warmer than normal.

The fish will like the cooler water temperatures and the extra nutrients pulled from the ocean floor. Sunbathers won't be so thrilled, though.

``You'll have more fog and clouds than normal,'' said Joseph S. D'Aleo, chief meteorologist with Weather Services International in Maryland.

``If you want to spend a lot of time at the beach, you might be a little disappointed.''

Temperatures were relatively cool last summer, as well, because La Nina pushed out El Nino fairly early in the year, D'Aleo said. That gave some relief after a heat wave scorched the Valley in 1997, with highs regularly bubbling into the mid-90s.

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PHOTO Anastasia and Matthew Brown of Encino stroll along Topanga State Beach under a cloudy sky.

Evan Yee/Daily News