Wondering Why the Rainfall Isn’t Normal? Maybe Because It Never Is : Storms: Downtown Los Angeles records dating from the late 1800s reveal a remarkable range in yearly precipitation.

It’s been raining on and off since Thanksgiving. The house smells like a moldy seventh-grade science experiment. You waste away dreary afternoons longing for the days of water rationing.

Enough rain already, all right? This can’t possibly be normal in Southern California.

Normal? Perhaps you hadn’t noticed, but it hasn’t been normal here for years. Sixteen years to be exact, and even then it wasn’t quite right.

Technically speaking, normal is 14.89 inches of yearly precipitation measured at the Los Angeles Civic Center. In 1977, 14.97 inches fell at the downtown collection post, close enough to make it the most normal year on record.

Never mind that the rest of the state suffered through one of the driest periods in history that year; it was almost normal in Los Angeles, and that doesn’t happen very often.

A review of downtown rain charts dating to the late 1800s reveals a remarkable absence of normality: Not only has rainfall never been precisely normal, but we’ve been in striking distance only a handful of years this century.

The region fell a sprinkle or two short in 1903 and again in 1934, the year dust and wind storms sent thousands of migrants our way from the Great Plains. It also got close in 1991, but what good is normal when it is accompanied by low-flush toilets and parched back yards, compliments of a chronic statewide drought?

Apparently unburdened by such considerations, weather forecasters, water bureaucrats and reporters relish in talking and writing about normal weather--sometimes inaccurately--taking for granted it is something we know and love. The recent drought seems to have made things only worse; normal has become sentimentalized as the halcyon days of rain for everyone.

“The weather is back to normal,” an ebullient Jerry Gewe of the Los Angeles Department of Water and Power said after declaring the drought over in Los Angeles early this month.

As a matter of fact, Los Angeles was receiving a lot of rain, but the weather was several downpours beyond normal: Rainfall the previous four weeks had been four times greater than what the National Weather Service regards as normal.

There is nothing intrinsically mysterious about normal, as elusive and fleeting as it may be. It is a simple calculation, known among mathematicians as the average. Take the total recorded rainfall since 1878 (the earliest year available), divide it by 115 (the number of years since then), and you arrive at 14.89 inches.

“Normal is good because at least it gives you a ballpark,” said Pat Rowe, a spokeswoman for the National Weather Service, which compiles the rainfall data. “That way people can see how things compare.”

Even so, the number means more in places where it rains and snows like clockwork, according to Maurice Roos, the state’s chief hydrologist. Typically, that is the case in much of Northern California, particularly along the coast. But in semiarid outposts such as Los Angeles the only certainty about weather is that there isn’t much of it--except of course, when there is.

Normal here is a moving target. A series of heavy storms can transform a dry year into a wet one virtually overnight. Historically, the skies have been known to drop more rain one year than in the previous three, then get stingy all over again. As recently as 1983, the Civic Center recorded 34 inches of rain, then measured less than 9 inches the next two years.

“We have a lot of years that are dry and not quite so many that are wet,” said Roos. “Especially in the last few decades, there haven’t been many in the middle.”

Historian Norris Hundley Jr. has warned against thinking “in terms of averages and regular cycles” when trying to grasp California’s changing weather picture. In a recent book on the history of water in the state, Hundley points to studies of tree rings dating from prehistoric times that reveal “great variation” in rainfall.

Ken Turner, a watershed manager for the state Department of Resources, said a lot of confusion about normal rainfall could be avoided if officials referred to median precipitation instead of averages. Simply put, that would help eliminate problems associated with erratic wet and dry periods by singling out what happens smack in the statistical middle of a sequence of years.

But median figures are more difficult to compute and more complex to explain, and no one is expecting them to roll off the tongues of Fritz Coleman or Willard Scott anytime soon. “Averages are easy to do,” Turner conceded.

Roos acknowledged the shortcomings of today’s lexicon, but he defended the use of normal as a helpful tool in deciphering rainfall statistics for the public. At the National Weather Service, Rowe offered a simpler explanation for her agency’s continued compilation of “normal data:”

“Everybody always asks,” she said.