Forecaster Predicts La Niña
Will Bring More Dry Weather

By David Bowser

There is good news and bad news about the hot, dry weather that has spread across Texas and Oklahoma this summer. The good news is that it has nothing to do with La Niña. That’s also the bad news — the drouth of La Niña has yet to arrive.

El Niño’s sister is indeed associated with drouth, but a forecaster who has tracked such weather patterns for two decades says the dry conditions over a large part of Texas are not related to the developing La Niña.

"La Niña has a lag time as far as how it affects the weather patterns, and it doesn't usually show up until the fall," explains Ed Andrade, lead forecaster at the National Weather Service in Amarillo.

"It just happens to be the worst of both worlds right now. We're dry now, and we're forecasting the continuation of dry weather based on the cold phase that could be fairly significant."

El Niño is a natural occurrence of warming water that occurs around Christmas off the Pacific Coast of South America. La Niña is its counterpart, when the Eastern Pacific turns cold.

Due in large part to new remote, bobbing weather collecting stations in the Pacific, the National Climate Prediction Center in Washington D.C., has been able to accurately predict El Niño and La Niña occurrences for only the past year or so.

Andrade wrote his master's thesis on the El Niño phenomenon back in the mid-1980s, a time when little was known about the Southern Oscillation, as it is officially called. Since then, the National Oceanic and Atmospheric Administration has dropped a series of data collecting buoys across the Western Pacific where El Niño has its origins.

The abnormal warming of the El Niño cycle occurs every few years on average, though it appears those cycles are coming closer together. Andrade, however, warns that there is not yet enough data to draw solid conclusions concerning the length or strength of the cycles. La Niña of 1995-96 was strong and followed by a strong El Niño this past year, however, and the National Climate Prediction Center is forecasting a very strong La Niña for 1998-99.

"El Niño pretty much phased out or died in early May, very quickly," Andrade says. "The same time it phased out very quickly, the increased up-welling, the cool ocean water, of the Pacific caused water temperatures on the surface to become below normal. That trend is becoming very apparent now; we're going into an opposite phase, a cool phase."

The National Climate Prediction Center says there will be a strong La Niña by late fall and early winter.

"It's in the developing phase now," Andrade says. "The data that's out there confirms that. They expect it to continue to intensify and become pretty strong."

Andrade says La Niña is predicted to be a Category IV, the top end of the scale, which usually has some negative impact on precipitation on the southern U.S.

"With El Niño, we saw all the rain last winter and early spring," he says. "La Niña is the exact opposite."

The cold ocean waters of the Eastern Pacific tends to result in a large area of below normal precipitation across the southern U.S.

"Texas is very much included in that," he adds.

The climate prediction center is forecasting relatively dry conditions beginning in the fall, continuing through the upcoming winter and ending in the spring, in April and May of 1999. The center was confident about their forecasts concerning El Niño. They are also confident about their forecasts concerning La Niña.

"We're kind of dry now," Andrade says. "The southern Panhandle is dry. The northern Panhandle has had quite a bit of rain over the last several weeks. They got some last month, too. So they're a little bit better off as far as soil moisture, but from about Interstate 40 south, it's been quite dry."

Overall, he says, spring rains have been below normal.

"If we don't get a decent summer rainfall, then when we go into fall and winter, drier than what we normally get, it's going to have some pretty significant consequences for this area, especially in the spring," he says.

The forecast is for below normal precipitation through May.

"That's when we start getting into our rainy season," he says. "We could have a fairly prolonged dry period, in some cases, drouth conditions.

He said 1996 was the best example of what La Niña can do.

"We had a Category Four La Niña beginning in late 1995 through early spring of 1996," Andrade says. "That resulted in some of the driest weather during that period we've seen in the Panhandle in quite some time. It's looking like it could very well happen again."

The only good part to that, he says, was that when La Niña weakened in early June, 1996, the Texas Panhandle ended up with significant rain the rest of the summer. There was significant flooding in the northern Panhandle, and Amarillo made up its rainfall from late June through August.

"But that may have been just because the monsoons were more active that year," Andrade says.

Neither La Niña nor El Niño typically have any effect in the summer. There is a lot that effects weather patterns during the summer months, but the El Niño/La Niña cycle is not one of them, he says.

"Their biggest effect is in the fall and spring," he says.

The forecast for dry weather this fall and next spring is for a large part of the central Plains, Andrade says.

"It's going to be the heart of the wheat belt and the southern tip of the United States, places that have been dry already, like Florida," he says. "Even if they get some summer rains, they'll become dry again."

El Niño/La Niña aren't normally associated with temperature changes, Andrade says, but only with precipitation.

During El Niño years, there tend to be more hurricanes in the Eastern Pacific, which translates into more moisture for the desert Southwest.

"The Eastern Pacific is our best source for hurricane moisture, up along the coast of Mexico," Andrade says.

In La Niña years, there are fewer hurricanes in the Eastern Pacific and more in the Atlantic.

"We don't often get much hurricane moisture from the Atlantic storms unless they go directly to Texas," Andrade notes. "Then we get some residual moisture from those hurricanes. The Eastern Pacific side, up along Baja California, down through the coast of Mexico, that's our best location to get moisture from the tropics coming up."

And for right now it appears La Niña is giving the southern U.S. and central Plains a cold shoulder.