Woodward, Okla. —
DRY WEATHER COULD CONTINUE AS PART OF "DECADAL" PATTERN
Weather experts say the conditions causing the current drought could continue for a while.
Oklahoma Climatologist Gary McManus explained that weather patterns are a result of the natural changing or “oscillation” of ocean temperatures at the tip of South America.
Those changes usually follow a “decadal” pattern, that is, they last about 2 to 3 decades, McManus said. This is called Pacific Decadal Oscillation or PDO.
There are two different types of PDO, he said. One involves warm ocean temperatures, also known as El Niño and the other involves cooler ocean temperatures, also known as La Niña.
So for instance, during the drought here in the 1950s and the fairly dry pattern that followed until about 1975, the ocean down in South America was going through a cooler phase, McManus said. When that happens, it causes warmer and drier weather to dominate here, he said.
“Then, from 1975 through about 1995 or 1998, we had that wonderful wet phase where we had more rain,” McManus said.
That means ocean temperatures in that 20 or so year span between 1975 to 1998 in South America were warmer. So that created, for the Western half of the US, cooler and wetter weather, he said. That is called El Niño.
So McManus believes sometime around 1995 to 1998, the PDO changed back, as it naturally does, to a La Niña cycle.
What’s that mean for us?
“It could mean we have another decade or so to go before the overall pattern changes,” he said.
That doesn’t mean that every single year will be a drought though, McManus said.
“There will be some rainy years; it just means when you look at it over time you see that there were more dry years than rainy years during that phase,” he said. “And when there are dry years, they are pretty nasty.”
Some good news, McManus said as far as he can see, there is still a fair chance the spring will bring some much needed rain. His climate model is what he called “neutral” at the moment, meaning ocean temps are a little cool but not so cool that it qualifies as a full on La Niña.
“Right now, it is really hard to predict but we do see signs of an El Niño building, which could bring wetter weather in the late summer and possibly into fall,” he said.