Weather Blog

La Nina weakens, but Seattle still in 'heating slump'

In yesterday's blog, I wrote about how the long range prediction is still for a cooler than average June and summer.

That touched off a flurry of e-mails (OK, three) of people saying they heard that La Nina is weakening, so where's our sunny and 78 already?

First of all, a quick recap on La Nina. That is the "sibling" of the pattern El Nino.  El Nino is the warming of the waters in the equatorial Pacific Ocean.  That makes it warmer and drier around here. La Nina is the opposite -- it's a cooling of the ocean waters there.

That temperature change shifts trade winds and in chain reactions, affects the weather patterns of several places on the globe.  Locally, it can affect the position of the jet stream -- La Nina keeps it closer to home; El Nino sends it farther away. For La Nina, it typically means a wetter and cooler winter and spring. The fact that there was skiing in mid May seems to indicate that we can agree that's what occurred.

NOAA forecasters say La Nina is showing signs of weakening as temperatures in the ocean should be back to neutral status starting about now through July. (Read more at NOAA's site here.) However, La Nina conditions have some momentum behind them and still exist, which is likely why we're staring out the window at a continued cool and wet start to June, just like May, April and the last half of March was.

La Nina's influence is typically negligible in the summer months, but long range forecasts for the summer predict cooler but drier than normal conditions. (And again, that doesn't mean it'll be cloudy and 60 all summer long. We'll still get some sunny and warm days; just perhaps a few less than usual. And we still have to make up for two summers ago when it hardly rained and we went way over quota on sunny days.)

But climate forecasting is not just La Nina/El Nino. There are several other factors of climate in play -- likely some that still remain undiscovered. For instance, there is research into something called the Pacific Decadal Oscillation (or "PDO" for those playing government acronym bingo. If so, I should mention the official acronym for El Nino/La Nina is "ENSO" -- short for "El Nino/Southern Oscillation.")

Anyway, the PDO is also a change in Pacific Ocean temperatures, but it's more gradual and seems to go in 20-40 year periods than the more typical 1-2 year cycles of ENSO.  (Read more about PDO at this link.) From, 1925-1946 and again from 1977 to the turn of the century, we were in an apparent warm phase. On the other hand, we were in an apparent cool phase between 1890-1924 and again from 1947-1976 (And gee, all those snowstorm records from the mid 50s for Seattle.) 

Could we be due to head into another cool phase?  Guess we'll see. But it's important to note that you can still have El Nino/La Nina on top of these greater phases. A warm phase might enhance an El Nino period and limit a La Nina period. And vice versa.

But then again, there could be other climate phases on even longer periods of hundreds or thousands of years! Good to know there will always be jobs for climate researchers.

Now, you read this and I'm sure all sorts of global warming questions come to mind. This is not meant to be any confirmation or debunking of global warming. It's an issue that is so much more complicated than just ENSO/PDO, which are small parts of the greater climate machine that is Mother Nature. 

But one thing I will say that we hear all the time as weather forecasters, and that is people taking very short periods of weather and either declaring it is global warming, or that global warming is a farce.

For instance, the weather the past 10 weeks or so. I've heard so many people on the street (and since unlike Steve Pool, no one knows by sight that I'm a meteorologist) say "Oh, this rainy weather proves Global Warming is false" or "this cool spring proves it's all much ado about nothing."

Global Warming is not about the weather this week in Western Washington. The record 90-degree day two weeks ago no more proves Global Warming is here than the 53-degree day today proves that it's false.

A good example is baseball (isn't it always?) Take Ichiro. He has a lifetime batting average of .331. But let's say you're at Safeco Field and the game goes 12 innings and he goes 0-for-6.  That doesn't mean he's no longer a .331 hitter. (OK, maybe it means he's now a .330999998 hitter). It just means he had a bad day. Or even if he goes in a 2-for-23 slump, it doesn't mean he's lost his swing.  Conversely, if he goes 5-for-6, that doesn't mean we go and put him up there above Ty Cobb for highest career batting average.

Global warming is about the average temperature of the Earth on a global scale. Scientists are finding that that average temperature is rising, when you factor in every location. The debate rages on whether it's significant or what's its cause, and whatnot. But it's about overall climate shifts.

Note that it still gets cold from time to time in California, despite being a warmer climate. It's just that if the global temperature gradually rises, you can expect perhaps 6 days a year over 90 in Seattle as opposed to 2-3, and maybe that snowstorm that dropped 2 feet of snow at 3,000 feet this year only drops it at 4,000 feet in 50 years. Still, add that up aggregately and it could have impacts on the region (maybe the Cascades now only get half their snowpack that they do now, which would affect ski runs and water supply, to name a few.)

Or, back to the baseball analogy, if Ichiro's average were to undergo "global warming", maybe his career average is .333 in 2010, and .336 in 2015, and .339 in 2020, etc.  He's still going to go through slumps, but now he's hitting a little more frequently than he was before.

That's the simplistic answer to a very complex topic. But the main point was -- just because it's been chilly for a while here in Western Washington, doesn't mean global warming is a farce, just like when that stretch of 90 degree weather comes later this summer, won't prove it's true.

And as for right now, let's just say Seattle is in a "heating slump" :)