From Cliff High Volume Weather Blog
Cliff Mass
It is clear that La Nina is not going away, and may last into next winter.
Cold water is entrenched over the central and eastern tropics of the Pacific (La Nina’s definition) and the latest forecast model runs suggest a continued possibility of fall into the fall.
Some of you have asked: what does this imply for our summer weather?
Let me tell you.
But first, the bottom line: La Nina’s summer impact is modest, but will push the western side of our region toward cooler than normal conditions.
Impacts
During La Nina years, sea surface temperatures off the West Coast are often cooler than normal, and those cooling effects spread inland.
To illustrate, this is the sea surface temperate difference from normal during the summer months (May to September) during La Nina years. Blue is cooler than usual.
And if we average the surface air temperatures for the summer in La Nina and subtract the normal, we find that the summer temperatures are cooler than normal (e.g. green in the image below). ) occurs from California to Washington during the La Nina summer (temperature anomalies in degrees Celsius shown below).
By contrast, precipitation on the West Coast is mostly unchanged…perhaps slightly drier west of the Cascades. I suspect this is because colder water works against thunderstorms. Interestingly, La Nina seems to have more impact in the summer than the US Midwest
Summer versus winter
La Nina (and El Nino) have more of an impact on West Coast weather during winter and early spring than in summer. The atmosphere is much more active during the cool season, with stronger currents, more activity in the midlands, and more interaction between the tropics and the midlands.
A record-breaking spring
As I’ll detail in a future blog, we’re on track to “enjoy” the coolest spring in half a century. Currently, the average April/May high temperature at SeaTac is the second-lowest in the last 50 years (see below). And there’s a lot of cold temperatures ahead.
And in Yakima, this spring has been the coldest so far.
La Nina is partly responsible… but not all.
And I hate to tell you this…. The record cold will return this weekend. So don’t be in a hurry to put the sweater away.
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