I’ve received several emails asking about the impact of a developing El Niño phenomenon on our summer weather.
And some media has suggested that El Nino will cause heatwaves to intensify worldwide…so people are a bit worried (some samples below)
Bottom Line: The correlation of El Nino (warmer-than-normal water in the central and eastern tropical Pacific) in the Northwest summer is rather weak. El Nino signal tends to increase after January 1st.
NOAA provides some graphics and research on the subject.
For example, below is correlate between summer (July-August temperatures) and temperatures in the central/eastern tropical Pacific (Nino3.4 area). A positive value would be consistent with El Nino causing summer temperatures to warm.
Interestingly, El Nino leads to COOLER over most of the US. But western Washington and Oregon are the most prominent, with a modest positive correlation of about 0.4. This means that about 16% of the variation in summer temperatures in our region can be explained by warmer tropical sea surface temperatures.
But you probably don’t want to know about correlations, but how much warmer it could be.
Here are answers for the area around western Washington for June-August. It suggests that mean temperatures (red lines) are about 0.5 degrees Fahrenheit warmer during an El Nino summer than a neutral (normal) summer. Not much.
Perhaps a better map shows unusual-than-normal summer (May to September) temperatures during El Nino years (below). Near normal (within 0.5 degrees typical) in the Northwest and cooler than normal in the Southwest and high plains.
What about summer rainfall during El Nino years? As shown below, rainfall is nearly normal in the western US, slightly wetter than usual in the central US but slightly drier than usual in the Northeast.
I’ll show you more graphics, but the answers are consistent. El Nino’s effect on weather is very weak or non-existent in the Pacific Northwest during the summer and thus provides meteorologists with no useful forecasting signals during their warm season. ta.
Sorry…. wish I could say more!
Consistent with the above, the latest Central Europe model seasonal forecast predicts near-normal rainfall in the North West for June/July/August.
As for temperatures, conditions are expected to be near normal in Washington, Oregon and California but warmer than usual in southwestern Canada.
A prediction of near-normal conditions likely won’t attract much media attention. Can you imagine this?
