About a week ago we wrote about a slowdown in La Nina development that could have pattern implications through at least the month of July. Now, there is evidence that this slow-down is ending just as quickly as it began. Below, we show the weekly Nino 3.4 update from the Climate Prediction Center, published each Monday. As can be seen, the last two weeks we saw waters warm rather significantly across the key area. 

Of course, this came after SST anomalies across the Nino region rapidly plummeted, so some time of stabilization was not all that much of a surprise. Still, if it were sustained it could work to delay La Nina impacts for the country, especially as most climate models did not show much of a slowdown in the cooling of the Pacific. However, there is now increasing evidence that this slowdown in La Nina development is already coming to an end as trade winds begin to shift directions again and help aid waters cool. As seen below, the latest Daily SST Anomaly from NOAA shows significant cooling right along the equator. 

This can be more clearly seen by the CDAS daily Nino index. We always emphasize that this number is extraordinarily volatile, because it is just a small number of buoys working to create this index. Still, we can see how sea surface temperatures across the region quickly rose then fell over the last couple of weeks. 

This has been seen across the Pacific, as closer to South American in Nino Region 1+2 we have similarly seen cooling over the past week, though temperatures are briefly bouncing positive again. This Region clearly shows the type of volatility we can see on a daily basis, and why the Climate Prediction Center and most agencies prefer to smooth the data on a weekly basis. 

Without getting too technical, part of the reason we are seeing this volatility is from the Madden/Julian Oscillation, a shorter-timescale measure of convection (or storminess) in tropical regions. As can be seen below on the GFS ensemble forecast, the MJO has been quite active, and interestingly looks to be looping around on the exact same path that it took in the middle of May. 

If the MJO follows mid-May well, which is quite possible now that Pacific SSTs are near where they were then, we could easily see a similar global weather pattern set up. We are near where the MJO was on May 18th, and the 7-day mean temperatures ending May 25th looks like this below. 

That's a very different look than the most recent 7-day forecast from the GFS ensembles gives us, as seen here. 

Yet it's quite similar to what the Recurring Rossby Wave Train Theory would forecast for the 6-10 Day period. 

(Click on image to enlarge)

Our model guidance has been significantly struggling to nail down how the Pacific is going to impact our upcoming pattern, and though many atmospheric indicators appear to align with the mid/late May weather patterns that set up, most model output shows very different output. Over the coming days, we should get a good clue as to whether atmospheric indicators and theory-based forecasting will outperform the weather models, or at least whether models will begin to trend towards this forecast. If so, it would be evidence of that connection between variable Pacific Ocean temperatures and the downstream pattern across the United States.