La Nada continues, what it means for the monsoon - Tucson News Now

La Nada continues, what it means for the monsoon

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Today the NOAA Climate Prediction Center (CPC) released the latest El Niño/Southern Oscillation update

Sea-surface temperatures (SSTs) in the equatorial East Pacific Ocean remain average, which means the conditions is considered 'neutral'.

We have Tucson News Now have nicknamed this condition 'La Nada'.

What does that mean? There is no La Niña or El Niño brewing. 

La Niña is cooler than average temperatures in that area of the ocean. 

El Niño is just the opposite.

Both of these conditions can influence weather patterns worldwide, including the monsoon right here in Arizona.  

The fact that an El Niño is not forecasted to form this spring or in the early summer may be good news for Southeast Arizona.

While the connection between monsoon rain totals and El Niño/La Niña is not strong, in general an El Niño in the spring and early summer can lead to a drier monsoon. 

La Niña has the opposite effect. 

So what does La Nada mean for the monsoon? It's a coin toss on whether things will be good or bad in regards to rainfall.

The best we can say at this point is that the monsoon rainfall will be near average.

There are many other factors that go into forecasting the monsoon, which runs from mid-June to the end of September.

These factors include moisture conditions in the Plains states and northern Mexico, plus spring snowpack in the Rocky Mountains.

These can have positive and negative effects on the monsoon outlook. 

The forecast is for neutral conditions to remain through the rest of the year.

But the CPC says "There is still low confidence in the forecasts for the latter half of the year, partly because of the so-called "spring barrier," which historically leads to lower model skill for forecasts made between March and May. Forecast confidence will increase over the next few months. The current forecast indicates that ENSO-neutral will likely continue into the second half of the Northern Hemisphere summer 2013."

In the graph below all the different color represent computer models that track La Niña and El Niño conditions.

The thick yellow line in the middle shows the average change added from all the models.

If that yellow line stays within 0.5° of the '0' line (or average line) then the conditions are considered neutral in the equatorial East Pacific Ocean.

The letters at the bottom of the graph represent three month blocks.

For example, MAM equal March, April, and May.

You can see the yellow line does go up above the 0 line this summer but it doesn't increase enough for the forecast to show an El Niño forming.  


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