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John Lindsey mug shot

The latest guidance from the CPC and other long-range forecast centers indicate the current weak El Niño condition will continue into late fall or perhaps into winter.

However, at this time of the year, we’re in the so-called “Spring Predictability Barrier.” In spring, the El Niño Southern Oscillation (ENSO) is often in transition from one phase to another. For example, an El Niño condition could be decaying and passing through neutral condition to a La Niña phase, or vice versa.

Of course, as you get closer to winter, the models become more accurate because there’s less time for inaccurate oceanographic and atmospheric data to be amplified at model initialization.

With that said, the CPC ensemble forecasts — we’ll explain that term in a minute — indicate that warmer than normal sea surface temperature will continue through November 2019. Some of the model solutions indicate as much as 1.5 degrees warmer than normal while the consensus line indicates a neutral condition — El Nothing or El Nada — range between plus 0.5 and minus 0.5 degrees Celsius anomaly levels — or the sector between El Niño and La Niña by January 2020.

Since 1950, NOAA has used sea surface temperatures (SST) in a central equatorial region of the Pacific Ocean called Niño 3.4 as the standard for classifying El Niño (warmer-than-normal SST) and La Niña (cooler-than-normal SST) events. The fortunetelling SST cycles in Niño 3.4 are categorized by the amount they deviate from the average SST — in other words, an anomaly.

A weak El Niño is classified as an SST anomaly between 0.5 and 0.9 degrees Celsius. A moderate El Niño is an anomaly of 1.0 to 1.4 degrees Celsius. And a strong El Niño ranges from 1.5 to 1.9 degrees Celsius. A very strong El Niño anomaly is anything above 2.0 degrees Celsius (or 3.6 degrees Fahrenheit).

Jan Null is recognized as an expert on El Niños and their relationship to California’s weather. According to Null’s studies, weak and moderate El Niños give near average rainfall along the Central Coast, much like this rain season which runs from July 1, 2018 to June 30, 2019.

However, strong El Niño events can produce about 140 percent of above-normal rainfall for our area and even greater amounts in other parts of the state.

So what is ensemble forecasting?

Well, the atmosphere is a fluid; sure, it’s not as dense as water but it does behave like a liquid. Mathematical equations that express the laws of physics for thermodynamics and fluid dynamics can be written for computer programs to estimate or predict the state of the sky in the future.

These computer programs are called numerical weather models and collect weather information from weather balloons, marine buoys, ship and surface observations, aircraft, satellites and other oceanographic resources.

Unfortunately, since the atmosphere is chaotic, the smallest of errors are multiplied as you look further into the future.

To overcome this problem, multiple forecasts are created with slightly different physical measurements of the atmosphere and ocean at the start or initialization of each model run. As each model run is initialized with different parameters, dissimilar forecast solutions emerge.

The output from this collection of runs is called an ensemble forecast. The yield from these models is frequently displayed as spaghetti diagrams.

For example, a hurricane track map may show diverse courses the storm may take. Meteorologists can compare the different courses and take a consensus and hopefully provide a more accurate forecast.

With that being said, the predictions of El Niño conditions are often wrong, like last year for example. However, if the current models verify we could see higher than normal amounts for rainfall in California this winter, but there are no guarantees, only time will tell the story.

PG&E Tip: At PG&E, the safety of customers and employees is a top priority. As spring temperatures arrive, home improvement and construction work steadily increases. If you have plans for a home improvement project, like planting shrubs and trees, installing a fence or anything else requiring digging?

Make sure you Call 811 at least two days in advance to have all underground lines marked first, this is a free service. Operators answering calls and emails will dispatch all necessary utilities to properly mark underground utility lines with paint or flags. Underground Service Alert of Northern/Central California and Nevada (USA North) is staffed 24 hours a day, seven days a week, and will provide Spanish and other translation services.

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John Lindsey is PG&E’s Diablo Canyon marine meteorologist and a media relations representative. Email him at pgeweather@pge.com or follow him on Twitter @PGE_John.

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