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article imageThere's a 50 percent chance La Niña could form this fall

By Karen Graham     Jul 13, 2020 in Environment
The National Oceanic and Atmospheric Administration (NOAA) issued a La Niña watch last week, which means the agency believes La Niña could form this fall. This could cause an uptick in Atlantic storm development.
No, this does not mean we have to be peering out the front door, expecting a La Nina to come down the street, but NOAA's terminology is a good way to give a heads-up to planners for energy, agriculture, disaster management, and other sectors, says Climate.gov.
And, you could say that a La Nina watch has a greater chance of developing than a neutral or El Niño watch. Currently, there is a 50-55 percent chance of a La Nina forming. This is not a strong possibility because you could also say there is a 40 to 45 percent chance it won't form. Does that make sense?
Like her counterpart, El Nino, La Niña changes global atmospheric circulation and influences global weather and climate. The most impactful characteristic of La Niña in North America is its role in the Atlantic hurricane season.
Sea Surface Temperature (SST) as of July 4  2020
Sea Surface Temperature (SST) as of July 4, 2020
Climate.gov.
This is due to weaker vertical wind shear and trade winds, along with less atmospheric stability. At the same time, the opposite takes place in the Pacific, where fewer hurricanes are expected due to strong vertical wind shear.
This year's hurricane season is currently on pace to match the number of named storms during the historic 2005 hurricane season -- a season which also saw a La Niña develop in the Autumn, according to CNN.
Keep in mind that one of the factors negating the formation of La Nina in the current forecast is the lack of a substantial source of cooler-than-average water under the surface of the tropical Pacific. Subsurface temperatures in the central Pacific are close to normal, with some cooler-than-average water remaining in the east.
So that is why the forecast is set at 50-55 percent. But there are also indications that the trade winds in the central Pacific will strengthen over the next week or so. If this happens, we could see some more ocean surface cooling.
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Climate.gov.
La Nina, El Nino and ENSO
Here's a quick refresher course on the El Niño-Southern Oscillation (ENSO). Basically, ENSO is a recurring climate pattern involving changes in the temperature of waters in the central and eastern tropical Pacific Ocean. This means ENSO can be one of three conditions - El Nino, La Nina, or Neutral.
The pattern has a three to a seven-year cycle where the surface waters across a large area of the tropical Pacific Ocean warm-up or cool down by 1 to 3 degrees Celsius.
This ENSO cycle has a direct effect on rainfall distribution in the tropics and can have a strong influence on weather across the United States and other parts of the world.
More about ENSP, la nina, 50 percent, Hurricanes, NOAA
 
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