On September 14, the Climate Prediction Center released an update on the ongoing El Niño phenomenon and what we can expect through the end of the year.
The El Niño Southern Oscillation (ENSO) is a recurring climate phenomenon involving changes in sea surface temperatures of the Pacific Ocean. Warming and cooling directly affect the distribution of precipitation in the tropics and can have a strong influence on the weather here in the United States and around the world.
There are main phases for ENSO, La Niña, Neutral and El Niño. A weak El Niño is currently in place and is expected to continue through the Northern Hemisphere winter, which for climate record keeping purposes corresponds to the months of December, January and February. It is possible that it will strengthen by winter if sea surface temperatures continue to warm.
During an El Niño period, the ocean surface of the central Pacific and eastern Pacific warms above average. The warmer the ocean surface, the stronger El Niño is. Along with warm sea surface temperatures, low-level winds weaken and blow from west to east.
During an El Niño event, the northern half of the United States may experience warmer and drier conditions than normal. The southern half of the country may experience cooler and wetter conditions than normal.
For the Tennessee Valley in particular, the area is split, with Tennessee experiencing drier than normal conditions. For north and south Alabama, there is a greater risk of cooler than normal temperatures and wetter than normal conditions.
Latest El Niño fall/winter season:
The last time the Tennessee Valley experienced an El Niño during the fall and winter seasons was in 2018. It was a weak El Niño, but Huntsville and other places in the Tennessee Valley recorded above-average precipitation and temperatures. The average fall temperature was 64.7 degrees, nearly a degree warmer than normal, while precipitation was only 2.5 inches above normal.
The Tennessee Valley could see warmer and wetter conditions than average this fall
The 2018 winter season was the wettest on record in Huntsville, with more than 30.50 inches of rain falling. This was about 14.6 inches above normal and the area recorded only a trace of snow that winter. The average temperature was 47.5 degrees, 2.5 degrees above normal. This ranks as the tenth hottest temperature on record.
Normal fall season:
As fall approaches, temperatures will gradually drop. During a normal fall season in the Tennessee Valley, the average temperature ranges from about 60 degrees to 64 degrees. Last year, Huntsville saw highs in the 70s in early September and a few days recorded 70s at the end of the month. For Huntsville, the average high temperature in September is 86.5 degrees, October is 76 degrees, and November is 64 degrees.
The first climatological day of autumn is only September 23. For climate record keeping purposes, the fall season includes the months of September, October and November.
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