On September 14th, the Climate Prediction Center released an update on the ongoing El Niño and what we could expect heading into the end of the year.
The El Niño Southern Oscillation (ENSO) is a recurring climate pattern involving changes in the sea surface temperatures of the Pacific Ocean. The warming and cooling pattern directly affects the rainfall distribution in the tropics and can have a strong influence on the weather here in the United States and across the World.
There are main phases to the ENSO, La Niña, Neutral, and El Niño. El Niño is currently occurring and is forecast to continue through the Northern Hemisphere Winter; December through January. Currently, a weak El Niño is ongoing, but there is the potential it could strengthen by the winter if sea surface temperatures continue to warm.
During an El Niño period, the ocean surface of the Central and Eastern Pacific warms above average. The warmer the ocean surface the stronger the El Niño. Along with warm sea surface temperatures, the low-level winds weaken and blow west to east.
During an El Niño pattern, the northern half of the U.S. can experience warmer and drier than normal conditions. The southern half of the country can experience cooler and wetter than normal conditions.
For the Tennessee Valley specifically, the area is split with Tennessee experiencing drier than normal conditions. For North Alabama and South, there is a greater chance for cooler than normal temperatures and wetter than normal conditions.
Last El Niño Fall/Winter Season:
The last time the Tennessee Valley experienced El Niño during the Fall and Winter seasons was in 2018. It was a weak El Niño, but Huntsville and other locations across the Tennessee Valley recorded above-average rainfall and temperatures. The fall average temperature was 64.7 degrees which was nearly a degree warmer than normal while the rainfall was just 2.50 inches above normal.
The Winter Season of 2018 was the wettest on record for Huntsville when over 30.50 inches of rain fell. That was about 14.60 inches above normal and the area only recorded a trace of snow that Winter Season. The average temperature was 47.5 degrees, which was 2.5 degrees above normal; that ties the tenth warmest on record.
Normal Fall Season:
As we head into the fall, the temperatures will gradually cool down. During a normal fall season in the Tennessee Valley, the average temperature ranges from around 60 degrees to 64 degrees. Last year, Huntsville saw highs in the 70s in early September and a few days recorded 70s in the later part of the month. For Huntsville, the average high temperature for September is 86.5 degrees, October is 76 degrees and November is 64 degrees.
The climatological first day of fall isn’t until September 23rd, for record-keeping purposes, the fall season consists of the months of September, October, and November.