SAVANNAH, Ga. (WSAV) — Weather is cyclonic – swirling areas of high and low pressure systems bringing tropical cyclones, tornadoes, thunderstorms, coastal flooding, ice and snow storms, and even excessive heat all around the globe.
Weather patterns do change. We see this every day but usual longer, decadal changes are caused by ocean & atmospheric interactions. One of the more well-known cycles is called ENSO (AKA El Niño-Southern Oscillation).
There are two phases of ENSO: El Niño, the warm phase, or La Niña, the cold phase. We talk about this cycle during hurricane season with how El Niños or La Niñas can affect tropical systems.
South Carolina Emergency Officials had a news conference last week over winter weather preparedness. They mentioned that while severe winter weather is rare here, it does happen like the ice storm of 2014. This 7 year old example made me think of the weather folklore – weather comes in 7 year cycles.
ENSO events occur every 3-7 years in the Pacific Ocean with either El Niño or La Niña lasting up to 1 year. This is where the 7 year cycle folklore comes from. Each event brings a change in weather patterns.
El Niño VS La Niña
Normally in the Pacific Ocean, trade winds along the equator blow east to west, bringing warm water towards Asia with up-welling of cold water to replace the missing warm water near South America. El Niño and La Niña patterns try to change this normalcy and end up changing global weather patterns.
As an El Niño develops, trade winds weaken. This allows warm water to instead to be brought back east. In a La Niña pattern, stronger than normal easterly trade winds are able to push even more warm water towards Asia. This leads to a stronger up-welling of colder, deeper ocean water brought to the surface.
Warm water near the equator influences not only where the jet stream sits but also the weather patterns it drives. During an El Niño, warm waters allows the Jet Stream to move further south, causing the southeast to be wetter and cooler than usual.
During an La Niña pattern, cold waters push the Jet Stream more north, causing the south to be warmer abd drier than normal. It can cause a more severe hurricane season.
Currently, La Niña conditions have developed in the Pacific Ocean according to the National Oceanic and Atmospheric Administration.
7-Year Weather Cycles: 2021-2008
Now let’s test to see if the 7 year cycle myth is true. I looked back from 2021-2008 to see if there would be any correlations for winter storms, excessive heat, coastal flooding, and severe weather over a 3-7 year stretch and then compared it to a possible El Niño and La Niña pattern at the time.
From 2008 to 2021, there have been only 2 instances of a 7-year weather pattern occurring. Around the 4th of July earlier this year, we were dealing with Tropical Storm Elsa. 7 years earlier in 2014, we were tracking Hurricane Arthur around the same time. The other instance was the 2018 and 2011 winter storm events, both happening in early January.
Most repeat events happen every 3-4 years with the exception of spring severe storms occurring almost every April.
|Winter Storm||January 3, 2018||La Niña|
|Winter Storm||February 11-13, 2014||Neutral|
|Winter Storm||January 28-29, 2014||Neutral|
|Winter Storm||January 10, 2011||Major La Niña|
|Winter Storm||February 12-13, 2010||El Niño|
|Excessive Heat||May 25-31, 2019||Neutral|
|Excessive Heat||August 2016||Neutral|
|Excessive Heat||July – August 2010||Early La Niña|
|Coastal Flooding||November 3-11, 2021||Early La Niña|
|Coastal Flooding||December 22-24, 2019||Neutral|
|Coastal Flooding||November 28, 2018||Early El Niño|
|Coastal Flooding||Sept 25 – Oct 7, 2015||Strengthening El Niño|
|Severe Wx / Heavy Rain||April 23, 2020||Neutral|
|Severe Wx / Heavy Rain||April 19, 2020||Neutral|
|Severe Wx / Tornadoes||April 13, 2020||Neutral|
|Heavy Rain||June 10-12, 2019||Neutral|
|Severe Wx||April 19, 2019||El Niño|
|Severe Thunderstorms||April 3, 2017||Neutral|
|Severe Thunderstorms||June 17, 2016||Neutral|
|Severe Thunderstorms||April 25, 2015||Early El Niño|
|Severe Thunderstorms||April 19, 2015||Early El Niño|
El Niño and La Niña cycles drive larger scale weather patterns. It does have some influence on our day to day weather, but we see more of their influence with cooler or warmer temperatures and wetter or dry patterns over a longer period of time.
Hurricane season storms flourish when we are under a La Niña as this pattern leads to weaker wind shear and less atmospheric stability. The record-breaking 2020 hurricane season started out under neutral conditions but as we saw last year, storms quickly amplified as La Niña conditions became stronger through the end of the season.
While swirling areas of high and low pressure drive different weather patterns across the Coastal Empire and Lowcountry, weather is still be unpredictable weeks to years in advance. With winter storms occurring here every 3-4 years with under a La Niña set up, does this mean we are due for one soon? I guess we will just have to wait and see.