Weather Blog: A New Normal for Hurricane Season

AUGUSTA, Ga. (WRDW/WAGT) - In this weather blog we will be talking about entering a new “climate normal” period, what it means for the hurricane season, and our daily records for temperature and rainfall here in the CSRA.

Let’s first start with talking about what a “climate normal” is in general. In its most basic form, a climate normal can be thought of like an average. This average is taken over a 30 year period and acts as a baseline to compare current and past conditions like temperature and rainfall. Every 10 years this average is updated and this year marks the beginning of a new period. This new period spans from January 1st, 1991 to December 31st, 2020 and will replace the previous period from 1981-2010. Not only does this period act as a baseline to compare conditions but it can help to showcase a changing climate. These new climate normals are also used for the regulation of power companies, energy load forecasting, and many other sectors that affect our daily lives.

Below you can see the difference in the monthly averaged high temperature between the 1981-2010 period and the new 1991-2020 period. While there wasn’t much of a change in our summer months, both the fall and winter saw an increase in temperature of about 1°F.

These 4 images show the difference in temperature when comparing the 1981-2010 and 1991-2020... — These 4 images show the difference in temperature when comparing the 1981-2010 and 1991-2020 time periods. Notice in our area the greatest change in temperatures have occurred in January and October.(NOAA)

While we can’t solely blame climate change for this increase, it does agree with the general trend in averaged temperatures over the last 100 years or so. The temperature difference between the two periods also tends to agree with one theory that winter months are influenced more by climate change.

Global Temperature Anomalies(Climate Central)

Not only do we see an increase in global temperatures over land but ocean temperatures have also been on the rise. Check out the image below showing an increase in average global sea surface temperatures from 1901-2015.

This graph shows how the average surface temperature of the world’s oceans has changed since... — This graph shows how the average surface temperature of the world’s oceans has changed since 1880. This graph uses the 1971 to 2000 average as a baseline for depicting change. Choosing a different baseline period would not change the shape of the data over time. The shaded band shows the range of uncertainty in the data, based on the number of measurements collected and the precision of the methods used.(NOAA)

Nearly every corner of the planet’s oceans are experiencing some kind of warming. The only exception is off the coast of Greenland with data suggesting a cooling trend. Even though we are seeing cooler ocean temperatures, this is still the result of climate change. The Arctic is one of the places on Earth that is warming at a significant rate and all of these warmer temperatures have caused the melting of land ice on Greenland, this runoff flows into the North Atlantic Ocean and mixes with the salty water. This mixture causes a change in ocean salinity and eventually leads to a temperature difference that we see above, there are also other effects like disruptions to the ocean currents.

With warmer ocean temperatures around a majority of the world, including the tropics, this could lead to stronger tropical systems. Hurricanes and Tropical Storms draw their strength from the ocean waters and if those waters are warmer it’s likely that storms that do form will have more energy to work with. While it still isn’t possible to prove that a specific storm or hurricane could have been caused by climate change, it is known that climate change has impacted ocean temperatures which could, in turn, have impacts on the strength of a tropical system.

So can we expect more hurricanes and storms in the future as a result of climate change? We’ll the answer isn’t so straight forward, yes, climate change is having an effect on the oceans, but it’s hard to determine if those effects have impacted the typical Hurricane Season. When scientists determine what the average hurricane season will look like they use the same climate normals as mentioned above. As we transition into the new climate period (1991-2020) the number of storms in an average season has increased to 14 named storms, 7 hurricanes, and 3 major hurricanes. This is an increase in 2 named storms and 1 hurricane.

Number of named storms and hurricanes increase with new climate normals.(NOAA)

Now it’s important to mention that climate change alone isn’t responsible for this increase. Scientists now have better technology that can help to detect more storms such as new satellites and better hurricane reconnaissance that provide data on the strength of a hurricane. Several storms that formed in the last Hurricane Season were found and categorized sooner thanks to newer and more advanced technology.

As we get closer to another potential active Hurricane Season it is important to be keep in mind the forces that drive our tropical systems and how they might be changing. Even small increases could lead to significant impacts along our coastal and inland communities.