EACHUS: sweating while sweating it out
Into the summer we go. There are some things southerners know for sure about this time of year. It is going to be hot, it is going to be humid and SEC Football is only about three months away. What we don't know is most concerning, and that is if whether or not the tropics will supply any shenanigans. Using history and long term global trends, it is time to predict the climate story for Summer 2015.
As I predicted in November, winter ended up being cooler than average with near normal rainfall and even a few flirtations with frozen precipitation. January was the coldest month and February was coldest relative to average. Still, it wasn't as chilling and there weren't as many freezes as winter 2013-14.
That being said, I've identified 5 years since 1950 with numbers similar to this past winter. In addition to that, I'm including 8 summers in which El Nino was prominent as it is expected to be this year. Armed with the all-time averages for comparison, let's see how the upcoming summer may shape up.
The 3 Predictions:
-Confidence levels in the predictions are given in five levels from low (1) to high (5).
-Predictions qualified with "slightly" refer to numbers above or below average but within the normal range.
-Predictions qualified with "well" refer to numbers outside of the normal range.
1. Moderate confidence prediction (3): SLIGHTLY ABOVE AVERAGE TEMPERATURES
• Average summer temperature: 80.7°
• Normal range in summer temperature: 79.6 - 81.8°
In the 8 El Nino summers considered, there was little change from normal summer temperatures. However, the 5 similar years from the past had a consistent bias to warmer temperatures-pushing the predictive mercury up a bit. Another interesting trend was discovered. Despite July normally being the warmest month of the year, in 4 of the 5 similar years, August was the hottest month.
*Bonus Prediction (3): August will be more of scorcher than usual
2. Moderately high confidence prediction (4): NORMAL PRECIPITATION
• Average summer precipitation: 20.7"
• Normal range in summer precipitation: 15.0 - 26.4"
In the 5 similar years considered, none strayed from the normal range of precipitation. For the 8 El Nino summers, 2 were just below and 2 were just above. Strangely, the wettest year examined (1991, 27"), involved no tropical precipitation. The next two wettest comparable summers in the group of 13 were 2011 and 1987. Each brought nearly 10" of tropical precipitation. With summertime pop-up storms a given; only tropical rain could bust this prediction.
3. Moderate confidence prediction (3): SLIGHTLY BELOW AVERAGE TROPICAL ACTIVITY
12 named storms, 6 hurricanes, 3 major--those are the historical averages for the Atlantic Hurricane Season. Among 5 similar years from the past and 8 El Nino summers, 4 of 13 have produced below normal tropical cyclone activity. While that may provide some reassurance, I assure you that history can assure nothing more.
In our similar summers, 2004, 2007 and 2011 brought very active hurricane seasons. Matthew, Humberto and Lee were all tropical storms that dumped heavy rain in Louisiana.
El Nino summers tend to produce less "action" across the basin, and in 7 of the 8 El Nino summers used in this study that was the case. However, a closer examination reinforces the adage that "it only takes one." In 1957, there were only 8 named storms but 3 of them affected Louisiana-Major Hurricane Audrey, and Tropical Storms Bertha and Esther. Major Hurricane Betsy struck in 1965 when there were just 6 named storms. These years included two of the strongest El Ninos on record.
Remember, while the meteorological sciences have advanced to the point of being able to predict, with confidence, the amount of activity there will be, we cannot yet estimate months in advance where that will occur.
Louisiana averages a hurricane strike every 7-8 years. The last was Isaac in 2012.
In summary, we should expect to sweat through a seasonably hot summer while sweating it out over a couple of tropical systems--even if fewer than normal.
Making the Predictions:
80 years of Baton Rouge area weather data was collected and analyzed. Examining past weather statistics and identifying trends allows forecasters to identify long-term trends and patterns. In addition, global circulations such as the El Nino Southern Oscillation were considered. Believe it or not, water temperatures in the Western Pacific can and do have a large impact on weather around the globe!
Predictions based on large scale patterns and climate statistics are certainly viable but much more prone to error than near-term forecasts given on a daily basis. For that reason, stick with the WBRZ Weather team for timely and accurate updates throughout this upcoming summer!
Please, stay connected and share your thoughts with me!
If you have any questions or feedback regarding this research, please contact Meteorologist Josh Eachus at: