Looking Ahead to Hurricane Season

The 2018 Atlantic hurricane season begins in a little more than six weeks on June 1.  That follows the unusually active and record-setting 2017 hurricane season in Atlantic Ocean Basin (that includes the Atlantic Ocean, Gulf of Mexico and Caribbean Sea).  The distinguished group of scientists at Colorado State University (CSU) recently issued their April outlook for the upcoming Atlantic hurricane season.

The CSU forecast is for a slightly busier than average season with 14 tropical storms, of which seven become hurricanes, including three “major” hurricanes.  A hurricane is considered “major” when it becomes a Category 3 hurricane on the Saffir-Simpson Wind Scale with sustained winds of at least 111 mph.  According to the National Hurricane Center, an average Atlantic hurricane season features 12 tropical storms, of which between six and seven become hurricanes with two that intensify into major hurricanes.  A tropical cyclone becomes a tropical storm when sustained winds around the center of the storm reach 39 mph.  A tropical storm becomes a hurricane when sustained winds reach at least 74 mph.  

A key factor that scientists consider in tropical weather forecasting is the presence of El Nino or La Nina (also known as the “ENSO” status).  ENSO is the El Nino Southern Oscillation that refers to a periodic shift in wind direction and sea surface temperature in the tropical east Pacific.  El Nino contributes to less favorable conditions for tropical storm formation in the Atlantic Ocean Basin.  Meanwhile, an episode of La Nina can lead to more favorable conditions.  The ENSO status can also be in a neutral phase without either El Nino or La Nina.

La Nina conditions weakened during the month of February 2018 and NOAA expects a transition from La Nina conditions to ENSO neutral conditions during the rest of the spring.  That could help create an environment more favorable for tropical storm formation in the Atlantic Ocean Basin.  Another key factor meteorologists consider in tropical weather forecasting are sea surface temperatures.  That’s because tropical storms and hurricanes rely on warm sea surface temperatures to intensify (typically at least 80 degrees Fahrenheit).  Sea surface temperatures are also expected to be above average for the core of the hurricane season from August through October. 

The 2017 hurricane season was one for the record books in the Atlantic Ocean with a total of 17 tropical storms, including 10 hurricanes of which 6 became major hurricanes.  Last year was the first time on record that three Category 4 hurricanes made landfall in the United States (Harvey, Irma and Maria).  That was magnified by the fact that prior to last season, no major hurricane had made landfall in the United States since 2005 (also a new record).  

There have been other active Atlantic hurricane seasons where the United States was largely spared any significant tropical storm or hurricane impacts such as in 2010 when a total of 19 tropical storms developed.  That helps illustrate that while the total number of tropical storms and hurricanes that develop is important, where each storm tracks is equally important.  Colorado State University, along with NOAA will issue updates to their 2018 hurricane forecasts to coincide with the start of the Atlantic hurricane season on June 1.

This post was filed from Melbourne, Australia, where I am looking into some local weather and climate issues for a few days.