Hurricane Season: August and September Likely To Be Busy
We're approaching the two month mark of the Atlantic hurricane season, which began on June 1st and continues through November 30th. It is still early in the game but the 2017 season has been pretty active so far. Activity of tropical cyclones can be measured with this number called ACE, or Accumulated Cyclone Energy. The ACE of a season is the sum of the ACEs for each storm and takes into account the number, strength, and duration of all the tropical cyclones in the season. In the tweet below, it mentioned how 95% of all ACE has been generated after July 21st. This shows how the first couple months of the season are very quiet in comparison to what's to come on average.
One of the reasons why June and July aren't too active is because there is oftentimes a lot of dry air in the main development region of the Atlantic, which is located between the Windward and Leeward Islands of the Caribbean and the western African coast. As we get into August and September, however, that dry air errodes.
If you haven't seen the forecast for this year, an above average hurricane season is anticipated, and that forecast is still on track. Forecasters look at long-range modeling to get a sense of the conditions. One of that modeling shows where there the areas of enhanced convection will be during a certain time period. In August, numerous models show the above average convection, or thunderstorms, in the Atlantic. This translates to more storms in the basin and more opportunities for tropical cyclones to form.
We can also look at the forecast rainfall anomalies for extended time periods, and in August the forecast calls for above average rainfall across the Gulf of Mexico, Caribbean, and around Bermuda. This can represent tropical systems because they contain a lot of rain.
As you can tell, there are many factors that lead me and forecasters to conclude that this year's Atlantic hurricane season is going to be an active one. Above average ocean water temperatures also add to this forecast and below average wind shear, two ingredients conducive for tropical cyclone development.
