Sunday, September 10 marks the climatological ‘peak’ of hurricane season in the Atlantic basin, due to a number of meteorological factors that support tropical cyclone development during this time of year. What exactly are they? Let’s break it down.
- June 1 marks the official start of the season, but mid-August through mid-October is the climatological window where the highest number of tropical cyclones are typically found.
- September 10 sits in this timeframe and is deemed the ‘peak’ of the Atlantic hurricane season as the environment turns more favorable for tropical development.
- Wind shear, which inhibits tropical development, often decreases during this timeframe.
- Warm ocean temperatures, a fuel for development, continue to warm thanks to the hot summer sun.
- Tropical waves, which are pieces of energy that help form tropical cyclones, continue to move off the coast of Africa.
- Into the fall season, wind shear starts to increase again as overall air and water temperatures start to cool, typically leading to a lower number of tropical cyclones.
Atlantic characteristics around this time of year
While frequent tropical waves come off the coast of Africa throughout the hurricane season, the environment in which they enter into is more favorable for development during the mid-August to mid-October timeframe.
Wind shear, which is the change in wind speed and/or direction with height, is stronger earlier in the season. This acts against tropical development as wind speeds increase with height, inhibiting system growth.
Around this time of year, however, wind shear often decreases in the Atlantic basin, allowing more tropical systems to strengthen when combined with other favorable environmental conditions.
Ocean temperatures & moisture availability
Speaking of other favorable conditions, ocean temperatures continue to rise during the summer months in the Northern Hemisphere due to the natural tilt of the Earth towards the sun.
Warmer water temperatures act as a fuel for tropical cyclone development along with plenty of moisture content (which isn’t hard to find over ocean waters!).
Why September 10?
According to NOAA, the exact date of September 10 is the day you are most likely to find a tropical cyclone somewhere in the Atlantic, statistically speaking. All of these factors are typically in-sync at this time and make it easier for tropical systems to blossom and sustain themselves.
Sea surface temperatures generally keep warming into late September and early October, but wind shear starts to increase again as we head into the fall season, once again working against tropical cyclone development.
Activity in the tropics
As expected, there is activity to monitor in the Atlantic basin as we approach the peak of hurricane season. Most notably, Hurricane Lee is just north of the Lesser Antilles, and is expected to track to the northwest in the coming days, likely strengthening even more as it does so. As of Friday, Hurricane Lee was already a category 5 hurricane and may rank as one of the strongest on record in the Atlantic basin. It is not expected to interact with land until it surges north and weakens some. Those in New England and eastern Canada should pay close attention to its track.
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