Updated outlook now predicts 85% chance of above-normal Atlantic hurricane season.
The 2020 Atlantic hurricane season has been a busy one so far, with a record-setting nine named storms having formed by early August. By comparison, only Andrea (a short-lived subtropical storm in the Atlantic) and Barry (a category 1 hurricane that brought over 20 inches of rain to southern Louisiana) had developed by this point in 2019. Statistically, two named storms is about average for early August.
Now consider this: we still haven’t entered the most intense period of the hurricane season.
Historically, ~85% of major hurricanes (categories 3-5, with maximum sustained winds of at least 111 miles per hour) in the Atlantic occur after August 20, according to Colorado State University meteorologist Philip Klotzbach. Considering that the ninth named storm does not usually form until October 4, we are about two months ahead of schedule this year.
So, it shouldn’t be surprising that NOAA’s Climate Prediction Center is now saying that an “extremely active” hurricane season is possible for the Atlantic Basin. NOAA has also increased the number of potential storms in its annual August update to the Atlantic Hurricane Season Outlook, which was released last week. The first 2020 outlook was issued in May.
“This year, we expect more, stronger, and longer-lived storms than average, and our predicted ACE [Accumulated Cyclone Energy] range extends well above NOAA’s threshold for an extremely active season,” said Gerry Bell, Ph.D., lead seasonal hurricane forecaster at NOAA’s Climate Prediction Center.
Highlights of the Updated 2020 Outlook
- 19 to 25 named storms are now predicted (was 13 to 19 in May’s 2020 outlook, an average year has 12)
- 7 to 11 named storms will become hurricanes (was 6 to 10)
- 3 to 6 of the hurricanes will be classified as major (unchanged)
- Likelihood of above-normal hurricane season is now 85% (was 60%)
Storms receive names when they become tropical storms, which have maximum sustained winds of 39 to 73 miles per hour. Once a storm’s winds reach 74 miles an hour, they become known as a hurricane. Storm names are determined by the World Meteorological Organization.
Factors Contributing to an Active Season
- Warmer than average Atlantic Ocean and Caribbean sea surface temperatures
- Weaker tropical Atlantic trade winds
- Enhanced west African monsoon
The updated outlook also noted one other factor that could contribute to an active storm season: the potential of a La Nina forming. In a La Nina period, cooler waters in the Pacific Ocean weaken the levels of wind shear (variations in wind speed or direction) in the Atlantic. Higher levels of wind shear can disrupt a storm’s vertical structure and weaken it. Conversely, lower levels of wind shear allow storms to develop and intensify.
Regardless of how many storms are forecast, tropical weather events can affect any coastal area. Tropical storms can be unpredictable, and often change course or strength with little notice. Therefore, being prepared is critical.
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