2017 Atlantic Hurricane Season: Drivers and predictions
Friday, April 7, 2017, 6:50 PM - Early predictions issued by hurricane researchers at Colorado State University (CSU) indicate that it will be a slightly below-average Atlantic hurricane season in 2017, thanks in part to a developing El Niño event in the equatorial Pacific as well as recent anomalous cooling in the tropical Atlantic.
The CSU forecast, produced by a team led by Dr. Philip Klotzbach and Michael M. Bell, calls for an expected 11 named storms during the Atlantic hurricane season, which runs from June 1 to November 30. Of those, researchers expect four to become hurricanes and two to reach major hurricane strength (Saffir/Simpson Category 3-4-5) with sustained winds of 180 km/h or greater. These numbers mean that 2017 hurricane activity will be about 85 per cent of the average season, which based on long term climatological average, is 11 named storms, six hurricanes, and two hurricanes of Category 3 strength or greater.
These seasonal forecasts are developed using a variety of techniques, taking into account current weather patterns around the globe, numerical modeling, and statistical analysis. The results give us an understanding of how different weather patterns, or what forecasters call "drivers" will affect the development of tropical storms. In particular, forecasters look for factors which are favorable for storms to form and strengthen – such as warm water, and factors which limit storm potential – such as wind shear.
Some of the drivers which will be in play in 2017
Factor #1: El Nino
The weak La Niña of this past winter has dissipated, and now forecasters are watching for the potential development of a weak to moderate El Niño, which could form by the peak of the Atlantic hurricane season.
El Niño is characterized by a pool of warmer than normal water in the equatorial Pacific. El Niño is part of a cycle, or "oscillation" – a pattern that swings back and forth like a pendulum. As we move into the early summer of 2017, we are already beginning to see some of the El Niño pattern as water temperatures have begun to warm up.
This will have an impact on the upcoming hurricane season because El Niño tends to increase upper-level westerly winds across the Caribbean into the tropical Atlantic, tearing apart hurricanes as they try to form.
Factor # 2: Anomalous cooling in the tropical Atlantic
Like El Niño in the Pacific, Atlantic water temperatures have their own cycles which affect global weather patterns. One long-term cycle is known as the Atlantic Multi-decadal Oscillation (AMO). Current water temperature patterns in the North Atlantic are trending colder than normal, and that too can have an impact on the upcoming season.
"Most of the North Atlantic has anomalously cooled over the past month, and the tropical Atlantic is now slightly cooler than normal," cite researchers. "In addition to providing less fuel for tropical cyclone formation and intensification, cooler tropical Atlantic sea surface temperatures are associated with a more stable atmosphere as well as drier air, both of which suppress organized thunderstorm activity necessary for hurricane development."
Potential U.S. Impacts
The team anticipates a below-average probability for major hurricanes making landfall along the United States coastline and in the Caribbean. Below is a look at probabilities for at least one major (Category 3,4 or 5) hurricane landfall on each of the following coastal areas:
- Entire U.S. coastline - 42% (average for last century is 52%)
- U.S. East Coast, including Peninsula Florida - 24% (average for last century is 31%)
- Gulf Coast from the Florida Panhandle westward to Brownsville - 24% (average for last century is 30%)
Despite the below-average season predicted, residents are reminded that it only takes one hurricane making landfall to make it an impactful season. Residents should prepare the same for every season, regardless of how much activity is predicted. For hurricane preparedness tips, click here.
The CSU team will issue forecast updates on June 1, July 3 and August 2. Additionally, The Weather Network will release it's own predictions on May 24 along with its official U.S. Summer 2017 Weather Outlook. Check back for updates!
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With files from The Weather Network meteorologists Michael Carter and Dr. Doug Gillham.