June 1st marks the traditional start to the hurricane season in the North Atlantic, with tropical storms normally appearing in the Eastern Pacific from the middle of May and both seasons coming to a close at the end of November. With hurricanes increasingly occurring out of season, the strongest typhoon ever recorded since records began occurring last year, ongoing climate change and El Niño in decline, there is a lot of interest to see what will happen this year.
What Can We Expect In 2016?
The 2016 Atlantic season is expected to be the most active since 2012 and kicked off early when Hurricane Alex formed for three days in the northern Atlantic Ocean in January. According to the National Hurricane Centre, Alex was the first hurricane to form in January since 1938 and the first to persist in January since Hurricane Alice in 1955.
Meteorologists are forecasting that this year’s Atlantic tropical storm season will return to near average levels after a comparatively quiet season in 2015. It will also be influenced by the rapid shift from a strong El Niño last year to a developing La Niña later this year, where the likely impact is to cause the early part of the hurricane season to be less active, while the second half may be more active.
In terms of numbers, the Colorado State University predicts that the season will be near normal with 13 named storms, 6 hurricanes and 2 major hurricanes; whilst the North Carolina State University believes that the season will be very active with up to 18 named storms, 11 hurricanes and 5 major hurricanes. By contrast, the United Kingdom Meteorological Office (UKMO) is predicting a slightly above average season with 14 named storms and 8 hurricanes, as does The Weather Company, an IBM business, which predicts 3 major hurricanes as well.
Hurricane Alex (Image: NOAA)
Meanwhile, the University College of London predicts that 2016 will be about 20% below the long term average with figures of 12, 6 and 2 respectively. Collectively, these imply a slightly more active season than normal, noting that last year was one of the least active on record – despite the tragic loss of the El Faro off the Bahamas.
There are three key factors that help to determine the development of tropical storms: pressure, Sea Surface Temperature (SST) and wind shear, and all three have slightly differing patterns than normal. This year’s higher-than-average pressure readings (from the Azores High) in the Atlantic result in stronger SE trade winds which give rise to cooler sea surface temperatures off Africa that subsequently increase the air pressure. The higher winds, cooler sea surface and higher pressure readings are all associated with fewer storms, particularly off the African coast which is the traditional breeding ground for hurricanes in the Atlantic.
Elsewhere, the high pressure readings recorded in the SE tropical Pacific during February and March traditionally signify the demise of El Niño and a shift to La Niña. This shift to La Niña conditions is also associated with reduced vertical wind shear, especially across the Western Caribbean, and thus represents the potential for a more active season.
Putting this all together implies a near or slightly above average season where hurricane development will tend to occur further west in the Caribbean rather than develop off the African coast. This season therefore has greater potential for systems to go ashore in the US compared to the quiet year last year when El Niño likely played a significant suppressing role in the 2015 Atlantic hurricane season. This was due to greater than normal wind shear and more dry air over the Caribbean Sea in the peak season months of August and September than normal.
In the Eastern Pacific, activity for 2015 was well above the long-term mean with 18 named storms, 13 hurricanes, and 9 major hurricanes, which was the highest total since reliable records began in 1971. However, with the demise of El Niño, this region is expected to be less active, and as such meteorologists are predicting a near average or slightly above average season with around 17 named storms, 9 hurricanes, and 4 major hurricanes.
In the NW Pacific, Tropical Storm Risk.com (TSR) predict that it will be a quiet season, with 22 tropical storms, 13 typhoons, and 6 intense typhoons developing across the rest of the year. The declining El Niño water temperatures and shear across the Pacific should favour tropical cyclone formation further west, which could see more typhoons going ashore in the Western Pacific Rim region. Westernpacificweather.com predicts a slightly more active year with up to 25 tropical storms, 16 typhoons and 6 super typhoons. The main factor behind the TSR forecast for a below normal NW Pacific typhoon season is the declining El Niño associated with stronger trade wind strength over the region 2.5N-12.5N, 120E-180E, which leads to lower cyclonic vorticity over the NW Pacific region where most intense typhoons form. Although there have not yet been any typhoons in the NW Pacific, the typhoon season runs throughout the year, and most tropical cyclones typically develop between May and October. Our advice is not to be complacent!
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