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NEW adjustments to 2018 Atlantic Hurricane Season Forecast

Dr. Mario Picazo
Meteorologist, PhD

Friday, August 3, 2018, 6:16 PM - The latest forecast published by the Tropical Meteorology Team at Colorado State University (CSU) Department of Atmospheric Sciences shows new adjustments to the Atlantic Hurricane season forecast update released back in early July. What was initially going to be an average to slightly above average Atlantic hurricane season, has now been downgraded to less than they originally anticipated.

With over two months of the season gone by, there has been very little activity, although the season will most likely pick up as we move into the typically more active weeks of August and September. The new numbers released by CSU now shown a total of 12 named storms (average 12), 5 hurricanes (average 6.5) and now only 1 major hurricane category 3 or stronger (average 3).

(SEE ALSO: Where do we find hurricanes in the late summer?)

Three storms have formed so far this year. Alberto was a subtropical system that formed on May 25 in the Caribbean Sea and made landfall a few days later in Laguna Beach, Florida. With Alberto forming before June 1, the official start of the hurricane season, this is the fourth consecutive year in which a preseason storm formed.

In July Beryl (Category 1) crossed the Atlantic into the Caribbean before shifting north and dissipating well east of New England. A few days later came Chris -- the strongest storm so far in the Atlantic this year -- with winds peaking at 168 km/h (Category 2). After weakening and touching land in Newfoundland, it moved into the North Atlantic and vanished.

Pictured above: Hurricane Chris -- NOAA

Key Ingredients for a less active 2018 season

The key ingredients that will most likely cause this 2018 hurricane season to be average or below average include:
  1. The tropical Atlantic surface water temperature values are close or below their long time average. According to SST data, since 1981 in many areas values are the coldest on record for the beginning of August. If it remains in this cold, less energetic mode throughout the season, storms will have less fuel for development and intensification. The atmosphere will also be in a more stable than usual mode, with a higher probability of dry air entrainment in the region, which are ingredients that tend to suppress organized thunderstorm activity needed for hurricane development. 
  2. Ocean temperature forecasts still push for significant probability (65 per cent) that El Niño will form during the September-October-November period, while the chance of seeing neutral conditions is a close 33 per cent. El Niño tends to increase upper level westerly winds across the Caribbean into the tropical Atlantic, tearing apart developing tropical storms that can eventually evolve into hurricanes. For that reason, if it does get stronger than anticipated, we could see an even less active second half of the season. 
  3. Greater wind shear across the region, especially in the Caribbean Sea has been observed in the month of July. Using data since 1979, Michael Lowry, a FEMA atmospheric scientist, has shown how this July 2018 has been the fifth July with the highest wind shear values in the region. A situation one would expect to see with a hefty El Niño pattern in the Pacific, although as mentioned earlier, it has yet to reach that point and could come perhaps later in the year. 

Image courtesy of NOAA. El Niño model forecast as of July 2018.


Dr. Klotzbach, the lead researcher of the released forecast, also points out that the 2018 Atlantic Hurricane Season is looking a lot like those of 1968, 1986, 1993, 1994 and 2002, where multiple impacts occurred despite the season being overall less active. Even if we expect fewer storms this year, one can be enough to cause significant damage.

Image courtesy of NOAA. Tracks of historical hurricane landfalls.


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