The Oceanic and Atmospheric Administration (NOAA) has recommended the US is experiencing an earlier-than-normal Atlantic hurricane season which is expected to continue until hurricane season ends on 29 November 2021. For the 2019 season NOAA officials anticipate 14 named storms (winds of 39 mph or more), seven hurricanes and three major hurricanes (Category 3, 4 or 5, with winds of 111 mph or more).
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On average, about 12 storms form by 30 September and six become hurricanes. The season normally ends in November but due to the above-average number of hurricanes and intense hurricanes in the Atlantic during the previous decade, the season was extended by about four weeks.
If the season ends as projected, it will be the 11th season since the invention of the modern computer-modelled weather satellites, which track and predict changes in atmospheric circulation, that has produced 20 tropical cyclones (winds of 39 mph or more) or greater. If the season ends on 29 November as expected, it will be the longest active season for the US Atlantic hurricane basin since 2005, when 23 storms emerged.
Following are high- and low-end odds for the 21 named storms (winds of 39 mph or more), seven hurricanes and three major hurricanes in the Atlantic basin during the 2019 season.
Category 1, 2 and 3
Meeting tropical storm criteria but lacking the strength to achieve hurricane status; a hurricane must have winds of 74 mph or more
Category 4 or 5
Meteorologists consider two classes of hurricanes: major hurricanes and major storms
Category 4 storms have winds of 111 mph or more
Category 5 hurricanes have winds of sustained 110 mph or more
The National Hurricane Center has determined that a ranking system is inadequate to determine how dangerous a storm is based solely on wind speeds. The hurricane center defines major hurricanes as having sustained winds of 111 mph or more.
In February, the hurricane center released a scale that uses storm surge, wind damage and inland flooding to assess hurricane intensity. Storm surge, the rise of water above the sea level caused by a hurricane, is the most dangerous category to a coastal community as it can reach 11ft to 16ft. Wind damage is measured by wind-speed calculations and potential storm surge, as well as storm surge potential, by the measurement of ocean water. Damages are calculated by taking into account the value of uninsured assets, whether damage occurred inside a house or office building, as well as damaged structures after the storm has passed. In urban areas, especially elevated areas, property values are higher than for lower-lying areas, resulting in greater property loss. Damages from wind could be much greater than losses from storm surge in heavy urban storm surge. The maximum strength and intensity are determined through chemical analyses, which assess the strength of the primary and secondary damage that occurs at various temperatures. The hurricane center also uses the western position and potential intensity of the storm to give an approximate strength. The western position is laterally corrected for the equatorial region of the storm and the position is adjusted for rotation instability. Hurricane-intensity findings often change as they are updated or as new analyses are performed.
For the season this year, officials expect Hurricane Florence to be a major hurricane, the first in at least 39 years. But the Atlantic basin has seen above-average hurricane activity since the beginning of the 1990s. For the record, the last Category 4 hurricane to hit the United States was Hurricane Wilma, which hit the Florida panhandle in 2005. Category 5 hurricanes that hit the US included Hurricane Charley (August 2004), Charley (August 2004), and Ivan (August 2004).