2021 Atlantic hurricane season outlook
OMAHA, Neb. (WOWT) - Hurricane Preparedness Week runs from May 9th through the 15th. Though we may not live in a hurricane zone, I thought now would be a good time to discuss the outlook for the upcoming hurricane season.
The official Atlantic hurricane season spans June 1st to November 30th, with its statistical peak on September 10th. The National Hurricane Center is not changing the official start date of the season, but will begin issuing regular storm forecasts for the Atlantic basin beginning on May 15th this year. This change is due to consecutive years of early tropical cyclone activity.
May 15th is the official start of the Eastern Pacific hurricane season, which also runs through November 30th.
Hurricane names are decided by the World Meteorological Organization (WMO). For the Atlantic basin, there are lists of alternating female and male names on a six-year rotation. If a storm is particularly strong or deadly, that name will “retire” and a substitute name will be used the next time around. Only 21 names are included on the list – rather than 26 – due to the shortage of Q, U, X, Y, and Z names.
You may recall in 2020, the Greek Alphabet was used for just the second time to name tropical cyclones. As was the case in 2005, the Atlantic basin surpassed 21 names last year, so the NHC had to move on to the supplemental Greek list.
However, the WMO Hurricane Committee announced back in March of this year that the Greek Alphabet will no longer be used as a supplemental list. The WMO claimed the Greek Alphabet was “distracting and confusing”. Not to mention, there was no formal plan on how to retire Greek names if a cyclone was particularly strong or destructive.
Beginning this year, if the Atlantic basin surpasses 21 named storms, an additional list of 21 names (A – W) will be used.
You may recall, our local climate normals were updated at the beginning of May to account for the 1991 to 2020 climate period. The “averages” related to the hurricane season were also updated, increasing slightly. The average number of named storms per season increased from 12 to 14; the average number of hurricanes per season increased slightly from 6 to 7. The average number of major hurricanes (Category 3 or stronger) remained the same at 3.
2021 HURRICANE SEASON OUTLOOK
Hurricane researchers at Colorado State University are predicting an above-average tropical season. The forecast CSU released in April predicts 17 named storms, 8 hurricanes, and 4 major hurricanes.
The researchers’ thoughts behind their forecast: “Current weak La Niña conditions may transition to neutral ENSO by this summer/fall, but the odds of a significant El Niño seem unlikely. Sea surface temperatures averaged across the tropical Atlantic are currently near average, while subtropical Atlantic sea surface temperatures are warmer than normal.”
La Nina conditions often increase Atlantic hurricane activity due to a weakening of wind shear. El Nino conditions increase wind shear over the Atlantic basin, which is “bad” for storm longevity and intensity.
You can keep an eye on the upcoming hurricane season by visiting the National Hurricane Center’s website: https://www.nhc.noaa.gov/
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