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Behind the Forecast: Why 2020 Atlantic Hurricane Season is breaking records

Listen to Science Behind the Forecast with Meteorologist Tawana Andrew every Friday on 89.3 WFPL at 7:45 a.m.
Published: Aug. 28, 2020 at 10:44 AM EDT
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LOUISVILLE, Ky. (WAVE) - The 2020 hurricane season has already been a record-breaking one, and we have not yet reached its peak. Tropical systems have been forming at a break-neck pace.

As of August 27th, there have been ten records have been broken for the earliest named storms. Before August 1, 2020, nine named storms had formed in the Atlantic Basin, the most since 1966, according to National Oceanic and Atmospheric Administration (NOAA).

Earliest Tropical CycloneFormation DatePrevious Record (Next Earliest)Formation Date
CristobalJune 2, 2020ColinJune 5, 2016
EdouardJuly 6, 2020EmilyJuly 11, 2005
FayJuly 9, 2020FranklinJuly 21, 2005
GonzaloJuly 22, 2020GertJuly 24, 2005
HannaJuly 24, 2020HarveyAugust 3, 2005
IsaiasJuly 30, 2020IreneAugust 7, 2005
JosephineAugust 13, 2020JoseAugust 22, 2005
KyleAugust 14, 2020KatrinaAugust 24, 2005
LauraAugust 21, 2020LuisAugust 29, 1995
MarcoAugust 22, 2020MariaSeptember 2, 2005
LeeSeptember 2, 2011

So, why so many storms? Well, warm water in the Gulf of Mexico, Caribbean Sea, and the Atlantic Ocean is the perfect fuel for hurricanes. Hurricanes need water near or hotter than 80° Fahrenheit over a depth of 50 meters to get going. Sensors in the Gulf of Mexico show water temperatures in the mid-80s in many locations.

Saharan dust drifting across the Atlantic Basin, called the Saharan Air Layer (SAL), helped to limit storm formation from mid-June through early July. A single storm formed from June 10 through July 4 as the layer of Saharan dust stretched across the Atlantic Ocean. That dust, and the dry air that accompanied it, faded as July ended and August began.

The Saharan Air Layer is detrimental to the development of tropical systems. The SAL can slash the amount of Tropical moisture in the air by half. A strong jet of wind within the Saharan Air Layer can break up a developing storm easily. The dust also absorbs solar radiation, preventing clouds from forming and stabilizing the atmosphere.

NASA Earth Observatory image of Laura making landfall by Joshua Stevens, using VIIRS data from...
NASA Earth Observatory image of Laura making landfall by Joshua Stevens, using VIIRS data from NASA EOSDIS/LANCE and GIBS/Worldview and the Suomi National Polar-orbiting Partnership, and Black Marble data from NASA/GSFC.(Visible Earth/NASA)

The amount of wind shear over the Atlantic basin is also well below average. Wind shear is the difference in wind speed or direction as you ascend in the atmosphere. Strong wind shear inhibits the development of a storm or rips it apart once it’s formed.

The potential La Niña later this year also will help with the formation of hurricanes in the Atlantic. La Niña the periodic cooling of the central and eastern Pacific Ocean near the equator. It is associated with weaker winds in the upper and lower levels of the atmosphere; this reduces the wind shear that can rip a developing hurricane apart. It also decreases the sinking air and atmospheric stability, priming the Atlantic region for hurricanes.

NOAA also credits weaker tropical Atlantic trade winds and an enhanced west African monsoon season as reasons for the active hurricane season. With an enhanced west African monsoon season, more tropical waves are tracking off of the West African coast.

I’ve broken down before how hurricanes form; here’s a quick recap. For a hurricane to form, warm moisture rises and condenses into clouds, which eventually become thunderstorms. Eventually, an area of low-pressure forms as wind rotates in the atmosphere. Once wind speeds reach 74 mph, the storm is officially a Category 1 hurricane on the Saffir-Simpson scale.

An update to the 2020 Atlantic Hurricane Season Outlook in early August called for 19 to 25 named storms, seven to eleven of which will become hurricanes, including three to six major hurricanes. Keep in mind that the average hurricane season produces 12 named storms, of which six become hurricanes, and three of those become major hurricanes.

As a reminder, the Atlantic hurricane season lasts from June 1st through November 30th with its peak around September 10th. Around 95% of hurricanes and major hurricanes form between August and October.

If more than 21 tropical systems form, then Greek letters will be used. The letters Q, U, X, Y, and Z are skipped in the list of Atlantic hurricane names.

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