Season of Storms

This is the time of year when most major tropical storms form in the Atlantic Ocean and begin their journey westward. The hurricane season normally begins in late spring (May of June) and ends in late fall (November or December). September in the peak month.

Atlantic hurricanes can generally be more frequent and intense between the time La Niña and El Niño conditions are present, although it is not a hard and fast rule. This year (2020) is one of those years. So far there have been eight storms of hurricane intensity out of 24 tropical or subtropical cyclones.

According to the US National Weather Service:

El Niño produces stronger westerly wind at upper levels of the atmosphere across the tropical Atlantic than in normal non-El Niño seasons. This increases the total vertical wind shear, basically shearing the tops from developing storms before a healthy circulation can form. El Niño events generally suppress Atlantic hurricane activity so fewer hurricanes than normal form in the Atlantic during August to October, the peak of Atlantic hurricane season.

During La Niña, westerly winds high in the atmosphere weaken. This results in an expanded area of low vertical wind shear, allowing more Atlantic hurricanes to develop during La Niña events. La Niña increases the number of hurricanes that develop and allows stronger hurricanes to form.

The chances for the continental U.S. and the Caribbean Islands to experience a hurricane increase substantially during La Niña and decrease during El Niño.

El Niño and La Niña also influence where Atlantic hurricanes form. During La Niña, more hurricanes form in the deep Tropics from weather disturbances that originate over North Africa. These systems have a much greater likelihood of becoming major hurricanes, and of eventually reaching the U.S. and the Caribbean Islands.

The incidence of hurricanes is higher during the neutral phase (when neither El Niño nor La Niña are in effect) than during El Niño. Although hurricanes occur more often during La Niña episodes, significant tropical weather events have occurred during the neutral phase. For example, the record shattering 2005 hurricane season that included Katrina and Rita occurred during the neutral phase. Hurricane Andrew, the most destructive United States hurricane of record, made landfall along the Gulf coast during a neutral phase of the El Niño/Southern Oscillation in 1992.

Superstorm Sandy, struck in 2012, during the tail end of an extended (2012-2012) La Niña event. It was the one of 18 named storms that year and the second major hurricane of the season. Damage totaled US$70 billion along its route from the Caribbean to New England, with 233 people killed. While only a category 3 storm, what made it so devasting was that it came ashore in the highly populated and developed area of New Jersey and New York.

Radar image of Hurricane Sandy on 29 October 2012 as it approached the Jersey shore

The Great New England Hurricane was also one of those. It struck New England in late September 1938 was a major storm that just preceded the 1938-39 La Niña event. Few people will remember this event or perhaps even read much about it as it competed with pre-WWII news out of Europe. But it was one of the deadliest storms to hit North America. The 1938 hurricane season produced nine tropical storms of which four developed into hurricanes.

Its westward track across the Atlantic missed most of the land masses around the Caribbean. It rapidly developed into a category 5 storm east of Florida with over 160 mph (260 kph) sustained winds. Coming up against a cold front, it then took a right angle turn to the north. It decreased in intensity but was still at category 3 when it made landfall on Long Island.

According to the National Hurricane Center:

Blue Hill Observatory, Massachusetts measured sustained winds of 121 mph with gusts to 183 mph (likely influenced by terrain). A U.S. Coast Guard station on Long Island measured a minimum pressure of 27.94 in. Storm surges of 10 to 12 ft inundated portions of the coast from Long Island and Connecticut eastward to southeastern Massachusetts, with the most notable surges in Narragansett Bay and Buzzards Bay. Heavy rains before and during the hurricane produced river flooding, most notably along the Connecticut River. This hurricane struck with little warning and was responsible for 600 deaths and $308 million in damage in the United States.”

Nearly 9,000 homes and buildings were destroyed, and 15,000 damaged. Nearly 3,000 ships were sunk or wrecked. Power lines were downed across the region, causing widespread blackouts. Innumerable trees were fell ed, and 12 new inlets were created on Long Island. Railroads were destroyed and farms were obliterated (This Day in History).

Aftermath of Great New England Hurricane of 1938 – photos from The Boston Globe archive (other photos on National Weather Service website here)

Hurricanes are one of those types of events that cause widespread destruction. Prediction as to how and when the biggest ones may occur is still difficult. Even the less intense storms can be devastating if they come onshore where there are many people.

·         The deadliest storm was the 1900 Great Galveston Hurricane when between 8,000 and 12,000 people were killed. It struck a lowland region with a very high population.

·         The costliest was Hurricane Katrina in 2005 with damage tagged at US$160 billion.

·         The highest wind speed at landfall was recorded during the Hurricane Allen onslaught in 1969, which attained sustained winds of 190 mph (305 kph).

·         The most active season was 2005 when 15 storms developed into hurricanes.

It is difficult to see any trend in the number or intensity of hurricanes over the last century and a half.

The point here is that what we see today in terms of natural disasters is not dissimilar to what has gone on in the centuries past. Mother Nature frequently interferes with communities and the lives of people, in uncontrollable ways. And she will continue to do so.