New York City and other parts of the Northeast have seen several prolific rainy events this year. Heavy precipitation of historic proportions and catastrophic flooding caused by multiple events this summer and early fall have caused the loss of tens of lives and billions of dollars in damage. The city’s rainfall count so far this year ranks third.
Since the start of summer, a big reason places like New York City have been above average in terms of precipitation may be linked to an ocean phenomenon known as the marine heat wave, according to AccuWeather Senior Long-Range Meteorologist Paul Pastelok.
In its most basic definition, a marine heat wave is an extended period during which sea surface temperatures are unusually high, according to the National Oceanic and Atmospheric Administration (NOAA).
Higher water temperatures allow more moisture to evaporate from the ocean into the atmosphere. When storms can tap an abundance of moist air into the atmosphere, more rain can fall harder and faster.
A daily map of sea surface temperature anomalies (degrees above / below normal) for November 1, 2021, shows that the marine heat wave continues through the fall, as the show the red areas off the mid-Atlantic coast of the United States (NOAA)
AccuWeather forecasters say a marine heat wave over part of the Atlantic Ocean, just off the United States coast between Delaware and eastern New England, has resulted in an overabundance of humid air in parts of the central Atlantic and northeast during the second half of the year and is likely a key factor in the severity and frequency of heavy rainfall events.
This current wave of warm water dates back to July 2020. It has become warmer and gradually spread over the past summer, according to AccuWeather long-term forecaster Paul Pastelok.
“This warm body of water has been through some big storms this season and hasn’t been ruffled,” Pastelok said. He noted that if there had been several storms moving south to north from the tropics in recent months, then perhaps this region would have cooled.
The 3-day total precipitation is shown for four recent events affecting New York City: early July, Hurricane Henri, Hurricane Ida, and late October in the northeast. Yellow indicates precipitation greater than 4 inches. (NOAA).
“It might take several big Northeasters to really bring these water temperatures down,” he said. While the long-term AccuWeather team anticipates the potential for a few big storms this year, which could lower sea surface temperatures in late winter, there may be more heat waves at all. moment in the future, he added.
Until June 1, the start of the meteorological summer, New York City was actually slightly behind normal in terms of precipitation. Then disastrous thunderstorms began to arrive. In November, parts of the I-95 corridor had precipitation up to 16 inches above normal.
In early July, severe thunderstorms triggered widespread flooding problems in the New York metropolitan area. Just a day later, Elsa, as a tropical storm, would reinvigorate the flooding problems in the area.
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In late August, Henri, which made landfall in New England as a tropical storm, brought torrential rains to New York City and broke several precipitation records, including the wettest hour on record in the central park. During the hour between 10 p.m. and 11 p.m. on August 21, 1.94 inches of rain flooded Central Park, where official weather records are taken in New York City. As the National Weather Service (NWS) put it, this interval was “the wettest hour on record” for the city, with records dating back to the late 1860s.
This new record would not last very long.
Ida, a storm that will live in the infamy of many southern and eastern states, struck Louisiana as a Category 4 hurricane on August 29, then passed through the eastern half of the country and arrived in the northeastern United States as a tropical rain storm. the calendar has changed to September.
Ida was going to trigger widespread rain of 6 to 8 inches in the New York metro area. As a result, September 1 marked Central Park fifth wettest day on record, according to the National Weather Service (NWS).
Less than two weeks after setting a new record for the wettest hour on record, Central Park recorded a staggering 3.15 inches of rain in the hour between 8:51 p.m. and 9:51 p.m. Ida, once again shattering the record . Ida’s rainfall also prompted the NWS to release the first flash flood emergency for New York City.
The damage caused to the Big Apple and surrounding areas by the Ida flood precipitation has been catastrophic. Floodwaters quickly overwhelmed roads and subways, leaving many stranded. Water also spurted out in low areas and basements, flooding everything in its path.
More than 50 deaths have been attributed to Ida’s impact on the northeast, according to ABC News.
“As Ida headed northeast from the Gulf Coast, the storm bands of rain intensified as the storm moved closer to the mid-Atlantic,” Pastelok said. “The storm boosted the very hot and humid situation over these hot spots, resulting in rainfall rates of 2 to 3 inches and about 9 inches of rain.”
Changes in ocean currents and ocean salinity over the past 10 to 20 years, likely influenced by climate change, may also contribute to these coastal marine heatwaves.
“The oceans are a heat sink for the Earth system,” said Jonathan Porter, chief meteorologist at AccuWeather. “In other words,” he added, “it’s a place where the Earth’s system stores excess heat from the atmosphere. Since the atmosphere has warmed considerably over the years. decades due to climate change, it is not surprising to see sea surface temperatures exceeding their long-term averages in many parts of the world. ”
And that’s a trend that has continued this year. Temperatures across the contiguous United States during the summer of 2021 were the hottest on record in American history, according to NOAA, and July 2021 has earned the dubious distinction of “the world’s hottest month of all the time”.
A 2018 study published in the scientific journal Nature detailed how maritime heatwaves have become more frequent over the past century.
“From 1925 to 2016, the global average frequency and duration of marine heat waves increased by 34% and 17%, respectively, resulting in a 54% increase in the annual number of marine heatwave days worldwide,” said Researchers.
In addition to the precipitation attributed to these notable events, frequent smaller-scale storms this summer and fall have pushed New York City into the record books.
As of October 31, the Central Park Registration Station in New York City recorded 57.21 inches of precipitation for the year – the third-highest annual cumulative total in history.
Even if it didn’t rain another drop in the city for the rest of the year, 2021 would end up being the 15th wettest year on record. Just another 1.22 inches of precipitation in the remaining two months of the year will catapult 2021 into the top 10 wettest years on record.
The rainiest year on record occurred in New York City in 1983, when an incredible 80.56-inch rain fell. Almost 2 feet of rain falls between the cumulative total of 2021 and the title of the wettest year on record in New York.
The archives of the Central Park Observation Station date back over 150 years, to 1869.
While there’s a pretty big gap between 2021’s cumulative total and the title of the wettest year on record, AccuWeather forecasters say Mother Nature should offer plenty of opportunities to catch up.
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