Hurricanes are limited to certain areas, but extreme rainfall from other types of storms can occur just about anywhere – think of intense cloudbursts during the summer monsoon in the Desert Southwest, or organized thunderstorm systems like the one that caused deadly flooding in Tennessee in August 2021. For example, the upper right panel shows that in the northeastern U.S., the amount of rain in the heaviest precipitation events increased by 55% from 1958-2016. This figure shows four different metrics of heavy precipitation change. Observed changes in heavy precipitation across the U.S., from the 4th National Climate Assessment. The latest National Climate Assessment, in 2018, described a trend toward increasing precipitation in the Northeast and also warned that aging infrastructure in the region isn’t prepared to handle the water. Unfortunately, this is not a linear process: A small bit of added moisture can lead to a lot more rain. When weather patterns that bring together the ingredients for heavy rainfall, like hurricanes, occur in a warmer world, more moisture is available, and more rain falls. This is also why the intensity of rainfall is expected to increase as the climate warms. It explains why heavy rain occurs year-round in the tropics, whereas it is much more likely in summer than winter in the U.S. This is formally known as the Clausius-Clapeyron relation.īecause the amount of rain that a storm produces is closely connected to the amount of water vapor in the air, this means that, all else being equal, heavy downpours are more likely in a warmer climate. With every 1 degree Celsius (1.8 F) increase in temperature, there can be about 7% more moisture in the air. The reasons are fairly simple: Warmer air can have more water vapor in it. Yet, heavy downpours are becoming more common in the region as the climate warms. The remains of Hurricanes Agnes (1972), Floyd (1999), Irene (2011), Lee (2011) and Sandy (2012), among others, all brought widespread rainfall and flooding through the area. The extreme rainfall arrived with tornadoes in several states, including Maryland and New Jersey.Įxtreme rain and flash flooding aren’t new to the Northeast, and they often result from hurricanes or their remnants. Weather stations in New York City saw rain rates over 3 inches per hour. Newark, New Jersey, recorded 8.41 inches of rain, their most ever in a single day, shattering the old record by over 1.5 inches. That led to major flash flooding and at least 50 deaths in the region, in addition to at least 17 deaths earlier along the Gulf Coast.
The widespread, intense rainfall overwhelmed rivers and drainage systems in the highly populated corridor from Philadelphia to New York to Boston. Weather forecasters saw the disaster coming.įorecasters emphasized the threat of flash flooding well ahead of its arrival, and the National Oceanic and Atmospheric Administration’s Weather Prediction Center issued a rare “ high risk” of excessive rainfall outlook for parts of the Northeast a day in advance. That was happening as Ida’s remnants moved toward the Northeast. That moist air is lifted along the fronts, and long-lasting, very heavy rain can result. Even though they no longer have the intense winds that they did in the tropics, they still bring tropical humidity. CoCoRaHS Mapping System, CC BY-ND From tropical to extratropicalĪs hurricanes move northward from the tropics, they often transition from their characteristic circular shape to become “extratropical cyclones” with warm and cold fronts extending outward from the low pressure at the center.
0 kommentar(er)
