Flash floods swamp New York and New Jersey | DW News

Key Concepts:

• Flash floods
• Climate change
• Atmospheric moisture
• Precipitation efficiency
• Cold front
• Lee trough
• Convergence
• Backbuilding storms
• Wireless Emergency Alerts

Flash Floods in New Jersey and New York City

• Severe storms caused flash floods in New Jersey and New York City, leading to travel disruptions and prompting caution from officials.
• In New Jersey, two people died when their vehicle was swept away by floodwaters. A cemetery and numerous cars were submerged.
• The Governor of New Jersey attributed the increasing frequency of extreme weather events to climate change, noting that some areas experienced flooding for the first time.
• New York City: Passengers were stranded in a Manhattan subway car due to flooding. Service resumed by Tuesday morning. Some New Yorkers displayed a business-as-usual attitude, having experienced similar flooding before.

Meteorological Analysis of the Storm

• Matthew Kapuchi, a meteorologist and atmospheric scientist, provided an analysis of the storm.
• The heaviest rain had shifted south and east to the Virginia Tidewater. The previous day saw an "absolute deluge" along Interstate 95.
• One location in Union County, New Jersey, recorded 16.7 cm of rain in 3-4 hours, with 9.88 cm falling between 5 and 6 p.m.
• This rainfall rate is described as roughly a once-every-100-to-200-year event.

Reasons for the Exceptionally Heavy Storm

• The intersection of two weather boundaries: a slow-moving cold front and a lee trough east of the Appalachian Mountains.
• The lee trough fostered convergence, leading to air rising and generating storms.
• Individual storm cells were "backbuilding," regenerating, and pulling in more moisture from the south. These storms merged over Union County, New Jersey.
• The National Weather Service issued a "considerable episode" flash flood warning, triggering Wireless Emergency Alerts.

Climate Change and Atmospheric Moisture

• Human-induced climate change is increasing atmospheric moisture, making downpours more likely.
• The background state of the atmosphere is becoming more moist, increasing precipitation efficiency.
• Higher rainfall rates occur because more of the raindrop makes it to the ground without evaporating due to the moisture present.
• Data shows a 9.5% increase in atmospheric moisture every 10 years during July in Union County, New Jersey, since 1998.
• The northeastern US has seen a 70-75% uptick in heavy rain and flash flood events during the summertime months.

Political Discourse and Climate Change

• Political leaders may use weather events to support their agendas.
• Weather is random at times, but the background climate is favoring more precipitation extremes.

Synthesis/Conclusion

The flash floods in New Jersey and New York City were caused by a confluence of weather factors, exacerbated by increased atmospheric moisture due to climate change. The rising frequency and intensity of such events raise concerns about the impacts of climate change and the need for mitigation and adaptation strategies. The meteorologist emphasized that while individual weather events can be random, the overall trend indicates a greater likelihood of precipitation extremes due to a warmer, more moist atmosphere.