The Physical Mechanisms of Hurricane Ida’s Extreme Rainfall in New York City: Insights from the Warn-on-Forecast System

Details

• Journal Title:
  Weather and Forecasting
• Personal Author:
  Janoski, Tyler P. ; Booth, James F. ; Galarneau, Thomas J.
• NOAA Program & Office:
  Education and outreach ; OAR (Oceanic and Atmospheric Research) ; CESSRST (Cooperative Science Center for Earth System Sciences and Remote Sensing Technologies) ; NSSL (National Severe Storms Laboratory)
• Description:
  The remnants of Hurricane Ida demonstrated the destructive potential of extratropically transitioning storms in New York City (NYC) on 1–2 September 2021. Central Park set a new hourly rainfall record of 3.47 in. (88.14 mm) from 0100 to 0200 UTC 2 September, far exceeding the city’s stormwater capacity. Historic flash flooding killed 13 residents and caused hundreds of millions of dollars in damage. Despite the impacts, the physical mechanisms responsible for this record-breaking rainfall in NYC remain underexplored. In this study, we use the National Oceanic and Atmospheric Administration (NOAA) National Severe Storms Laboratory’s Warn-on-Forecast System (WoFS), an ensemble forecast and data assimilation system, to examine the role of atmospheric processes across spatial scales in producing extreme hourly rainfall rates in NYC. We apply multiple analysis techniques, including ensemble sensitivity analysis and direct comparison of the wettest and driest ensemble members. We also implement a new front-detection algorithm to investigate how front location influences individual supercell trajectories. Our analyses support past findings that low-topped supercells embedded in Ida produced the highest rainfall rates. The number and trajectory of these storms were shaped by the synoptic circulation, which affected the steering flow, and by the strength of the low-level jet transporting tropical moisture and instability to the slow-moving warm front. Additionally, NYC rainfall rates were sensitive to the strength and position of the warm front, with variations shifting maximum precipitation too far northwest in some members. Our results highlight important features at the synoptic, meso-, and convective scales with the potential to improve the predictability of future extreme rainfall events.
• Source:
  Weather and Forecasting, 40(12), 2755-2773
• DOI:
  https://doi.org/10.1175/WAF-D-25-0098.1
• ISSN:
  0882-8156 ; 1520-0434
• Format:
  pdf
• Publisher:
  American Meteorological Society
• Document Type:
  Journal Article
• Funding:
  Grant no. NA22SEC4810016
• Rights Information:
  Other
• Compliance:
  Submitted
• Main Document Checksum:
  urn:sha-512:51a58f0da918c259df5173c65f6b08004ab7b050a4ff389ca1db0eefec1e9e059d971b315db24bf5aa3954147e2da248f928bd5fdf4890104574bf755f1be168
• File Type: