Ida Brings Record Flooding in September 2021

October 6, 2021 // Article by: Cody Hewitt

The bulk of September's weather was completely overshadowed by the remnants of Hurricane Ida on the very first day. Beyond that, the month ended up being rather mundane with relatively above average temperatures. In retrospect, the quieter weather after the soaking Ida gave was at least beneficial for post-storm cleanup.

During the last days of August, Hurricane Ida had devastated Louisiana as it made landfall in Port Fourchon. While it quickly weakened through Mississippi and Tennessee, plenty of tropical moisture remained as it swirled toward the Northeast on the 1st. What made the remnants so impactful were both the excessive moisture interacting with a stalled front across the Mid-Atlantic and a strong jet stream aloft. All of this converged into a deluge roughly from West Chester, PA on northeast toward Boston, MA. Along the I-95 corridor, upwards of 4 – 8” of rain fell, along with locally higher amounts up to 9”+. Waters rapidly rose across the area thanks to excessive rainfall rates exceeding 2-3” per hour, resulting in flooded roads and eventually swollen streams. The flooding rivaled Tropical Storms Irene and Lee back in 2011, and Hurricane Floyd in 1999. Newark Airport’s observations recorded 8.44” of rain, breaking an all-time record for daily rainfall, while Central Park recorded 3.15” in one hour alone, setting another all-time record. Needless to say, this type of rainfall has a 1 in 1000 chance of occurring in a given year, with the surrounding areas still experiencing a 1 in 100 to 500 year event.

Outside of the flooding, a tornado outbreak occurred on the same day across Maryland, New Jersey, and Pennsylvania. Most of these occurred during the afternoon and were EF-0 to EF-1 strength, but a handful were EF-2, two of which touched down in Annapolis, MD and Fort Washington, PA. An EF-3 clocking in with 150 mph winds bulldozed through a neighborhood in Mullica Hill, NJ, causing extensive damage. EF-3’s are quite rare to begin with in the region as only four have been reported in the last 15 years. Sadly, 57 people died across the Northeast, largely as a result of rushing water or flooded cars engulfed by deep waters.

Ironically, beautiful weather followed as high pressure quickly nudged in and gave the Northeast cool, dry weather for cleanup into the weekend and second week of the month. Thankfully, no significant rainfall occurred behind Ida’s remnants or the rest of the month for that matter, and severe weather was put on the backburner given the shrinking days and gradual cooldown as we progressed through early fall. With that said, the month was slightly warmer than average. The 3rd week in particular, saw highs reaching into the 80s, but the region didn’t have any scorching heat waves or record breakers. Nighttime lows gradually slid into the 50s and even 40s across the interior Northeast, especially after the 20th. Cold fronts swept through occasionally, which also helped keep any additional tropical storms away from the Eastern Seaboard. One cold front did spin-up an EF-0 in Coventry, CT on the 8th, but beyond some gustier storms, severe weather was sparse.

Overall, what could’ve been an very active month was squeezed into a two day span. Nonetheless, the impacts lingered beyond that as streams and rivers took time to recede. Thanks to such an incredibly wet start, everyone was above normal in terms of precipitation. Allentown, PA recorded its 7th wettest September on record, while Newark, NJ observed its wettest in recorded history at 10.50”!