Real-Time Monitoring Field Observations: A Fall Nor’easter

September 25 - 28, 2026

Author

Stone Living Lab

A rare September Nor’easter hit the coast of New England this weekend, bringing multiple days of gusty winds, heavy rain, strong waves, and coastal flooding. The Stone Living Lab’s (SLL) Real-Time Monitoring Network captured the impact of the storm throughout the Massachusett coast (Figure 1). The weather station, wave buoys, tide gauges, and overland flood sensors provided detailed insights into the impacts of the storm.

Figure 1: Map of the SLL Real-Time Monitoring Network.

Winds and Waves

Wind speeds and wave heights rapidly picked up Friday afternoon and continued to rise, peaking Saturday night. Wind speeds were elevated throughout the entire weekend and the highest wind gust observed by the Rainsford Island Weather station was 50.6 MPH at 9:15 PM Saturday (Figure 2). Both wave buoys observed elevated wave heights, though the Boston Harbor Entrance buoy had more fluctuations in waves while the North Shore buoy experienced a continual rise in waves until the peak of a maximum wave height of 18.4 ft at 4:20 AM on September 27 (Figure 3). The Harbor Entrance wave buoy observed a maximum wave height of 11.1 ft at 11:40 PM on September 26 (Figure 4).

Tides

The SLL Real-Time Monitoring Network includes tide gauges at Thompson Island proposed as Cathleen Stone Island, Gallops Island, and Essex. We also monitor tides near our overland flood sensors through NOAA tide gauges, including Boston (Figure 5), Fall River, and Falmouth. With a full moon on September 26, the tides were predicted to be the highest of the month prior to the development of the storm. The addition of the storm and resulting storm surge brought coastal flooding and high waters around noon and midnight each day.

Table 1 shows the maximum water level observed at each tide gauge in the network. The tide gauge at Thompson Island proposed as Cathleen Stone Island (CSI) observed the highest water level at 12.8 ft at 1:42 PM on September 28, while Boston observed a maximum water level of 12.5 ft around noon on September 28. The difference between the maximum observed water level by the Gallops Island, Thompson Island proposed as Cathleen Stone Island, and Boston tide gauges is particularly interesting given their proximity to each other. The difference highlights the variation of storm impacts and surge within the Harbor.

Location Time (EDT) Maximum Water Level
Boston 2026-09-28 12:42:00 12.47
Essex 2026-09-27 00:17:00 12.34
Fall River 2026-09-28 09:42:00 6.64
Falmouth 2026-09-26 08:18:00 4.30
Gallops 2026-09-28 12:48:00 12.09
Thompson Island/CSI 2026-09-28 13:42:00 12.79
Table 1: Highest observed water level at each tide gauge.

Another notable observation is the difference between the predicted and observed water levels at the NOAA tide gauges. NOAA uses a harmonic tide prediction to forecast tide heights at their stations. While it is normal for the tide to be higher than predicted due to ocean conditions, the Boston tide gauge was a foot above predicted water levels starting on Friday and was more than two feet over predicted Saturday evening. Water levels were close to the National Weather Service (NSW) Coastal Flooding Thresholds, but did not exceed the thresholds (Figure 5).

Figure 5: Predicted and observed water levels with NWS flood thresholds from the NOAA tide gauge in Boston. Hover over the lines to see the water levels.

Flooding

The combination of strong winds, high waves, and elevated tides led to coastal flooding across Massachussetts. The Lab’s network of overland flood sensors observed flooding at Tenean Beach (Figure 6), Long Wharf (Figure 7), Marshfield (Figure 8), and Fall River. Tenean Beach, Long Wharf, and Marshfield experienced flood events with each high tide. Flood levels up to 1.6 ft were observed at Tenean Beach. Long Wharf and Marshfield both had maximum flood depths of 0.5 ft. The Fall River sensor saw less flooding with a single incident of 0.17 ft. The location of the Fall River sensor is intended to capture flooding associated with rain events rather than tidal or coastal flooding, so the single instance was likely associated with heavy rain.

The variations in the timings and extent of the flood depths is due to site characteristics (Figure 9). Tenean Beach tends to a see rapid rise in water with the tide and an extended period of time until the flood waters recede.

The overland flood sensor is over a walkway that drains to an adjacent marsh through a pipe.The water tends to pool and slowly drains while the tide goes out of the marsh.

Meanwhile, Long Wharf flooding rises and falls quicker with the tides. The water drains out of the area as the tide falls without the drainage delay experienced at Tenenan Beach. Marshfield is a bit different from Tenean Beach and Long Wharf. The sensor is behind a seawall, and the observed flooding is from waves crashing and spilling over the wall. As waves overtop the wall, flooding increases but the flooding peak is extended and choppier as the waves continue to spill over the wall during the highest tides. Marshfield also saw flooding outside of the high tide due to the waves.

Figure 9: Overlay of flooding at Long Wharf, Marshfield, and Tenean Beach.

Real-Time Monitoring

The Stone Living Lab’s Real-Time Monitoring Network is constantly observing and tracking flooding and ocean conditions. Check out the SLL Current Coastal Conditions Dashboard to see what conditions look like in Boston Harbor and beyond.

Disclaimer: Data are collected in real-time, not quality controlled, and may be inaccurate. Real-time data may contain errors such as inaccurate sensor readings either from instrument errors or sensor obstruction. Additionally, overland flood sensors only collect flooding data directly beneath the sensor. Flooding may have occurred in communities with sensors but might not have been captured in the data.