August 12, 2021 Orchard Beach Lightning Event

A complex of thunderstorms developed early in the day across Pennsylvania, tracked across the state, across New Jersey, and eventually into portions of New York City in the early evening. The storms were severe at times, but the greatest impact was from lightning which resulted in a fatality and several injuries at Orchard Beach in the Bronx.

Satellite shows a wave of weak convection coming off Lake Erie, then rapidly developing into a cluster of intense thunderstorms across north central Pennsylvania. The redevelopment of thunderstorms along the associated outflow can be seen from northeastern Pennsylvania, northern New Jersey, and eventually into southeastern New York.

Reflectivity from the regional radar mosaic shows the storms tracking from Pennsylvania to New York City before dissipating over Long Island.

Base reflectivity from NWS New York, NY (KOKX) shows the thunderstorm complex tracking from Bergen county in New Jersey, across the Hudson River, and into southeastern New York. The Bronx and southern portions of Westchester county were hardest hit. The lightning injuries and fatality occurred at Orchard Beach, which is located near City Island in the Bronx.

Notice how the thunderstorms cling to the outflow boundary across the northern portion of the complex. This allows for the storm activity to be maintained. Weakening of the cells can be see in the outflow dominant portions of the complex, where the outflow boundary eventually outruns the convection.

Base velocity data from KOKX radar shows the cold pool driven winds associated with the bowing complex of thunderstorms. The gusty winds associated with the complex produced some isolated severe thunderstorm wind damage across Passaic and Bergen counties in New Jersey.

As the thunderstorms got closer to New York City, 40 knot (46 mph) winds were reported at Teterboro Airport. The exact same wind speeds were later recorded at LaGuardia Airport. Elevated stations over the water reported higher wind gusts as the storms reached the Long Island Sound, with a mesonet station near Larchmont, NY reporting 60 kt (69 mph) at an elevation of 40 ft.

The following graphic shows the extent of the cloud to ground lightning associated with the convective complex.

Note: Not all of the lightning strikes, particularly across Pennsylvania, are from the complex which eventually impacted New York City.

A view of the 15 minute cloud to ground lightning data shows the intense clustering of lightning across the Bronx. The area around Orchard Beach, where the fatality and multiple injuries occurred, is highlighted below.

Note: The fatality was not included in the  LSR Summary  as it occurred after the initial storm report was issued.

This  article from the New York Times  details the reported injuries and fatality associated with the thunderstorm complex.

A hot and humid air mass set the stage for thunderstorm development on August 12, 2021. The region was in the midst of a major heat wave, with heat indices across the area over 100 F. The record high of 98 degrees at LaGuardia was tied on the date, and a new record of 98 degrees was established at Newark.

The upper level pattern shows ridging up the Atlantic Seaboard and troughing over the Upper Midwest.

The mid-level analysis shows the extent of the heat, with 850 mb temperatures above 20 C for most of the Tri-State Region.

When storms rapidly developed over north central Pennsylvania, SPC mesoanalysis indicated surface based Convective Available Potential Energy (CAPE) building to around 3000 J/kg across much of the state, with no Convective Inhibition (CIN). This allowed for thunderstorms to regenerate and intensify quickly during the early afternoon hours.

As the cold pool driven thunderstorms approached the New York City Metropolitan Area, there was roughly 2000 to 3000 J/kg of surface based CAPE to work with, along with no CIN. This allowed for thunderstorms to continuously regenerate or hold together along the outflow all the way to the coast.

It was not until storms reached Long Island and eventually hit some convective inhibition did they dissipate. The quick dissipation was further enabled by the lack of upper level support.

A Severe Thunderstorm Warning was issued for the cluster of storms as they approached the Tri-State Area:

As the thunderstorms got closer to New York City, and weakened, a Special Weather Statement was issued:

Shortly thereafter, a Special Marine Warning was issued as the storms moved east:

Eventually, the storms weakened further and dissipated over eastern Long Island.

You can check out more of our storm summaries back on our  NWS New York, NY Local Storm Archive .