In a statement to The Washington Post, Delta confirmed the aircraft “diverted to New York-JFK out of an abundance of caution following a mechanical issue” resulting from hail. Forty-three passengers were on board the Airbus A319 aircraft, which suffered damage to its flight navigation system.
The aircraft will be out of service for several days pending repairs and maintenance.
Fight 1076 took off from Palm Beach International Airport in Florida on time at 4:03 p.m. after an 18-minute taxi. It was scheduled to land at New York’s LaGuardia Airport at 6:31 p.m., but instead made an emergency landing at JFK around 6:36 p.m. Passengers deplaned at the gate shortly after 7 p.m.
Initial media reports indicated the hail was in the vicinity of New York City around the time the plane was landing. However, radar and flight data analysis suggests the aircraft likely ran into hail over Gloucester County in southern New Jersey about a half-hour before landing.
Storms had blossomed over central New Jersey earlier in the afternoon, bringing severe winds and large hail while prompting a rare “flash flood emergency” in Philadelphia. A number of creeks rapidly rose to near major flood stage as water rescues were conducted with vehicles submerged in Philadelphia’s northern suburbs.
The initial blast of storms brought a surge of cool air to the surface, that “cold pool” expanding radially outward and kicking up storms from New York to the Mid-Atlantic.
An unsettled Monday
Radar archives confirm that thunderstorm activity had largely wrapped up in the New York area as the aircraft was approaching around 6:30 p.m. Earlier storms did bring a 59 mph wind gust to Glen Cove on Long Island at 5:20 p.m., some 12 miles east of La Guardia.
Instead, data suggests that the aircraft, which had begun its initial descent over the Delmarva Peninsula at 5:52 p.m. after crossing over the Chesapeake Bay, flew into developing storms near the Delaware Bay shortly after 6 p.m.
Storms on Monday were very strong “pulse” storms, meaning they rapidly developed but also quickly collapsed. That makes predicting them a challenge, particularly since so much can change in the span of one sweeping radar scan.
A rapidly developing storm
Notice the radar shortly after 6 p.m., north of Vineland, N.J. The low-level scan at 6:02 reveals strong storms to the west — avoided by the aircraft — while lesser, seemingly more manageable showers and a few thundershowers were present in between.
However, a higher-elevation scan made by a steeper radar beam captured very significant radar echoes north of Vineland at 6:06 p.m., with storm tops over 40,000 feet. Oftentimes, storms in pulse environments can produce severe hail aloft before much rain has even fallen to the surface. That appears to be the case here.
It’s likely that the aircraft either flew very close to or directly through the cloud at between 19,000 and 22,000 feet — precisely the level at which serious hail was present. The aircraft was traveling at about 415 mph.
It appears hail was likely between 1 and 1.5 inches in diameter — sufficient to damage the nose cone, but not quite large enough to shatter a windshield.
Doppler radar also revealed “low correlation” at that altitude, meaning there were jagged, irregular, or chaotic shapes — commensurate with large hail — in the cloud. Raindrops typically possess much greater correlation.
Possible detection issues
Some may wonder why, if the plane has a radar, it would fly into the storm to begin with. It’s important to stress that airplanes usually have X-band radar, meaning their wavelengths are shorter than the S-band instruments utilized by the National Weather Service. That makes aircraft radar more sensitive and detailed over shorter distances, but their beams can’t travel as far.
And amid stormy environments, the signals can easily become “attenuated,” losing detecting power as they plow through dense or heavy precipitation.
While hail was not reported in the area, it’s not uncommon for storms to produce hail aloft that melts before reaching the ground.
“A storm that well-developed would suggest that the potential was there for some hail, not only reaching the ground but churning around in the storm itself,” said Dean Iovino, a meteorologist at the National Weather Service in Mount Holly, N.J.
Hail a major danger to aviation
It’s not the first time that commercial flights have had rough run-ins with severe hail.
In June 2018, an American Airlines flight made an emergency landing in El Paso, after flying into a severe hailstorm. Meteorologists expressed disbelief that the aircraft knowingly flew into such perilous and predictable conditions, the tempests shredding the nose cone and shattering the windshield. One meteorologist referred to the incident as potential “aeronautical malpractice.”
Last year, a China Southern Airlines Airbus A380 was dented by severe hail, which also destroyed the windshield.