North Haven Tornado

It would be fair to say I wasn’t expecting severe weather today but I also wasn’t surprised to see a tornado hit North Haven. We had a somewhat unstable environment and a bit of low level wind shear. We get these setups with a fair amount of regularity in the summer and once in a great while they’re able to produce a tornado. Today was one of those days.

On Monday I sent this Tweet out about the conditional severe weather threat.

What transpired was this. Shortly after 1 p.m. we had two mini-supercells develop – one over New Haven and another over Long Island Sound. The storm that moved toward North Haven was rotating – and right around the threshold where you would have to be concerned about a developing tornado.

I sent out this Tweet at 1:31 p.m. as the storm moved through Hamden. The National Weather Service issued a Severe Thunderstorm Warning that included a “tornado possible” tag but the rotation was not quite strong enough to issue a tornado warning but boy was it close!

The rotation shown by this storm (approximately 40-50 knots of delta-V) is quite close to the median value for all northeast tornadoes in recent years. Here’s a look at the radar data from the storm that really developed rotation over the Westville section of New Haven and produced the tornado over the Quinnipiac River on the Hamden/North Haven line.

OKX Radar 1705 UTC
OKX Radar 1716 UTC
OKX Radar 1725 UTC
OKX Radar 1727 UTC
OKX Radar 1735 UTC

It does appear that the lofted debris from this tornado produced a subtle tornado debris signature. This means that our radar was able to detect tornado debris more than 2,000 feet in the air tumbling through the cloud. Incredible!

The 16z HRRR sounding for New Haven does show an environment that was favorable for tornadoes.


Here you can see about 200 m2/s2 storm relative helicity in the lowest 3km of the atmosphere along with sufficient surface-based instability. What is important to note here as well is the very low lifted condensation level (LCL) at about 900 feet above the ground! This is a somewhat classic setup for weak/spin-up tornadoes in southern New England with a super humid and somewhat sheared atmosphere.

The SPC mesoanalysis shows this as well with just shy of 200 m2/s2 effective storm relative helicity on the Connecticut shoreline.

This tornado is a great example of how important it is to be aware when these low probability/high impract severe weather events can occur. There was no tornado watch in effect – in fact there was no part of Connecticut even mentioned by the Storm Prediction Center as an area where severe storms were expected (not even a marginal risk). Occasionally, a small area of sufficient shear and instability can overlap on an otherwise unimpressive severe weather day and result in a spinner. Thankfully, no one was hurt.


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