Big Hailstorm from Sharon to Westbrook

Getting pockets of severe hail is not unusual  in Connecticut. Getting a several mile-wide swath of severe, and in some cases significant hail, from the New York border right down to coastal Middlesex County is unusual! The July 1 severe weather event was one of the more prolific hail producers I’ve seen in a few years. In fact the 2″ diameter hail reported in Killingworth and Clinton was the largest hail report in Middlesex County since 1995.

This is where the largest hail fell on July 1st. The red shading is where severe hail (1″ or greater in diameter) fell while the yellow shading is the area that received significant hail (2″ or greater in diameter). In general significant hail is enough to start causing property damage.

The evening 00z OKX sounding showed enough instability to produce severe thunderstorms (CAPE about 2000 j/kg). The 12z OKX sounding was fairly similar. The question was how much would the boundary layer dry out and during the day. As it turned out the boundary layer remained relatively moist yielding more impressive instability than forecast.

The 3 p.m. OKX Vad Wind Profile showed slightly more shear than modeled earlier in the day. More backed winds in the boundary layer not only helped keep the BL moist when combined with a somewhat more veered mid level flow than models had indicated resulted in a favorable shear/instability combination for supercells.

While thunderstorms were expected across the state thanks to a solid 500 mb shortwave rotating around a trough overhead a combination the somewhat more impressive instability and shear than modeled lead to a more impressive severe weather event than I originally anticipated. Almost all of the damage and sig severe reports came from one beast of a supercell that developed near the Catskills and moved into Connecticut. This is what the supercell looked like prior to dropping egg size hail in Watertown. CLASSIC!

0.5º ENX Base Reflectivity and Storm Relative Velocity at 2:48 p.m.

You can see here the strong mesocyclone at about 6500ft AGL (also visible at the 1.4º tilt at about 13,000ft AGL) and a V-Notch or what I prefer to call a Flying Eagle. This develops as air is forced around the core of the storm – indicative of a very powerful updraft. In addition three-body scatter spikes or hail spikes are visible from the storms large hail core. Other tilts show the 65 dbz level reaching 27,000ft AGL level. Yup… that’s a big hailer!

The supercell also showed another classic signature on doppler radar with strong storm top divergence (over 100 knots).

ENX 4.3º Storm Relative Velocity

This storm relative velocity image at about 35,000 feet AGL shows a strongly divergent flow along a radial near the top of the storm’s updraft. This is why you get a beautiful anvil from a mature cumulonimbus cloud. Generally over 100 knots of storm top divergence means big hail is fairly likely.

The supercell continued southeast right to the Sound, somewhat reminiscent but not as impressive as the June 1995 storm, eventually dropping golf ball and egg size hail in Clinton and Killingworth. Here are two vertical cross sections from the Sound north-northeast into Middlesex County. The y-axis is the vertical with each white line equal to 10,000 feet AGL.

While North Madison only reported hail to the size of quarters Killingworth and Clinton were slammed with significant/2″ diamater hail as the storm’s core collapsed. The suspended hail began to accelerate toward earth as the updraft weakened dropping the largest hail in Middlesex County since the 1995 super-hail supercell which dropped baseballs in Deep River and Essex.

Each severe weather event unique and this was no exception. Our models did not do a particularly good job with either boundary layer moisture, boundary layer veered winds (those 2 really go hand-in-hand) and mid level lapse rates. Using actual soundings, observations, and data like OKX’s Vad Wind Profile was vital in determining the severity of the threat once things developed. Though not particularly well forecast this event was fascinating to watch unfold on Doppler Radar.

A Look Back at the Biggest Hail Storm in Decades

[youtube=http://www.youtube.com/watch?v=sDRX-H9zNdc]

June 20, 1995 was a sultry and oppressive day. Temperatures in the 90s down to the water with dew points in the mid 70s drove heat index values above 100º. At the same time an elevated mixed layer (EML) moved overhead creating an exceptionally unstable and volatile air mass.

This weather balloon sounding from Albany shows the EML with very steep lapse rates between 650mb and 500mb. This means that the temperature above 10,000 feet was decreasing very rapidly with height (nearly 10ºC/km). With an oppressively hot and humid airmass in place the atmosphere was primed for a big explosion.

That explosion came north of the Massachusetts border when a supercell developed and began moving south.

What was remarkable about this storm was the amount of large hail it dropped during its trek through Connecticut. Baseball-sized hail was reported in 3 towns – Vernon, Manchester, and Deep River.

The relatively isolated storm (typical of EML days) continued to move due south and produced a gorgeous looking radar image. The outflow boundary of rain cooled air surged west across Hartford and Waterbury while a backdoor cold front that started near Boston around 10 a.m. finally caught up with the storm at the mouth of the Connecticut River.

The storm was the most intense over Deep River and Lyme, possibly due to the interaction with the backdoor cold front moving from east to west. Here’s an excerpt from the National Weather Service Storm Data publication.

A cold front moving across the area generated severe thunderstorms which produced large hail and gusty winds. Baseball-size hail lasted for up to 20 minutes in Deep River causing hundreds of thousands of dollars in damage. The hailstones broke hundreds of windows in buildings and automobiles, tore holes in roofs, dented siding and automobiles, and ruined gardens. Some automobiles were totaled.  In one historic building, the hail broke 25 windows, including a 100-year curved window. Thirty-two windows were smashed in an elementary school and its roof was damaged. Most of the damage was covered by insurance.

Here’s a 3-D cross section of the Deep River supercell as it crossed the Connecticut River. What is remarkable is how high the hail core of this storm was.

In fact this storm had 70 dbz radar echoes up to 30,000 feet with 60dbz up to 45,000 feet! That’s just wild. Here are some memories from people on my Facebook page.

 

People in Deep River still remember the hail storm vividly. Arlene Macmillan sent me these pictures of the hail (and hail damage) at her house from the 1995 storm. You can see ripped off leaves, broken shutters and windows, along the piles of hail stones. Arlene recalls the largest of the stones being billiard ball size (which is 2.25″ in diameter).

Courtesy: Arlene Macmillan / Deep River
Courtesy: Arlene Macmillan / Deep River
Courtesy: Arlene Macmillan / Deep River
Courtesy: Arlene Macmillan / Deep River
Courtesy: Arlene Macmillan / Deep River
Courtesy: Arlene Macmillan / Deep River

I asked Arlene a few questions about what she remembered from that day: The biggest stones were the size of billiard balls. I got my car into the garage before the hail started. My husband was around Middletown, driving home, when he saw a black cloud over Deep River. He arrived at home less than 5 minutes after hail stopped, and saw a foot high pile of leaves covering the ground. Nothing happened to his car, not even rain. We rented out another house behind ours. $3,000 in glass damage alone at both. Sorry I don’t have a picture of our house. It was sided with weathered cedar shakes and looked as though the house had been machine gunned.

While the storm had a broad mesocyclone and was rotating during its lifetime it never produced a tornado. The rotation remained broad and aloft and never came to the surface. The closest the storm came to becoming tornadic was south of Deep River in Essex and Old Saybrook when the rotation began to lower following the interaction with the backdoor cold front.

The overall setup was not conducive to tornadoes but certainly was conducive to mega-hail, particularly where the complex interaction between the supercell and a backdoor cold front was taking place over Lyme and Deep River.

Widespread Wind Damage

Connecticut Light and Power Outages

An unusually widespread wind damage event occurred across Connecticut earlier this evening with a maximum of 146,000 power customers in the dark. It appears widespread 45-60 mph wind gusts were common with pockets of 60-70 mph wind gusts where tree damage and power outages are more concentrated.

I can’t recall a severe weather event producing this many power outages in recent memory which is partially due to the fact this storm impacted virtually every town from Salisbury to Stonington.

There were a few areas were heavier pockets of damage occured including weste central Connecticut (New Milford, Brookfield, Warren, Woodbury), north central Connecticut (Enfield, Suffield), northeast Connecticut (Willington, Asheford, Eastford, Pomfret, Woodstock), and along the shoreline (Westbrook, Old Saybrook, Essex, Clindon, Deep River, Chester, and Killingworth).

Before these storms became prolific wind producers they were prolific hail producers. Here’s a shot Jennifer and Michael sent in from Colebrook.

Hail in Colebrook