The Bethel/Newtown tornado on May 16, 2007 was a classic Quasi Linear Convective System Tornado in Connecticut. The tornado formed on the northern side of a bow echo that had developed over Westchester County.
- Time: 20:03 UTC / May 16, 2007
- Towns: Bethel & Newtown
- Strength: EF-1
- Path Length: 4.5 Miles (discontinuous)
- Max Gate-to-Gate Shear (ΔV): 48 knots
- Storm Type: QLCS (Forward Inflow Notch Tornado)
The tornado was part of a bow echo that produced 2 microbursts in Redding and Middletown and a swath of damaging winds reported in Danbury, Newtown, Easton, Southbury, Bethany, and Cromwell.
Here’s how Storm Data describes the damage in Newtown from the tornado that touched down on the Newtown/Bethel town line.
An EF-1 tornado touched down near the Rock Ridge Country Club, just north of Route 302. It traveled east to northeast and passed just south of the main town center in Newtown. The tornado passed across Route 25, South Main Street and lifted along Sugarloaf Road, between Toddy Hill Road and Berkshire Drive.
High winds damaged many trees which fell through houses and cars along this path, which was approximately 4.5 miles with an average path width of 100 yards. There was a well defined narrow track of discontinuous damage, where the damage converged in toward the track center. Eye witness reports of funnel clouds were observed.
Storm data lists the touchdown time at 20:08 UTC which seems about 5 minutes too late based on radar data. The actual touchdown was likely around 20:03 UTC.
The weather map on May 16, 2007 was fairly typical for a severe weather day in Connecticut. A fairly sharp trough in the Great Lakes was sliding east with weak height falls over Connecticut during the afternoon.
The morning weather balloon launch in Albany showed modest instability with 1182 j/kg of SBCAPE with strong deep layer shear. 0-6km shear was on the order of 57 knots in ALB and on Long Island at OKX 0-6km shear was 47 knots. These values are certainly supportive of storm organization.
The surface weather map was a bit complex as is typical for early in the severe weather season. A cold front was moving through the Hudson River Valley with temperatures in the 80s out ahead of the front from New Jersey through White Plains, Danbury, and Hartford. The warm sector was quite small with a stalled warm from from North Adams, MA to Worcester southeast toward Cape Cod. North of that front northerly and northeasterly winds off the cold North Atlantic had dropped temperatures into the 50s across coastal Massachusetts. You can see a tight temperature gradient as well with 79F reported in Taunton, MA and 54F in nearby Plymouth, MA.
The dew point depression in Danbury prior to tornadogenesis at 19z was 25ºF which would imply a fairly high LCL. The relatively dry air near the surface and high LCL is somewhat surprising for a tornado day in Connecticut. What is not surprising is the number of severe wind reports given the large temperature/dew point spread and what we can infer is a sizable amount of DCAPE.
Having toured the damage in Newtown following the tornado the vortex appeared to only make contact with the ground on hill tops – several hundred feet above the average elevation along the track. Given relatively high LCLs this makes sense – that the tornado struggled through its discontinuous 4.5 mile track.
Storm Scale Environment / Radar Analysis
Radar indicates the storm became a mature bow echo approximately 30 minutes before tornadogenesis in Rockland and Westchester Counties near and north of the Tappan Zee Bridge. A large swath of 50-60 knot winds appeared on radial velocity from Peeksille to Tarrytown at 19:34 UTC.
North of the bow echo’s apex just north of Ossining there’s approximately 40 knots of gate-to-gate shear a full 30 minutes before tornadogenesis. As the storm moved northeast it became tornadic on the Bethel/Newtown line.
There are some signs of a forward inflow notch developing by 19:58 and by 20:07 that becomes much better established with a developing kink in the QLCS north of the bow’s apex. The low level mesocyclone weakens by 20:11 UTC shortly after the tornado lifts while the reflectivity signature remains quite impressive with a notable forward inflow notch (the classic S shape).
Low level delta V maxed out at 48 knots with this storm at approximately 2,500 ft AGL immediately before tornadogenesis. The mesocyclone associated with this storm was fairly deep for a QLCS spin-up. Over Bethel the mesocyclone was coherent from 2,500 ft AGL with the 48 knot gate-to-gate delta V up through 16,000 feet. The storm weakened as it moved through Newtown with the mesocyclone only apparently from 2,500 ft AGL to 9,000 ft AGL by the time it reached the Housatonic River.