Live Blog: Severe Weather in the Northeast

Updates

8:25 pm: After that rapid spurt of activity with numerous tornado-warned cells, things rapidly calmed down. Nonetheless, severe weather remains possible this evening until the frontal boundary moves offshore. An isolated tornado is still not out of the question. Surely many NWS offices will have a busy time with damage surveys tomorrow.

6:25 pm: Possible tornado near Lincoln, RI. From WPRI’s TJ Del Santo.

6:15 pm: Incredible video from a tornado-warned storm near Garnet Valley, PA.

6:04 pm: Tornado Warning for areas just south of Philadelphia in the New Jersey suburbs. Strong rotation on that cell.

6:03 pm: Severe Thunderstorm Warning issued for the New York City metropolitan area.

5:53 pm: 

5:51 pm: Another cell has gone tornado-warned, just northeast of Baltimore. From my count there are 5 tornado warnings on the go right now.

5:40 pm: Tornado warning also issued for Chester County, PA as well.

5:37 pm: Just like that, a third tornado-warned cell, this one near Meredith, NH. It is getting active out there!

5:30 pm: Now two cells to be concerned about. The Woonsocket cell is rotating strongly (right image), and a new tornado-warned cell has formed over northern New Hampshire near the Canadian border (left and center images, the left image showing a debris signature). Both are likely producing tornadoes right now. Take cover if in the path of either storm!

CINx2fYWwAAfAJf CINx2SKWEAANbJm CINxaHoWgAAB7z3

5:16 pm: Woonsocket cell now tornado-warned for strong rotation. Take cover if in the path!

5:10 pm: There are several cells worth watching. One with close interest is this cell north of Providence which has developed upper-level rotation and a possible hook echo. A Severe Thunderstorm Warning is in effect on this cell.

CINtVB3WgAEwm77

Radar image of the Woonsocket cell (from Twitter user @wxfanmatt) at 5:08 pm EDT.

4:10 pm: Action appears to be ready to shift southward as well. The SPC has introduced a Severe Thunderstorm Watch (#346) for the Mid-Atlantic south of the existing watches. This includes the Delmarva, Jersey Shore, Philadelphia, Baltimore, Washington DC, Richmond, Roanoke and the central Appalachians. Damaging wind is the main threat, but hail and perhaps an isolated tornado are also possible.

3:50 pm: As expected, a new Tornado Watch (#345) has been issued, covering most of southern New England northward through Maine and New Hampshire. A few tornadoes are most likely in this area.

3:40 pm: A new Severe Thunderstorm Watch, #344, has been issued for the Hudson Valley, New York City region and most of Vermont. Damaging winds and large hail are both threats, and isolated tornadoes are also mentioned.

2:50 pm: The much-advertised second round of severe weather looks to be developing along both the cold front and an associated upper trough spanning from the St. Lawrence Valley through the Appalachians. This is where a tornado risk is likely to develop this afternoon. Expect a Tornado Watch to be posted for New England, eastern New York and the NYC region soon.

1:55 pm: The SPC has mentioned that a Severe Thunderstorm Watch is likely to be issued by mid-afternoon for the mid-Atlantic region south of Watch #342, including Baltimore and Washington DC. Damaging winds are the main threat, with large hail also possible.

Original Post

It’s a very active day in the Northeast and Mid-Atlantic as severe weather of all types is already underway and is expected to only intensify this afternoon. Nearly the entire region is at risk.

The Storm Prediction Center has maintained an enhanced threat for severe weather (current Day 1 outlook) from southern New England through nearly the entire Mid-Atlantic and back into the central Appalachians. Damaging wind is likely the most significant threat for southern areas. In New England and eastern New York, a few to several tornadoes are possible as well. Given the shear parameters in place, I wouldn’t even rule out one or two strong tornadoes.

NAM_221_2015062312_F09_EHI_1000_M

Low level energy-helicity index EHI) at 5:00 pm EDT June 23, 2015. Yellow areas are more conducive, red areas quite conducive for tornadic development.

NAM_221_2015062312_F09_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND

Storm relative helicity at 5 pm EDT June 23, 2015. Most areas are marginal in terms of spin, but areas farther east and other isolated spots are more conducive.

That said, to get to full potential, the shear and spin in the atmosphere right now must sustain itself through peak heating this afternoon. A Severe Thunderstorm Watch (#341) is in effect until 4 pm for southern New England and the New York City region, and another watch (#342) is in effect until 7 pm for much of Pennsylvania and New Jersey away from the NYC region. The northern areas will likely be placed into a Tornado Watch later this afternoon, and additional watches are likely in the Mid-Atlantic including the Baltimore and DC areas.

The area of greatest shear is farther north in northern New England and southeastern Canada, however, instability is lacking there. We will definitely keep an eye on that area as well.

As for timing, my best guess for the greatest threat is:

  • Northern New England – Mid-afternoon (conditional on atmospheric destabilization)
  • Southern New England – Late afternoon west, early evening east
  • New York City region – Late afternoon
  • Philadelphia/Delaware Valley/South Jersey – Late afternoon west, early to mid-evening east
  • Baltimore and DC regions – Early evening north/west, mid to late evening south/east

Stay here all day for updates…and remember, safety is most important.

Forecaster Craig Ceecee

Leave a Reply