Alert archive / Massachusetts / Tornado Watches in 2020
Tornado Watch 417
The Storm Prediction Center issued this tornado watch at Aug 4, 2020, 12:43 PM EDT for 4 states. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 4, 2020, 12:43 PM EDT (16:43 UTC)
- Expired
- Aug 4, 2020, 6:48 PM EDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Strongest gust expected
- 70 kt
All 32 counties
Capitol Planning Region, CT, Northeastern Connecticut Planning Region, CT, Northwest Hills Planning Region, CT, Barnstable County, MA, Berkshire County, MA, Bristol County, MA, Dukes County, MA, Essex County, MA, Franklin County, MA, Hampden County, MA, Hampshire County, MA, Middlesex County, MA, Nantucket County, MA, Norfolk County, MA, Plymouth County, MA, Suffolk County, MA, Worcester County, MA, Albany County, NY, Columbia County, NY, Dutchess County, NY, Greene County, NY, Rensselaer County, NY, Saratoga County, NY, Schenectady County, NY, Ulster County, NY, Warren County, NY, Washington County, NY, Bristol County, RI, Kent County, RI, Newport County, RI, Providence County, RI, Washington County, RI
The radar
The Albany radar (KENX), 119 km from the middle of the area, began a volume at 16:42 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 50%
- One or more EF2 to EF5 tornadoes
- 20%
- Ten or more severe wind reports
- 30%
- One or more gusts of 65 knots or more
- 30%
- Ten or more severe hail reports
- 5%
- One or more hailstones of 2 inches or more
- 5%
- Six or more combined severe hail and wind reports
- 40%
Warnings issued inside it
6 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 4, 1:38 PM EDT | Tornado Warning | ALY | Albany, Columbia, Rensselaer | 26 min |
| Aug 4, 1:57 PM EDT | Tornado Warning | BOX | Middlesex, Worcester | 25 min |
| Aug 4, 2:59 PM EDT | Tornado Warning | BOX | Capitol Planning Region | 27 min |
| Aug 4, 3:45 PM EDT | Flash Flood Warning | ALY | Albany, Greene, Schoharie, Ulster | 3 hr |
| Aug 4, 4:03 PM EDT | Flash Flood Warning | ALY | Albany, Greene, Rensselaer, Saratoga, Schenectady, Schoharie | 3 hr |
| Aug 4, 4:58 PM EDT | Tornado Warning | BOX | Middlesex, Worcester | 21 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Albany, NY (KALY), launched 12:00Z, 4.7 hours before the alert went out and 105 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 71 J/kg
- Mixed-layer CIN
- -67 J/kg
- Mixed-layer LCL
- 818 m above ground
- 0-6 km bulk shear
- 41 kt
- 0-1 km storm-relative helicity
- 135 m²/s²
- 0-3 km storm-relative helicity
- 223 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.6
The text
As transmitted.
740 WWUS20 KWNS 041641 SEL7 SPC WW 041641 CTZ000-MAZ000-NHZ000-NYZ000-RIZ000-VTZ000-CWZ000-050100- URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 417 NWS Storm Prediction Center Norman OK 1240 PM EDT Tue Aug 4 2020 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of northern Connecticut Massachusetts southern New Hampshire eastern New York northern Rhode Island southern Vermont Coastal Waters * Effective this Tuesday afternoon and evening from 1240 PM until 900 PM EDT. * Primary threats include... A few tornadoes possible Isolated significant damaging wind gusts to 80 mph possible SUMMARY...In association with the north-northeastward progression of Isaias, thunderstorm activity will form and spread northward across the region this afternoon through early evening, in an environment conducive to the development of a few tornadoes. The tornado watch area is approximately along and 50 statute miles north and south of a line from 35 miles north northwest of Poughkeepsie NY to 30 miles east southeast of Boston MA. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU7). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Tornado Watch means conditions are favorable for tornadoes and severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. && OTHER WATCH INFORMATION...CONTINUE...WW 416... AVIATION...Tornadoes and a few severe thunderstorms with hail surface and aloft to 0 inches. Extreme turbulence and surface wind gusts to 70 knots. A few cumulonimbi with maximum tops to 450. Mean storm motion vector 17035. ...Kerr
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 4, 6:45 AM EDT | Mesoscale Discussion | SPC | 3 hr | |
| Aug 4, 7:23 AM EDT | Tornado Watch | SPC | Greater Bridgeport Planning Region, Lower Connecticut River Valley Planning Region, Naugatuck Valley Planning Region, Southeastern Connecticut Planning Region | 9 hr |
| Aug 4, 11:13 AM EDT | Mesoscale Discussion | SPC | 92 min | |
| Aug 4, 11:34 AM EDT | Mesoscale Discussion | SPC | 86 min | |
| Aug 4, 3:05 PM EDT | Mesoscale Discussion | SPC | 85 min | |
| Aug 4, 5:44 PM EDT | Mesoscale Discussion | SPC | Essex, Middlesex, Suffolk | 2 hr |
Nearby
Tornado Watches in Massachusetts, 2020Tornado Watches in New York, 2020Tornado Watches in Rhode Island, 2020Every tornado watch in 2020
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.