Improving Tornado Detection and Lead Time: The July/August, 2018 Tornadoes in Southern New England Joseph W. DelliCarpini NOAA/NWS Boston/Norton, MA Jonathan E. O’Brien UAlbany NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Motivation and Objectives Verification showed a need to improve tornado detection and lead time in southern New England (BOX CWA) Improve understanding of synoptic and mesoscale patterns associated with these tornadoes in order to raise situational awareness Improve recognition of radar signatures that may indicate a tornado is developing Development of a “detection scale” to assist forecasters in the warning decision making process NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Methodology Update of previous study (Brooks et al, 2008) which included tornadoes in the WFO BOX County Warning Area from 1997 to 2006 Reviewed 17 of the 22 tornadoes between 2007 and 2017 Most were EF-0 (9) or EF-1 (6) One EF-2 (Chelsea/Revere, MA in July, 2014) One EF-3 (Westfield/Springfield/Monson/Brimfield/Charlton in June, 2011) Data Sources North American Regional Reanalysis (NARR) for synoptic environments SPC Mesoanalysis Archive for mesoscale environments GR2Analyst for radar data NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Synoptic Classification: Type A Closed 500 hPa low over Ontario or Hudson Bay Divided into 3 sub-categories based on closed low placement 9 of 17 events fall in this group; “Dominant” SNE tornado pattern A3 A1 A2 NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Type A Example June 1, 2011 Westfield-Springfield-Monson- Brimfield-Charlton EF-3 NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Synoptic Classification: Type B-1 (Zonal Jet) Open trough near the western Great Lakes with a shortwave near New England 5 of 17 events (2 of 5 were B-1) June 23, 2015: Wrentham, MA EF-0 NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Synoptic Classification: Type B-2 (Disjointed Jet) Open trough near the western Great Lakes with a shortwave near New England 5 of 17 events (3 of 5 were B-2) September 1, 2013: Shutesbury, MA EF-0 NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Synoptic Classification: Type C Deep trough over the East-Central US Strong right entrance jet positioning 2 in this study July 1, 2013: Enfield, CT EF-1 NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Synoptic Classification: Type E Cold pool aloft. 850-500 hPa temperatures 8-10°C colder than in other events Steep lapse rates, other parameters less favorable May 9, 2013: Stoughton, MA EF-0 NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Storm-Relative Helicity Instability and Shear Surface-Based CAPE Storm-Relative Helicity (0-3 km) Type A and B: Usually 1000 J Kg-1 or more but can vary widely Type C: 600 J kg-1 Type D: 500 J kg-1 [remnants of Allison (2001) from prior study] Type E: 350 J kg-1 Types A, B, C, and D: 150 m2s-2 or higher, can be lower in A and B if CAPE is high Type E: 100 m2s-2 or less Some events with lower 0-3km SRH make up for it by concentrating most SRH in the lowest 1 km 0-1km SRH >=150 m2s-2 -or- 0-500m SRH >=95 m2s-2 is especially conducive to tornadoes NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Moisture: Dew Point and Precipitable Water Types A, B, C, and D: Average 20-23°C (68-73°F) Type E: Average 10-15°C (50-60°F) Types A and B: Average 43 mm (1.7”) Type C: Average 48 mm (1.9”) Type D: Average 38 mm (1.5”) Type E: Average <=25 mm (<=1”) Higher moisture = Lower LCL NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Summary of Synoptic and Mesoscale Environments Tornadoes in southern New England formed in one of a few prevailing synoptic patterns Closed 500 hPa lows accounted for a majority of the events Mesoscale parameters can vary widely and often “trade” with one another CAPE and 0-3km shear, in particular “Tropical” moisture and presence of a surface boundary is necessary Stronger tornadoes are rare and need high CAPE and shear (6/1/11) Similar to environments in the Plains 0-1 km SRH (150+) and especially 0-500 m SRH (95+) seemed to be the best discriminators between tornadic and non-tornadic events NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Tornado Detection Scale Goal: Provide more accurate and consistent guidelines to help forecasters issue Tornado Warnings Empirical scale based upon past tornado events and “false alarms” Largely based upon radar signatures Rotational velocity [Vr = (Inbound+Outbound)/2] Normalized Rotation (“NROT”) Also includes some environmental factors Highly recommend VCP 212 with SAILS 3 for one-minute low level scans! NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Boston/Norton, MA NROW XIX Albany, NY NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Testing The Scale: Detection Radar data for 21 of 22 tornadoes from 2007-2017 4 score as a zero Not detected by radar, including two “fair weather” tornadoes 3 score below a 9 (2 below a 5) Marginal cases 14 score as a 9+ at or before touchdown: “Reasonably detectable” cases POD = 0.67 NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Testing The Scale: False Alarms Data for 23 “False Alarm” Tornado Warnings reviewed from 2007-2017 13 of 23 would have scored 9+ on the scale Shows potential for lowering false alarm rate (by 43% in this case) “Control Cases” Reviewed a similar number of storms that did not have Tornado Warnings issued, did not produce tornadoes, but would have scored 9+ on the scale There were only a couple of cases NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

BOX Tornado Verification Statistics 2007-2017 POD = 0.52 FAR = 0.81 Average Lead Time = 9 minutes 2018 (July/August) POD = 0.60 FAR = 0.20 Average Lead Time = 10 minutes 2018 POD = 0.67 FAR = 0.54 National GPRA Goals: POD 0.72 FAR 0.71 Lead Time 13 minutes NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Ashford, CT EF-0 Tornado: 1957 UTC July 17 0.5 REF and SRM NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Boston/Norton, MA NROW XIX Albany, NY NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Douglas, MA EF-1 Tornado: 0627 UTC July 26 0.5 REF and SRM NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Boston/Norton, MA NROW XIX Albany, NY NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Woodstock, CT & Dudley/Webster, MA Tornadoes: 4 Aug Woodstock, CT 0.5 SRM 1334 UTC Dudley/Webster, MA 0.5 SRM 1356 UTC NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Woodstock, CT Boston/Norton, MA NROW XIX Albany, NY NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Dudley/Webster, MA Boston/Norton, MA NROW XIX Albany, NY NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

Future Work Update the tornado database with the 8 tornadoes in 2018: Ashford, CT EF-0 (July 17) Douglas, MA EF-1 (July 26) Upton, MA EF-1 (July 26) Woodstock, CT EF-0 (August 4) Dudley/Webster, MA EF-1 (August 4) Mansfield, CT EF-0 (October 2) North Providence/Lincoln, RI EF-1 (October 23) Norton, MA EF-1 (October 23) Hardwick, MA EF-1 (October 23) Hubbardston, MA EF-0 (October 23) Woods Hole, MA EF-0 (October 29) Continue to test and tweak the detection scale based upon recent events Share with neighboring WFOs and add nearby events NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY

References *Brook, D. 2008: Reanalysis of Southern New England Tornado Events from 1997–2006 to Improve Forecast Verification, Lyndon State College, 32   *Brook, D., J. DelliCarpini, and D. Vallee, 2008: WFO Taunton Southern New England Tornado Playbook. 11 pp. *Gibson Ridge Software, 2013: GR2Analyst Version 8.15.11.9038. *LaPenta, K. D., L. F. Bosart, T. J. Galarneau Jr., and M. J. Dickinson, 2005: A Multiscale Examination of the 31 May 1998 Mechanicville, New York, Tornado. Wea. Forecasting, 20, 494–516. *Mesinger, F. et. al., 2006: North American Regional Reanalysis. Bull. Amer. Meteor. Soc., 87, 343–360. *National Weather Service Weather Forecast Office Louisville, KY, cited 2017: What is Dual- Polarization Radar and What Can it do for Me? [https://www.weather.gov/media/lmk/soo/Dual_Pol_Overview.pdf]  *Rasmussen, 2003: Refined Supercell and Tornado Forecast Parameters. Wea. Forecasting, 18, 530-535 NATIONAL WEATHER SERVICE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Boston/Norton, MA NROW XIX Albany, NY