NWS WFO Philadelphia/Mt. Holly, NJ The 08 June 2016 Severe Weather Event in the Mid Atlantic NROW XVII November 3, 2016 Jared Klein NWS WFO Philadelphia/Mt. Holly, NJ

90 Severe Thunderstorm Wind Events (Source: NOAA Storm Data) Motivation High impact event Convective wind gusts 60–75 mph lead to extensive wind damage; most widespread in SE PA & S NJ Numerous downed trees and wires 90,000+ power outages Isolated structural damage to buildings Additional 50–60 mph gust reports south of convective line in E MD & DE 90 Severe Thunderstorm Wind Events (Source: NOAA Storm Data) Roof torn off. Camden County College. Source NJ.com Partial roof collapse in AC apt bldg. Source PressofAtlanticCity.com

Motivation High impact event Extent of severe weather event under predicted by both NWP models and human forecasters SPC Day 1 Outlook and Prelim. Reports Valid: 1300 UTC 06/08/2016 to 1200 UTC 06/09/2016 SPC Mesoscale Discussion (issued 1550 UTC 06/08/2016)

Motivation High impact event Extent of severe weather event under predicted by both NWP models and human forecasters Unique players on multi scales

Motivation High impact event Extent of severe weather event under predicted by both NWP models and human forecasters Unique players on multi scales Limited predictability of severe weather in HSLC setups previously documented

1500 UTC Surface Analysis

1500 UTC SPC Mesoanalysis SBCAPE/SBCIN 0-6 km Shear (kt)

0.5° Base Reflectivity (Z), Lightning and SVR Polygons from WFO PHI QLCS Signatures KDIX Radar Animation: 1329–1838 UTC 8 June 2016 0.5° Base Reflectivity (Z), Lightning and SVR Polygons from WFO PHI 0.5° Base Velocity (V) Note: Dover, DE WSR-88D (KDOX) radar was out during the 8 June 2016 event

Using MRMS Data to Assess Vertical Storm Structure Low-topped convection organized/intensified as it moved downstream through E PA, C/NE MD, DE & NJ late morning & early afternoon Increasingly well-defined comma structure provides evidence of a deepening mesolow Weak (< 30 dBZ) echoes (w/ embedded 40 dBZ convective cells) at -10°C height implies evaporative cooling occurring within the mid-tropospheric jet 50 dBZ Echo Top (ft MSL) ~ Updraft core height 30 dBZ Echo Top (ft MSL) ~ Storm top height 18 dBZ Echo Top (ft MSL) ~ Cloud top height Isothermal Reflectivity at -10°C ~ Mid-level jet

1200 UTC 8 June 2016 RAOB Sounding at KPIT Where did these damaging winds originate from and how did they reach the surface? ~675-525 mb layer: Represents conditionally unstable bottom portion of the mid-tropospheric jet 50-70 kt westerly winds ~6.9 C/km lapse rate Dry layer (RH <50%) -10 ˚C

HRRR BUFKIT Sounding at Millville, NJ (KMIV) Valid at 1600 UTC 08 June 2016 (F001) Valid at 1700 UTC 08 June 2016 (F002)

Multi-scale Interactions Two Discrete Swaths of Damage Thunderstorm wind damage: Coincides w/ low-level jet Non-thunderstorm wind damage: Coincides w/ mid-level jet CCB or Sting Jet? Gust front? Both loops: GOES E WV Satellite Imagery, MRMS Composite Z (>30 dBZ) and CG lightning strikes. UL image: 700-500 hPa wind speeds (every 5 kt w/ thicker contours starting at 55 kt) from HRRR analysis. LR image: 850 hPa wind speeds (every 5 kt w/ thicker contours starting at 30 kt) from HRRR analysis

Sting Jet Structure 1500 UTC Surface Analysis L H

Cloud Structure and Role of Boundary Layer Heating 7 7.5 8 8.5 9 9.5 10 GOES Visible Satellite Imagery and 0–3 km AGL Lapse Rates (°C km-1) using RAP Analysis

Sting Jet Checklist Similarities Differences Frontal fracture w/ bent-back warm front(s) Descending mid-tropospheric jet streak near base of trough Dry slot wrapping around base of trough Damaging winds near tail of comma head Browning (2004) and Clark et al. (2005) proposed that evaporative cooling may also enhance the descent rate of sting jet airstreams* Strong surface low displaced well to the north over SE Canada No rapidly deepening surface low closer to the damaging wind event over the northern mid Atlantic Comma head structure didn’t become well defined until system moved offshore (several hours after the event on land) *Challenge to quantitatively differentiate generation of damaging wind gusts from convective processes vs. sting jet mechanism in an observational study

HRRR BUFKIT Sounding at KMIV HRRR BUFKIT Sounding at KMIV Model Review HRRR BUFKIT Sounding at KMIV Valid at 1600 UTC 8 June 2016 (F001) HRRR BUFKIT Sounding at KMIV Valid at 1700 UTC 8 June 2016 (F002) Notes: HRRR struggled to consistently capture the strength of the low-level wind field during the morning runs. Meanwhile, HRRR runs before 1300 UTC 8 June 2016 inadequately captured the strength of the mid-level jet and showed run-to-run inconsistencies

NAM BUFKIT Sounding at KMIV GFS BUFKIT Sounding at KMIV Model Review (cont.) NAM BUFKIT Sounding at KMIV Valid at 1700 UTC 8 June 2016 (F005) GFS BUFKIT Sounding at KMIV Valid at 1800 UTC 8 June 2016 (F006) Note: Forecast soundings above correspond to the time closest to the peak of the low-level wind field according to each respective model runs

NCAR Ensemble Prediction System Prob of Hourly Max Sfc Wind Speed ≥ 20 ms-1 w/in 25 miles (1800 UTC 08 June 2016) Ensemble Max Sfc Wind Speed (1800 UTC 08 June 2016) Source: NCAR CAM Ensembles from 0000 UTC 08 June 2016 Run (https://ensemble.ucar.edu/)

Takeaways Complex multi-scale interactions contributed to a significant severe weather episode on 8 June 2016.  The descending mid-tropospheric jet was found to contain several characteristic similarities (e.g., frontal fracture and dry air intrusion) and differences (e.g., absence of a deep surface cyclone located nearby) with sting jets.  Utility of rapid refresh hi-res CAM in near term Importance of having a dedicated forecaster assigned to a meso-analyst role. Can be a difference maker in picking out many of the subtle observational details that models may have missed. Use observations to modify soundings and compare to near-term forecast soundings to identify possible mechanisms for transport of strong winds down to the surface. 

QUESTIONS? COMMENTS? Jared.Klein@noaa.gov

References Oscar Martínez-Alvarado, Laura H. Baker, Suzanne L. Gray, John Methven, and Robert S. Plant, 2014: Distinguishing the Cold Conveyor Belt and Sting Jet Airstreams in an Intense Extratropical Cyclone. Mon. Wea. Rev., 142, 2571–2595, doi: 10.1175/MWR-D-13-00348.1. Browning, K. A., 2004: The sting at the end of the tail: Damaging winds associated with extratropical cyclones. Quart. J. Roy. Meteor. Soc., 130, 375–399, doi:10.1256/qj.02.143. Clark, P. A., K. A. Browning, and C. Wang, 2005: The sting at the end of the tail: Model diagnostics of fine-scale three-dimensional structure of the cloud head. Quart. J. Roy. Meteor. Soc., 131, 2263–2292, doi:10.1256/qj.04.36. David M. Schultz and Joseph M. Sienkiewicz, 2013: Using Frontogenesis to Identify Sting Jets in Extratropical Cyclones. Wea. Forecasting, 28, 603–613, doi: 10.1175/WAF-D-12-00126.1.