The 22 May 2014 Duanesburg, NY, Tornadic Supercell Brian Tang, Matt Vaughan, Kristen Corbosiero, Ross Lazear, & Lance Bosart University at Albany, SUNY Tom Wasula, Ian Lee, & Kevin Lipton National Weather Service, Albany, NY December 1, 2015 Capital Region AMS Local Chapter Meeting CSTAR

Brian, Ross, and Kristen’s Excellent Adventure (with a Tornado) December 1, 2015 Capital Region AMS Local Chapter Meeting CSTAR

x 1500 1600 1700 1800 1900 2000 UTC 1515 UTC: Initiation occurs in the Adirondacks

Hey Ross, there’s a right mover coming toward us! x 1500 1600 1700 1800 1900 2000 UTC 1700 UTC: Cell moves toward the SSE and intensifies 0—6 km shear vector Hey Ross, there’s a right mover coming toward us! I love supercells!

It’s still there! Let’s go chasing! x 1500 1600 1700 1800 1900 2000 UTC 1830 UTC: Supercell continues to intensify in the Mohawk Valley It’s still there! Let’s go chasing! Let’s go! I’m joining!

x 1500 1600 1700 1800 1900 2000 UTC 1920 UTC: 4” (10 cm) hailstone in Amsterdam, NY, tying NY state record Source: CBS

Reflectivity Differential Reflectivity 1905 UTC

Source: NOAA

Signature for large hail Reflectivity Differential Reflectivity >70 dBz reflectivities ZDR around zero Signature for large hail >70 dBz reflectivities ZDR around zero Wet Bulb -> Zero 1905 UTC

Differential Reflectivity >70 dBz reflectivities ZDR around zero >70 dBz reflectivities ZDR around zero Wet Bulb -> Zero 1905 UTC

x 1500 1600 1700 1800 1900 2000 UTC 1933 UTC: Tornado touches down near NY-30 in Montgomery County @#$^&#)&*!!! @#*(*&@#$!!! Um….guys?!

x 1500 1600 1700 1800 1900 2000 UTC 1945 UTC: Tornado reaches peak strength, producing EF-3 damage in Duanesburg/Delanson, NY. Mostly <EF-2 damage. Matt Vaughan Source: Times Union

Correlation Coefficient AT 351 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO INDICATE A TORNADO ON THE GROUND WITH A TORNADIC DEBRIS SIGNATURE JUST SOUTH OF DUANESBURG IN SCHENECTADY COUNTY Reflectivity Correlation Coefficient Low correlation coefficients Pronounced hook echo and debris ball 1951 UTC

What made this event unique? Significant (record-tying hail, only 8 F/EF-3+ tornadoes in NY state since 1985) Isolated in Albany CWA Unexpected from a predictive skill standpoint What synoptic/mesoscale ingredients came together to make this event possible? SPC

Weak synoptic forcing. N-S speed gradient in 500-hPa winds. Surface relative vorticity (x 10-5 s-1) CAPE (J kg-1) heights temperature mean sea level pressure

Elevated mixed layers advected over region. 1200 UTC

1815 UTC Cool, maritime airmass Warm, unstable airmass L H

Analogous to thermal contrast that forces a sea breeze

1530 UTC m 16° C 1009.2 hPa 18° C 1009.1 hPa 36 km between KSCH and KYN0, 50 km between KALB and KNY0. 17.8° C 1009.2 hPa

1830 UTC m 20° C 1006.7 hPa 22° C ? 18° C 1008.7 hPa 17.2° C 1008.8 hPa

1830 UTC m Δp=2 hPa L H ageostrophic wind

moisture flux convergence 1830 UTC m moisture flux convergence

Modified sounding yields ~2000 J kg-1 of CAPE 1200 UTC

CAPE maximized in the Mohawk Valley due to moisture flux convergence and insolation 1800 UTC CAPE and Streamlines J kg-1 As a result, surface-based… Local area of >2000 J/kg with local maxima right along the Mohawk River of >2500 J/kg. Get a similar value modifying the Buffalo sounding with local surface observations in the Mohawk Valley. Note that in the Hudson Valley, CAPE is generally <1000 J/kg. So, here we have an example of where mesoscale inhomogeneities can cause large variations in instability across small distances. After 1920 UTC, the tornadic phase of the supercell began as the storm crossed from Montgomery to Schenectady counties, around the time when it crosses an instability/thermal gradient. The cool side of the thermal gradient was characterized by low LCLs, 400-600 m AGL, which was the 1st ingredient favorable for a tornado. mesocyclone track X 1800 UTC position

moisture flux convergence Higher wind shear Mohawk Valley and south Elevated mixed layer Moisture flux convergence overlapping with surface insolation to generate instability Supercell dynamics EML moisture flux convergence higher wind shear

Large low-level shear along the stationary front 1900 UTC 0-1 km Shear A B 2nd ingredient is the low-level shear. Vectors give the 0-1 km shear, shading is the 3 hr change in the shear magnitude from 1600 to 1900 UTC (red increase, blue decrease). Shear increases to a values at or above 10 m/s, especially in the area where the supercell becomes tornadic. Southeasterlies/easterlies undercutting westerlies. 0-1 km layer averaged streamwise vorticity approaches 10^-2 s^-1, with maximum values near the surface of 1.5-2 x 10^-2 s^-1. Narrow zone (20-30 km across) along the boundary where the low-level shear is very high. Shading is 1900 − 1600 UTC change in shear mesocyclone track X 1900 UTC position

Supercells are most likely to produce tornadoes on cool side of boundaries (but not too far into cool air) 0—1 km shear maximized z 1 km 0 km A B T−Td: >5°C <2°C lower lifting condensation levels warmer downdrafts

Lessons learned from this fortuitous science opportunity: Severe weather forecasting remains challenging, particularly when the synoptic-scale conditions are ambiguous Watch for terrain interactions and baroclinic boundaries that may increase the local risk for severe weather (hard to discern ahead of time!) If you decide to storm chase, understand the risk and know what you’re doing