1. 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

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

3. x
UTC
1515 UTC: Initiation occurs in the Adirondacks

4. Hey Ross, there’s a right mover coming toward us!x
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!

5. It’s still there! Let’s go chasing!x
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!

6. x
UTC
1920 UTC: 4” (10 cm) hailstone in Amsterdam, NY, tying NY state record
Source: CBS

7. Reflectivity
Differential Reflectivity
1905 UTC

8. Source: NOAA

9. 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

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

11. x
UTC
1933 UTC: Tornado touches down near NY-30 in Montgomery County
@#$^&#)&*!!!
Um….guys?!

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

13. 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

14. 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

15. 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

16. Elevated mixed layers advected over region.
1200 UTC

17. 1815 UTC
Cool, maritime airmass
Warm, unstable airmass L H

18. Analogous to thermal contrast that forces a sea breeze

19. 1530 UTC m
16° C
hPa
18° C
hPa
36 km between KSCH and KYN0, 50 km between KALB and KNY0.
17.8° C
hPa

20. 1830 UTC m
20° C
hPa
22° C ?
18° C
hPa
17.2° C
hPa

21. 1830 UTC m
Δp=2 hPa L H
ageostrophic wind

22. moisture flux convergence
1830 UTC m
moisture flux convergence

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

24. 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, m AGL, which was the 1st ingredient favorable for a tornado.
mesocyclone track X
1800 UTC position

25. 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

26. 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 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

27. 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

28. 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