RAPID-SCAN DOW RADAR OBSERVATIONS OF TORNADOES DURING VORTEX2 2009 and 2010Joshua Wurman, Karen Kosiba, Paul C. Robinson Center for Severe Weather Research

C enter for S evere W eather R esearch

Rapid-Scan DOW is an NSF facilityDOWs are supported by NSF-ATM-0734001

and -0966095 and -0946926Analysis supported by NSF-ATM-0801041

VORTEX2 supported by SPO grant NSF-ATM-0724318 and others

DOW7

Rapid-Scan

DOW6

Observations:Green = DOW7 radius and locationsMaroon = DOW6Blue = Rapid-Scan

Rapid-ScanDOW7

DOW6Booker, TX:

13 June 2010Tribune, KS:25 May 2010

DOW713 km south

DOW7Observations

Rapid-ScanObservations

0.5 ° 1.3 °

3.0 ° 4.0 °

Left: An example scan through the tornado by the Rapid-Scan DOW. All four elevations were taken at 23:40:39 UTC. Note the lack of the reflectivity eye at the four degree elevation scan.

Right: Map detailing observations obtained by the Rapid-Scan DOW (blue) and DOW 7 (green). Circles denote radius of maximum winds observed by respective radars.Note the additional observations available from the Rapid-Scan DOW.

Rapid oscillations resolved by Rapid-Scan, not by DOW-7

Goshen County,

WY: 5 June 2009

• Six simultaneous elevations scanned• Full volume updates every seven seconds.• 50 or 25-meter gate spacing• 0.8 – 0.9 degree beam width• 4D resolution @ 2 km

28 m x 30 m x 25 m x 7 s = 150,000 m3s

Above: Comparisons of DOW-measured Doppler velocity (left) and radar reflectivity (right) as observed by DOW 6 (top) and Rapid-scan DOW (bottom), indicating good agreement on both large-scale and fine-scale (black circles) circulations.

9310 MHz0.5o

9354 MHz1.3o

9478 MHz3.0o

9562 MHz4.0o

9649 MHz5.3o

9730 MHz6.2o

Above: DOW-measured Doppler velocity (left) and radar reflectivity (right) from each channel of the rapid-scan radar. Time of observation was 01:09:20 GMT

Bovina, CO: 11 June 2010

22:14:07 22:14:07 22:14:14 22:14:21 22:14:28 22:14:35 22:14:42 22:14:49

22:14:57 22:14:57 22:15:04 22:15:11 22:15:18 22:15:25 22:15:32 22:15:39

Above. Seven-second observations of the Rapid-Scan DOW delta-V at three different elevations (left). An FFT analysis of channel 4 reveals periodic oscillations in tornado intensity approximately every 1.1-1.8 minutes (center). These ~ 1 minute oscillations are not captured by the 1-minute DOW7 observations (right).

Above. Ground-based velocity track display (GBVTD) analyses derived from 7-second Rapid Scan DOW observations. Color contours indicate the tangential winds and vectors denote the secondary circulation.

Left. Axisymmetric radial and tangential wind profiles derived from the Rapid-Scan DOW using the GBVTD technique at 130 m AGL. Divergence is present outside of the radius of maximum winds, while farther outside the radius of maximum winds weak inflow is observed.

Upgraded Rapid-Scan System

22:11:16 22:11:23 22:11:30 22:11:34 22:11:44

Above: Evolution of the velocity (left, in images) and reflectivity (right, in images) from 2214:07-2115:39 UTC. DOW 7 (outlined in magenta) completes a volume approximately every one minute , whereas the Rapid-scan DOW (outlined in blue) completes a volume every seven seconds. Images are shown for the lowest elevation scan for both radars. Note the rapid evolution of the tornado that occurs on timescales of < one minute.

Left: An example Rapid-Scan observation of velocity (left) and reflectivity (right) at a single elevation angle. The structure of the inner debris ring is well captured.

Right: The entire evolution of the Booker, TX tornado was captured by the DOW radar network. Above: Delta-V as measured by DOW 7

(green) and Rapid-Scan DOW (red), capturing tornado genesis, intensification and demise.

DOW 6 at 0112:51 UTC

Rapid-Scan DOW at 0112:55 UTC