Transcript The Utility of Considering Dual-Pol Radar Signatures in the Tornado Warning Process MICHAEL L.

The Utility of Considering Dual-Pol
Radar Signatures in the Tornado
Warning Process
MICHAEL L. JUREWICZ, SR. AND CHRISTOPHER
GITRO
NOAA/NWS, BINGHAMTON, NY
NORTHEAST REGIONAL OPERATIONAL
WORKSHOP
10 DECEMBER 2013
Outline
 Motivation
 Previous Research
 Methodology / Latest Results
 Summary / Conclusions
 Future Work
Motivation
* Tabulated for the
WFO’s in our study
(ALY, BGM, BOX, BTV,
BUF, CAR, CTP, GYX,
OKX, PBZ, and PHI)
* Total of 62 events for
these offices; with 27 of
them fully warned and 8
partially warned; for a
POD = 0.5 (well
below expected
performance
standards)
* FAR stats (0.79)
were similarly below
established goals
NWS ER Tornado Warning
Statistics for 2012-2013
Previous Research
Drop Size Sorting / Zdr Arc
From Romine, et.
al, 2008
* Enhanced Kdp (blue) gets
displaced left of enhanced Zdr
(orange) via preferential size sorting
From Kumjian and
Ryzhkov, 2009
* Conceptual schematic of differing
hydrometeor descents and Zdr arcing
* EF -1 tornado was on
the ground at this time
(near Trinity, AL)
* Note the westward
displacement of Kdp
maxima (lower right)
versus Zdr maxima
(lower left)
* Also, note the arcshaped configuration of
the Zdr pattern (lower
left)
Radar 4-Panel from Northern
Alabama at 1620 UTC, 27 April 2011
(from Crowe, et. al, 2012)
* EF -1 tornado was on
the ground at this time
(near Trinity, AL)
* Note the westward
displacement of Kdp
maxima (lower right)
versus Zdr maxima
(lower left)
* Also, note the arcshaped configuration of
the Zdr pattern (lower
left)
Zdr Max
Radar 4-Panel from Northern
Alabama at 1620 UTC, 27 April 2011
(from Crowe, et. al, 2012)
Methodology / Latest Results
Methodology
 Favorable initial results (Crowe, et. al, 2012) were further
put to the test over the Northeastern U.S. (New England,
NY, PA, and NJ)

30 Storms (17 Non-tornadic and 13 Tornadic) were chosen from the
2012 and 2013 convective seasons, each within a potentially
favorable synoptic environment for tornadogenesis:
ML CAPE > 700 J/kg
 0-6 km Shear > 40 kt
 0-1 km Shear > 20 kt
 0-1 km SRH > 100 m2/s2


Many radar/storm-scale parameters were tabulated at the lowest tilt

Including specific Zdr and Kdp maximum values, and their separation
distances (nmi)
 AWIPS/GR2 Analyst sampling and distance measuring tools
* EF -1 tornado was on
the ground at this time
(near Elmira, NY)
* Once again, note the
westward displacement
of Kdp maxima (lower
right) versus Zdr
maxima (lower left)
* Also, note the
developing arc-shaped
region of enhanced Zdr
(lower left)
Radar 4-Panel from Central New
York at 2010 UTC, 26 July 2012
* EF -1 tornado was on
the ground at this time
(near Elmira, NY)
* Once again, note the
westward displacement
of Kdp maxima (lower
right) versus Zdr
maxima (lower left)
* Also, note the
developing arc-shaped
region of enhanced Zdr
(lower left)
Zdr
Max
x
Radar 4-Panel from Central New
York at 2010 UTC, 26 July 2012
Statistical Correlations
 Strongest correlations to tornadic development
(either same volume scan or in the near future):




Zdr and Kdp separation (nmi) – 0.50
Maximum gate-gate shear (kt) – 0.38
Maximum SRM increase within a volume scan – 0.30
Existence/development of a Zdr arc – 0.23
 Given approximately 300 data points (radar volume
scans), these values are statistically significant to the
99th percentile (Gibbons, 1976)
360°
* All 30 storms in the
database represented
* Note the typically
much larger horizontal
separation for tornadic
storms (red)
* For the non-tornadic
storms (blue), little
separation was typically
seen (data points tightly
clustered around the
center of the plot)
340°14
12
320° 10
8
300°
6
280°
260°
240°
220°
200°
4
2
0
180°
020°
040°
060°
080°
100°
120°
140°
160°
Polar Plot of Kdp maxima (red for tornadic
storms and blue for non-tornadic storms)
versus Zdr maxima (center point)
6
* Looking at +/- 3
volume scans from T=0
* T=0 is either the time
of initial tornado
touchdown or tornado
warning issuance (null
events)
* Note the large
differences in separation
magnitude between T-2
and T=0
5
4
Mean Null
Separation
3
Mean Tor
Separation
2
1
0
T-3 T-2
T-1 T=0 T+1 T+2 T+3
Horizontal Separations (nmi, yaxis) of Zdr and Kdp maxima over
time
80
* Once again, looking at
+/- 3 volume scans from
T=0
* T=0 is either the time
of initial tornado
touchdown or tornado
warning issuance (null
events)
* Rotational velocity
couplet seems to spike in
intensity near T=0 for
tornadic storms
70
60
50
Mean Null SRM
40
Mean Tor SRM
30
20
10
0
T - 3 T - 2 T - 1 T = 0T + 1 T + 2T + 3
Trends of Maximum Gate-Gate
Shear (kt, y-axis (Storm Relative
Motion)) over time
Summary / Conclusions
Take Home Points
 Horizontal separation of Zdr and Kdp maxima via drop
size sorting (enhanced low-level helicity) seemed to be a
reliable indicator of tornadogenesis


Matches previous research well over the Southeastern U.S.
Initially promising results perhaps warrants consideration in the
tornado warning process
 Gate-gate shear values tend to maximize right around the
time of touchdown (T=0) in tornadic storms
 Although there was a general tendency for Zdr arc
formation in Northeast U.S. tornadic storms, drop size
sorting appeared to be the more readily apparent
phenomenon via radar interrogation
Future Work
 Publish results
 Develop methods to make Zdr/Kdp separations
easier to recognize in real-time
 Continue to evaluate these processes in coming
convective seasons
Questions ?