The 26 July, 2012 Twin Tier severe weather and tornado outbreak:

Part II : radar analysis

Mike Evans, WFO Binghamton, NY

OutlineReflectivity and conceptual modelsRotational velocity and local researchSpectrum widthNew dual polarization variables

Tornado tracks across the southern tier of New York

Damage near downtown Elmira

Mosaic radar reflectivity

Broken S conceptual model

Reflectivity through 1st tornado

Reflectivity 3rd and 4th tornado

Rotational velocity through 1st tornado

Normalized rotation – 1st couplet

Rotational velocity 3rd through 4th tornado

Normalized rotation

Rotational velocity and low-level shear vs. tornado occurrence

0-1 km helicity for this case around 150 m2/s2

Rotational velocity time trend – 1st couplet

Rotational velocity time trend – 2nd couplet

Spectrum width through the 1st tornado

Spectrum width – 3rd and 4th tornado

Previous study using spectrum width (Spoden et. al. 2012)

Spectrum width associated with the 1st couplet

Spectrum width time trend – 2nd couplet

Recent work with dual polarization variables

Modeling studies indicate that Zdr arcs on the southern edge of the forward flank precipitation shield, are associated with enhanced storm relative helicity.

Enhanced shear is also indicated by separation between maxima of Zdr (large drops) and KDP (maxima of liquid water).

Reflectivity, Zdr and KDP – 1951z

Event SummaryRadar reflectivity with this event was suggestive of a

supercell, not a broken-S.Rotational velocities observed on the KBGM radar were

near the low-end of what has historically been observed with tornadoes in this area.

Rotation associated with the Steuben county storm appeared to develop at low and mid-levels simultaneously.

Spectrum width values greater than 20 kts were associated with the two primary tornadoes over the central, southern tier of New York.

Some similarities noted with previous work related to dual pol (ZDR and KDP) variables.

ReferencesCrowe, C.C., C.J. Schultz, M. Kumjian, L.D. Carey and W.A. Petersen,

2012: Use of dual-polarization signatures in diagnosing tornadic potential.  Electronic J. Operational Meteor 2012-EJ5 - June 2012.

Kumjian, M., and A. Ryzhkov, 2008: Polarimetric signatures in supercell thunderstorms, Journal of Applied Meteorology and Climatology, 47, 1940-1961.

Lane, J. D., and P. D. Moore, 2006: Observations of a non-supercell tornadic thunderstorm from a Terminal Doppler Weather Radar. Preprints, 23rd Conf. on Severe Local Storms, St. Louis, MO, Amer. Meteor. Soc.

Romine, G.S., D.W. Burgess, R.B. Wilhelmson, 2008: A dual-polarization-radar-based assessment of the 8 May, 2003 Oklahoma City area tornadic supercell, Mon. Wea. Rev., 136, 2849-2870.

Spoden, P.J., R.A. Wolf and L.R. Lemon, 2012: Operations uses of spectrum width, Electronic Journal of Severe Storms Meteorology, 7, 1-28.