Observed and Simulated Multi-bands in Northeast U.S. Winter Storms S ARA A. G ANETIS 1, B RIAN A. C OLLE 1, S ANDRA E. Y UTER 2, AND N ICOLE C ORBIN 2 1 School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York 2 Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina NROW XV12 November

2 Previous Work on Snowbands Moisture Instability Lift Single Band Nonbanded Novak et al Climatology of banded structures in Northeast U.S. extratropical cyclones for 5 years ( ) that identified 88 cases, 75 banded, 48 single bands & 13 nonbanded Novak et al cases, 30 single-banded cases for Band-relative composites using 3-hourly 32- km (NARR) data and hourly 20-km RUC data

NROW XV12 November Previous Work on Microphysics within East Coast Storms Stark et al. (2013) Case studies examining microphysical evolution of snowbands

NROW XV12 November Novak et al Confirmed the capability of a mesoscale model in simulating single-banded storms Observation 4-km MM5 Simulation Previous Work on Utilization of Mesoscale Models

NROW XV12 November What about Multi-bands? Reflectivity [dBZ] Dec 2010 OKX 0.5° Reflectivity

NROW XV12 November Fewer studies have focused on or discussed smaller-scale multi-bands found in the comma head of cool season (Oct – Mar) extratropical cyclones and include observational studies e.g. Uccellini and Koch 1987; Shields et al. 1991; Nicosia and Grumm 1999 theoretical and/or idealized studies e.g. Xu 1992; Pizzamei et al. 2005; Morcrette and Browning 2006 Previous Work on Multi-bands Novak et al Cross-section of vertical velocity for a saturated region in the presence of negative moist geostrophic potential vorticity (Xu 1992). Stable Unstable VTVT

NROW XV12 November Science Questions  What are the frequency of occurrence and characteristics of observed banded precipitation structures in Northeast U.S. winter storms and are they in agreement with those of previous studies? How often do multi-bands transition into a single band and vice-versa?  How do environmental parameters differ among the different banded precipitation structures and how could the differences be used to enhance conceptual knowledge? Do multi-bands always form in an environment of instability?  Can a mesoscale model run down to 1.33-km grid spacing simulate the different observed precipitation structures?

NROW XV12 November Dataset Creation Methodology 123 Cyclone Dates Reporting ≥ 1” snow in 24 h 71 Cyclone Dates w/ Radar Data from KDIX, KOKX, KBOX Source: US Census Bureau Coastal Northeast U.S. cool season (Oct – Mar) snow storms from Goal  Using stitched radar data (NCState) from DIX, OKX, BOX: Classify events or time periods during which different banded precipitation structures were observed within cases 50 Cyclone cases with radar data available for entire duration of storm Terrain Height [m]

NROW XV12 November Band Description Band Type Single band Linear structure 20–100 km in width, >250 km in length, with an intensity >30 dBZ maintained for at least 2 h Multi-bands >3 finescale (5–20-km width) bands with periodic spacing and similar spatial orientation, with intensities >5 dBZ over the background reflectivity maintained for at least 1 h Both single band and multi-bands Both above single band and multi-bands criteria are met within 250 km Nonbanded None of the above criteria are met and this may also be classified as "cellular" where reflectivity features >30 dBZ are not ellipsoidal in shape to be classified as multibands Classification Methodology Single band

NROW XV12 November Classification Methodology Band Description Band Type Single band Linear structure 20–100 km in width, >250 km in length, with an intensity >30 dBZ maintained for at least 2 h Multi-bands >3 finescale (5–20-km width) bands with periodic spacing and similar spatial orientation, with intensities >5 dBZ over the background reflectivity maintained for at least 1 h Both single band and multi-bands Both above single band and multi-bands criteria are met within 250 km Nonbanded None of the above criteria are met and this may also be classified as "cellular" where reflectivity features >30 dBZ are not ellipsoidal in shape to be classified as multibands Multi-bands

NROW XV12 November Classification Methodology Band Description Band Type Single band Linear structure 20–100 km in width, >250 km in length, with an intensity >30 dBZ maintained for at least 2 h Multi-bands >3 finescale (5–20-km width) bands with periodic spacing and similar spatial orientation, with intensities >5 dBZ over the background reflectivity maintained for at least 1 h Both single band and multi-bands Both above single band and multi-bands criteria are met within 250 km Nonbanded None of the above criteria are met and this may also be classified as "cellular" where reflectivity features >30 dBZ are not ellipsoidal in shape to be classified as multibands Both Single & Multi-bands

NROW XV12 November Classification Methodology Band Description Band Type Single band Linear structure 20–100 km in width, >250 km in length, with an intensity >30 dBZ maintained for at least 2 h Multi-bands >3 finescale (5–20-km width) bands with periodic spacing and similar spatial orientation, with intensities >5 dBZ over the background reflectivity maintained for at least 1 h Both single band and multi-bands Both above single band and multi-bands criteria are met within 250 km Nonbanded None of the above criteria are met and this may also be classified as "cellular" where reflectivity features >30 dBZ are not ellipsoidal in shape to be classified as multibands Non-banded

NROW XV12 November Preliminary Event Results Terrain Height [m] 68 Events 12 Single bands (18%) 22 Multi-bands (32%) 14 Both single bands and multi-bands (21%) 20 non-banded (29%) Comparison to previous studies Less events over a longer time period compared to Novak et al events, 48 exhibited single bands Multi-band Transitions within 13 cases Both  Multi: 4 Multi  Both  Multi: 2 Multi  Both: 2 Single  Both: 2 Multi  Both  Single: 1 Multi  Single  Both: 1 Single  Both  Single: 1 Spatial Distribution Moisture Instability Lift

NROW XV12 November Composite Methodology 3-hourly NARR Data ( ) One NARR file per event, but cyclone can be sampled more than once N-3 N0 N+3 Multi-bands Both Single & Multi-bands

NROW XV12 November Composite Results: 300 mb Single BandMulti-bands Both Single & Multi-bands Non-banded Wind Speed [kt ]

NROW XV12 November Composite Results: 700 mb Single BandMulti-bands Both Single & Multi-bands Non-banded Relative Humidity [%]

NROW XV12 November Composite Results: Forcing for Lift Single BandMulti-bands Both Single & Multi-bands Non-banded Frontogenesis [K (100 km 3 h) -1 ] Hypothesis: There is low-to-mid- level frontogenesis inducing an ageostrophic vertical circulation that provides forcing for lift for both single bands and multi-bands 850 mb Frontogenesis

NROW XV12 November Composite Results: Instability Single BandMulti-bands Both Single & Multi-bands Non-banded

NROW XV12 November Mesoscale Modeling Methodology Dec 2010 Case Both single and multi-bands 26/ /0800 Weather Research and Forecasting (WRF) mesoscale model v h Simulation 0600 UTC 26 – 1200 UTC 27 Initial and boundary conditions from 6-hourly 0.5° GFS 1/12 th degree SST data from NCEP 4 one-way nested domains (36, 12, 4, 1.33 km) 40 vertical levels with model top set to 50 hPa 5-layer thermal diffusion surface layer scheme (Dudhia 1996) Kain-Fritsch cumulus parameterization (Kain 2004 ) applied to 36 and 12 km domains only explicitly resolves updrafts and downdrafts Planetary Boundary Layer Parameterization Scheme Microphysics Parameterization Scheme MYJ (Janjic 1994) order scheme with local mixing and used in operational NAM Thompson (Thompson et al. 2008)--predicts graupel and also predicts the number concentration of ice in addition to the mass concentration, despite being a single-moment scheme YSU (Hong et al. 2006)– Diagnostic non-local closure scheme WSM6 (Hong and Lim 2006)– single moment that also predicts the mass concentration of graupel  Resultant dataset: 4 simulations run down to 1.33-km grid spacing of Dec 2010 multi-bands 36 km 12 km 4 km 1.33

NROW XV12 November Mesoscale Model Results: 0000 UTC 27 Dec 2010 Simulated Reflectivity OKX 0.5° Reflectivity [dBZ] MYJ PBL / Thom MPMYJ PBL / WSM6 MP YSU PBL / Thom MP YSU PBL / WSM6 MP 1-km AGL Stitched

NROW XV12 November Mesoscale Model Results: 0000 UTC 27 Dec 2010 OKX Sounding MYJ PBL / Thom MP MYJ PBL / WSM6 MP YSU PBL / Thom MP YSU PBL / WSM6 MP OKX Sounding

NROW XV12 November Mesoscale Model Results: 850 mb Geopotential Height 26/180027/ / /0600 MYJ PBL / Thom MP MYJ PBL / WSM6 MP YSU PBL / Thom MP YSU PBL / WSM6 MP

NROW XV12 November Mesoscale Model Results: Dec 2010 Simulated Reflectivity 00 UTC 27 Dec 2010 Reflectivity [dBZ] OKX 0.5° Reflectivity WRF 1.33-km Domain 500-m AGL Simulated Reflectivity FH 18 Valid 00 UTC 27 Dec 2010 FH 19 Valid 01 UTC 27 Dec 2010 FH 21 Valid 03 UTC 27 Dec UTC 27 Dec UTC 27 Dec 2010 B B’

NROW XV12 November FH 18 Valid 00 UTC 27 Dec FH 19 Valid 01 UTC 27 Dec FH 21 Valid 03 UTC 27 Dec B B’ B B Reflectivity [dBZ] Frontogenesis [K (100 km h) -1 ] Simulated Reflectivity, θes, Circulation Vectors Frontogenesis, θe, Circulation Vectors

NROW XV12 November Summary & Ongoing Work  Multi-bands are found in 53% of 50 cyclones exhibiting ≥ 1”/h snowfall amounts between in the Northeast coastal region and are an important part of the precipitation structure evolution  Multi-bands occur during a less developed period of the baroclinic wave with weaker frontogenesis than single band times, but more instability.  The MYJ PBL & Thompson microphysics schemes provided the most representative simulation of multi-bands for Dec 2010 case  Is this configuration true for a larger variety of similar cases? What about varying IC/BCs?  A high-resolution gridded dataset is necessary to quantify the evolution of stability, moisture and lift attributed to the evolution of the banded precipitation structures in these coastal cyclones Thank you!