Observed and Simulated Multi-bands
in Northeast U.S. Winter Storms
SARA A. GANETIS1, BRIAN A. COLLE1, SANDRA E. YUTER2, AND NICOLE CORBIN2
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 XV
12 November 2014
1
Previous Work on Snowbands
Lift
Moisture
Novak et al. 2004
•
Instability
Novak et al. 2010
Climatology of banded structures in
•
Northeast U.S. extratropical cyclones for 5
•
years (1996-2001) that identified 88 cases,
75 banded, 48 single bands & 13 nonbanded
Single Band
Single Band
NROW XV
75 cases, 30 single-banded cases for 2002-08
Band-relative composites using 3-hourly 32km (NARR) data and hourly 20-km RUC data
Nonbanded
Nonbanded
12 November 2014
2
Previous Work on Microphysics within East Coast Storms
Stark et al. (2013)
• Case studies examining microphysical
evolution of snowbands
NROW XV
12 November 2014
3
Previous Work on Utilization of Mesoscale Models
Novak et al. 2009
•
Confirmed the capability of a mesoscale model in simulating single-banded storms
Observation
4-km MM5
Simulation
NROW XV
12 November 2014
4
What about Multi-bands?
26-27 Dec 2010 OKX 0.5° Reflectivity
Reflectivity [dBZ]
NROW XV
12 November 2014
5
Previous Work on Multi-bands
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
Cross-section of vertical velocity for a saturated
region in the presence of negative moist
geostrophic potential vorticity (Xu 1992).
VT
Stable
NROW XV
Unstable
12 November 2014
Novak et al. 2006
6
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 XV
12 November 2014
7
Dataset Creation Methodology
• Coastal Northeast U.S. cool season (Oct – Mar) snow storms
from 1997-2014
• 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
123 Cyclone Dates
Reporting ≥ 1” snow
in 24 h
Source: US Census Bureau
71 Cyclone Dates
w/ Radar Data from
KDIX, KOKX, KBOX
Terrain Height [m]
50 Cyclone cases with
radar data available for
entire duration of storm
NROW XV
12 November 2014
8
Classification Methodology
Band Type
Band Description
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
NROW XV
12 November 2014
Single band
9
Classification Methodology
Band Type
Band Description
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
NROW XV
12 November 2014
Multi-bands
10
Classification Methodology
Band Type
Band Description
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
NROW XV
Both Single & Multi-bands
12 November 2014
11
Classification Methodology
Band Type
Band Description
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
NROW XV
12 November 2014
Non-banded
12
Preliminary Event Results
Spatial Distribution
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. 2004
•
162 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
Terrain Height [m]
Lift
Moisture
NROW XV
Instability
12 November 2014
13
Composite Methodology
•
•
3-hourly NARR Data (1997-2014)
One NARR file per event, but cyclone can be
sampled more than once
Multi-bands Both Single & Multi-bands
N-3
Multi-bands
NROW XV
N0
N+3
Both Single & Multi-bands
12 November 2014
14
Composite Results: 300 mb
Single Band
Both Single &
Multi-bands
NROW XV
Multi-bands
Wind Speed [kt]
12 November 2014
Non-banded
15
Composite Results: 700 mb
Single Band
Both Single &
Multi-bands
NROW XV
Multi-bands
Relative Humidity
[%]
12 November 2014
Non-banded
16
Composite Results: Forcing for Lift
Single Band
Hypothesis:
There is low-to-midlevel frontogenesis
inducing an
ageostrophic
vertical circulation
that provides forcing
for lift for both single
bands and
multi-bands
Both Single &
Multi-bands
Multi-bands
Frontogenesis
[K (100 km 3 h)-1]
-5 -2 -1 1 2
Non-banded
5
850 mb
Frontogenesis
NROW XV
12 November 2014
17
Composite Results: Instability
Single Band
Multi-bands
Both Single &
Multi-bands
Non-banded
Hypothesis:
There is larger
instability in the lowto-midlevel
environment for
multi-bands
950-925
𝒅𝜽𝒆𝒔
𝒅𝒛
𝒅𝜽𝒆𝒔
≤0
𝒅𝒛
𝒅𝜽𝒆𝒔
>0
𝒅𝒛
NROW XV
12 November 2014
18
Mesoscale Modeling Methodology
•
26-27 Dec 2010 Case
•
•
Both single and multi-bands 26/1700 - 27/0800
Weather Research and Forecasting (WRF)
mesoscale model v. 3.6.1
•
•
•
•
•
•
•
30-h Simulation 0600 UTC 26 – 1200 UTC 27
Initial and boundary conditions from 6-hourly 0.5° GFS
1/12th 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
1.33
4 km
12 km
36 km
Microphysics Parameterization Scheme
MYJ (Janjic 1994)-- 1.5-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 26-27 Dec 2010 multi-bands
NROW XV
12 November 2014
19
Mesoscale Model Results:
0000 UTC 27 Dec 2010 Simulated Reflectivity
OKX 0.5°
MYJ PBL / Thom MP
MYJ PBL / WSM6 MP
YSU PBL / Thom MP
YSU PBL / WSM6 MP
1-km AGL Stitched
Reflectivity [dBZ]
NROW XV
12 November 2014
20
Mesoscale Model Results:
0000 UTC 27 Dec 2010 OKX Sounding
OKX Sounding
MYJ PBL / Thom MP
MYJ PBL / WSM6 MP
YSU PBL / Thom MP
YSU PBL / WSM6 MP
NROW XV
12 November 2014
21
Mesoscale Model Results: 850 mb Geopotential Height
26/1800
27/0000
MYJ PBL / Thom MP
27/0300
27/0600
MYJ PBL / WSM6 MP
YSU PBL / Thom MP
YSU PBL / WSM6 MP
NROW XV
12 November 2014
22
Mesoscale Model Results: Dec 2010 Simulated Reflectivity
01 UTC 27 Dec 2010
03 UTC 27 Dec 2010
WRF 1.33-km Domain 500-m AGL
Simulated Reflectivity
OKX 0.5° Reflectivity
00 UTC 27 Dec 2010
NROW XV
FH 18 Valid
00 UTC 27 Dec 2010
FH 19 Valid
01 UTC 27 Dec 2010
FH 21 Valid
03 UTC 27 Dec 2010
B
B’
Reflectivity [dBZ]
12 November 2014
23
B
B’
FH 18 Valid
00 UTC 27 Dec
B
B’
B
FH 19 Valid
01 UTC 27 Dec
B’
FH 21 Valid
03 UTC 27 Dec
Simulated Reflectivity, θes, Circulation Vectors
Reflectivity [dBZ]
Frontogenesis, θe, Circulation Vectors
Frontogenesis [K (100 km h)-1]
-70
NROW XV
-30
0
30
12 November 2014
70
24
Summary & Ongoing Work
 Multi-bands are found in 53% of 50 cyclones exhibiting ≥ 1”/h snowfall
amounts between 1997-2014 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 26-27 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!
sara.ganetis@stonybrook.edu
http://flurry.somas.stonybrook.edu/band_study/
NROW XV
12 November 2014
25