climatological aspects of ice storms in the northeastern u.s
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Climatological Aspects of Ice Storms in the Northeastern U.S.
Christopher M. Castellano, Lance F. Bosart, and Daniel KeyserDepartment of Atmospheric and Environmental Sciences
University at Albany, State University of New York, Albany, NY
John Quinlan and Kevin LiptonNOAA/NWS/WFO Albany, NY
37th Annual Northeastern Storm Conference3 March 2012, Rutland, VT
NOAA/CSTAR Grant: NA01NWS4680002
Motivation and Objectives
Data and Methodology
Ice Storm Climatology
Composite Analysis
Summary
Outline
Ice storms endanger human life and safety, undermine public infrastructure, and disrupt local and regional economies
Ice storms present a major forecast challenge due to the combined influence of synoptic, mesoscale and microphysical processes
Ice storms are historically most prevalent and destructive in the northeastern U.S.
Motivation
Fig 2. Changnon (2003). The amount of loss (millions of dollars expressed in 2000 values) from ice-storm catastrophes in each climate region during 1949–2000. Values in parentheses are the average losses per catastrophe.
Fig 3. Changnon (2003). The number of ice-storm catastrophes in each climate region during 1949–2000. Values in parentheses are those catastrophes that only occurred within the region.
Motivation
Establish a 17-year climatology (1993–2010) of ice storms in the northeastern U.S.
Determine environments conducive to ice storms and dynamical mechanisms responsible for freezing rain
Provide forecasters with greater situational awareness of synoptic and mesoscale processes that influence the evolution of ice storms
Objectives
Identified ice storms using NCDC Storm Data:1. Any event listed as an “Ice Storm” 2. Any event with freezing rain resulting in “significant” or “heavy” ice
accumulations (≥ 0.25” ice accretion)3. Any event with damage attributed to ice accretion
Classified individual ice storms by size:
Data and MethodologyIce Storm Climatology
Size Counties Affected CWAs AffectedLocal ≤ 3 AND ≤ 3
Regional 4 – 12 AND ≤ 6
Sub-synoptic 13 – 48 AND ≤ 6
Synoptic > 48 OR > 6
Identified 35 ice storms impacting WFO Albany’s CWA
Created synoptic composite maps from 2.5° NCEP/NCAR reanalysis data
Generated a composite cross-section using 0.5° CFSR (Climate Forecast System Reanalysis) data
Performed analyses at t = 0, t−24 h, and t−48 h preceding each event
Composite Analysis
Data and Methodology
Geographical Domain
BGMBUF
CTPCLE
RLX
ALYBOX
BTV
CAR
GYX
OKXPHIPBZ
LWX
Ice Storms by Year
93-94
94-95
95-96
96-97
97-98
98-99
99-00
00-01
01-02
02-03
03-04
04-05
05-06
06-07
07-08
08-09
09-10
0
2
4
6
8
10
12
14
16
Year (Oct-Apr)
Num
ber o
f Ice
Sto
rms
N = 136
Ice Storms by Month
OCT NOV DEC JAN FEB MAR APR0
5
10
15
20
25
30
35
40
45
50
Month
Num
ber o
f Ice
Sto
rms
N = 136
Ice Storms by County
Ice Storms1 - 56 - 1011 - 1516 - 2021 - 2526 - 3031 - 35> 35
Ice Storms by CWAs Impacted
1 2 3 4 5 6 7 8 9 10 11 120
5
10
15
20
25
30
35
40
45
50
Number of CWAs Affected
Num
ber o
f Ice
Sto
rms
N = 136
23.5%(32)
28.7%(39)
29.4%(40)
18.4%(25)
LocalRegionalSub-synopticSynoptic
N = 136
Ice Storms by Size
500-hPa geopotential height (black contours, every 6 dam) and anomalies (shaded, every 30 m)
t – 48 h
N = 35
500-hPa geopotential height (black contours, every 6 dam) and anomalies (shaded, every 30 m)
t – 24 h
N = 35
500-hPa geopotential height (black contours, every 6 dam) and anomalies (shaded, every 30 m)
t = 0
N = 35
850–700-hPa layer wind (arrows, m s-1), 850–700-hPa layer 0°C isotherm (dashed contour), precipitable water (green contours, every 4 mm), and standardized precipitable water anomalies (shaded, every 0.5 σ)
N = 35
t – 48 h
850–700-hPa layer wind (arrows, m s-1), 850–700-hPa layer 0°C isotherm (dashed contour), precipitable water (green contours, every 4 mm), and standardized precipitable water anomalies (shaded, every 0.5 σ)
N = 35
t – 24 h
850–700-hPa layer wind (arrows, m s-1), 850–700-hPa layer 0°C isotherm (dashed contour), precipitable water (green contours, every 4 mm), and standardized precipitable water anomalies (shaded, every 0.5 σ)
N = 35
t = 0
300-hPa wind speed (shaded, every 5 m s-1), 1000–500-hPa thickness (dashed contours, every 6 dam), and mean sea-level pressure (solid contours, every 4 hPa)
N = 35
t – 48 h
300-hPa wind speed (shaded, every 5 m s-1), 1000–500-hPa thickness (dashed contours, every 6 dam), and mean sea-level pressure (solid contours, every 4 hPa)
N = 35
t – 24 h
300-hPa wind speed (shaded, every 5 m s-1), 1000–500-hPa thickness (dashed contours, every 6 dam), and mean sea-level pressure (solid contours, every 4 hPa)
N = 35
t = 0
Frontogenesis (shaded, every 0.5 K 100 km -1 3 h-1), theta (black, every 2 K), wind speed (green, every 5 m s-1), omega (dashed red, every 5 μb s-1),
and circulation (arrows)
N = 35
t = 0
Climatological frequency is highest between Dec and Mar (maximum in Jan)
Sharp gradients in frequency exist across coastal plains, as well as near regional and synoptic topographic features
Greatest frequencies occur over elevated terrain, along prominent mountain ranges, and within protected river valleys
Summary: Ice Storm Climatology
Frequency of ice storms is inversely related to the number of CWAs impacted
81.6% (111) of ice storms qualified as either local, regional, or sub-synoptic, whereas 18.4% (25) qualified as synoptic
Ice storms are predominately governed by mesoscale dynamics, but large variability in spatial extent suggests the importance of synoptic–mesoscale linkages
Summary: Ice Storm Climatology
Ice storms are coincident with an amplifying ridge along the East Coast and upstream trough across the central U.S
Ice storms occur near the equatorward entrance region of an upper-level jet, within an amplifying thermal ridge
Ice storms are accompanied by low-to-midlevel moisture transport and warm-air advection via deep southwesterly flow
Ice storms occur on the poleward side of a surface warm front, suggesting the importance of ageostrophic cross-frontal circulations
Summary: Composite Analysis
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