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