New England Tornado Hazard

Regional Climatology & Risk

Mary D. Stampone

Department of Geography

New Hampshire State Climate Office

University of New Hampshire

Presentation for thePlymouth State University

Environmental Science & Policy Colloquium

September 19, 2012

National Tornado Statistics

Time-Series

Tornado

Statistics by US State

http://www.spc.noaa.gov/wcm/#data

New England

states have the

fewest average

annual tornado

occurrence of

the lower 48.

National Tornado Statistics

Record Tornado

New Hampshire

July 28, 2008

http://www.erh.noaa.gov/gyx/

Just before noon, a

tornado touched down

near Deerfield, NH.

This tornado cut a 50 mile

path over 80 minutes to

the Maine border

New England Tornadoes

New England

Tornado

Influences

Lewis (2007)

Public

misconceptions

about tornado

influences

strengthen belief

that “tornadoes do

not happen here.”

Tornado Origins

(1981-2010)

New England Tornadoes

http://www.erh.noaa.gov/box/

Prior to the 2011 Joplin

tornado, the Worchester

MA tornado of 1953 was

the deadliest US tornado

since 1950.

Deadliest US Tornadoes:

Worchester, MA

June 9, 1953

New England Tornadoes

http://www.erh.noaa.gov/box/

A supercell thunderstorm

produced three

tornadoes including an

EF3 tornado that

traveled 39 miles from

Westfield to Charlton, MA.

Tornado Outbreak

Springfield, MA

June 1, 2011

http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=50854

National Tornado Statistics

http://www.spc.noaa.gov/wcm/#data

Area-Weighted

Time-Series

Tornado

Statistics by US

State

New England

states have the

fewest average

annual tornado

occurrence east

of the Rockies.

National Tornado Statistics

Tornado

Data

(1951-2011)

http://www.spc.noaa.gov/wcm/#data

Tornado data for 1951 to 2010 obtained from the Storm

Prediction Center “Storm Data” publication for NCDC.

Dataset Includes:

Location

Path Lengths

Time

Magnitude

Injuries/Fatalities

Damages

New England Tornado Climatology

New England

Tornado

Climatology

(1951-2010)

http://www.spc.noaa.gov/wcm/#data

A lack of consistency

in older tornado

reports reduces

confidence in the

accuracy of the

data.0

20

40

60

80

100

120

140

1951-60 1961-70 1971-80 1981-90 1991-00 2001-10

Tota

l To

rna

do

Re

po

rts

Decade

CT MA ME NH RI VT

*

*RI - No reports prior to 1971.

*

New England Tornado Climatology

New Hampshire

Tornado

Climatology

(1951-2010)

http://www.spc.noaa.gov/wcm/#data

An unusually high

number of

tornado reports

from 1961 to

1973.

0

5

10

15

20

25

30

35

40

1951-60 1961-70 1971-80 1981-90 1991-00 2001-10

Tota

l N

um

be

r o

f Ev

en

ts

Unknown F0 F1 F2 F3 F4 F5

CT MA ME NH RI VT

New England Tornado Climatology

New England Tornado

Climatology

(1981-2010)

http://www.spc.noaa.gov/wcm/#data

The most recent climate

normal period is of

reasonable length and

consistency for analysis.

0

10

20

30

40

50

60

70

Tota

l To

rna

do

Re

po

rts

Decade

1981-90 1991-00 2000-10

New England Tornado Climatology

New England Tornado Climatology

(1981-2010)

http://www.spc.noaa.gov/wcm/#data

New England Tornado Climatology

New England

Tornado

Climatology

(1981-2010)

http://www.spc.noaa.gov/wcm/#data

Tornadoes occur

most often during

warm season

from May

through

September. 0

5

10

15

20

25

Tota

l To

rna

do

Re

po

rts

CT MA ME NH RI VT

New England Tornado Climatology

New England

Tornado

Climatology

(1981-2010)

http://www.spc.noaa.gov/wcm/#data

Tornadoes occur

most often during

the afternoon

hours and rarely

occur over night. 0

5

10

15

20

25

Tota

l To

rna

do

Re

po

rts

CT MA ME NH RI VT

New England Tornado Climatology

New England

Tornado

Climatology

(1981-2010)

http://www.spc.noaa.gov/wcm/#data

Locations of New

England tornado

origins.

Highest highest

tornado density

occurs over

southeastern CT.

Tornadoes per 100 km2

1-2

1

<1

New England Population Distribution

Distribution of

New England

Urban Centers

http://2010.census.gov/2010census/data/

Southern New

England is part of

the densely

populated

northeast

corridor.

Image Source: Annemarie

Schneider/NASA Landsat

Distribution of Urban Surfaces (2010)

Providence

BostonWorchester

ConnecticutRiver

Valley

New England Population Distribution

Distribution of

New England

Urban Centers

http://www.spc.noaa.gov/wcm/#data

Parts of southern

New England’s most

densely populated

urban/suburban

landscapes

are located within

the areas of highest

tornado

occurrence.

Total hazard is a

function of event

occurrence and

potential impact

Population Density& Tornado Tracks

Population Density

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

-2 -1.5 -1 -0.5 0 0.5 1 1.5 2

Torn

ad

o O

cc

urr

en

ce

Tornado Impact

New England Tornado Hazard

Total Tornado Hazard for New

England Counties

(High/Low Continuum)

http://www.spc.noaa.gov/wcm/#data

Tornado occurrence

calculated as an index accounting for tornado

count and intensity (SPC).

Impact assessed as the people/property that could be impacted by a tornado (US Census Bureau 2010).

Median

Me

dia

n

http://2010.census.gov/2010census/data/

High

Occurrence/Low

Impact

High

Occurrence/High

Impact

Low

Occurrence/Low

Impact

Low

Occurrence/High

Impact

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

-2 -1.5 -1 -0.5 0 0.5 1 1.5 2

Torn

ad

o O

cc

urr

en

ce

Tornado Impact

Total hazard is a

function of event

occurrence and

potential impact

New England Tornado Hazard

Total Tornado Hazard for New

England Counties

(High/Low Continuum)

http://www.spc.noaa.gov/wcm/#data

Median

Me

dia

n

20 Counties (30%) 13 Counties (19%)

13 Counties (19%) 21 Counties (30%)

ProvidenceNew Haven

Fairfield

NorfolkWindham

http://2010.census.gov/2010census/data/

New England Tornado Hazard

Total Tornado Hazard for

New England Counties

(High/Low Continuum)

Densely populated counties of

southern New England coincide

with the region’s highest

tornado occurrence.

These areas have the

highest hazard relative to

the rest of the region.

http://www.spc.noaa.gov/wcm/#data http://2010.census.gov/2010census/data/

*

** *

**

New England Tornado Hazard

Total Tornado Hazard for

New England Counties

(Product of Occurrence

and Impact)

http://www.spc.noaa.gov/wcm/#data

Tornado probability of

occurrence

multiplied by the

probability of impact

humans/infrastructure.

Evaluated as a product may

overstate the relative hazard.*

*

*

*

*

*

*

*

*

**

*

Next Step:

Beyond knowing where tornadoes are most likely to occur and the areas

where the impact will be highest, it is important to understand the

mechanisms that lead to the formation of tornadoes. Studies indicate

areas of enhanced convection and increased storm frequency during the

warm season that coincide with areas of highest tornado occurrence

(Lombardo & Colle 2010, 2011; Waslua et. al 2002; Murray & Colle 2011).

Prepare database of detailed weather observations (where available)

for the time of each tornado.

Compare the weather characteristics during each event to the general

atmosphere conditions associated with regional convective and other

severe thunderstorm events.

Resources:

Storm Prediction Center (SPC) Storm http://www.spc.noaa.gov/wcm/#data

US Census Bureau (2010) http://2010.census.gov/2010census/data/

Dixon, R.W., A.E. Mercer, J. Choi, and J.S. Allen (2011) Tornado Risk Analysis: Is Dixie Alley and Extension of Tornado Alley? Bulletin of the American Meteorological Society 92(4), 433-441

Dixon, R.W. and T.W Moore (2012) Tornado Vulnerability in Texas. Weather, Climate, and Society. 59-67. doi: 10.1175/WCAS-D-11-00004.1

Lewis, T.R. (2006) The Tornado Hazard In Southern New England:

History, Characteristics, Student and Teacher Perceptions. Journal of Geography 105, 258-266.

Questions?

New Hampshire State Climate Office

The New Hampshire State Climate Office (NHSCO) resides within the Department

of Geography at the University of New Hampshire.

The NHSCO is officially recognized by the American Association of State

Climatologists and the National Oceanic and Atmospheric Administration (NOAA).

http://www.unh.edu/stateclimatologist/ Follow on Twitter at: https://twitter.com/nh_sco