United States Tornado Touchdown Points 1950-2004

Frequently-anticipated questions:

• What does this data set describe?
  1. How should this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  3. What similar or related data should the user be aware of?
• How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How should this data set be cited?

   National Weather Service, Storm Prediction Center, 200509, United States Tornado Touchdown Points 1950-2004: National Atlas of the United States, Reston, VA.

   Online Links:

   • <http://nationalatlas.gov/atlasftp.html?openChapters=chpclim#chpclim>

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -159.68

   East_Bounding_Coordinate: -67.20

   North_Bounding_Coordinate: 49.07

   South_Bounding_Coordinate: 19.50

3. What does it look like?

4. Does the data set describe conditions during a particular time period?

   Beginning_Date: 19500101

   Ending_Date: 31-Dec-2004

   Currentness_Reference: Ground condition

5. What is the general form of this data set?

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?

      This is a Point data set. It contains the following vector data types (SDTS terminology):

      • Entity point (46931)

   2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000278. Longitudes are given to the nearest 0.000278. Latitude and longitude values are specified in Decimal degrees.

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is GRS1980.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257222.
      

7. How does the data set describe geographic features?

   Tornado touchdown point

   The point where a violently rotating column of air, in contact with both the ground and with the base of a powerful thunderstorm, first made contact with the ground. (Source: National Atlas of the United States)

   Shape

   The representation of the entity in the data. (Source: National Atlas of the United States)

   Value	Definition
   Point	1-dimensional element

   Tornadx020

   Internal sequence number. (Source: National Atlas of the United States)

   Range of values
   Minimum:	1
   Maximum:	46931

   Year

   The year in which the tornado occurred. (Source: National Atlas of the United States)

   Range of values
   Minimum:	1950
   Maximum:	2004

   Num

   The number of the tornado in the State, for a given year. (Source: National Oceanic and Atmospheric Administration, Storm Prediction Center)

   Range of values
   Minimum:	1
   Maximum:	232

   State

   The two-digit code for the State in which the tornado touched down. (Source: National Atlas of the United States)

   Formal codeset
   Codeset Name:	Codes for the Identification of the States, the District of Columbia and the Outlying Areas of the United States, and Associated Areas; (Federal Information Processing Standard (FIPS) 5-2): Washington, DC, National Institute of Standards and Technology.
   Codeset Source:	U.S. Department of Commerce

   Month

   The month in which the tornado occurred. (Source: National Atlas of the United States)

   Range of values
   Minimum:	1
   Maximum:	12

   Day

   The day of the month on which the tornado occurred. (Source: National Atlas of the United States)

   Range of values
   Minimum:	1
   Maximum:	31

   Date

   The date on which the tornado occurred, in the format month/day/year. (Source: National Atlas of the United States)

   Range of values
   Minimum:	1/3/1950
   Maximum:	12/29/2004

   Tor_no

   A count of tornadoes during the year. If a tornado with evidence of damage lifts off and touches down again within two miles, it is considered the same tornado. (Source: National Oceanic and Atmospheric Administration, Storm Prediction Center)

   Range of values
   Minimum:	1
   Maximum:	1817

   No_sts

   The number of States traversed by the tornado. Note that this is not a count of tornadoes, it is a count of the records, in the source data base, associated with one tornado. (Source: National Oceanic and Atmospheric Administration, Storm Prediction Center)

   Range of values
   Minimum:	1
   Maximum:	3

   State_tor

   An indication of whether the record describes a tornado that affected several States or only a single State. (Source: National Atlas of the United States)

   Value	Definition
   0	The tornado affected more than one State, and this record describes the tornado's entire path.
   1	The tornado affected only one State.

   Segno

   A flag indicating the nature of the record. (Source: National Oceanic and Atmospheric Administration, Storm Prediction Center)

   Value	Definition
   1	The record is for a tornado's entire path.

   STLAT

   The latitude of the point where the tornado touched down. (Source: National Atlas of the United States)

   Range of values
   Minimum:	18.20
   Maximum:	61.02

   STLON

   The West longitude of the point where the tornado touched down. (Source: National Atlas of the United States)

   Range of values
   Minimum:	64.90
   Maximum:	163.53

   SPLAT

   The latitude of the point where the tornado lifted off. (Source: National Atlas of the United States)

   Value	Definition
   0.00	The tornado lift-off point could not be differentiated from the touchdown point, or the tornado lift-off point is unknown.

   Range of values
   Minimum:	18.40
   Maximum:	61.02

   SPLON

   The West longitude of the point where the tornado lifted off. (Source: National Atlas of the United States)

   Value	Definition
   0.00	The tornado lift-off point could not be differentiated from the touchdown point, or the tornado lift-off point is unknown.

   Range of values
   Minimum:	64.90
   Maximum:	163.53

   LGTH

   The length of the tornado track in tenths of a statute mile (146 = 14.6 miles). Tracks may be nonlinear, so the length may not be the same as the great-circle distance from the touchdown point to the lift-off point. (Source: National Oceanic and Atmospheric Administration, Storm Prediction Center)

   Value	Definition
   0	The tornado touched down and lifted off at the same point, or the length of the tornado track is unknown.

   Range of values
   Minimum:	1
   Maximum:	3000

   Width

   For tornadoes prior to 1994, the mean tornado path width in tens of feet (528.00 = 5280.0 feet or 1 mile.) This is the mean width along the entire track. The minimum width is assumed to be 30 feet. A width was computed for each State that a tornado affected, and the mean was calculated from those values.

   For tornadoes from 1994 and later, the maximum width in tens of feet. (Source: National Atlas of the United States)

   Value	Definition
   0.00	The width of the tornado track is unknown.

   Range of values
   Minimum:	0.01
   Maximum:	999.00

   Fatal

   The number of fatalities caused by the tornado. Prior to 1994, the value 0 may indicate that the number of fatalities is unknown. (Source: National Oceanic and Atmospheric Administration, Storm Prediction Center)

   Range of values
   Minimum:	0
   Maximum:	116

   INJ

   The number of injuries caused by the tornado. Prior to 1994, the value 0 may indicate that the number of injuries is unknown. (Source: National Oceanic and Atmospheric Administration, Storm Prediction Center)

   Range of values
   Minimum:	0
   Maximum:	1740

   Damage

   For 1995 and earlier, property damage caused by the tornado, in dollars as indicated by a code value. For 1996 and later, property damage caused by the tornado, in millions of dollars. (Source: National Atlas of the United States)

   Value	Definition
   0.00	The amount of tornado damage is unknown.
   1.00	The tornado damage was less than $50.
   2.00	The tornado damage was between $50 and $499
   3.00	The tornado damage was between $500 and $4,999.
   4.00	The tornado damage was between $5,000 and $49,999.
   5.00	The tornado damage was between $50,000 and $499,999.
   6.00	The tornado damage was between $500,000 and $4,999,999.
   7.00	The tornado damage was between $5,000,000 and $49,999,999.
   8.00	The tornado damage was between $50,000,000 and $4999,999,999.
   9.00	The tornado damage was $500,000,000 or more.

   Range of values
   Minimum:	0.00
   Maximum:	1000.00

   F_Scale

   The damage classification according to the Fujita Tornado Damage Scale. The categories are based upon the estimated maximum winds occurring within the funnel. Wind estimates associated with damage are crude at best. Only one classification is given for each tornado. See <http://www.spc.noaa.gov/faq/tornado/f-scale.html> and <http://www.ncdc.noaa.gov/oa/satellite/satelliteseye/educational/fujita.html> for detailed information on the Fujita Tornado Scale. (Source: National Oceanic and Atmospheric Administration, Storm Prediction Center)

   Value	Definition
   -9	No F-Scale damage classification estimate is available.
   0	Estimated maximum wind speeds of 40-72 mph. Gale Tornado. Light damage: Some damage to chimneys; breaks twigs and branches off trees; pushes over shallow-rooted trees; damages signboards; some windows broken. Winds are below hurricane force.
   1	Estimated maximum wind speeds of 73-112 mph. Moderate Tornado. Moderate damage: Peels surfaces off roofs; mobile homes pushed off foundations or overturned; outbuildings demolished; moving autos pushed off the roads; trees snapped or broken. (Hurricane wind speed begins at 73 mph.)
   2	Estimated maximum wind speeds of 113-157 mph. Significant Tornado. Considerable damage: Roofs torn off frame houses; mobile homes demolished; frame houses with weak foundations lifted and moved; boxcars pushed over; large trees snapped or uprooted; light-object missiles generated.
   3	Estimated maximum wind speeds of 158-206 mph. Severe Tornado. Severe damage: Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forests uprooted; heavy cars lifted off the ground and thrown; weak pavement blown off roads.
   4	Estimated maximum wind speeds of 207-260 mph. Devastating Tornado. Devastating damage: Well constructed homes leveled; structures with weak foundations blown off some distance; cars thrown and disintegrated; large missiles generated; trees in forest uprooted and carried some distance away.
   5	Estimated maximum wind speeds of 261-318 mph. Incredible Tornado. Incredible damage: Strong frame houses lifted off foundations and carried considerable distance to disintegrate; automobile-sized missiles fly through the air in excess of 300 ft (100 m); trees debarked; incredible phenomena will occur.

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • National Weather Service, Storm Prediction Center

2. Who also contributed to the data set?

3. To whom should users address questions about the data?
   NOAA Storm Prediction Center
   SPC Warning Coordination Meteorologist
   1313 Halley Circle
   Norman, OK 73069
   USA
   

   405-579-0747 (voice)
   [email protected]
   

   Hours_of_Service: Monday - Friday 8:00 AM - 5:00 PM Eastern Time

Why was the data set created?

These data are intended for geographic display and analysis at the national level, and for large regional areas. The data should be displayed and analyzed at scales appropriate for 1:2,000,000-scale data. No responsibility is assumed by the National Weather Service or the National Atlas of the United States in the use of these data.

How was the data set created?

1. From what previous works were the data drawn?

   ONETOR5004 (source 1 of 1)

   National Oceanic and Atmospheri, National Weather Service, Storm Predicti, 200505, Tornado Statistics 1950-2004: NOAA Storm Prediction Center, Norman, OK.

   Online Links:

   • <http://www.spc.noaa.gov/wcm/>

   Type_of_Source_Media: Online

   Source_Contribution: Spatial and attribute information.

2. How were the data generated, processed, and modified?

   Date: Aug-2005 (process 1 of 1)

   The ASCII text file of tornado statistics for the years 1950 to 2004 was downloaded from the Storm Prediction Center and imported into Excel. Header text was added, then the file was loaded into ArcView and saved as a shapefile. Continuation records without latitude and longitude were deleted, as were records where latitude and longitude were 0.0. Records were deleted for ten tornadoes with touchdown points that fell in Canada, Mexico, the ocean, or Lake Michigan. For tornadoes that affected several States, the records with State information were deleted, but the records with full-path information were retained. Fields were converted from decimal values to integers where appropriate, and several typographic errors were corrected. Unnecessary attribute fields were deleted. The numeric State FIPS code was recalculated as a string and the values for Puerto Rico and the U.S. Virgin Islands were corrected. A final shapefile was created.

   Data sources used in this process:

   • ONETOR5004

3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

1. How well have the observations been checked?

2. How accurate are the geographic locations?

3. How accurate are the heights or depths?

4. Where are the gaps in the data? What is missing?

   This map layer includes the known tornado touchdown points in the United States, Puerto Rico, and the U.S. Virgin Islands, from 1950 through 2004. Tornadoes were deleted if their touchdown points fell outside the United States or in large water bodies. Records missing latitude and longitude values were also deleted.

5. How consistent are the relationships among the observations, including topology?

   No tests for logical consistency have been performed on this map layer.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: None

Use_Constraints:

None. Acknowledgement of the National Atlas of the United States of America and (or) the National Oceanic and Atmospheric Administration, National Weather Service, Storm Prediction Center would be appreciated in products derived from these data.

1. Who distributes the data set? (Distributor 1 of 1)
   Earth Science Information Center, U.S. Geological Survey
   507 National Center
   Reston, VA 20192
   

   1-888-ASK-USGS (1-888-275-8747) (voice)
   

   Contact_Instructions:

   In addition to the address above there are other ESIC offices throughout the country. A full list of these offices is at <http://ask.usgs.gov/esic_index.html>.

2. What's the catalog number I need to order this data set?

3. What legal disclaimers am I supposed to read?

   Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made by the U.S. Geological Survey or the National Oceanic and Atmospheric Administration regarding the utility of the data on any other system, nor shall the act of distribution constitute any such warranty. No responsibility is assumed by the U.S. Geological Survey or the National Oceanic and Atmospheric Administration in the use of these data.

4. How can I download or order the data?
   • Availability in digital form:

     Data format:	ESRI Shapefile
     Network links:	<http://nationalatlas.gov/atlasftp.html?openChapters=chpclim#chpclim>

     Data format:	SDTS
     Network links:	<http://nationalatlas.gov/atlasftp.html?openChapters=chpclim#chpclim>

   • Cost to order the data: There is no charge for the map layer.

Who wrote the metadata?

Dates:

Last modified: 19-Jun-2006

Metadata author:

Peg Rawson
National Atlas of the United States
12201 Sunrise Valley Dr
Reston, VA 20192

703-648-4183 (voice)
[email protected]

Metadata standard:

FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)