Sample Data Sets

Hurricanes Data

The U.S. National Hurricane Center records intensity and track information for tropical cyclones at six-hour intervals. The Hurricanes data set is an "extended best-track" (EBT) data set that adds six measured size parameters to the best-track data. The data were prepared by DeMaria, Pennington, and Williams (2004). The cyclones from 1988 to 2003 are included.

The version distributed with SAS/IML Studio is Version 1.6, released February 2004. An earlier version of the EBT data was analyzed in Mulekar and Kimball (2004) and Kimball and Mulekar (2004).

The data as assembled by DeMaria include the following variables.

name: storm name
date: date of observation, in SAS date format
hms: time of observation (UTC), in SAS time format
latitude: latitude of observation, in degrees north latitude
longitude: longitude of observation. Note: DeMaria encodes this variable as degrees west longitude. For ease of plotting, this variable is recoded as a (usually) negative value in degrees east longitude.
wind_kts: maximum low-level sustained wind speed, in knots
min_pressure: minimum central sea-level pressure, in hPa
pressure_outer_isobar: pressure of outer closed isobar, in hPa
radius_eye: radius of eye (if an eye exists), in nautical miles. Note: A nautical mile is one minute of latitude, or approximately 1.15 statute miles.
radius_max_wind: radius at which maximum wind speed was measured, in nautical miles
radius_64kt: average radius of 64-knot (hurricane strength) winds, in nautical miles
radius_50kt: average radius of 50-knot winds, in nautical miles
radius_34kt: average radius of 34-knot (tropical storm strength) winds, in nautical miles
radius_outer_isobar: radius of outer closed isobar, in nautical miles
storm_type: indicator of whether the system was purely tropical, subtropical, or extra-tropical
month: month
day: day of the month
time: time of day (UTC)
year: year
ID: storm identification number
radius_34kt_ne: radius of 34-knot (tropical storm strength) winds northeast of the storm’s center, in nautical miles
radius_34kt_se: radius of 34-knot (tropical storm strength) winds southeast of the storm’s center, in nautical miles
radius_34kt_sw: radius of 34-knot (tropical storm strength) winds southwest of the storm’s center, in nautical miles
radius_34kt_nw: radius of 34-knot (tropical storm strength) winds northwest of the storm’s center, in nautical miles
radius_50kt_ne: radius of 50-knot winds northeast of the storm’s center, in nautical miles
radius_50kt_se: radius of 50-knot winds southeast of the storm’s center, in nautical miles
radius_50kt_sw: radius of 50-knot winds southwest of the storm’s center, in nautical miles
radius_50kt_nw: radius of 50-knot winds northwest of the storm’s center, in nautical miles
radius_64kt_ne: radius of 64-knot (hurricane strength) winds northeast of the storm’s center, in nautical miles
radius_64kt_se: radius of 64-knot (hurricane strength) winds southeast of the storm’s center, in nautical miles
radius_64kt_sw: radius of 64-knot (hurricane strength) winds southwest of the storm’s center, in nautical miles
radius_64kt_nw: radius of 64-knot (hurricane strength) winds northwest of the storm’s center, in nautical miles

The storm_type variable is encoded as follows:

$\ast$	Tropical system
W	Tropical wave
D	Tropical disturbance
S	Subtropical storm
E	Extra-tropical storm
L	Remnant low

In addition to these variables, the data set contains the following variables, suggested in the analyses of Mulekar and Kimball (2004) and Kimball and Mulekar (2004). Missing values were converted to the SAS missing value.

category: indicator variable that corresponds to the Saffir-Simpson wind intensity scale
wind_mph: maximum low-level sustained wind speed, in miles per hour. This variable is computed as wind_kts times 1.15.
radius_64kt: average of nonmissing values of the 64-knot radii in the northeast, southeast, southwest, and northwest directions
radius_50kt: average of nonmissing values of the 50-knot radii in the northeast, southeast, southwest, and northwest directions
radius_34kt: average of nonmissing values of the 34-knot radii in the northeast, southeast, southwest, and northwest directions

The category variable is encoded according to the value of wind_kts (wind speed) as in Table A.2.

Table A.2: The Saffir-Simpson Intensity Scale

Category	Description	Wind Speed (Knots)
TD	Tropical depression	22–33
TS	Tropical storm	34–63
Cat1	Category 1 hurricane	64–82
Cat2	Category 2 hurricane	83–95
Cat3	Category 3 hurricane	96–113
Cat4	Category 4 hurricane	114–134
Cat5	Category 5 hurricane	135 or greater