create_full_track: Impute hurricane tracks to finer time scale

Description

Inputs data on a hurricane's track and imputes to a finer time resolution.
For example, if the hurricane tracks are recorded at 6-hour intervals, this
could be used to impute locations and windspeeds at 15-minute intervals.
This function also does some reformatting necessary for later functions in
the stormwindmodel package.

Usage

1
2

Arguments

hurr_track

Dataframe with hurricane track data for a single
storm. The dataframe must include columns for date-time (year, month, day,
hour, minute; e.g., "198808051800" for August 5, 1988, 18:00 UTC),
latitude, longitude, and wind speed (in knots). The column
names for each of these must be date, latitude,
longitude, and wind. See the example floyd_tracks
dataset for an example of the required format.

tint

Interval (in hours) to which to interpolate the tracks. The
default is 0.25 (i.e., 15 minutes)

Details

The function uses natural cubic splines for interpolation, both for location
and for wind speed. Degrees of freedom are based on the number of available
observations for the storm.

Value

A version of the storm's track data with
latitude, longitude, and wind speed interpolated between
observed values. Also, wind speed is converted in this function to m / s
and the absolute value of the latitude is taken (necessary for further
wind speed calculations). Finally, the names of some columns are
changed (tclat for latitude, tclon for longitude, and
vmax for wind speed.)

Note

This function imputes between each original data point, and it starts
by determing the difference in time between each pair of data points.
Because of this, the function can handle data that includes a point
that is not at one of the four daily synoptic times (00:00, 06:00, 12:00,
and 18:00). Typically, the only time hurricane observations are given
outside of synoptic times for best tracks data is at landfall.

After imputing the tracks, longitude is expressed as a positive number.
This is so the output will work correctly in later functions to fit the
wind model. However, be aware that you should use the negative value of
longitude for mapping tracks from the output from this function.