Documentation for the Tropical Cyclone Observations-Based (TC-OBS) Database

This page provides documentation for the TC-OBS Database. The following tables provide information about the file and dimensional structure of the new database, as well as details about the various parameters contained therein. The database contains the full complement of Best Track/HURDAT2 parameters for the period 1989-2014, as well as a series of new obsevations-based estimates that comprise the core of the new database. Also provided are interpolated versions of some of the key Best Track parameters to facilitate easy comparison between the TC-OBS parameters and the Best Track.

The database is still under construction, but significant portions are now complete. The current status of each parameter is indicated in the tables below using the following key:

• complete: Parameter values have been finalized -- the database contains full data for this parameter.
• validation: Parameter values have been computed, but need to be validated prior to being considered as 'complete'.
• in progress: Work is actively underway on the methods used to estimate this parameter.
• future work: These are parameters that were not part of the original proposed scope of work, but which could be of interest for a future version of the database.

In total, there are 87 parameters defined in the database, including dimension sizes, coordinate variables, reference Best Track parameters, and the new observations-based parameters.

The table applies to version 0.38 of the TC-OBS Database, built 19 January 2016. This is release candidate #1 (RC1).

NOTE: A final version of the database will be built for release to the RPI member companies within the next day or so.

A full set of validation plots are currently being generated. These can be viewed on the applications page.

Parameters defining the file structure, etc.

Dimension Sizes

The TC-OBS Database includes 6 dimensions. The respective size of each dimension is given in the following table.

Parameter	Type	Size	Status
nmaxcyclones	integer	405	complete
nmaxtimepoints_BT	integer	160	complete
nmaxtimepoints	integer	1200	complete
nmaxquadrants	integer	4	complete
nmaxradialpoints	integer	501	complete
nmaxwindthresholds	integer	7	complete

Coordinate Variables

A coordinate variable is provided for each dimension in the TC-OBS A coordinate variable whose dimension is itself. This is useful for using coordinate subscripting and also helps to define the NetCDF file structure in a manner that is self-describing. The following table lists the coordinate variables used in the TC-OBS Database.

Parameter	Type	Values	Units	Status
cyclone	integer	[0 ... 404]	unitless	complete
timepoint_BT	integer	[0 ... 159]	unitless	complete
timepoint	integer	[0 ... 1199]	unitless	complete
quadrant	integer	[0 ... 3]	unitless	complete
radius	integer	[0 ... 500]	n mi	complete
threshold	integer	[0 ... 6]	unitless	complete

Ancillary parameters related to the coordinate variables

A couple ancillary parameters provide the central azimuth of each quadrant and the value of each wind speed threshold (used to define the thresholds of interest for the wind radii and radii exceedance probability parameters).

Parameter	Type	Values	Units	Status
quadrant_central_azimuth	integer	[45, 135, 225, 315]	degrees (measuring clockwise from north)	complete
wind_speed_threshold	integer	[34, 50, 64, 83, 96, 113, 137]	knots	complete

Tunable parameters for the objective methods

The objective methods used to construct the observations-based output parameters have several parameters that control how much influence a nearby observation has versus one that is further away. Since these can be tuned to get results with different characteristics, the value of each tunable parameter is provided for purposes of database provenance.

Parameter	Type	Value	Unit	Status
observational_influence_window_half_width_time	float	6	hours	complete
efolding_time_scale_for_observation_influence	float	4	hours	complete
efolding_data_scale_for_background_influence	float	0.6666667	effective observational data points	complete
efolding_scale_for_fuzzy_classification	float	0.10	effective closeness to the maximum value of the observational classification parameter within the moving window	complete

Metadata Parameters

Parameters which indicate availability of data from various datasets for the given cyclone

Each of the following parameters simply indicates if data from each of the three source datasets was available for a given cyclone. The remaining two parameters indicate if track information is available for the cyclone from the Willoughby-Rahn center-finding method.

Parameter	Type	Rank	Status
VDM_data_present	logical	1	complete
FLIGHT_data_present	logical	1	complete
QSCAT_data_present	logical	1	complete
FLIGHT_wind_center_trak_file_present	logical	1	complete
FLIGHT_wind_center_fixs_file_present	logical	1	complete

Parameters that provide metadata about each cyclone

A number of cyclone-level metadata parameters are provided in the database. Each of these parameters provides one item of metadata per cyclone. These metadata range from the stormname and stormid given to the cyclone, to information as to which basin it was in, what peak development status the cyclone achieved, how many data points are present for the cyclone, and whether the storm made landfall.

Parameter	Type	Rank	Source	Status
CYCLONE_BT_npoints	integer	1	computed quantity	complete
CYCLONE_TCOBS_npoints	integer	1	computed quantity	complete
CYCLONE_ATCF_stormid	string	1	NHC post-season ATCF storm table	complete
CYCLONE_ATCF_stormstatus	string	1	NHC post-season ATCF storm table	complete
CYCLONE_ATCF_begin_date	string	1	NHC post-season ATCF storm table	complete
CYCLONE_ATCF_end_date	string	1	NHC post-season ATCF storm table	complete
CYCLONE_ATCF_peak	string	1	NHC post-season ATCF storm table	complete
CYCLONE_ATCF_stormbasin	string	1	NHC post-season ATCF storm table	complete
CYCLONE_ATCF_stormyear	string	1	NHC post-season ATCF storm table	complete
CYCLONE_ATCF_stormnumber	string	1	NHC post-season ATCF storm table	complete
CYCLONE_ATCF_cyclone_number	string	1	NHC post-season ATCF storm table	complete
CYCLONE_ATCF_all_stormbasins	string	1	NHC post-season ATCF b-decks	complete
CYCLONE_ATCF_all_subregions	string	1	NHC post-season ATCF b-decks	complete
CYCLONE_ATCF_all_stormnames	string	1	NHC post-season ATCF b-decks	complete
CYCLONE_ATCF_all_stormstatii	string	1	NHC post-season ATCF b-decks	complete
CYCLONE_IBTrACS_stormid	string	1	IBTrACS (v03r07)	complete
CYCLONE_TCOBS_cyclone_made_landfall	logical	1	computed quantity	complete
CYCLONE_TCOBS_closest_approach_to_land	float	1	computed quantity	complete

Best Track (HURDAT2) Parameters

'Best Track' parameters from the NHC post-season ATCF b-decks

The Best Track parameters provided in the database come from the NHC post-season archive ATCF b-decks. Since HURDAT2 is built from these b-decks, the data parameters provided here are equivalent to the respective parameters in HURDAT2. Each parameter includes one value for each time point in the cyclone's lifetime. Output is generally 6-hourly except when off-synoptic time points are included (e.g., to indicate the exact time of landfall, peak intensity, or a status change of the cyclone).

Parameter	Type	Rank	Source	Unit	Status
BT_time	integer	2	NHC post-season ATCF b-decks	seconds since 1970-01-01 00:00:00.0 UTC	complete
BT_yyyymmddhhmm	string	2	NHC post-season ATCF b-decks	(human-readable date/time)	complete
BT_subregion	string	2	NHC post-season ATCF b-decks	('A' = Arabian Sea, 'B' = Bay of Bengal, etc.)	complete
BT_stormname	string	2	NHC post-season ATCF b-decks	(ATCF-assigned stormname, e.g. KATRINA)	complete
BT_stormstatus	string	2	NHC post-season ATCF b-decks	('TD' = Tropical Depression, 'TS' = Tropical Storm, etc.)	complete
BT_latitude	float	2	NHC post-season ATCF b-decks	degrees_north	complete
BT_longitude	float	2	NHC post-season ATCF b-decks	degrees_east	complete
BT_central_pressure	integer	2	NHC post-season ATCF b-decks	millibar	complete
BT_maximum_sustained_wind	integer	2	NHC post-season ATCF b-decks	knots	complete
BT_wind_radii	integer	4	NHC post-season ATCF b-decks	nautical_mile	complete

'Best Track' parameters read from HURDAT2

One Best Track parameter is not found in the NHC post-season archive ATCF b-decks: the storm record identifier. This parameter indicates the nature of regular and/or special Best Track points (corresponding to landfall, change of status, peak intensity, etc.). A value for the record identifier is generally only provided for these special circumstances. The remainder of the time, this parameter will be set to _FillValue. Output is generally 6-hourly except when off-synoptic time points are included.

Parameter	Type	Rank	Source	Unit	Status
HURDAT2_record_identifier	string	2	HURDAT2	('L' = Landfall, 'W' = Peak max sustained wind speed, etc.)	complete

Non-'Best Track' Parameters from b-decks

Parameters from the NHC post-season b-decks which are NOT part of 'Best Track' collection

The ATCF b-decks also contain a number of parameters that are NOT best-tracked during the post-season analysis. As such, these quantities consist of operationally-estimated values (which may have been revised post facto during a later forecast cycle). These parameters are NOT included in HURDAT2. Prior to 2004, the b-decks did not provide values for many of these parameters. Thus, data from the NOAA/NESDIS Extended Best Track have been used to fill in any gaps. In the event in which a value was present for a given time both in the b-deck and in the Extended Best Track, the b-deck value is used. Generally, the Extended Best Track values are copied from the ATCF a-decks, so they still represent operationally-estimated values.

Each parameter includes one value for each time point in the cyclone's lifetime. Output is generally 6-hourly except when off-synoptic time points are included (e.g., to indicate the exact time of landfall, peak intensity, or a status change of the cyclone).

Parameter	Type	Rank	Source	Unit	Status
BDECK_cyclone_depth	string	2	NHC post-season ATCF b-decks		complete
BDECK_forecaster_initials	string	2	NHC post-season ATCF b-decks		complete
BDECK_estimated_seas_maximum_height	integer	2	NHC post-season ATCF b-decks	feet	complete
BDECK_cyclone_translation_speed	integer	2	NHC post-season ATCF b-decks	knots	complete
BDECK_cyclone_translation_direction	integer	2	NHC post-season ATCF b-decks	degrees (measuring clockwise from north)	complete
BDECK_outermost_closed_isobar_pressure	integer	2	NHC post-season ATCF b-decks	millibar	complete
BDECK_outermost_closed_isobar_radius	integer	2	NHC post-season ATCF b-decks	nautical mile	complete
BDECK_maximum_sustained_surface_wind_radius	integer	2	NHC post-season ATCF b-decks	nautical_mile	complete
BDECK_maximum_gust_surface_wind	integer	2	NHC post-season ATCF b-decks	knots	complete
BDECK_eye_diameter	integer	2	NHC post-season ATCF b-decks	nautical_mile	complete

Parameters defining the TC-OBS time output grid

Parameters that provide time information for each point in the cyclone's lifetime in the TC-OBS output time grid

These time-related parameters provide a value for each time point in the cyclone's lifetime. Output is generally hourly and also includes all of the off-synoptic time points from the Best Track time grid.

Parameter	Type	Rank	Source	Unit	Status
TCOBS_time	integer	2	constructed	seconds since 1970-01-01 00:00:00.0 UTC	complete
TCOBS_yyyymmddhhmm	string	2	constructed	(human-readable date/time)	complete
TCOBS_time_since_first_data_point	float	2	constructed	hours	complete

Parameters related to cyclone position

Reference Best Track position, interpolated to the output grid of the TC-OBS output parameters

To allow comparison between the TC-OBS track and the Best Track, the Best Track cyclone position values are interpolated to the TC-OBS output time grid using cubic-spline interpolation. Generally, output is hourly except when additional off-synoptic time points are included. Each parameter provides a value for every time point in the each cyclone's lifetime. Output is generally hourly and also includes all of the off-synoptic time points from the Best Track time grid.

Parameter	Type	Rank	Source	Unit	Status
BT_latitude_interpolated	float	2	interpolated from Best Track	degrees_north	complete
BT_longitude_interpolated	float	2	interpolated from Best Track	degrees_east	complete

TC-OBS output parameters related to the position of the cyclone wind center

The TC-OBS Database provides the following observationally-estimated parameters that are related to the precise location of the cyclone wind center. Several additional parameters are also included that are related to the position of the cyclone wind center relative to land. Each parameter provides a value for every time point in each cyclone's lifetime. Output is generally hourly and also includes all of the off-synoptic time points from the Best Track time grid.

Parameter	Type	Rank	Source	Unit	Status
TCOBS_wind_center_position_latitude	float	2	observations-based estimate	degrees_north	complete
TCOBS_wind_center_position_longitude	float	2	observations-based estimate	degrees_east	complete
TCOBS_wind_center_position_uncertainty	float	2	observations-based estimated uncertainty	nautical_mile	validation
TCOBS_wind_center_position_data_source_flag	integer	2	data source flag	unitless	future work
TCOBS_cyclone_translation_speed	float	2	calculated quantity	knots	validation
TCOBS_cyclone_translation_direction	float	2	calculated quantity	degrees	validation
TCOBS_distance_to_nearest_land	float	2	calculated quantity	nautical_mile	complete
TCOBS_wind_center_over_land	logical	2	calculated quantity	unitless ('True' or 'False')	complete

Parameters related to cyclone intensity

Reference cyclone intensity, interpolated to the output grid of the TC-OBS output parameters

To allow comparison between the TC-OBS intensity parameters and those of the Best Track, the Best Track intensity values are interpolated to the TC-OBS output time grid using linear interpolation (linear interpolation is used for this quantity, rather than cubic-spline interpolation, to ensure that the interpolated values do not overshoot the Best Track values). Each parameter provides a value for every time point in the each cyclone's lifetime. Output is generally hourly and also includes all of the off-synoptic time points from the Best Track time grid.

Parameter	Type	Rank	Source	Unit	Status
BT_maximum_sustained_surface_wind_interpolated	float	2	interpolated from Best Track intensity value	knots	complete

TC-OBS output parameters related to the cyclone intensity (maximum sustained surface wind)

The TC-OBS Database provides the following observationally-estimated parameters that are related to the maximum sustained surface wind speed anywhere in the cyclone. An additional parameter may eventually be included which provides the strongest maximum sustained surface wind in the weakest quadrant of the cyclone (this is useful for estimating the asymmetry of the wind field). Each parameter provides a value for every time point in each cyclone's lifetime. Output is generally hourly and also includes all of the off-synoptic time points from the Best Track time grid.

Parameter	Type	Rank	Source	Unit	Status
TCOBS_maximum_sustained_surface_wind	float	2	observations-based estimate	knots	complete
TCOBS_maximum_sustained_surface_wind_uncertainty	float	2	observations-based estimate	knots	complete
TCOBS_maximum_sustained_surface_wind_data_source_flag	integer	2	observations-based estimate	unitless	future work
TCOBS_maximum_sustained_surface_wind_in_weakest_quadrant	float	2	observations-based estimate	knots	future work
TCOBS_maximum_sustained_surface_wind_in_each_quadrant	float	3	observations-based estimate	knots	future work

Parameters related to minimum central pressure

Reference Best Track minimum central pressure, interpolated to the output grid of the TC-OBS output parameters

To allow comparison between the TC-OBS pressure parameter and that of the Best Track, the Best Track central pressure values are interpolated to the TC-OBS output time grid using cubic-spline interpolation. Each parameter provides a value for every time point in the each cyclone's lifetime. Output is generally hourly and also includes all of the off-synoptic time points from the Best Track time grid.

Parameter	Type	Rank	Source	Unit	Status
BT_central_pressure_interpolated	float	2	interpolated from Best Track intensity value	millibar	complete

TC-OBS output parameters related to the cyclone minimum central pressure

The TC-OBS Database provides the following observationally-estimated parameters that are related to the minimum central pressure of the cyclone. Each parameter provides a value for every time point in each cyclone's lifetime. Output is generally hourly and also includes all of the off-synoptic time points from the Best Track time grid.

Parameter	Type	Rank	Source	Unit	Status
TCOBS_central_pressure	float	2	observations-based estimate	millibar	future work
TCOBS_central_pressure_uncertainty	float	2	observations-based estimate	millibar	future work
TCOBS_central_pressure_data_source_flag	float	2	observations-based estimate	millibar	future work

Parameters related to the location of the maximum sustained surface wind

Reference b-deck radius of maximum winds (not a 'Best Track' quantity), interpolated to the output grid of the TC-OBS output parameters

The Best Track Database does not currently include a parameter related to the location of the maximum surface wind (e.g., radius of maximum wind), however the b-decks do contain a non-'Best Track' parameter for this. To allow comparison between the TC-OBS parameter, this b-deck values for this parameter are interpolated to the TC-OBS output time grid using cubic-spline interpolation. Each parameter provides a value for every time point in the each cyclone's lifetime. Output is generally hourly and also includes all of the off-synoptic time points from the Best Track time grid.

Parameter	Type	Rank	Source	Unit	Status
BDECK_maximum_sustained_surface_wind_radius_interpolated	float	2	interp. from b-deck (non-'Best Track') value	nautical_mile	complete

TC-OBS output parameters related to the location of the maximum sustained surface wind

The TC-OBS Database provides the following observationally-estimated parameters that are related to the location of the maximum sustained surface wind in the cyclone. Each parameter provides a value for every time point in each cyclone's lifetime. Output is generally hourly and also includes all of the off-synoptic time points from the Best Track time grid.

Parameter	Type	Rank	Source	Unit	Status
TCOBS_maximum_sustained_surface_wind_radius	float	2	observations-based estimate	nautical_mile	complete
TCOBS_maximum_sustained_surface_wind_radius_uncertainty	float	2	observations-based estimate	nautical_mile	complete
TCOBS_maximum_sustained_surface_wind_azimuth	float	2	observations-based estimate	degrees	validation
TCOBS_maximum_sustained_surface_wind_coherence	float	2	observations-based estimate	unitless	validation
TCOBS_maximum_sustained_surface_wind_latitude	float	2	observations-based estimate	degrees_north	future work
TCOBS_maximum_sustained_surface_wind_longitude	float	2	observations-based estimate	degrees_east	future work

Parameters related to the radial extent of surface winds (e.g., size)

Reference Best Track wind radii, interpolated to the output grid of the TC-OBS output parameters

To allow comparison between the TC-OBS wind radii parameter and that of the Best Track, the Best Track wind radii values are interpolated to the TC-OBS output time grid using cubic-spline interpolation. Each parameter provides a radius value for every time point in the each cyclone's lifetime for each of the four quadrants and the first three of the wind speed thresholds (34-, 50-, and 64-kt). Output is generally hourly and also includes all of the off-synoptic time points from the Best Track time grid.

Parameter	Type	Rank	Source	Unit	Status
BT_wind_radii_interpolated	float	2	interpolated from b-deck (non-'Best Track') value	nautical_mile	complete

TC-OBS output parameters for wind radii and size-related quantities

The TC-OBS Database provides the following observationally-estimated parameters that are related to the radial extent of maximum sustained surface winds of various thresholds. The wind radii parameter provides a value for every time point in each cyclone's lifetime for each of the seven wind speed thresholds (34-, 50-, 64-, 83-, 96-, 113-, and 137-kt) for each of the four quadrants of the cyclone. Output is generally hourly and also includes all of the off-synoptic time points from the Best Track time grid.

Parameter	Type	Rank	Source	Unit	Status
TCOBS_wind_radii	float	4	observations-based estimate	nautical_mile	complete
TCOBS_wind_radii_uncertainty	float	4	observations-based estimate	nautical_mile	complete
TCOBS_wind_radii_data_source_flag	float	4	observations-based estimate	unitless	future work

Parameters that provide alternative metrics for intensity and size

TC-OBS output parameters that provide alternative metrics to the traditional intensity and size parameters

The TC-OBS Database provides several observations-based estimates of alternative metrics for intensity and wind radii. The first alternative metric is related to the radial extent of maximum sustained surface winds of various thresholds. The wind exceedance parameter provides a value for probability of exceeding the given wind threshold for each time point in each cyclone's lifetime for each of the seven wind speed thresholds (34-, 50-, 64-, 83-, 96-, 113-, and 137-kt) for each of the four quadrants of the cyclone. The azimuthal average surface wind speed provides a metric which is less variable than the maximum sustained surface wind. Output is generally hourly and also includes all of the off-synoptic time points from the Best Track time grid.

Parameter	Type	Rank	Source	Unit	Status
TCOBS_sustained_surface_wind_azimuthal_average	float	2	observations-based estimate	knots	complete
TCOBS_multiple_wind_maxima_probability	float	2	observations-based estimate	unitless	future work
TCOBS_wind_exceedance_probability	integer	4	observations-based estimate	unitless	future work

This page was last updated 03 January 2016 by Jonathan Vigh.