8.6 Cyclones / Hurricanes / Typhoons

Wind and pressure fields created by severe storms can affected flooding and inundation in coastal areas. It is possible to apply a cyclone / hurricane / typhoon boundary within TUFLOW to capture these affects. Cyclone / hurricane / typhoon wind and pressure fields with the Holland parametric model (Holland, 1980) can be read in with either of the .tcf commands below (which are treated identically):

Read GIS Cyclone == <gis_line_layer> | <gis_point_layer>
Read GIS Hurricane == <gis_line_layer> | <gis_point_layer>

This command can be used to read a cyclone, hurricane or typhoon track. The attributes of the GIS layers are listed in Table 8.14 and are all float values. See Queensland Government (2001) for further information on the GIS attributes. The line layer defines the track of the cyclone. The point layer specifies the time the cyclone arrives at each point coordinate along the track, as well as associated parameters such as pressure and wind speed (see Table 8.14). It is not necessary to have points snapped to every vertex of the line – values will be interpolated between the digitised points. There must be points with attribute data snapped to the start and end of the polyline track.

The optional NO PRESSURE and NO WIND options deactivate the pressure/wind fields respectively. E.g. Read GIS Cyclone NO WIND == <gis_line_layer> | <gis_point_layer> will only apply the pressure field and ignore the wind.

Table 8.14: **GIS Attribute Details for Cyclone (2d_cyc) layer**
No.	Default GIS Attribute Name	Description	Type
1	Time	Time in hours.	Float
2	p0	Pressure at the eye (hPa).	Float
3	pn	Pressure of surrounds (hPa).	Float
4	R	Radius to maximum winds (m) (or ft if using Units == US Customary).	Float
5	B	Peakedness. See Queensland Government (2001).	Float
6	rho_air	Density of air (kg/m³) (or lb/ft³ if using Units == US Customary). If zero, Density of Air is used.	Float
7	km	A boundary layer (B/L) coefficient that transfers gradient level wind speeds to the mean near-surface wind. If zero, equation C.20 in the Queensland Government (2001) is used.	Float
8	ThetaMax	Line of maximum wind (degrees). See Queensland Government (2001).	Float
9	DeltaFM	Asymmetry factor. See Queensland Government (2001).	Float
10	bw_speed	Background wind speed in m/s (or ft/s if using Units == US Customary). Ignored if less than or equal to zero.	Float
11	bw_dirn	Background wind direction in degrees relative to East (0°), North (90°), etc..	Float

The generation of the wind and pressure fields are based on Appendix C of “Queensland Climate Change and Community Vulnerability to Tropical Cyclones – Ocean Hazards Assessment – Stage 1” (Queensland Government, 2001).

The wind and pressure fields can be output using the WI10 and AP options for Map Output Data Types. The background wind is applied outside R (the radius of maximum winds), if it exceeds the cyclone/hurricane wind speed.

Note: that Latitude must be specified (via .tcf command “Latitude == <latitude_value>”).