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Tropical Cyclone Module

Tropical Cyclone Module

30 Mar, 2023

The extreme and rapid changes in atmospheric pressure and wind fields in a tropical cyclone may strongly influence hydrodynamics and waves in a water body, especially in nearshore areas. Storm surges induced by pressure depletion and strong winds tend to pile up water against the shore; subsequent coastal inundation and erosion can cause severe damage. Beyond the flooding issues due to cyclones, modeling their environmental impacts from erosion, spills, and contaminant transport are essential. 

The Tropical Cyclone Module allows the user to import, and edit tropical cyclone tracks and data from a range of different sources. These tracks can then be displayed and managed in EE before running EFDC+ to compute the impact of the cyclone wind and pressure fields on the model hydrodynamics.

Cyclone Models in EFDC+

With this module, EFDC+ will internally generate the cyclone fields during the simulation using very lightweight cyclone track data and a parametric cyclone model. Four existing models address tropical cyclones:

  •  

    • Holland (1980)

    • Hubbert et al. (1991)

    • McConochie et al. (2004) and

    • Willoughby et al. (2006).

All four of these approaches are available in the new EEMS Tropical Cyclone module. The Holland (1980) model uses symmetric pressure and gradient wind profiles without the inflow angle. Hubbert et al. (1991) is a variation on the Holland (1980) model but applies a constant inflow angle and bearing of the maximum wind speed relative to the cyclone’s direction of movement.

The McConochie et al. (2004) model is similar to Hubbert et al. (1991) but uses a distance-dependent inflow angle and a wind speed-dependent boundary layer coefficient. In Willoughby et al. (2006), the gradient wind speed profile is determined based on the tangential wind component in the eye and the one beyond the transition zone. See the EFDC+ Theory Document for further details on these models. 

Pre-processing Data in EFDC+ Explorer

EFDC+ Explorer (EE) allows the user to import cyclone tracks in different formats. The pre-processing steps in EE include visualizing, editing, filling in the missing data, and other steps.

A number of online data sources are available to provide forecasts and archives of cyclone tracks. Some of the cyclone track formats supported by EEMS are:

– NOAA (National Oceanic and Atmospheric Administration of the United States)

Cyclone tracks are provided in HURDAT2 format with two datasets: the Atlantic hurricane database for 1851-2020 and the Northeast and North Central Pacific hurricane database for 1949-2020.

– JTWC (Joint Typhoon Warning Center of the U.S Navy)

The JTWC best track data source includes the following datasets: Southern Hemisphere (1945-2019), Northern Indian Ocean (1945-2019), and Western North Pacific Ocean (1945-2019).

– RSMC (Regional Specialized Meteorological Centre)

Six regional centers provide cyclone track forecasts and archives for different regions around the world as shown in Table 1 below.

Table 1 Tropical Cyclone Regional Specialised Meteorological Centres (RSMCs) in the world

RSMC Miami-Hurricane Center

NOAA/NWS National Hurricane Center, USA.

The Caribbean Sea, Gulf of Mexico,

North Atlantic and eastern North Pacific Oceans

RSMC Tokyo-Typhoon Centre

Japan Meteorological Agency

Western North Pacific Ocean

and the South China Sea

RSMC-tropical cyclones New Delhi

India Meteorological Department

North Indian Ocean

The Bay of Bengal and the Arabian Sea

RSMC La Réunion-Tropical Cyclone Centre

Météo-France

South-West Indian Ocean

(including the Mozambique Channel)

RSMC Nadi-Tropical Cyclone Centre

Fiji Meteorological Service

South-West Pacific Ocean

RSMC Honolulu-Hurricane Center

NOAA/NWS, USA

Central North Pacific Ocean

Activate the Tropical Cyclone Module

The Graphical User Interface (GUI) for the Tropical Cyclone module in EE can be activated from the Wind Forcing entry in the Hydrodynamics module, as shown in Figure 1. A dropdown list allows you to select the parametric cyclone model as shown in Figure 2, including:

  • Holland (1980),

  • Hubbert et al. (1991),

  • McConochie et al. (2004), and

  • Willoughby et al. (2006).

To use a tropical cyclone model, select from the drop-down list as shown in Figure 2.

Figure 1. Activate the Cyclone Module.

Figure 2. Cyclone Model selection.



To edit the selected cyclone module, the user clicks on the Edit button, then the Tropical Cyclone Module will be displayed as shown in Figure 3:

  • Cyclone Model: this field contains the selected cyclone models as described above and in the Figure 2.

  • Number of Tracks: this shows the number of cyclone tracks that have been imported.

  • Base Date: It will be taken from the EFDC+ model's base date (e.g 2005-01-01).

  • In the General tab, the default values are filled for air density, ambient pressure, and the bearing angle of maximum wind speed relative to the forward direction of the cyclone. However, the user can modify these fields' values. The value for UTM Zone is taken from the UTM Zone of the model set. (see Figure 4)

  • In the Tracks tab, It shows information on the selected cyclone track as Number of Points and track properties. The Figure 5 shows the Tracks tab without any tracks imported.



Figure 3. Tropical Cyclone Module form.

Figure 4. Tropical Cyclone Module: General tab.