Radius of maximum wind

The radius of maximum wind (RMW) of a tropical cyclone is defined to be the distance between the center of the cyclone and its band of strongest winds. It is considered an important parameter in atmospheric dynamics and tropical cyclone forecasting.S. A. Hsu and Adele Babin. [http://www.nwas.org/ej/hsu/hsu_babin_2005.pdf Estimating the Radius of Maximum Winds Via Satellite During Hurricane Lili (2002) Over the Gulf of Mexico.] Retrieved on 2007-03-18.] It should be noted that this quantity has also been recently used in the study of tornadoes. [Donald W. Burgess and Michael A. Magsig. [http://www.wdtb.noaa.gov/modules/sls00/M3RADAR.pdf Understanding WSR-88D Signatures for the 3 May 1999 Oklahoma City Tornado.] Retrieved on 2007-03-18.]

Determination of RMW

Aircraft

The RMW is traditionally measured by reconnaissance aircraft in the Atlantic basin.S. A. Hsu and Adele Babin. [http://www.nwas.org/ej/hsu/hsu_babin_2005.pdf Estimating the Radius of Maximum Winds Via Satellite During Hurricane Lili (2002) Over the Gulf of Mexico.] Retrieved on 2007-03-18.] It can also be determined on weather maps as the distance between the cyclone center and the system's greatest pressure gradient.

atellite

The distance between the coldest cloud top temperature and the warmest temperatature within the eye, in infrared satellite imagery, is one method of determining RMW. The reason why this method has merit is that the strongest winds within tropical cyclones tend to be located under the deepest convection, which is seen on satellite imagery as the coldest cloud tops.S. A. Hsu and Adele Babin. [http://www.nwas.org/ej/hsu/hsu_babin_2005.pdf Estimating the Radius of Maximum Winds Via Satellite During Hurricane Lili (2002) Over the Gulf of Mexico.] Retrieved on 2007-03-18.]

Its average value in the Atlantic Basin

An average value of 47 km/29.4 miles was calculated as the mean of all hurricanes with a central pressure between a pressure of 909 hPa and 993 hPa. [ S. A. Hsu and Zhongde Yana. [A Note on the Radium of Maximum Winds for Hurricanes.] Retrieved on 2007-03-18.]

What RMW helps determine

The radius of maximum wind helps determine the direct strikes of tropical cyclones. Tropical cyclones are considered to have made a direct strike to a landmass when a tropical cyclone passes close enough to a landmass that areas inside the radius of maximum wind are experienced on land. [National Weather Service. [http://www.weather.gov/glossary/index.php?letter=d Glossary: D.] Retrieved on 2007-03-18.]

The radius of maximum wind is used within the maximum potential intensity equation. The Emanuel equation for Maximum Intensity Potential relies upon the winds near the RMW of a tropical cyclone to determine its ultimate potential. [Kerry A. Emanuel. [http://wind.mit.edu/~emanuel/pcmin/pclat/pclat.html Maximum Intensity Estimation.] Retrieved on 2007-03-18.]

The highest storm surge is normally coincident with the radius of maximum wind. Because the strongest winds within a tropical cyclone lie at the RMW, this is the region of a tropical cyclone which generates the dominant waves near the storm, and ultimately ocean swell away from the cyclone. [Edward J. Walsh and C. Wayne Wright. [http://www.onr.navy.mil/sci_tech/32/reports/docs/05/mmwalsh5.pdf Hurricane Wave Topography and Directional Wave Spectra in Near Real-Time.] Retrieved on 2007-03-18.]

ee also

*Eye (cyclone)
*Ocean swell
*Storm surge
*Tropical cyclone
*Wind

References