Radius of maximum wind
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The radius of maximum wind, or 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.[1] It should be noted that this quantity has also been recently used in the study of tornadoes.[2]
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[edit] Determination of RMW
[edit] Aircraft
The RMW is traditionally measured by reconnaisance aircraft in the Atlantic basin.[1] It can also be determined on weather maps as the distance between the cyclone center and the system's greatest pressure gradient.
[edit] Satellite
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.[1]
[edit] 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.[3]
[edit] What RMW helps determine
[edit] Direct Strikes of tropical cyclones
It is considered a direct strike to a landmass when a tropical cyclone passes close enough to an airmass that areas inside the radius of maximum wind are experienced on land.[4]
[edit] Maximum Potential Intensity
The Emanuel equation for Maximum Potensity Potential relies upon the winds near the RMW of a tropical cyclone to determine its ultimate potential.[5]
[edit] Storm surge
The highest storm surge is normally coincident with the radius of maximum wind.
[edit] Swell generation within tropical cyclones
Due to the fact that 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.[6]
[edit] See Also
[edit] References
- ^ a b c S. A. Hsu and Adele Babin. Estimating the Radius of Maximum Winds Via Satellite During Hurricane Lili (2002) Over the Gulf of Mexico. Retrieved on 2007-03-18.
- ^ Donald W. Burgess and Michael A. Magsig. Understanding WSR-88D Signatures for the 3 May 1999 Oklahoma City Tornado. Retrieved on 2007-03-18.
- ^ S. A. Hsu and Zhongde Yana. [A Note on the Radium of Maximum Winds for Hurricanes.] Retrieved on 2007-03-18.
- ^ [National Weather Service. http://www.weather.gov/glossary/index.php?letter=d Glossary: D.] Retrieved on 2007-03-18.
- ^ Kerry A. Emanuel. Maximum Intensity Estimation. Retrieved on 2007-03-18.
- ^ Edward J. Walsh and C. Wayne Wright. Hurricane Wave Topography and Directional Wave Spectra in Near Real-Time. Retrieved on 2007-03-18.
