The tropical cyclone (TC) outer surface wind structure is an important consideration in warnings for maritime activities and landfall. Analyses of observations of the low-level wind structure are required for improved warnings of critical threshold wind values, such as the 35-kt and 50-kt wind radii. The objectives of this research are to use the NASA scatterometer (NSCAT) surface wind observations to specify these critical wind radii and thus to describe the characteristics of nine western North Pacific TCs during the 15 September 1996 to 30 June 1997 period. Because these NSCAT observations are not reliable for wind speeds exceeding 30-35 kt, a partial conservation of angular momentum profile is assumed from 300 km into the TC maximum wind radius and the 35-, 50-, and 100-kt radii are calculated. Critical wind radii values in four quadrants (front, right, rear, and left) of the TCs are found to be comparable to the Joint Typhoon Warning Center (JTWC) critical wind radii values issued in warnings. An outer vortex wind profile beyond the set radius assuming a linear slope dependent on the TC latitude is used to determine the radial extent of cyclonic winds (i.e., a size estimate). In general, this estimate of radial extent of cyclonic winds is also comparable to the radius of zero winds estimated by determining where the cyclonic flow turned to anticyclonic flow in the NSCAT sea-surface wind swaths