Intensity and Inner-Core Structure of Typhoon Haiyan (2013) near Landfall: Doppler Radar Analysis

Abstract

Abstract The intensity and inner-core structure of an extremely intense tropical cyclone, Typhoon Haiyan (2013), were examined using real-time ground-based Doppler radar products from the Guiuan radar over the period of about 2.5 h immediately before the storm approached Guiuan in Eastern Samar, Philippines. Haiyan’s wind fields from 2- to 6-km altitude were retrieved by the ground-based velocity track display (GBVTD) technique from the Doppler velocity data. The GBVTD-retrieved maximum wind speed reached 101 m s−1 at 4-km altitude on the right side of the track. The relatively fast forward speed of Haiyan, about 11 m s−1, increased maximum wind speed on the right-hand side of the storm. Azimuthal mean tangential wind increased with height from 2 to 5 km, and a local maximum of 86 m s−1 occurred at 5-km altitude. The central pressure was estimated as 906 hPa with an uncertainty of ±4 hPa by using the GBVTD-retrieved tangential wind and by assuming gradient wind balance. The radius of maximum radar reflectivity was about 23 km from the center, a few kilometers inside the radius of maximum wind. The reflectivity structure was highly asymmetric at and above 3-km altitude, and was more symmetric below 3-km altitude in the presence of relatively weak vertical shear (~4 m s−1). The center of the eyewall ring was tilted slightly downshear with height.