| << | Profiling of Wind | >> |
Abstract
Observations from a Doppler radar, a wind profiler, a meteorological tower, and radiosondes were used to study the evolution of a thin-line echo that were observed in the radar reflectivity field over the Kanto Plain of Japan as Typhoon Higos passed in October 2002. Similar thin-line echoes are often observed with gust fronts. In addition, the thin-line echo was accompanied by gusty winds with wind speeds comparable to those of F2 tornadoes and followed by cold airflows, and passed the field site of the Meteorological Research Institute (MRI) in Tsukuba, Japan. Data from the MRI instrument array and from a surface observation network revealed that the thin-line echo was caused by a gust front.
Although it was demonstrated that the thin-line echo was due to a gust front, this gust front could not be categorized as a so-called thunderstorm gust front because it had no parent thunderstorm; rather, observations showed that the gust front in the present study was generated in a weak precipitation region between the typhoon center and a trailing outer rainband to the southwest. Doppler radar and wind profiler observations suggest that relatively strong downdrafts in the weak precipitation region and large momentum transported by the downdrafts from aloft (~ 4 km) to lower levels produced and maintained near-surface high winds behind the gust front.