ABSTRACT
Whirl Wind and Strong Wind Analysis Based On C-Band Doppler Radar
(Case Study Sidoarjo 15 February, 22 November, and 8 Desember 2017)
By
ANANGGIRIEZA NUGRAHA
11.13.0087
It has been acknowledged by BNPB report in 2017 that period of whirlwind and strong
wind phenomena is occurred along 2017 in Sidoarjo Regency. This was reported in the disaster
event report by BNPB. The damage caused by this incident was large enough to reach 1507
houses damage. This condition is an indication of atmospheric conditions and is also supported
by other factors, such as population density in the region. This research was conducted by the
identification and analysis of the occurrence of whirlwind and strong wind from the point of
view of atmospheric conditions. Through this study, the author intends to know the condition
of the atmosphere when the incidence of whirlwind and strong wind, knowing the parameters
of the atmosphere that can be a sign of whirlwind and strong wind, and identify the differences
between tornado and strong wind based on weather radar image.
This research was conducted by analysis and identification on some parameters, i.e.
atmospheric lability index which is the result of upper air observation, surface observation
(synoptic), and weather radar image identification. This process of analysis and identification
was conducted using the location of observation data closest to the location of the incident in
Krian Sub-district (Keboharan and Terung Kulon Villages) and Waru Sub-district (Tambak
Rejo, Tambak Sumur and Tambak Sawah Villages) on 15 February, 22 November and 8
December 2017. The results show that the atmospheric conditions of whirlwind and strong
wind are volatile, the largest lability index occurring on November 22, 2017 (LI = [-4.7]; KI =
39.2; CAPE = 2548 J / kg). The parameters that can be used as a sign of whirlwind and strong
wind occurrence are the decrease in air temperature, air pressure, and increase in humidity
significantly, and followed by rain with thunder at the time after the incident. Differences of
whirlwind and strong wind are also identified through weather radar images, in the event of a
whirlwind seen comma echo pattern, this pattern is not seen in strong wind (December 8, 2017).
Keywords: Whirlwind, strong wind, atmospheric lability, weather radar