The Role of Tropical Cyclone Cempaka System Toward Spatial Daily Rainfall Total in Indramayu District, West Java Province, Indonesia

A Tropical Cyclone (TC) as a low air pressure system which grows in the tropical region, has a significant role  to the pattern of spatial daily rainfall total condition in certain places. Especially, places where located near this TC system position. The TC Cempaka system which had occurred over Southern part of Java Coast during 25-29 November 2017, has a significant role as well in relation to the spatial condition of daily rainfal total in Indramayu District, West Java Provinced, Indonesia. The spatial condition of daily rainfall total in Indramayu District happens spreading evenly when the Cempaka TC system is still in Low Pressure Area (LPA) and Tropical Depression (TD) states. This daily rainfall total shows having higher variation from very light intensity of less than 5 mm/day up to heavy intensity of 21 - 50 mm/day. This daily rainfall total condition has a good agreement with the season condition as Rainy Season (Wet Season) from October to March. In contrary, when the TC system had already declared to be a TC Cempaka system in mature state, the spatial condition of daily rainfall total over Indramayu District shows less variation and intensity. Commonly the spatial intensity of daily rainfall total during the mature state of TC Cempaka system activity seems only for very light (less than 5 mm/day) and light intensities (5 - 20 mm/day). This less daily rainfall total condition has clearly relationship with the wind speed condition over the region. Higher intensity in wind speed influences less developping potential convective cloud formation which is able to produce rainfall

Atmospheric Dynamics Analysis of Tropical Cyclone Cempaka

Tropical Cyclone (TC) is a cyclone which emerges, develops, and dissipates in the tropical waters. Indonesian waters where is located in the tropics as a maritime continent, becomes one of the region for emerging a TC in the world. The World Meteorological Organization (WMO) c.q. the Tropical Cyclone Committee (TCC) had already designated the Jakarta Tropical Cyclone Warning Center (TCWC) to monitor and report the activity of TCs in the area responsibility of 90° - 125° E 0° - 10° S. This Jakarta TCWC has started operating since 24 March 2008. In the end of November 2017, the TC named Cempaka developed. This TC Cempaka caused the appearance of extremee weather especially in Southern parts of Java Island coast. At least recorded some occurrences of extremeely heavy rainfalls in Pacitan Regency reaching up to 383 mm/day, floods, landslides, and strong winds of 41-53 knots in the surface.Domination of unstable atmospheric condition, strong convective lability, high potential thunderstorm occurrences, and strong convective condition are shown persistently during 27-29 November 2017. Cyclonic air masses over Southern part of Java Island have been detected since 23 November 2017. The monsoon activity seems to be weakened over this region in relation to the existence of this tropical disturbance. The thickness of wet air mass reaches up to 200 mb having a significant role to maintain supporting water vapor to the development of TC Cempaka. The Madden Julian Oscillation (MJO) has also contributed to support the emerging of TC Cempaka in this case

Impact-based forecasting in South East Asia – what underlies impact perceptions?

The move towards impact-based forecasting presents a challenge for forecasters, who must combine information not just on what the weather might be, but also on what the weather might do. Yet different hazards and impacts are qualitatively distinct, meaning such information cannot be easily or straightforwardly integrated. The present study aimed to provide a way of characterising seemingly disparate impacts. In a collaboration between UK psychologists and partners from three meteorological organisations in Indonesia, Malaysia and the Philippines, the psychometric paradigm was employed to investigate how forecasters and stakeholders perceive weather-related impacts. Participants provided ratings of nine categories of impacts on a total of 10 characteristics, as well as providing an overall impact severity rating. Principal components analysis revealed differing component solutions across countries, which explained around 75% of the variance in perceptions. There were some similarities across all countries, with the characteristics ‘worry’ and ‘destructiveness’ loading positively together, as well as ‘likelihood of harm’ and ‘seriousness of harm’. We did not find strong evidence to indicate that forecasters and stakeholders perceive impacts in different ways. Our results highlight the complex nature of impact perceptions, which are characterised not just by objective factors such as impact scope and duration, but also subjective factors, such as worry and perceived severity

Judgment and decision strategies used by weather scientists in southeast Asia to classify impact severity

Impact-based weather forecasting requires forecasters to predict what weather might do (impact information), rather than solely what weather might be (meteorological information). In a collaboration between the UK Met Office, UK psychologists, and weather scientists in Indonesia, Malaysia, The Philippines, and Vietnam, the present study employed Judgment Analysis and decision strategy comparisons to better understand weather scientists’ impact severity judgments. In the Judgment Analysis Task, weather scientists (from Indonesia, Malaysia, the Philippines, and Vietnam) made numerical and categorical severity judgments for 70 hypothetical heavy rainfall events, each described via six impacts (e.g., number of deaths, number of people affected). The hypothetical impacts were generated from a multivariate distribution estimated from a distribution of real rainfall events. Subsequently, participants provided categorical severity classifications for a list of impact values for each type of impact (Threshold Identification Task) to aid the identification of decision strategies. In all four countries, weather scientists’ severity judgments were best predicted by incorporating all six impacts via a compensatory judgment strategy. However, considerable individual differences were identified in the weights assigned to the different impacts and in the identified thresholds for each impact’s categorical severity classification. To improve impact-based forecasting, meteorological agencies should seek to enhance consistency among forecasters

Investigating the decision thresholds for impact-based warnings in South East Asia

The move towards impact-based forecasting presents a challenge for forecasters, who must combine information not just on what the weather might be, but also on what the weather might do. Such forecasts require an integration of both likelihood and impact severity information to issue a particular weather warning. The current pre-registered study focusses on forecasters' and stakeholders’ thresholds for determining the level of impact-based warnings, set in an area of the world particularly susceptible to extreme weather events. Set in the context of one hazard (heavy rainfall or river flooding), forecasters and stakeholders from Indonesia, Malaysia and the Philippines provided hypothetical impact-based warnings for impacts of varying likelihood. Results indicated generally good alignment with the warnings implied by previously developed impact tables. In the one country where a comparison was possible (the Philippines), we did not find evidence to suggest that forecasters and stakeholders use different thresholds for issuing warnings. We suggest that warning thresholds should be subject to regular monitoring wherever in the world an impact-based approach is used