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The northeastern depressed region of Bangladesh is highly susceptible to recurrent flash flooding due to excessive rainfall over these areas and in the upstream hilly regions. Two such severe pre-monsoon flash flood events occurred in 2016 and 2017. This research attempts to forecast both flash flood events using a coupled atmospheric-hydrological numerical weather prediction (NWP) model, namely the weather research and forecasting (WRF) model. The ARW (Advanced Research WRF) model is able to predict the rainfall over these areas with a lead time of 91 h. However, the discharge and water level are overestimated by the WRF-Hydro model. The model predicts a flash flood with a lag of approximately 12 h with respect to the highest amount of rainfall. The overall performances of the models were satisfactory. The two parameters, rainfall and subsequent discharge, which are required for delineation of lag time, were almost precisely simulated. Simulated values also had fewer errors, justified by the root mean squared error (RMSE) and mean absolute error values. The Nash–Sutcliffe efficiency criterion scores for model-derived discharge were close to 1.0, and the RMSE-observation standard deviation ratio scores were less than 0.5. This finding proves that the NWP models could be considered for forecasting flash flood events over selected areas of Bangladesh. [ABSTRACT FROM AUTHOR]

The physical and dynamical characteristics of pre-monsoon (March–May) thunderstorms (TS) are investigated over Bangladesh using the Weather Research and Forecasting (WRF) model. The model was run for 24-h using 6-hourly data sets as initial and lateral boundary conditions. The Milbrandt cloud microphysics scheme, Krain–Fritsch cumulus scheme, and Yonsei University planetary boundary layer are found to be the best combination by comparing the root mean square error of rainfall from 18 sensitivity experiments. The synoptic condition and atmospheric instability associated with three TS cases have been analyzed based on mean sea level pressure, convective available potential energy (CAPE), and thermodynamic indices. CAPE is found between 500 and 2700 J kg−1 at 0000 UTC for the TS cases. The presence of low-level southerly wind from the Bay of Bengal and upper-level westerly or north-westerly wind with speeds ranging from 5 to 30 m s−1 is found during the storms. The cloud characteristics and intensity were investigated based on Doppler Weather Radar and INSAT 3DR satellite observations. Cloud micro-physical hydrometeors and other composite features (e.g., cloud top and core precipitation altitude, length of squall line) were also studied by the model and then compared with available observed values. For 24-h rainfall, 2 × 2 contingency tables are computed using Model Evaluation Tools. Categorical skill scores such as proportion correct, frequency bias index, probability of false detection, false alarm ratio, and Gilbert skill score were calculated to evaluate the model's performance. The forecast goodness is found to be reasonably satisfactory after analyzing the significance of the skill scores. [ABSTRACT FROM AUTHOR]

The present study documents the first systematic assessment of a brothel in Bangladesh in terms of sexually transmitted disease (STD) and human immunodeficiency virus (HIV). A cross sectional study was undertaken on brothel-based commercial sex workers (CSWs) selected systematic random sampling to assess the prevalence of STDs and HIV among CSWs in a brothel setting. Two hundred and ninety-six CSWs were selected from a brothel with a population of 593 women. Following informed consent, endocervical and blood samples were obtained for the diagnosis of genital chlamydia, gonorrhoea, HIV and syphilis respectively. In addition, another 170 consecutive blood samples were collected from the total CSW population for HIV tests. All blood samples for HIV testing were made anonymous by removing patient identifiers before testing. Endocervical specimens were tested by polymerase chain reaction (PCR) for the diagnosis of genital chlamydia and gonorrhoea. Syphilis and HIV infections were diagnosed by serology. One hundred and sixty-nine (57.1%) of the women were Treponema pallidum haemagglutination (TPHA)-positive, 20 (6.8%) of the women were Venereal Disease Research Laboratory (VDRL)-positive at a greater than 1:8 dilution. Eighty-two (28%) of the women were found to be infected either by gonorrhoea or chlamydia. No HIV antibody was found in any of the 466 blood samples. A high prevalence of STDs and low prevalence of HIV in the CSWs in Bangladesh suggest potential for the rapid spread of HIV once it is introduced in this high-risk population. The opportunity to control STD and HIV infection in this population should not be missed, in order to prevent a large epidemic in the future. [ABSTRACT FROM AUTHOR]