scholarly journals PERBANDINGAN TEKNIK WARM DAN COLD START PADA MODEL WRF-3DVAR ASIMILASI DATA RADAR PADA PREDIKSI HUJAN LEBAT DI WILAYAH SURABAYA DAN SEKITARNYA

2020 ◽  
Vol 21 (1) ◽  
pp. 13-21
Author(s):  
Nayla Alvina Rahma ◽  
Jaka Anugrah Ivanda Paski
Keyword(s):  
False Alarm ◽  
Cold Start ◽  
Probability Of Detection ◽  
False Alarm Ratio ◽  
Warm Start ◽  
Constant Altitude ◽  
Position Indicator

Penelitian ini bertujuan untuk mengetahui perbedaan hasil prediksi hujan WRF-3DVAR asimilasi data radar dengan menggunakan teknik warm start (spin-up 12 jam) dan cold start (tanpa spin-up). Kejadian hujan yang dianalisis adalah kejadian hujan lebat tanggal 19-20 Januari 2019 di wilayah Surabaya dan sekitarnya. Data yang digunakan untuk simulasi adalah data Global Forescast System (GFS) dan data reflektivitas radar cuaca BMKG Surabaya produk Constant Altitude Plan Position Indicator (CAPPI). Analisis dilakukan dengan membandingan kondisi awal model pada parameter suhu dan kelembaban udara untuk mengetahui efek dari metode asimilasi data. Uji keandalan model dilakukan dengan melakukan verifikasi dikotomi (hujan/tidak hujan) hasil luaran model WRF dengan data hujan di 4 titik pengamatan, yaitu di Stasiun meteorologi Juanda, Stasiun meteorologi Perak, Stasiun Klimatologi Karangploso, dan Stasiun Geofisika Tretes. Hasil menunjukkan bahwa asimilasi data radar dengan mode cold start mempunyai hasil yang lebih baik dibandingkan dengan warm start, yang ditandai dengan lebih tingginya nilai Probability of Detection (POD) dan lebih rendahnya False Alarm Ratio (FAR). Asimilasi data dengan menggunakan mode cold start memiliki performa yang lebih baik dalam mendeteksi curah hujan per jam dengan ambang batas >1 mm dan >5 mm, sedangkan curah hujan >10 mm per jam lebih baik diprediksi menggunakan mode warm start.

scholarly journals Long-Term Performance Metrics for National Weather Service Tornado Warnings

2018 ◽  
Vol 33 (6) ◽  
pp. 1501-1511 ◽  
Author(s):  
Harold E. Brooks ◽  
James Correia
Keyword(s):  
False Alarm ◽  
Lead Time ◽  
Performance Metrics ◽  
Warning System ◽  
Probability Of Detection ◽  
False Alarms ◽  
National Weather Service ◽  
False Alarm Ratio ◽  
Tornado Warnings ◽  
Weather Service

Abstract Tornado warnings are one of the flagship products of the National Weather Service. We update the time series of various metrics of performance in order to provide baselines over the 1986–2016 period for lead time, probability of detection, false alarm ratio, and warning duration. We have used metrics (mean lead time for tornadoes warned in advance, fraction of tornadoes warned in advance) that work in a consistent way across the official changes in policy for warning issuance, as well as across points in time when unofficial changes took place. The mean lead time for tornadoes warned in advance was relatively constant from 1986 to 2011, while the fraction of tornadoes warned in advance increased through about 2006, and the false alarm ratio slowly decreased. The largest changes in performance take place in 2012 when the default warning duration decreased, and there is an apparent increased emphasis on reducing false alarms. As a result, the lead time, probability of detection, and false alarm ratio all decrease in 2012. Our analysis is based, in large part, on signal detection theory, which separates the quality of the warning system from the threshold for issuing warnings. Threshold changes lead to trade-offs between false alarms and missed detections. Such changes provide further evidence for changes in what the warning system as a whole considers important, as well as highlighting the limitations of measuring performance by looking at metrics independently.

scholarly journals An approach of constant false alarm ratio for improved target tracking

2020 ◽  
Vol 70 (3) ◽  
pp. 17-23
Author(s):  
Zvonko Radosavljević ◽  
Dejan Ivković
Keyword(s):  
False Alarm ◽  
Tracking Error ◽  
Probability Of Detection ◽  
Interacting Multiple Model ◽  
Multiple Model ◽  
Moving Targets ◽  
False Alarm Ratio ◽  
Motion Models ◽  
Areas Of Interest

Each radar has the function of surveillance of certain areas of interest. In particular, the radar also has the function of tracking moving targets in that territory with some probability of detection, which depends on the type of detector. Constant false alarm ratio (CFAR) is a very commonly used detector. Changing the probability of target detection can directly affect the quality of tracking the moving targets. The paper presents the theoretical basis of the influence of CFAR detectors on the quality of tracking, as well as an approach to the selection of CFAR detectors, CATM CFAR, which enables better monitoring by the Interacting Multiple Model (IMM) algorithm with two motion models. Comparative analysis of CA and CATM algorithm realized by numerical simulations has shown that CATM CFAR gives less tracking error with proportionally the same computer resources.

The Influence of Weather Watch Type on the Quality of Tornado Warnings and its Implications for Future Forecasting Systems

2021 ◽  
Author(s):  
Makenzie J. Krocak ◽  
Harold E. Brooks
Keyword(s):  
False Alarm ◽  
Lead Time ◽  
Severe Weather ◽  
Probability Of Detection ◽  
False Alarm Ratio ◽  
Tornado Warnings ◽  
General Improvement ◽  
The Difference ◽  
Tornado Warning

AbstractWhile many studies have looked at the quality of forecast products, few have attempted to understand the relationship between them. We begin to consider whether or not such an influence exists by analyzing storm-based tornado warning product metrics with respect to whether they occurred within a severe weather watch and, if so, what type of watch they occurred within.The probability of detection, false alarm ratio, and lead time all show a general improvement with increasing watch severity. In fact, the probability of detection increased more as a function of watch-type severity than the change in probability of detection during the time period of analysis. False alarm ratio decreased as watch type increased in severity, but with a much smaller magnitude than the difference in probability of detection. Lead time also improved with an increase in watch-type severity. Warnings outside of any watch had a mean lead time of 5.5 minutes, while those inside of a particularly dangerous situation tornado watch had a mean lead time of 15.1 minutes. These results indicate that the existence and type of severe weather watch may have an influence on the quality of tornado warnings. However, it is impossible to separate the influence of weather watches from possible differences in warning strategy or differences in environmental characteristics that make it more or less challenging to warn for tornadoes. Future studies should attempt to disentangle these numerous influences to assess how much influence intermediate products have on downstream products.

Examining sub-daily tornado warning performance and associated environmental characteristics

2021 ◽  
Author(s):  
Makenzie J. Krocak ◽  
Matthew D. Flournoy ◽  
Harold E. Brooks
Keyword(s):  
False Alarm ◽  
Probability Of Detection ◽  
Broad Sense ◽  
False Alarms ◽  
Environmental Characteristics ◽  
False Alarm Ratio ◽  
Intermediate Products ◽  
Tornado Warning ◽  
Operational Goal

AbstractIncreasing tornado warning skill in terms of the probability of detection and false alarm ratio remains an important operational goal. Although many studies have examined tornado warning performance in a broad sense, less focus has been placed on warning performance within sub-daily convective events. In this study, we use the NWS tornado verification database to examine tornado warning performance by order-of-tornado within each convective day. We combine this database with tornado reports to relate warning performance to environmental characteristics. On convective days with multiple tornadoes, the first tornado is warned significantly less often than the middle and last tornadoes. More favorable kinematic environmental characteristics, like increasing 0–1-km shear and storm-relative helicity, are associated with better warning performance related to the first tornado of the convective day. Thermodynamic and composite parameters are less correlated to warning performance. During tornadic events, over half of false alarms occur after the last tornado of the day decays, and false alarms are twice as likely to be issued during this time than before the first tornado forms. These results indicate that forecasters may be better “primed” (or more prepared) to issue warnings on middle and last tornadoes of the day, and must overcome a higher threshold to warn on the first tornado of the day. To overcome this challenge, using kinematic environmental characteristics and intermediate products on the watch-to-warning scale may help.

scholarly journals Verification of Tropical Cyclone Genesis Forecasts from Global Numerical Models: Comparisons between the North Atlantic and Eastern North Pacific Basins

2016 ◽  
Vol 31 (3) ◽  
pp. 947-955 ◽  
Author(s):  
Daniel J. Halperin ◽  
Henry E. Fuelberg ◽  
Robert E. Hart ◽  
Joshua H. Cossuth
Keyword(s):  
Tropical Cyclone ◽  
False Alarm ◽  
North Atlantic ◽  
North Pacific ◽  
Probability Of Detection ◽  
Early Years ◽  
Global Models ◽  
False Alarm Ratio ◽  
The North ◽  
The North Atlantic

Abstract Accurately forecasting tropical cyclone (TC) genesis is an important operational need, especially since the National Hurricane Center’s Tropical Weather Outlook product has been extended from 2 to 5 days. A previous study by the coauthors verified North Atlantic TC genesis forecasts from five global models out to 4 days during 2004–11. This study expands on the previous research by 1) verifying TC genesis forecasts over both the Atlantic and eastern North Pacific basins, 2) extending the forecast window to 5 days, and 3) updating the analysis period through 2014. Verification statistics are presented and compared between the two basins. Probability of detection and critical success indices generally are greater over the eastern North Pacific basin compared to the North Atlantic. There is a trade-off between models that exhibit a greater probability of detection and a greater false alarm ratio, and models that exhibit a smaller false alarm ratio and a smaller probability of detection. Results also reveal that the models preferentially miss TCs over the North Atlantic (eastern North Pacific) that have a relatively small radius of the outer closed isobar (radius of maximum wind) at the forecast genesis time. Overall, global models have become a more reliable source of TC genesis guidance during the past few years compared to the early years in the dataset.

scholarly journals Characteristics of Tornado Events and Warnings in the Southeastern United States

2019 ◽  
Vol 34 (4) ◽  
pp. 1017-1034 ◽  
Author(s):  
Alexandra K. Anderson-Frey ◽  
Yvette P. Richardson ◽  
Andrew R. Dean ◽  
Richard L. Thompson ◽  
Bryan T. Smith
Keyword(s):  
United States ◽  
False Alarm ◽  
Southeastern United States ◽  
Probability Of Detection ◽  
High Shear ◽  
Related Literature ◽  
False Alarm Ratio ◽  
Tornado Warnings ◽  
Tornado Warning

Abstract The southeastern United States has become a prime area of focus in tornado-related literature due, in part, to the abundance of tornadoes occurring in high-shear low-CAPE (HSLC) environments. Through this analysis of 4133 tornado events and 16 429 tornado warnings in the southeastern United States, we find that tornadoes in the Southeast do indeed have, on average, higher shear and lower CAPE than tornadoes elsewhere in the contiguous United States (CONUS). We also examine tornado warning skill in the form of probability of detection (POD; percent of tornadoes receiving warning prior to tornado occurrence) and false alarm ratio (FAR; percent of tornado warnings for which no corresponding tornado is detected), and find that, on average, POD is better and FAR is worse for tornadoes in the Southeast than for the CONUS as a whole. These measures of warning skill remain consistent even when we consider only HSLC tornadoes. The Southeast also has nearly double the CONUS percentage of deadly tornadoes, with the highest percentage of these deadly tornadoes occurring during the spring, the winter, and around local sunset. On average, however, the tornadoes with the lowest POD also tend to be those that are weakest and least likely to be deadly; for the most part, the most dangerous storms are indeed being successfully warned.

False Alarms, Tornado Warnings, and Tornado Casualties

2009 ◽  
Vol 1 (1) ◽  
pp. 38-53 ◽  
Author(s):  
Kevin M. Simmons ◽  
Daniel Sutter
Keyword(s):  
False Alarm ◽  
The United States ◽  
Probability Of Detection ◽  
False Alarms ◽  
Lead Times ◽  
Time Intervals ◽  
Standard Deviation Increase ◽  
False Alarm Ratio ◽  
Tornado Warnings ◽  
The Impact

Abstract This paper extends prior research on the societal value of tornado warnings to the impact of false alarms. Intuition and theory suggest that false alarms will reduce the response to warnings, yet little evidence of a “false alarm effect” has been unearthed. This paper exploits differences in the false-alarm ratio across the United States to test for a false-alarm effect in a regression model of tornado casualties from 1986 to 2004. A statistically significant and large false-alarm effect is found: tornadoes that occur in an area with a higher false-alarm ratio kill and injure more people, everything else being constant. The effect is consistent across false-alarm ratios defined over different geographies and time intervals. A one-standard-deviation increase in the false-alarm ratio increases expected fatalities by between 12% and 29% and increases expected injuries by between 14% and 32%. The reduction in the national tornado false-alarm ratio over the period reduced fatalities by 4%–11% and injuries by 4%–13%. The casualty effects of false alarms and warning lead times are approximately equal in magnitude, suggesting that the National Weather Service could not reduce casualties by trading off a higher probability of detection for a higher false-alarm ratio, or vice versa.

Intercomparison of High-Resolution Precipitation Products over Northwest Europe

2012 ◽  
Vol 13 (1) ◽  
pp. 67-83 ◽  
Author(s):  
C. Kidd ◽  
P. Bauer ◽  
J. Turk ◽  
G. J. Huffman ◽  
R. Joyce ◽  
...  
Keyword(s):  
High Resolution ◽  
False Alarm ◽  
Seasonal Cycle ◽  
Weather Forecasting ◽  
Ground Truth ◽  
Probability Of Detection ◽  
Naval Research ◽  
False Alarm Ratio ◽  
Northwest Europe ◽  
Bias Ratio

Abstract Satellite-derived high-resolution precipitation products (HRPP) have been developed to address the needs of the user community and are now available with 0.25° × 0.25° (or less) subdaily resolutions. This paper evaluates a number of commonly available satellite-derived HRPPs covering northwest Europe over a 6-yr period. Precipitation products include the Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA), the Climate Prediction Center (CPC) morphing (CMORPH) technique, the CPC merged microwave technique, the Naval Research Laboratory (NRL) blended technique, and the Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN) technique. In addition, the Geosynchronous Operational Environmental Satellite (GOES) precipitation index (GPI) and the European Centre for Medium-Range Weather Forecasting (ECMWF) operational forecast model products are included for comparison. Surface reference data from the European radar network is used as ground truth, supported by the Global Precipitation Climatology Centre (GPCC) precipitation gauge analysis and gauge data over the United Kingdom. Measures of correlation, bias ratio, probability of detection, and false alarm ratio are used to evaluate the products. Results show that satellite products generally exhibit a seasonal cycle in correlation, bias ratio, probability of detection, and false alarm ratio, with poorer statistics during the winter. The ECMWF model also shows a seasonal cycle in the correlation, although the results are poorer during the summer, while the bias ratio, probability of detection, and false alarm ratio are consistent through all seasons. Importantly, all the satellite HRPPs underestimate precipitation over northwest Europe in all seasons.

scholarly journals Estudio de la climatología ecuatorial andina con métodos numéricos: pronósticos de tiempo, validaciones y reconstrucción de la atmósfera

La Granja ◽  
2009 ◽  
Vol 10 (2) ◽  
pp. 16
Author(s):  
Enrique Palacios ◽  
Sheila Serrano Vincenti ◽  
Patricio Núñez
Keyword(s):  
False Alarm ◽  
Probability Of Detection ◽  
Forecasting Model ◽  
False Alarm Ratio ◽  
Model Version ◽  
Weather Research

La siguiente investigación, describe dos tipos de estudios acerca del clima y tiempo del Ecuador, implementando los modelos numéricos MM5 (Mesoescale Model versión 5) y WRF (Weather Research Forecasting Model), mostrando sus características principales e instalación para ajustarlo a las condiciones ecuatoriales. Los estudios que se realizan corresponden al pronóstico del tiempo del país, utilizando el modelo MM5 en variables como la temperatura, velocidad de viento y precipitaciones. El estudio de validación se lo hace sobre las precipitaciones de la ciudad de Quito a través de tablas de contingencia, estudiando los meses de agosto a octubre. Se logra así un POD (Probability of Detection) del 93,5% y un FAR (False Alarm Ratio) del 14%, evidenciando la temporada inusualmente seca que se registró en esas fechas. Asimismo se presenta la primera parte del estudio de la reconstrucción de la atmósfera ecuatorial, utilizando el modelo WRF, mostrando el estudio de los perfiles verticales de las velocidades de viento; para concluir este estudio será necesario examinar las series temporales de al menos 30 años. Se obtienen resultados preliminares con una zona de vientos máximos a los 17 km de altura, visualizando sobre este nivel una disminución de su intensidad.

scholarly journals The Identification and Verification of Hazardous Convective Cells over Oceans Using Visible and Infrared Satellite Observations

2008 ◽  
Vol 47 (1) ◽  
pp. 164-184 ◽  
Author(s):  
Michael F. Donovan ◽  
Earle R. Williams ◽  
Cathy Kessinger ◽  
Gary Blackburn ◽  
Paul H. Herzegh ◽  
...  
Keyword(s):  
False Alarm ◽  
Tropical Rainfall Measuring Mission ◽  
Probability Of Detection ◽  
Satellite Observations ◽  
Radar Reflectivity ◽  
False Alarm Ratio ◽  
Tropical Rainfall ◽  
Tropical Oceans ◽  
Internal Information ◽  
Convective Cells

Abstract Three algorithms based on geostationary visible and infrared (IR) observations are used to identify convective cells that do (or may) present a hazard to aviation over the oceans. The performance of these algorithms in detecting potentially hazardous cells is determined through verification with Tropical Rainfall Measuring Mission (TRMM) satellite observations of lightning and radar reflectivity, which provide internal information about the convective cells. The probability of detection of hazardous cells using the satellite algorithms can exceed 90% when lightning is used as a criterion for hazard, but the false-alarm ratio with all three algorithms is consistently large (∼40%), thereby exaggerating the presence of hazardous conditions. This shortcoming results in part from the algorithms’ dependence upon visible and IR observations, and can be traced to the widespread prevalence of deep cumulonimbi with weak updrafts but without lightning over tropical oceans, whose origin is attributed to significant entrainment during ascent.

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