Showing papers in "Monthly Weather Review in 2018"
TL;DR: In this paper, the authors used statistical postprocessing of systematic errors to obtain reliable and accurate probabilistic forecasts for ensemble weather predictions. But, this is done with distri...
Abstract: Ensemble weather predictions require statistical postprocessing of systematic errors to obtain reliable and accurate probabilistic forecasts. Traditionally, this is accomplished with distri...
220 citations
TL;DR: In this paper, a review of the literature on upper-tropospheric transient wave packets along the midlatitude jet stream is presented, with an emphasis on developments during the last 15 years.
Abstract: Rossby wave packets (RWPs) are Rossby waves for which the amplitude has a local maximum and decays to smaller values at larger distances. This review focuses on upper-tropospheric transient RWPs along the midlatitude jet stream. Their central characteristic is the propagation in the zonal direction as well as the transfer of wave energy from one individual trough or ridge to its downstream neighbor, a process called “downstream development.” These RWPs sometimes act as long-range precursors to extreme weather and presumably have an influence on the predictability of midlatitude weather systems. The paper reviews research progress in this area with an emphasis on developments during the last 15 years. The current state of knowledge is summarized including a discussion of the RWP life cycle as well as Rossby waveguides. Recent progress in the dynamical understanding of RWPs has been based, in part, on the development of diagnostic methods. These methods include algorithms to identify and track RWPs ...
137 citations
TL;DR: In this article, the authors assimilated all-sky every-10-min infrared radiances from Himawari-8 with a regional numerical weather prediction model and investigated its impact on real-world tropical cyclone (TC) analyses and forecasts for the first time.
Abstract: Japan’s new geostationary satellite Himawari-8, the first of a series of the third-generation geostationary meteorological satellites including GOES-16, has been operational since July 2015. Himawari-8 produces high-resolution observations with 16 frequency bands every 10 min for full disk, and every 2.5 min for local regions. This study aims to assimilate all-sky every-10-min infrared (IR) radiances from Himawari-8 with a regional numerical weather prediction model and to investigate its impact on real-world tropical cyclone (TC) analyses and forecasts for the first time. The results show that the assimilation of Himawari-8 IR radiances improves the analyzed TC structure in both inner-core and outer-rainband regions. The TC intensity forecasts are also improved due to Himawari-8 data because of the improved TC structure analysis.
109 citations
TL;DR: Wang et al. as mentioned in this paper reported that heavy rainfall occurred at both the inland frontal zone and coastal warm sector in southern China during 10-11 May 2014, which is a typical pattern in the early-summer rainy season.
Abstract: Heavy rainfall occurred at both the inland frontal zone and coastal warm sector in southern China during 10–11 May 2014, which is a typical pattern in the early-summer rainy season. To clar...
99 citations
TL;DR: The second generation GEFS/R model was used to train a contiguous United States (CONUS)-wide gridded forecast system as discussed by the authors, which is used to forecast the United States weather.
Abstract: Approximately 11 years of reforecasts from NOAA’s Second-Generation Global Ensemble Forecast System Reforecast (GEFS/R) model are used to train a contiguous United States (CONUS)-wide gridd...
96 citations
TL;DR: In this paper, the impacts of assimilating all-sky infrared satellite radiances from Himawari-8, a new-generation geostationary satellite that shares similar remote sensing technology, were explored.
Abstract: This study explores the impacts of assimilating all-sky infrared satellite radiances from Himawari-8, a new-generation geostationary satellite that shares similar remote sensing technology ...
69 citations
Pacific Northwest National Laboratory1, Lawrence Livermore National Laboratory2, National Center for Atmospheric Research3, Deutscher Wetterdienst4, University of Michigan5, Met Office6, University of Exeter7, University of Grenoble8, European Centre for Medium-Range Weather Forecasts9, Ghent University10, Royal Meteorological Institute11, University of Rostock12, Lawrence Berkeley National Laboratory13
TL;DR: In this article, the authors classified the resolved fluid dynamics, unresolved fluid dynamics and resolved fluid flow as resolved, unresolved and resolved components of a numerical weather, climate, or Earth system model.
Abstract: Numerical weather, climate, or Earth system models involve the coupling of components. At a broad level, these components can be classified as the resolved fluid dynamics, unresolved fluid ...
66 citations
TL;DR: In this article, the skill of the Arctic stratospheric retrospective ensemble forecasts (hindcasts) of the European Centre for Medium-Range Weather Forecasts extended-range system is analyzed with a focus on the focus of the polar regions.
Abstract: The skill of the Arctic stratospheric retrospective ensemble forecasts (hindcasts) of the European Centre for Medium-Range Weather Forecasts extended-range system is analyzed with a focus o...
63 citations
TL;DR: The use of convection-permitting (CP) forecast models in the tropics has lagged behind forecast models for numerical weather prediction in the US and the UK.
Abstract: Forecasting convective rainfall in the tropics is a major challenge for numerical weather prediction. The use of convection-permitting (CP) forecast models in the tropics has lagged behind ...
63 citations
TL;DR: In this article, the authors evaluate the impact of an interactive air-sea coupling between an operational global deterministic medium-range weather forecasting system and an ice-ocean forecasting system, and show that the most significant impact is associated with a decreased cyclone intensification, with a reduction in the tropical cyclone false alarm ratio.
Abstract: The importance of coupling between the atmosphere and the ocean for forecasting on time scales of hours to weeks has been demonstrated for a range of physical processes. Here, the authors evaluate the impact of an interactive air–sea coupling between an operational global deterministic medium-range weather forecasting system and an ice–ocean forecasting system. This system was developed in the context of an experimental forecasting system that is now running operationally at the Canadian Centre for Meteorological and Environmental Prediction. The authors show that the most significant impact is found to be associated with a decreased cyclone intensification, with a reduction in the tropical cyclone false alarm ratio. This results in a 15% decrease in standard deviation errors in geopotential height fields for 120-h forecasts in areas of active cyclone development, with commensurate benefits for wind, temperature, and humidity fields. Whereas impacts on surface fields are found locally in the vicin...
60 citations
TL;DR: In this article, the first practice of assimilating real-world all-sky GOES-16 ABI infrared brightness temperature (BT) observations using an ensemble-based data assimilation system is presented.
Abstract: This article presents the first practice of assimilating real-world all-sky GOES-16 ABI infrared brightness temperature (BT) observations using an ensemble-based data assimilation system co...
TL;DR: In this article, the authors examined the physical mechanism that was responsible for a heat wave in South Korea in August 2016 and showed that the anomalous high geopotential height over the Kamchatka Peninsula in 2016 was triggered by strong convection in the western-to-central subtropical Pacific through atmospheric teleconnections.
Abstract: It is important to understand the dynamical processes that cause heat waves at regional scales. This study examined the physical mechanism that was responsible for a heat wave in South Korea in August 2016. Unlike previous August heat waves over the Korean Peninsula, the intensity of the geopotential height over the Kamchatka Peninsula in August 2016 was the strongest since 1979, which acted as an atmospheric blocking in the downstream region of the Korean Peninsula. Therefore, the anomalous high geopotential height in Mongolia, where the surface temperature was quite high, was observed persistently in August 2016. This anomalous high in Mongolia induced northerly winds with warm temperatures onto the Korean Peninsula, which contributed to a heat wave in August 2016. We further showed that the anomalous high geopotential height over the Kamchatka Peninsula in August 2016 was triggered by strong convection in the western-to-central subtropical Pacific through atmospheric teleconnections, which was ...
TL;DR: It has been speculated, but not previously shown, that damage variability is caused by strong hurricanes as mentioned in this paper, but it has not previously been shown that it is the case for other types of hurricanes.
Abstract: Strong hurricanes cause severe, but highly variable, wind damage to homes and community infrastructure. It has been speculated, but not previously shown, that damage variability is caused b...
TL;DR: Satellite observations have revealed that some of the world's most intense deep convective storms occur near the Sierras de Cordoba, Argentina, South America as discussed by the authors, where a C-band, dual-polarization Doppler radar was used.
Abstract: Satellite observations have revealed that some of the world’s most intense deep convective storms occur near the Sierras de Cordoba, Argentina, South America. A C-band, dual-polarization Do...
TL;DR: In this paper, the authors evaluated the impact of assimilating high-resolution inner-core reconnaissance observations on tropical cyclone initialization and prediction in the 2013 version of the operational Hurricane Weather Research and Forecasting (HWRF) model.
Abstract: This study evaluates the impact of assimilating high-resolution inner-core reconnaissance observations on tropical cyclone initialization and prediction in the 2013 version of the operational Hurricane Weather Research and Forecasting (HWRF) model. The 2013 HWRF data assimilation system is a GSI-based hybrid ensemble-variational system that in this study uses the Global Data Assimilation System ensemble to estimate flow-dependent background error covariance. Assimilation of inner-core observations improves track forecasts and reduces intensity error after 18-24 h. The positive impact on the intensity forecast is mainly found in weak storms, where inner-core assimilation produces more accurate tropical cyclone structures and reduces positive intensity bias. Despite such positive benefits, there is degradation in short-term intensity forecasts that is attributable to spin-down of strong storms, which has also been seen in other studies.There are several reasons for the degradation of intense storms....
TL;DR: In this article, a new three-dimensional turbulent kinetic energy subgrid mixing scheme was developed using the Advanced Research version of the Weather Research and Forecasting (WRF) Model.
Abstract: A new three-dimensional (3D) turbulent kinetic energy (TKE) subgrid mixing scheme is developed using the Advanced Research version of the Weather Research and Forecasting (WRF) Model (WRF-A...
TL;DR: In this paper, the contribution of low-frequency (>100 d), Madden-Julian Oscillation (MJO), and convectively coupled equatorial wave (CCEW) variability to the skill in predicting convection and winds in the tropics at weeks 1-3 is examined.
Abstract: In this study, the contribution of low-frequency (>100 d), Madden-Julian Oscillation (MJO), and convectively coupled equatorial wave (CCEW) variability to the skill in predicting convection and winds in the tropics at weeks 1-3 is examined. We use subseasonal forecasts from the Navy Earth System Model (NESM), NCEP Climate Forecast System version 2 (CFSv2), and ECMWF during boreal summer 1999-2015. A technique for performing wavenumber-frequency filtering on subseasonal-to-seasonal (S2S) forecasts is introduced and applied to these datasets. This approach is better able to isolate regional variations in MJO forecast skill than traditional global MJO indices.Biases in the mean state and in the activity of the MJO and CCEWs are smallest in the ECMWF model. The NESM overestimates cloud cover as well as MJO, Equatorial Rossby, and Mixed-Rossby Gravity / Tropical Depression activity over the West Pacific. The CFSv2 underestimates convectively coupled Kelvin wave activity. The predictive skill of the mod...
TL;DR: The relationship between radial and azimuthal variations in the composite characteristics of convective bursts (CBs) is studied in this paper, that is, regions of the most intense upward motion in tropical cyclones.
Abstract: The relationship between radial and azimuthal variations in the composite characteristics of convective bursts (CBs), that is, regions of the most intense upward motion in tropical cyclones...
TL;DR: The authors identified four recurrent weather regimes over North America from October to March through k-means clustering applied to MERRA daily 500-hPa geopotential heights over the 1982-2014 pe...
Abstract: Four recurrent weather regimes are identified over North America from October to March through a k-means clustering applied to MERRA daily 500-hPa geopotential heights over the 1982–2014 pe...
TL;DR: In this paper, the authors propose a model to generate turbulence in nested large-eddy simulation (LES) domains, which can be used to simulate multiscale simulations with mesoscale and LES models.
Abstract: Realistic multiscale simulations involve coupling of mesoscale and large-eddy simulation (LES) models, thus requiring efficient generation of turbulence in nested LES domains. Herein, we ex...
TL;DR: A satellite-based investigation is performed of a class of tropical cyclones that unexpectedly undergo rapid intensification (RI) in moderate vertical wind shear between 5 and 10 m s−1 as mentioned in this paper.
Abstract: A satellite-based investigation is performed of a class of tropical cyclones (TCs) that unexpectedly undergo rapid intensification (RI) in moderate vertical wind shear between 5 and 10 m s−...
TL;DR: In this article, the role of large-scale circulation in causing extreme precipitation events was investigated, and it was found that, during winter, it often coexists with an upper-tropospheric Rossby wave train that has prominent anomalous southerlies over the region of interest.
Abstract: While much of India is used to heavy precipitation and frequent low pressure systems during the summer monsoon, toward the northwest and into Pakistan, such events are uncommon. Here, as much as a third of the annual rainfall is delivered sporadically during the winter monsoon by western disturbances. Such events of sparse but heavy precipitation in this region of typically mountainous valleys in the north and desert in the south can be catastrophic, as in the case of the Pakistan floods of July 2010. In this study, extreme precipitation events (EPEs) in a box approximately covering this region (25°–38°N, 65°–78°E) are identified using the APHRODITE gauge-based precipitation product. The role of the large-scale circulation in causing EPEs is investigated: it is found that, during winter, it often coexists with an upper-tropospheric Rossby wave train that has prominent anomalous southerlies over the region of interest. These winter EPEs are also found to be strongly collocated with incident western...
TL;DR: In this paper, the authors compare tropical and NH forecast skill for quantitative precipitation forecasts (QPFs) in the NCEP Global Forecast System (GFS) and ECMWF integrated forecast system (IFS) during January 2015-March 2016.
Abstract: Despite decades of research on the role of moist convective processes in large-scale tropical dynamics, tropical forecast skill in operational models is still deficient when compared to the extratropics, even at short lead times. Here we compare tropical and Northern Hemisphere (NH) forecast skill for quantitative precipitation forecasts (QPFs) in the NCEP Global Forecast System (GFS) and ECMWF Integrated Forecast System (IFS) during January 2015–March 2016. Results reveal that, in general, initial conditions are reasonably well estimated in both forecast systems, as indicated by relatively good skill scores for the 6–24-h forecasts. However, overall, tropical QPF forecasts in both systems are not considered useful by typical metrics much beyond 4 days. To quantify the relationship between QPF and dynamical skill, space–time spectra and coherence of rainfall and divergence fields are calculated. It is shown that while tropical variability is too weak in both models, the IFS is more skillful in pro...
TL;DR: In this paper, a data assimilation system (DAS) is described for global atmospheric reanalysis from 0-to 100-km altitude, applied to the 2014 austral winter of the Deep Propagating Gravity Wave Exper...
Abstract: A data assimilation system (DAS) is described for global atmospheric reanalysis from 0- to 100-km altitude. We apply it to the 2014 austral winter of the Deep Propagating Gravity Wave Exper...
TL;DR: In this article, nonhomogeneous regression models are used to statistically postprocess numerical ensemble weather prediction models, and such models are capable of forecasting full probabilistic weather prediction model.
Abstract: Nonhomogeneous regression models are widely used to statistically postprocess numerical ensemble weather prediction models. Such regression models are capable of forecasting full probabilit...
TL;DR: In this paper, the microphysics of convective cells in an outer rainband of Typhoon Nida (2016) using data collected by a newly upgraded operational polarimetric radar in China is analyzed.
Abstract: This study analyzes the microphysics of convective cells in an outer rainband of Typhoon Nida (2016) using data collected by a newly upgraded operational polarimetric radar in China. The li...
TL;DR: A prototype convection-allowing system using the Advanced Research version of the Weather Research and Forecasting (WRF-ARW) Model and employing an ensemble Kalman filter (EnKF) data assimilation technique has been developed and used during the spring 2016 and 2017 Hazardous Weather Testbeds as discussed by the authors.
Abstract: A prototype convection-allowing system using the Advanced Research version of the Weather Research and Forecasting (WRF-ARW) Model and employing an ensemble Kalman filter (EnKF) data assimilation technique has been developed and used during the spring 2016 and 2017 Hazardous Weather Testbeds. This system assimilates WSR-88D reflectivity and radial velocity, geostationary satellite cloud water path (CWP) retrievals, and available surface observations over a regional domain with a 3-km horizontal resolution at 15-min intervals, with 3-km initial conditions provided by an experimental High-Resolution Rapid Refresh ensemble (HRRR-e). However, no information on upper-level thermodynamic conditions in cloud-free regions is currently assimilated, as few timely observations exist. One potential solution is to also assimilate clear-sky satellite radiances, which provide information on mid- and upper-tropospheric temperature and moisture conditions. This research assimilates GOES-13 imager water vapor band ...
TL;DR: This work generates summer areal probabilistic maximum hourly precipitation forecasts across 11 regions of the Netherlands using the deterministic model HARMONIE–AROME as potential predictors and compares the skill of three statistical postprocessing methods: an extended logistic regression, a zero-adjusted gamma distribution, and a machine learning-based method, quantile regression forests (QRF).
Abstract: Probabilistic forecasts, which communicate forecast uncertainties, enable users to make better weather-based decisions. Using precipitation and numerous instability indices from the determi...
TL;DR: In this paper, the authors proposed an alternative approach to overcome the main difficulty of the En4DVar method caused by the use of adjoint models, which is called nonlinear least squares En4dvar (NLS-En4dVar) method.
Abstract: The En4DVar method is designed to combine the flow-dependent statistical covariance information of EnKF into the traditional 4DVar method. However, the En4DVar method is still hampered by its strong dependence on the adjoint model of the underlying forecast model and by its complexity, maintenance requirements, and the high cost of computer implementation and simulation. The primary goal of this paper is to propose an alternative approach to overcome the main difficulty of the En4DVar method caused by the use of adjoint models. The proposed approach, the nonlinear least squares En4DVar (NLS-En4DVar) method, begins with rewriting the standard En4DVar formulation into a nonlinear least squares problem, which is followed by solving the resulting NLS problem by a Gauss–Newton iterative method. To reduce the computational and implementation complexity of the proposed NLS-En4DVar method, a few variants of the new method are proposed; these modifications make the model cheaper and easier to use than the ...
TL;DR: In this article, the adaptive Bayesian scheme of Anderson uses available observations to update the Gaussian inflation distribution assigned for every state variable, and the likelihood function of the inflation is computed using model-minus-data innovation statistics.
Abstract: Spatially and temporally varying adaptive inflation algorithms have been developed to combat the loss of variance during the forecast due to various model and sampling errors. The adaptive Bayesian scheme of Anderson uses available observations to update the Gaussian inflation distribution assigned for every state variable. The likelihood function of the inflation is computed using model-minus-data innovation statistics. A number of enhancements for this inflation scheme are proposed. To prevent excessive deflation, an inverse gamma distribution for the prior inflation is considered. A non-Gaussian distribution offers a flexible framework for the inflation variance to evolve during the update. The innovations are assumed random variables, and a correction term is added to the mode of the likelihood distribution such that the observed inflation is slightly larger. This modification improves the stability of the adaptive scheme by limiting the occurrence of negative and physically intolerable inflat...