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Introduction to Tropical Meteorology, 2nd Edition, Chapter 9: Observations, Analysis, and Prediction
The chapter describes the challenges of tropical weather forecasting. We examine types of observations and weather analysis techniques used by tropical forecasters. Those analysis tools are applied to examples of tropical synoptic weather systems as well as mesoscale analysis and nowcasting. The last three sections focus on numerical weather prediction (NWP) including: the fundamentals, data assimilation, comparisons of statistical and dynamical models, ensemble techniques, cumulus convection in NWP, tropical cyclone prediction, and methods of forecast verification and validation. We have spec ...
Understanding the Role of Deterministic versus Probabilistic NWP Information
Understanding the Role of Deterministic versus Probabilistic NWP Information is part of the "NWP Training Series: Effective Use of NWP in the Forecast Process." This lesson first covers deterministic (single) NWP model forecasts and explains advantages and limitations through a case example. Then it discusses overcoming the limitations in deterministic forecasts through the use of ensemble forecast systems, and the use of deterministic and probabilistic forecasts together, through case examples.
Effective Use of High-Resolution Models
High-resolution models have transitioned from research into forecast operations, helping forecasters utilize additional mesoscale information after accounting for the inherent unpredictability of many small-scale phenomena. This module covers the major capabilities and limitations of models run without a convective parameterization using grid spacings of around 4 km or less. Model forecast interpretation issues are discussed, including introducing convective mode diagnostics such as updraft helicity and interpreting the forecast as an event prediction rather than as a precise point forecast. M ...
Introduction to the North American Ensemble Forecast System (NAEFS)
This webcast introduces the forecaster to the new multiple-forecast-center North American Ensemble Forecast System (NAEFS). Beginning with a brief review of the theory behind ensemble prediction, this presentation then introduces the elements of the NAEFS. These include the U.S. National Centers for Environmental Prediction’s Global Ensemble Forecast System (GEFS) and the Canadian Meteorological Center’s Ensemble Forecast System (CEFS). A description of each separate ensemble system is followed by a discussion of how the NAEFS improves the ensemble forecast over either the GEFS or CEFS alone. ...
How Models Produce Precipitation and Clouds - version 2
This module, part of the "NWP Training Series: Effective Use of NWP in the Forecast Process", explores how NWP models handle both grid-scale microphysical (precipitation) and convective processes through parameterizations and/or explicit methods, with an emphasis on how model treatment (and errors in the triggering) of these processes affects forecast depiction of precipitation and related forecast variables. Back in 2000, the subject matter expert for this module was Dr. Ralph Petersen of the National Centers for Environmental Prediction, Environmental Modeling Center (NCEP/EMC). Revisions to ...
Model Fundamentals - version 2
Model Fundamentals, part of the Numerical Weather Prediction Professional Development Series and the "NWP Training Series: Effective Use of NWP in the Forecast Process", describes the components of an NWP model and how they fit into the forecast development process. It also explores why parameterization of many physical processes is necessary in NWP models. The module covers background concepts and terminology necessary for learning from the other modules in this series on NWP. Back in 2000, the subject matter expert for this module was Dr. Ralph Petersen of the National Centers for Environmen ...
Intelligent Use of Model-Derived Products - version 2
This module, part of the "NWP Training Series: Effective Use of NWP in the Forecast Process", discusses three aspects of forecast guidance developed from raw NWP model data: Post-processing Statistical guidance Model assessment tools Post-processing methods, including a new section of downscaling of coarser resolution data, bias correction, and post-processing of ensemble forecast system data, are introduced. Interpolation of raw model data to produce the data seen by operational meteorologists is also described. Next, we present information on statistical guidance methods and techniques, incl ...
Influence of Model Physics on NWP Forecasts - version 2
This module, part of the "NWP Training Series: Effective Use of NWP in the Forecast Process", describes model parameterizations of surface, PBL, and free atmospheric processes, such as surface snow processes, soil thermal and moisture processes, surface vegetation effects such as evapotranspiration, radiative processes involving clouds and trace gases, and turbulent processes in the PBL and free atmosphere. It specifically addresses how models treat these processes, how such processes can potentially interact with each other, and how they can influence forecasts of sensible weather elements. B ...
Impact of Model Structure and Dynamics - version 2
Impact of Model Structure & Dynamics, part of the "NWP Training Series: Effective Use of NWP in the Forecast Process", explains how a model forecast, and thus interpretation of that forecast, is affected by the basic design of the model. Topics include how meteorological variables are represented in grid point and spectral models, fundamental differences between hydrostatic and nonhydrostatic models, horizontal resolution of orographic and free-atmosphere features, vertical coordinate systems and how they affect the vertical resolution of features in the model forecast, and the forecast impact ...
Effective Use of NWP in the Forecast Process: Introduction
This lesson, part of the "NWP Training Series: Effective Use of NWP in the Forecast Process", introduces the student to the full series. Motivation for the series is presented by Mr. LeRoy Spayd, Chief of the National Weather Service Training Division; this includes a demonstration of the value added by human forecasters to NWP forecasts through recent precipitation verification. Contributors to the series are acknowledged as well. Then Dr. Bill Bua, a member of the NWP Training Team, expands on points raised by Mr. Spayd by posing and answering a question on the role of NWP in the forecast pr ...
Understanding Assimilation Systems: How Models Create Their Initial Conditions - version 2
Understanding Assimilation Systems: How Models Create Their Initial Conditions, is part of the "NWP Training Series: Effective Use of NWP in the Forecast Process." This module explains the data assimilation process, including the role of the model itself as well as the observations. It provides learners an appreciation for how models use data as a function of model resolution and data type, how data influence the analysis, the limitations of data assimilation systems, the importance of initial conditions on the quality of NWP guidance, as well as the challenges of assessing the quality of NWP ...
Operational Use of Wave Watch III
In this webcast, Dr. Hendrik Tolman (NOAA Marine Analysis Branch) discusses the operational use of NOAA WAVEWATCH III. The NOAA WAVEWATCH III is a forecast system that predicts wind-generated ocean waves. Dr. Tolman discusses what WAVEWATCH III can and cannot predict along with the model physics, numerics, and forecast products. Numerous examples illustrate the practical effects of several recent model improvements including high-resolution hurricane winds, surf zone physics, wave partitioning, and use of a multi-grid mosaic. The webcast concludes with a discussion of future improvements plann ...
Wave Ensembles in the Marine Forecast Process
The NCEP Marine Modeling and Analysis Branch (MMAB) Ensemble Global Ocean Wave Forecast System (EGOWaFS) provides five-day forecasts of global winds, wind wave and swell conditions in probabilistic terms. This product became available early in 2007 both through an NCEP non-operational web page and, for raw data, through FTP for use by marine forecasters at NWS WFOs and other locations. The data from the EGOWaFS can be used in a number of ways, including:* As input to probabilistic marine forecasts for wind waves and swell* As input to a local wave ensemble, such as Simulated Waves Nearshore (S ...
Real-Time Mesoscale Analysis (RTMA): What is the NCEP RTMA and how can it be used?
The NCEP Real-Time Mesoscale Analysis (RTMA), provides current conditions in digital form on the NWS National Digital Forecast Database (NDFD) 5-km grid. This product was upgraded in early July 2007 to the point where its use by forecast offices is now encouraged for situational awareness, creating short-term forecast grids, and evaluating recent forecast grids and forecast bias. Unique to the RTMA is an uncertainty or error estimate for some of its analysis parameters. These uncertainty estimates perhaps could be used to determine when a forecast is “good enough”. This Webcast discusses why t ...
Using the WRF Mesoscale Model
This module provides insights on how to best use WRF mesoscale model guidance in the forecast process. Using two cases in southwest Asia where AFWA WRF is currently in use, it examines improvements offered by the WRF for forecasting fronts, topographic impacts, precipitation type, and hazards to aviation. The module also discusses some mesoscale model limitations, and offers strategies for transitioning between using mesoscale and global NWP guidance for medium-range forecasts, even when the models differ significantly.
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