WGNE Intercomparison of Tropical Cyclone Forecasts by Operational NWP Models: A Quarter Century and Beyond

2017 ◽  
Vol 98 (11) ◽  
pp. 2337-2349 ◽  
Author(s):  
Munehiko Yamaguchi ◽  
Junichi Ishida ◽  
Hitoshi Sato ◽  
Masayuki Nakagawa
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Weather Prediction ◽  
Japan Meteorological Agency ◽  
Global Models ◽  
Quarter Century ◽  
Consensus Forecasts ◽  
Numerical Experimentation ◽  
Intercomparison Project

Abstract Tropical cyclone (TC) track forecasts of operational numerical weather prediction (NWP) models have been compared and verified by the Japan Meteorological Agency (JMA) under an intercomparison project of the Working Group on Numerical Experimentation (WGNE) since 1991. This intercomparison has promoted validation of the global models in the tropics and subtropics. The results have demonstrated a steady increase in the global models’ ability to predict TC positions over the past quarter century. The intercomparison study started from verification for TCs in the western North Pacific basin with three global models. Up to the present date, the verification has been extended to all ocean basins where TCs regularly occur, and 12 global models participated in the project. In recent years, the project has been extended to include verification of intensity forecasts and forecasts by regional models. This intercomparison project has seen a significant improvement in TC track forecasts, both globally and in each TC basin. In the western North Pacific, for example, we have succeeded in obtaining an approximately 2.5-day lead-time improvement. The project has also demonstrated the benefits of multicenter track forecasts (i.e., consensus forecasts). Finally, the paper considers future challenges to TC track forecasting by NWP models that have been identified at the World Meteorological Organization’s (WMO’s) Eighth International Workshop on Tropical Cyclones (IWTC-8). We discuss the priorities and key issues in further improving the accuracy of TC track forecasts, reducing cases of large position errors, and enhancing the use of ensemble information.

Wind Structure Discrepancies between Two Best Track Datasets for Western North Pacific Tropical Cyclones

2016 ◽  
Vol 144 (12) ◽  
pp. 4533-4551 ◽  
Author(s):  
Jinjie Song ◽  
Philip J. Klotzbach
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Shape Parameter ◽  
Surface Wind ◽  
Japan Meteorological Agency ◽  
Wind Structure ◽  
Linear Relationships ◽  
Wind Analysis ◽  
Joint Typhoon Warning Center

Abstract Symmetric and wavenumber-1 asymmetric characteristics of western North Pacific tropical cyclone (TC) outer wind structures are compared between best tracks from the Joint Typhoon Warning Center (JTWC) and the Japan Meteorological Agency (JMA) from 2004 to 2014 as well as the Multiplatform Tropical Cyclone Surface Wind Analysis (MTCSWA) product from 2007 to 2014. Significant linear relationships of averaged wind radii are obtained among datasets, in which both gale-force and storm-force wind radii are generally estimated slightly smaller (much larger) by JTWC (JMA) than by MTCSWA. These correlations are strongly related to TC intensity relationships discussed in earlier work. Moreover, JTWC (JMA) on average represents a smaller (greater) derived shape parameter than MTCSWA does, implying that JTWC (JMA) typically assesses a more compact (less compact) storm than MTCSWA. For the wavenumber-1 asymmetry, large differences among datasets are found regardless of the magnitude or the direction of the longest radius. JTWC estimates more asymmetric storms than JMA, and it provides greater wavenumber-1 asymmetry magnitudes on average. Asymmetric storms are most frequently oriented toward the east, northeast, and north in JTWC and MTCSWA, whereas they are most frequently oriented toward the southeast, east, and northeast in JMA. The direction of the longest gale-force (storm force) wind radius in JTWC is statistically rotated 18° (32°) clockwise to that in JMA. Although the wind radii in JTWC are of higher quality than those in JMA when using MTCSWA as a baseline, there remains a need to provide a consistent and reliable wind radii estimating process among operational centers.

scholarly journals Global 7 km mesh nonhydrostatic Model Intercomparison Project for improving TYphoon forecast (TYMIP-G7): experimental design and preliminary results

2017 ◽  
Vol 10 (3) ◽  
pp. 1363-1381 ◽  
Author(s):  
Masuo Nakano ◽  
Akiyoshi Wada ◽  
Masahiro Sawada ◽  
Hiromasa Yoshimura ◽  
Ryo Onishi ◽  
...  
Keyword(s):  
Weather Prediction ◽  
Japan Meteorological Agency ◽  
Model Intercomparison ◽  
Atmospheric Models ◽  
Global Spectral Model ◽  
Global Models ◽  
Nonhydrostatic Model ◽  
Intercomparison Project ◽  
Mesh Models ◽  
Tc Prediction

Abstract. Recent advances in high-performance computers facilitate operational numerical weather prediction by global hydrostatic atmospheric models with horizontal resolutions of  ∼  10 km. Given further advances in such computers and the fact that the hydrostatic balance approximation becomes invalid for spatial scales  <  10 km, the development of global nonhydrostatic models with high accuracy is urgently required. The Global 7 km mesh nonhydrostatic Model Intercomparison Project for improving TYphoon forecast (TYMIP-G7) is designed to understand and statistically quantify the advantages of high-resolution nonhydrostatic global atmospheric models to improve tropical cyclone (TC) prediction. A total of 137 sets of 5-day simulations using three next-generation nonhydrostatic global models with horizontal resolutions of 7 km and a conventional hydrostatic global model with a horizontal resolution of 20 km were run on the Earth Simulator. The three 7 km mesh nonhydrostatic models are the nonhydrostatic global spectral atmospheric Double Fourier Series Model (DFSM), the Multi-Scale Simulator for the Geoenvironment (MSSG) and the Nonhydrostatic ICosahedral Atmospheric Model (NICAM). The 20 km mesh hydrostatic model is the operational Global Spectral Model (GSM) of the Japan Meteorological Agency. Compared with the 20 km mesh GSM, the 7 km mesh models reduce systematic errors in the TC track, intensity and wind radii predictions. The benefits of the multi-model ensemble method were confirmed for the 7 km mesh nonhydrostatic global models. While the three 7 km mesh models reproduce the typical axisymmetric mean inner-core structure, including the primary and secondary circulations, the simulated TC structures and their intensities in each case are very different for each model. In addition, the simulated track is not consistently better than that of the 20 km mesh GSM. These results suggest that the development of more sophisticated initialization techniques and model physics is needed to further improve the TC prediction.

scholarly journals Predicting Rapid Intensification Events Following Tropical Cyclone Formation in the Western North Pacific Based on ECMWF Ensemble Warm Core Evolutions

Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 847
Author(s):  
Russell L. Elsberry ◽  
Hsiao-Chung Tsai ◽  
Wei-Chia Chin ◽  
Timothy P. Marchok
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Weather Prediction ◽  
Rapid Intensification ◽  
Modified Technique ◽  
Tropical Cyclone Formation ◽  
Warm Core ◽  
Peak Intensity ◽  
Cubic Spline Curve

When the environmental conditions over the western North Pacific are favorable for tropical cyclone formation, a rapid intensification event will frequently follow formation. In this extension of our combined three-stage 7-day Weighted Analog Intensity Pacific prediction technique, the European Centre for Medium-range Weather Prediction ensemble predictions of the warm core magnitudes of pre-tropical cyclone circulations are utilized to define the Time-to-Formation (35 knots) and to estimate the Likely Storm Category. If that category is a Typhoon, the bifurcation version of our technique is modified to better predict the peak intensity by selecting only Cluster 1 analog storms with the largest peak intensities that are most likely to have under-gone rapid intensification. A second modification to improve the peak intensity magnitude and timing was to fit a cubic spline curve through the weighted-mean peak intensities of the Cluster 1 analogs. The performance of this modified technique has been evaluated for a sequence of western North Pacific tropical cyclones during 2019 in terms of: (i) Detection time in advance of formation; (ii) Accuracy of Time-to-Formation; (iii) Intensification stage prediction; and (iv) Peak intensity magnitude/timing. This modified technique would provide earlier guidance as to the threat of a Typhoon along the 15-day ensemble storm track forecast, which would be a benefit for risk management officials.

Tropical Cyclone–like Vortices Detection in the NCEP 16-Day Ensemble System over the Western North Pacific in 2008: Application and Forecast Evaluation

2011 ◽  
Vol 26 (1) ◽  
pp. 77-93 ◽  
Author(s):  
Hsiao-Chung Tsai ◽  
Kuo-Chen Lu ◽  
Russell L. Elsberry ◽  
Mong-Ming Lu ◽  
Chung-Hsiung Sui
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Prediction Models ◽  
Weather Prediction ◽  
Domain Size ◽  
Ensemble Forecast ◽  
Primary Objective ◽  
Mature Stage ◽  
Evaluation Tool

Abstract An automated technique has been developed for the detection and tracking of tropical cyclone–like vortices (TCLVs) in numerical weather prediction models, and especially for ensemble-based models. A TCLV is detected in the model grid when selected dynamic and thermodynamic fields meet specified criteria. A backward-and-forward extension from the mature stage of the track is utilized to complete the track. In addition, a fuzzy logic approach is utilized to calculate the TCLV fuzzy combined-likelihood value (TFCV) for representing the TCLV characteristics in the ensemble forecast outputs. The primary objective of the TCLV tracking and TFCV maps is for use as an evaluation tool for the operational forecasters. It is demonstrated that this algorithm efficiently extracts western North Pacific TCLV information from the vast amount of ensemble data from the NCEP Global Ensemble Forecast System (GEFS). The predictability of typhoon formation and activity during June–December 2008 is also evaluated. The TCLV track numbers and TFCV averages around the formation locations during the 0–96-h period are more skillful than for the 102–384-h forecasts. Compared to weak tropical cyclones (TCs; maximum intensity ≤ 50 kt), the storms that eventually become stronger TCs do have larger TFCVs. Depending on the specified domain size and the ensemble track numbers to define a forecast event, some skill is indicated in predicting the named TC activity. Although this evaluation with the 2008 typhoon season indicates some potential, an evaluation with a larger sample is necessary to statistically verify the reliability of the GEFS forecasts.

scholarly journals Consensus on Climate Trends in Western North Pacific Tropical Cyclones

2012 ◽  
Vol 25 (21) ◽  
pp. 7564-7573 ◽  
Author(s):  
Nam-Young Kang ◽  
James B. Elsner
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
North Pacific ◽  
Power Dissipation ◽  
Western North Pacific ◽  
Japan Meteorological Agency ◽  
Climate Trends ◽  
Speed Level ◽  
Quantile Method ◽  
Joint Typhoon Warning Center

Research on trends in western North Pacific tropical cyclone (TC) activity is limited by problems associated with different wind speed conversions used by the various meteorological agencies. This paper uses a quantile method to effectively overcome this conversion problem. Following the assumption that the intensity ranks of TCs are the same among agencies, quantiles at the same probability level in different data sources are regarded as having the same wind speed level. Tropical cyclone data from the Joint Typhoon Warning Center (JTWC) and Japan Meteorological Agency (JMA) are chosen for research and comparison. Trends are diagnosed for the upper 45% of the strongest TCs annually. The 27-yr period beginning with 1984, when the JMA began using the Dvorak (1982) technique, is determined to be the most reliable for achieving consensus among the two agencies regarding these trends. The start year is a compromise between including as many years in the data as possible, but not so many that the period includes observations that result in inconsistent trend estimates. The consensus of TC trends between the two agencies over the period is interpreted as fewer but stronger events since 1984, even with the lower power dissipation index (PDI) in the western North Pacific in recent years.

scholarly journals Experiments with a Simple Tropical Cyclone Intensity Consensus

2008 ◽  
Vol 23 (2) ◽  
pp. 304-312 ◽  
Author(s):  
Charles R. Sampson ◽  
James L. Franklin ◽  
John A. Knaff ◽  
Mark DeMaria
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Ensemble Methods ◽  
Forecast Model ◽  
Dynamical Model ◽  
Consensus Forecasts ◽  
Intensity Forecast ◽  
Forecast Models ◽  
The Individual

Abstract Consensus forecasts (forecasts created by combining output from individual forecasts) have become an integral part of operational tropical cyclone track forecasting. Consensus aids, which generally have lower average errors than individual models, benefit from the skill and independence of the consensus members, both of which are present in track forecasting, but are limited in intensity forecasting. This study conducts experiments with intensity forecast aids on 4 yr of data (2003–06). First, the skill of the models is assessed; then simple consensus computations are constructed for the Atlantic, eastern North Pacific, and western North Pacific basins. A simple (i.e., equally weighted) consensus of three top-performing intensity forecast models is found to generally outperform the individual members in both the Atlantic and eastern North Pacific, and a simple consensus of two top-performing intensity forecast models is found to generally outperform the individual members in the western North Pacific. An experiment using an ensemble of dynamical model track forecasts and a selection of model fields as input in a statistical–dynamical intensity forecast model to produce intensity consensus members is conducted for the western North Pacific only. Consensus member skill at 72 h is low (−0.4% to 14.2%), and there is little independence among the members. This experiment demonstrates that a consensus of these highly dependent members yields an aid that performs as well as the most skillful member. Finally, adding a less skillful, but more independent, dynamical model-based forecast aid to the consensus yields an 11-member consensus with mixed yet promising performance compared with the 10-model consensus. Based on these findings, the simple three-member consensus model could be used as a standard of comparison for other deterministic ensemble methods for the Atlantic and eastern North Pacific. Both the two- and three-member consensus forecasts may also provide useful guidance for operational forecasters. Likewise, in the western North Pacific, the 10- and 11-member consensus could be used as operational forecast aids and standards of comparison for other ensemble intensity forecast methods.

scholarly journals Is the Number of Tropical Cyclone Rapid Intensification Events in the Western North Pacific Increasing?

SOLA ◽  
2020 ◽  
Vol 16 (0) ◽  
pp. 1-5 ◽  
Author(s):  
Udai Shimada ◽  
Munehiko Yamaguchi ◽  
Shuuji Nishimura
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Rapid Intensification
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