scholarly journals Usability of Best Track Data in Climate Statistics in the Western North Pacific

2012 ◽  
Vol 140 (9) ◽  
pp. 2818-2830 ◽  
Author(s):  
Monika Barcikowska ◽  
Frauke Feser ◽  
Hans von Storch
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Japan Meteorological Agency ◽  
Strong Increase ◽  
Operational Parameters ◽  
China Meteorological Administration ◽  
Aircraft Observations ◽  
Center Position ◽  
Climate Statistics ◽  
Joint Typhoon Warning Center

Abstract Tropical cyclone (TC) activity for the last three decades shows strong discrepancies, deduced from different best track datasets (BTD) for the western North Pacific (WNP). This study analyzes the reliability of BTDs in deriving climate statistics for the WNP. Therefore, TC lifetime, operational parameters [current intensity (CI) number], and tracks are compared (for TCs identified concurrently) in BTD provided by the Joint Typhoon Warning Center (JTWC), the Japan Meteorological Agency (JMA), and the China Meteorological Administration (CMA). The differences between the BTD are caused by varying algorithms used in weather services to estimate TC intensity. Available methods for minimizing these discrepancies are not sufficient. Only if intensity categories 2–5 are considered as a whole, do trends for annually accumulated TC days show a similar behavior. The reasons for remaining discrepancies point to extensive and not regular usage of supplementary sources in JTWC. These are added to improve the accuracy of TC intensity and center position estimates. Track and CI differences among BTDs coincide with a strong increase in the number of intense TC days in JTWC. These differences are very strong in the period of intensive improvement of spatiotemporal satellite coverage (1987–99). Scatterometer-based data used as a reference show that for the tropical storm phase JMA provides more reliable TC intensities than JTWC. Comparisons with aircraft observations indicate that not only homogeneity, but also a harmonization and refinement of operational rules controlling intensity estimations, should be implemented in all agencies providing BTD.

Reliability Analysis of Climate Change of Tropical Cyclone Activity over the Western North Pacific

2011 ◽  
Vol 24 (22) ◽  
pp. 5887-5898 ◽  
Author(s):  
Fumin Ren ◽  
Jin Liang ◽  
Guoxiong Wu ◽  
Wenjie Dong ◽  
Xiuqun Yang
Keyword(s):  
Climate Change ◽  
North Pacific ◽  
Western North Pacific ◽  
Individual Characteristics ◽  
Japan Meteorological Agency ◽  
Accurate Information ◽  
China Meteorological Administration ◽  
The Past ◽  
Observational Techniques ◽  
Joint Typhoon Warning Center

Abstract Data homogeneity has become a significant issue in the study of tropical cyclones (TCs) and climate change. In this study, three historical datasets for the western North Pacific TCs from the Joint Typhoon Warning Center (JTWC), Japan Meteorological Agency (JMA), and China Meteorological Administration (CMA) are compared with a focus on TC intensity. Over the past 55 years (1951–2005), significant discrepancies are found among the three datasets, especially between the CMA and JTWC datasets. The TC intensity in the CMA dataset was evidently overestimated in the 1950s and from the late 1960s to the early 1970s, while it was overestimated after 1988 in the JTWC dataset, especially during 1993–2003. Large discrepancies in TC tracks exist in two periods of 1951–early 1960s and 1988–1990s. Further analysis reveals that the discrepancies are obviously related to the TC observational techniques. Before the era of meteorological satellites (1951–the early 1960s), and after the termination of aircraft reconnaissance (since 1988), large discrepancies exist in both TC intensity and track. That the intensity discrepancy was smallest during the period (1973–87) when aircraft reconnaissance data and the Dvorak technique were both available suggests that availability of the aircraft reconnaissance and the Dvorak method helps in reducing the TC intensity discrepancy. For those TCs that were included in all the three datasets, no significant increasing or decreasing trend was found over the past 50 years. Each of the three TC datasets has individual characteristics that make it difficult to tell which one is the best. For TCs that affect China, the CMA dataset has obvious advantages such as more complete and more accurate 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 Evaluation and Error Analysis of Official Forecasts of Tropical Cyclones during 2005–14 over the Western North Pacific. Part I: Storm Tracks

2017 ◽  
Vol 32 (2) ◽  
pp. 689-712 ◽  
Author(s):  
Xudong Peng ◽  
Jianfang Fei ◽  
Xiaogang Huang ◽  
Xiaoping Cheng
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Regional Distribution ◽  
The Philippines ◽  
Forecast Errors ◽  
China Meteorological Administration ◽  
Steering Flow ◽  
Forecasting Performance ◽  
The Right ◽  
Joint Typhoon Warning Center

Abstract Official forecasts of tropical cyclone (TC) tracks issued by the China Meteorological Administration (CMA); the Regional Specialized Meteorological Centre in Tokyo, Japan; and the Joint Typhoon Warning Center (JTWC) were used to evaluate the accuracies, biases, and trends of TC track forecasts during 2005–14 over the western North Pacific. Overall, the JTWC demonstrated the best forecasting performance. However, the CMA showed the most significant rate of improvement. Two main zones were discovered in the regional distribution of forecast errors: a low-latitude zone that comprises the South China Sea and the sea region east of the Philippines, and a midlatitude zone comprising the southern Sea of Japan and the sea region east of Japan. When TCs moved into the former zone, there were both translational speed and direction biases in the forecast tracks, whereas slow biases were predominated in the latter zone. Twelve synoptic flow patterns of TCs with the largest error have been identified based on the steering flow theory. Among them, the most two common pattern are the pattern with the combination of cyclonic circulations, subtropical ridges, and midlatitude troughs (CRT, 26 TCs), and the pattern of the TCs’ track that cannot be explained by steering flow (NSF, 6 TCs). In the CRT pattern, TCs move northwestward forced by the cyclonic circulations and the subtropical ridges and then turn poleward and eastward under the influence of the midlatitude troughs. In the NSF pattern, storms embedded in the southwest flow by the cyclonic circulation and the steering flow suggest TCs should turn to the right and move northeastward but instead TCs persisted in moving northwestward.

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 An Operational Rapid Intensification Prediction Aid for the Western North Pacific

2018 ◽  
Vol 33 (3) ◽  
pp. 799-811 ◽  
Author(s):  
John A. Knaff ◽  
Charles R. Sampson ◽  
Kate D. Musgrave
Keyword(s):  
Logistic Regression ◽  
Discriminant Analysis ◽  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Rapid Intensification ◽  
Linear Discriminant ◽  
Probabilistic Forecasts ◽  
Weighted Probability ◽  
Joint Typhoon Warning Center

Abstract This work describes tropical cyclone rapid intensification forecast aids designed for the western North Pacific tropical cyclone basin and for use at the Joint Typhoon Warning Center. Two statistical methods, linear discriminant analysis and logistic regression, are used to create probabilistic forecasts for seven intensification thresholds including 25-, 30-, 35-, and 40-kt changes in 24 h, 45- and 55-kt in 36 h, and 70-kt in 48 h (1 kt = 0.514 m s−1). These forecast probabilities are further used to create an equally weighted probability consensus that is then used to trigger deterministic forecasts equal to the intensification thresholds once the probability in the consensus reaches 40%. These deterministic forecasts are incorporated into an operational intensity consensus forecast as additional members, resulting in an improved intensity consensus for these important and difficult to predict cases. Development of these methods is based on the 2000–15 typhoon seasons, and independent performance is assessed using the 2016 and 2017 typhoon seasons. In many cases, the probabilities have skill relative to climatology and adding the rapid intensification deterministic aids to the operational intensity consensus significantly reduces the negative forecast biases.

Operational Evaluation of a Selective Consensus in the Western North Pacific Basin

2007 ◽  
Vol 22 (3) ◽  
pp. 671-675 ◽  
Author(s):  
Charles R. Sampson ◽  
John A. Knaff ◽  
Edward M. Fukada
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Systematic Approach ◽  
Prediction Models ◽  
Weather Prediction ◽  
Pacific Basin ◽  
Joint Typhoon Warning Center ◽  
Numerical Weather Prediction Models ◽  
North Pacific Basin

Abstract The Systematic Approach Forecast Aid (SAFA) has been in use at the Joint Typhoon Warning Center since the 2000 western North Pacific season. SAFA is a system designed for determination of erroneous 72-h track forecasts through identification of predefined error mechanisms associated with numerical weather prediction models. A metric for the process is a selective consensus in which model guidance suspected to have 72-h error greater than 300 n mi (1 n mi = 1.85 km) is first eliminated prior to calculating the average of the remaining model tracks. The resultant selective consensus should then provide improved forecasts over the nonselective consensus. In the 5 yr since its introduction into JTWC operations, forecasters have been unable to produce a selective consensus that provides consistent improved guidance over the nonselective consensus. Also, the rate at which forecasters exercised the selective consensus option dropped from approximately 45% of all forecasts in 2000 to 3% in 2004.

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.

scholarly journals Western North Pacific Tropical Cyclone Database Created by the China Meteorological Administration

2021 ◽  
Author(s):  
Xiaoqin Lu ◽  
Hui Yu ◽  
Ming Ying ◽  
Bingke Zhao ◽  
Shuai Zhang ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Tropical Cyclone ◽  
South China Sea ◽  
North Pacific ◽  
Western North Pacific ◽  
China Meteorological Administration ◽  
Ongoing Research ◽  
Detection Techniques ◽  
Long Period ◽  
Potential Applications

AbstractThis paper describes the access to, and the content, characteristics, and potential applications of the tropical cyclone (TC) database that is maintained and actively developed by the China Meteorological Administration, with the aim of facilitating its use in scientific research and operational services. This database records data relating to all TCs that have passed through the western North Pacific (WNP) and South China Sea (SCS) since 1949. TC data collection has expanded over recent decades via continuous TC monitoring using remote sensing and specialized field detection techniques, allowing collation of a multi-source TC database for the WNP and SCS that covers a long period, with wide coverage and many observational elements. This database now comprises a wide variety of information related to TCs, such as historical or real-time locations (i.e., best track and landfall), intensity, dynamic and thermal structures, wind strengths, precipitation amounts, and frequency. This database will support ongoing research into the processes and patterns associated with TC climatic activity and TC forecasting.

scholarly journals Extratropical Transition of Tropical Cyclones in the Western North Pacific: Their Frontal Evolution

2008 ◽  
Vol 136 (6) ◽  
pp. 2066-2090 ◽  
Author(s):  
Naoko Kitabatake
Keyword(s):  
Tropical Cyclones ◽  
North Pacific ◽  
Western North Pacific ◽  
Global Analysis ◽  
Potential Temperature ◽  
Japan Meteorological Agency ◽  
Extratropical Transition ◽  
Equivalent Potential ◽  
Typhoon Center ◽  
Baroclinic Zone

Abstract Extratropical transition (ET) in the western North Pacific during 2001–02 is examined in terms of frontal evolution and its environment using a gridded global analysis dataset produced by the Japan Meteorological Agency. According to the best-track data created by the Regional Specialized Meteorological Center (RSMC) Tokyo-Typhoon Center, 23 out of 52 (44%) tropical cyclones (TCs) completed ET during these two years. These ET cases are classified into three categories in terms of the lower-tropospheric equivalent potential temperature distributions, characteristics of the TCs, and their environments. Eight TCs (35% of all ET cases) had temporary warm secluded frontal patterns and then occluded patterns at the completion of ET, which is defined as a seclusion–occlusion (SO) type. This occurs downstream of an intense upper-tropospheric trough interacting with a TC, which is then likely to move northward while keeping its tropical characteristics and have a large impact on relatively high latitudes including all the Japan islands. Three TCs (13%) were apparently absorbed into vigorous preexisting fronts in the southwest of midlatitude cyclones; this situation is defined as a cold advection (CA) type. A TC of the CA type is likely to lose its tropical characteristics rapidly in strong cold advection that is equatorward of a relatively straight upper-tropospheric jet stream. The other 12 TCs (52%) were organized into an open-wave frontal cyclone, which is defined as an open-wave (OW) type. This has characteristics of both SO and CA and is more related to the midlatitude baroclinic zone compared with the SO type.

Future Change of Western North Pacific Typhoons: Projections by a 20-km-Mesh Global Atmospheric Model*

2011 ◽  
Vol 24 (4) ◽  
pp. 1154-1169 ◽  
Author(s):  
Hiroyuki Murakami ◽  
Bin Wang ◽  
Akio Kitoh
Keyword(s):  
North Pacific ◽  
General Circulation ◽  
Western North Pacific ◽  
Large Scale ◽  
Vertical Wind Shear ◽  
Circulation Model ◽  
Atmospheric Model ◽  
Japan Meteorological Agency ◽  
Global Atmospheric Model ◽  
Meteorological Research Institute

Abstract Projected future changes in tropical cyclone (TC) activity over the western North Pacific (WNP) under the Special Report on Emissions Scenarios (SRES) A1B emission scenario were investigated using a 20-km-mesh, very-high-resolution Meteorological Research Institute (MRI)–Japan Meteorological Agency (JMA) atmospheric general circulation model. The present-day (1979–2003) simulation yielded reasonably realistic climatology and interannual variability for TC genesis frequency and tracks. The future (2075–99) projection indicates (i) a significant reduction (by about 23%) in both TC genesis number and frequency of occurrence primarily during the late part of the year (September–December), (ii) an eastward shift in the positions of the two prevailing northward-recurving TC tracks during the peak TC season (July–October), and (iii) a significant reduction (by 44%) in TC frequency approaching coastal regions of Southeast Asia. The changes in occurrence frequency are due in part to changes in large-scale steering flows, but they are due mainly to changes in the locations of TC genesis; fewer TCs will form in the western portion of the WNP (west of 145°E), whereas more storms will form in the southeastern quadrant of the WNP (10°–20°N, 145°–160°E). Analysis of the genesis potential index reveals that the reduced TC genesis in the western WNP is due mainly to in situ weakening of large-scale ascent and decreasing midtropospheric relative humidity, which are associated with the enhanced descent of the tropical overturning circulation. The analysis also indicates that enhanced TC genesis in the southeastern WNP is due to increased low-level cyclonic vorticity and reduced vertical wind shear. These changes appear to be critically dependent on the spatial pattern of future sea surface temperature; therefore, it is necessary to conduct ensemble projections with a range of SST spatial patterns to understand the degree and distribution of uncertainty in future projections.

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