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 Using eXtreme Gradient BOOSTing to Predict Changes in Tropical Cyclone Intensity over the Western North Pacific

Atmosphere ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 341 ◽  
Author(s):  
Qingwen Jin ◽  
Xiangtao Fan ◽  
Jian Liu ◽  
Zhuxin Xue ◽  
Hongdeng Jian
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Prediction Models ◽  
Weather Prediction ◽  
Back Propagation ◽  
Absolute Error ◽  
Gradient Boosting ◽  
Lead Times ◽  
Intensity Prediction ◽  
Extreme Gradient Boosting

Coastal cities in China are frequently hit by tropical cyclones (TCs), which result in tremendous loss of life and property. Even though the capability of numerical weather prediction models to forecast and track TCs has considerably improved in recent years, forecasting the intensity of a TC is still very difficult; thus, it is necessary to improve the accuracy of TC intensity prediction. To this end, we established a series of predictors using the Best Track TC dataset to predict the intensity of TCs in the Western North Pacific with an eXtreme Gradient BOOSTing (XGBOOST) model. The climatology and persistence factors, environmental factors, brainstorm features, intensity categories, and TC months are considered inputs for the models while the output is the TC intensity. The performance of the XGBOOST model was tested for very strong TCs such as Hato (2017), Rammasum (2014), Mujiage (2015), and Hagupit (2014). The results obtained show that the combination of inputs chosen were the optimal predictors for TC intensification with lead times of 6, 12, 18, and 24 h. Furthermore, the mean absolute error (MAE) of the XGBOOST model was much smaller than the MAEs of a back propagation neural network (BPNN) used to predict TC intensity. The MAEs of the forecasts with 6, 12, 18, and 24 h lead times for the test samples used were 1.61, 2.44, 3.10, and 3.70 m/s, respectively, for the XGBOOST model. The results indicate that the XGBOOST model developed in this study can be used to improve TC intensity forecast accuracy and can be considered a better alternative to conventional operational forecast models for TC intensity prediction.

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.

scholarly journals Detectability and Configuration of Tropical Cyclone Eyes over the Western North Pacific in TRMM PR and IR Observations

2005 ◽  
Vol 133 (8) ◽  
pp. 2213-2226 ◽  
Author(s):  
Yasu-Masa Kodama ◽  
Takuya Yamada
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Tropical Rainfall Measuring Mission ◽  
Mature Stage ◽  
Precipitation Radar ◽  
Wind Speeds ◽  
Trmm Pr ◽  
Eye Diameter ◽  
Concentric Eyewalls

Abstract Statistics for 138 cases from 61 tropical cyclones over the western North Pacific during the five years from 1998 to 2002 were used to determine the detectability and configuration of tropical cyclone (TC) eyes and to reveal relations with TC intensity and life stages in satellite-based infrared (IR) and precipitation radar (PR) observations from the Tropical Rainfall Measuring Mission (TRMM). Tropical cyclone eyes were detectable in PR data in 89% of cases and in IR data in 37% of cases. Maximum sustained wind speeds in TCs were much greater when the eye was detected in both IR and PR data than in cases when the eye was detected only in PR data or when no eye was detected in either PR or IR data. An eye was detectable in both IR and PR data in the developing stage of only 18% of TCs although an eye was present in the PR data in 90% of cases. An eye was detected in both IR and PR data in 51% of the TCs during the mature stage. During the decaying stage, an eye was detected in both IR and PR data in 31% of cases. Eye diameter determined from PR observations was larger during the later stages. Most TCs had an eye less than 82.5 km in diameter during the developing stage. Tropical cyclone eyes embedded within concentric eyewalls appeared more frequently in the mature and decaying stages; this is consistent with findings from previous studies. In most cases, eye diameter was smaller in IR observations than in PR observations because an upper cloud shield extending from the eyewall partially covered the eye. For several TCs with concentric eye walls, however, eye diameter was smaller in PR observations. A shallow inner eyewall in the PR data and a deep outer eyewall in both IR and PR data characterized these cases.

scholarly journals Operational Performance of a New Barotropic Model (WBAR) in the Western North Pacific Basin

2006 ◽  
Vol 21 (4) ◽  
pp. 656-662 ◽  
Author(s):  
Charles R. Sampson ◽  
James S. Goerss ◽  
Harry C. Weber
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Prediction Models ◽  
Weather Prediction ◽  
Track Forecast ◽  
Forecast Performance ◽  
Barotropic Model ◽  
The North ◽  
Forecasting System ◽  
The Impact

Abstract The Weber barotropic model (WBAR) was originally developed using predefined 850–200-hPa analyses and forecasts from the NCEP Global Forecasting System. The WBAR tropical cyclone (TC) track forecast performance was found to be competitive with that of more complex numerical weather prediction models in the North Atlantic. As a result, WBAR was revised to incorporate the Navy Operational Global Atmospheric Prediction System (NOGAPS) analyses and forecasts for use at the Joint Typhoon Warning Center (JTWC). The model was also modified to analyze its own storm-dependent deep-layer mean fields from standard NOGAPS pressure levels. Since its operational installation at the JTWC in May 2003, WBAR TC track forecast performance has been competitive with the performance of other more complex NWP models in the western North Pacific. Its TC track forecast performance combined with its high availability rate (93%–95%) has warranted its inclusion in the JTWC operational consensus. The impact of WBAR on consensus TC track forecast performance has been positive and WBAR has added to the consensus forecast availability (i.e., having at least two models to provide a consensus forecast).

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 A Region-Dependent Seasonal Forecasting Framework for Tropical Cyclone Genesis Frequency in the Western North Pacific

2019 ◽  
Vol 32 (23) ◽  
pp. 8415-8435 ◽  
Author(s):  
Chao Wang ◽  
Bin Wang ◽  
Liguang Wu
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
Prediction Models ◽  
Temporal Correlation ◽  
Tropical Cyclone Genesis ◽  
Regional Variability ◽  
Empirical Prediction ◽  
Genesis Frequency

ABSTRACT It has been a common practice to predict total tropical cyclone (TC) genesis frequency over the entire western North Pacific (WNP). Here we show that TC genesis (TCG) exhibits distinct regional variability and sources of predictability. Therefore, we divide the WNP into four quadrants with 140°E and 17°N being dividing lines plus the South China Sea (SCS) to predict five subregional TCG frequencies as well as the entire WNP TCG frequency. Besides the well-known ENSO-induced seesaw relationship between the TCGs in the southeast and northwest quadrants, we found that 1) an enhanced TCG in the northeast WNP is associated with a pronounced anomalous cyclonic circulation, which is maintained through its interaction with the underlying sea surface temperature (SST) anomalies; 2) an active TCG in the southwest WNP is accompanied by a zonally elongated positive vorticity anomaly and SST warming over the equatorial eastern Pacific; and 3) the SCS TCG is influenced by the upper-level South Asia high through modulating large-scale environmental parameters. Physically meaningful predictors are identified and a set of empirical prediction models for TCG frequency is established for each subregion. Both the cross-validated reforecast for 1965–2000 and independent forecast for 2001–16 show significant temporal correlation skills. Moreover, the sum of the predicted TCG frequency in five subregions yields a basinwide TCG frequency prediction with a temporal correlation skill of 0.76 for the independent forecast period of 2001–16. The results indicate its potential utility to improve the TC forecasting in the WNP.

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.

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