Combined Three-Stage 7-Day Weighted Analog Intensity Prediction Technique for Western North Pacific Tropical Cyclones: Demonstration of Optimum Performance
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Authors
Hsiao-Chung Tsai
Elsberry, Russell L.
Subjects
Tropical cyclones
Advisors
Date of Issue
2019-12
Date
Publisher
American Meteorological Society (AMS)
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Abstract
The original 7-day weighted analog intensity Pacific (WAIP) prediction technique is improved by developing a new version for the preformation stage and combining it with the bifurcation version that is especially for the intensification stage and the ending-storm stage WAIP. This combined three-stage WAIP includes a calibrated intensity spread designed to include 68% of the verifying intensities. In this demonstration of the optimum performance of the combined WAIP, the Joint Typhoon Warning Center (JTWC) best tracks, the time to formation (T2F), and ending-storm time are utilized as inputs along with the initial intensity [i.e., either 15 or 20 kt (1 kt ≈ 0.51 m s−1)]. In the new “Before Formation” (defined as 25 kt) stage of the WAIP, the intensity evolution is represented by a square function between the initial intensity and the T2F (25 kt), and very small mean absolute errors (MAEs) and intensity spreads are achieved. In the bifurcation version, correct selections between two cluster WAIP intensity evolutions lead to MAEs that slowly increase to 17 kt at 144 h, and the intensity spreads are relatively small as well. Because the ending-storm time constrains the analog selection in the WAIP, the MAEs begin to decrease after 72 h and are only 10 kt at 156 h. A case study is presented as to how an ensemble storm-track forecast along with the T2F could provide WAIP 7-day intensity predictions beginning in the preformation stage, which indicates the potential for earlier guidance for the JTWC intensity forecasts of western North Pacific tropical cyclones.
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Article
Description
The article of record as published may be found at https://doi.org/10.1175/WAF-D-19-0130.1
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Sponsors
RLE has been supported by an Office of Naval Research Marine Meteorology Grant N00141712160 for the bifurcation and ending-storm versions of WAIP, and by the NOAA OAR Joint Hurricane Project Grant NA17OAR4590139 for the preformation stage WAIP. HCT is supported by the Taiwan Ministry of Science and Technology (MOST 107-2111-M-032-002).
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20 p.
Citation
Tsai, Hsiao-Chung, and Russell L. Elsberry. "Combined Three-Stage 7-Day Weighted Analog Intensity Prediction Technique for Western North Pacific Tropical Cyclones: Demonstration of Optimum Performance." Weather and Forecasting 34.6 (2019): 1979-1998.
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This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.