Ending storm version of the 7-day weighted analog intensity prediction technique for western North Pacific tropical cyclones
Authors
Tsai, Hsiao-Chung
Elsberry, Russell L.
Subjects
Advisors
Date of Issue
2017-12
Date
December 2017
Publisher
American Meteorological Society (AMS)
Language
Abstract
The weighted analog intensity prediction technique for western North Pacific (WAIP) tropical cyclones
(TCs) was the first guidance product for 7-day intensity forecasts, which is skillful in the sense that the 7-day
errors are about the same as the 5-day errors. Independent tests of this WAIP version revealed an increasingly
large intensity overforecast bias as the forecast interval was extended from 5 to 7 days, which was associated
with ‘‘ending storms’’ due to landfall, extratropical transition, or to delayed development. Thus, the 7-day
WAIP has been modified to separately forecast ending and nonending storms within the 7-day forecast interval.
The additional ending storm constraint in the selection of the 10 best historical analogs is that the
intensity at the last matching point with the target TC track cannot exceed 50 kt (where 1 kt = 0.51ms ¯¹).
A separate intensity bias correction calculated for the ending storm training set reduces the mean biases to
near-zero values and thereby improves the mean absolute errors in the 5–7-day forecast interval for the
independent set. A separate calibration of the intensity spreads for the training set to ensure that 68% of the
verifying intensities will be within the 12-h WAIP intensity spread values results in smaller spreads (or higher
confidence) for ending storms in the 5–7-day forecast intervals. Thus, some extra effort by the forecasters to
identify ending storm events within 7 days will allow improved intensity and intensity spread forecast
guidance.
Type
Article
Description
The article of record as published may be located at http://doi.org/10.1175/WAF-D-17-0151.1
Manuscript received 12 October 2017, in final form 22 November 2017
Manuscript received 12 October 2017, in final form 22 November 2017
Series/Report No
Department
Meteorology
Organization
Naval Postgraduate School (U.S.)
Identifiers
NPS Report Number
Sponsors
Naval Research Marine Meteorology section
Taiwan Ministry of Science and Technology
Taiwan Ministry of Science and Technology
Funder
105-2625-M-032-003
Format
7 p.
Citation
Weather and Forecasting, vol.32, (2229-2235)
Distribution Statement
Rights
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.