The Limited-Area Forecast Systems at the Central Weather Bureau in Taiwan

Jeng, Bao-Fong; Chen, Hway-Jen; Lin, Shwu-Ching; Leou, Tzay-Ming; Peng, Melinda S.; Chang, Simon W.; Hsu, Wen-Ling; Chang, C. P.

doi:10.1175/1520-0434(1991)006<0155:tlafsa>2.0.co;2

Cited by 11 publications

(3 citation statements)

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“…When compared with the previous limited area model at CWB (Jeng et al 1991), the NFS has better forecast scores and a reduced bias of excess precipitation existed in the previous model (Liou 2000). These are attributed in part to the improved parameterization of the subgridscale physical processes and better representation of the complex terrain in Taiwan.…”

Section: Introductionmentioning

confidence: 87%

Sensitivity of Typhoon Track Predictions in a Regional Prediction System to Initial and Lateral Boundary Conditions

Hsiao¹,

Peng²,

Chen³

et al. 2009

Journal of Applied Meteorology and Climatology

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Tropical cyclone (TC) track predictions from the operational regional nonhydrostatic TC forecast system of the Taiwanese Central Weather Bureau (CWB) are examined for their sensitivities to initial and lateral boundary conditions. Five experiments are designed and discussed, each using a combination of different initial and lateral boundary conditions coming either from the CWB or the National Centers for Environmental Prediction (NCEP) global forecast system. Eight typhoons in the western Pacific Ocean with 51 cases in 2004 and 2005 are tested with the five designed experiments for the 3-day forecast. The average track forecasts are the best when both the initial and lateral boundary conditions are from the NCEP global forecast system. This reflects the generally superior performance of the NCEP global forecast system relative to that of the CWB. Using different lateral boundary conditions has a greater impact on the track than using different initial conditions. Diagnostics using piecewise inversion of potential vorticity perturbations are carried out to identify synoptic features surrounding the featured typhoon that impact the track the most in each experiment. For the two cases demonstrated with the largest track improvement using NCEP global fields, the diagnostics indicate that the prediction of the strength and extent of the subtropical high in the western Pacific plays the major role in affecting these storm tracks. Using the analysis and predictions of the CWB global forecast system as the initial and lateral boundary conditions produces an overintensified subtropical ridge in the regional TC forecast model. Because most of the typhoons studied are located in the southwestern peripheral of the western Pacific subtropical high, the stronger steering from the more intense and extended high system is the main cause of the poleward bias in the predicted typhoon tracks in the operational run, which uses the CWB global forecast fields. The study suggests that, when efforts are made to improve a regional TC forecast model, it is also critically important to improve the global forecast system that provides the lateral boundary and initial conditions to the regional system.

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Section: Introductionmentioning

confidence: 87%

Sensitivity of Typhoon Track Predictions in a Regional Prediction System to Initial and Lateral Boundary Conditions

Hsiao¹,

Peng²,

Chen³

et al. 2009

Journal of Applied Meteorology and Climatology

Self Cite

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show abstract

“…In addition to the retrieved typhoon field, the other conventional fields that are needed to initialize and run the MM5 model for forecast are generated by a regional numerical weather prediction model; we use the operational NWP model of the Central Weather Bureau of Taiwan (Jeng et al 1991;Liou et al 1997). Once the initial condition is produced by 3DVAR, the MM5 model is used for the forecast.…”

Section: Data Assimilation and The Forecast Systemmentioning

confidence: 99%

The Analysis of Typhoon Structures Using Advanced Microwave Sounding Unit Data and Its Application to Prediction

Chou

Huang

et al. 2008

Journal of Applied Meteorology and Climatology

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In this study, the Advanced Microwave Sounding Unit (AMSU) data are used to retrieve the temperature and velocity fields of typhoons and assimilate them with the three-dimensional variational data assimilation (3DVAR) routines for uses in numerical model predictions for typhoons. The authors' procedure of an end-to-end typhoon prediction using an AMSU-based initial condition is similar to the framework developed by Zhu et al. in 2002 but differs from it by considering a downward integration approach in part of the retrieval process and with the starting point of the integration chosen as a constant 50-hPa field without any structure. The typhoon circulation from this retrieval is thus determined objectively from the AMSU observation alone, without a preimposed typhoon vortex structure, allowing an asymmetric structure even at the inner core of a typhoon. The results show that this procedure is capable of retrieving a reasonable typhoon circulation from the AMSU data. The impact of the AMSU data on the assimilated initial condition for prediction is shown to be especially notable in its modification of the upper-level circulation of the typhoons. With the downward integration, the error accumulates downward such that the current approach provides a relatively more accurate estimate of the upper-level circulation, important for the steering of a typhoon. Consistent with this, it is demonstrated that the inclusion of the AMSU data helps to improve the forecast of typhoon tracks for selected cases of typhoons. This approach is less satisfying in producing an accurate retrieval and prediction of the intensity of typhoons. The reasons for this shortcoming and possible future remedies are discussed.

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“…Since the 1980s, the CWB started to develop an atmospheric general circulation model (AGCM), namely the Global Forecast System (GFS). The GFS was originally designed to provide in-time large-scale background fields for operations of its companion limited-area model (Jeng et al, 1991) and the typhoon track forecast model (Peng et al, 1993). It was also intended to provide references for less than one-week forecasts.…”

Section: Introductionmentioning

confidence: 99%

Climate Characteristics of the CWB Global Forecast System:Hydrological Processes and Atmospheric Circulation

Chen¹,

Fong²,

Wang³

et al. 1999

Terr. Atmos. Ocean. Sci.

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The purpose of this paper is to document the climate characteristics of the Global Forecast System (GFS), which is an atmospheric general circu lation model developed at the Central Weather Bureau (CWB), Taiwan.This paper documents the winter (December-February) and summer (June August) climate characteristics of simulated hydrological processes and atmospheric circulation from a 2-year control simulation conducted with

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The Limited-Area Forecast Systems at the Central Weather Bureau in Taiwan

Cited by 11 publications

References 0 publications

Sensitivity of Typhoon Track Predictions in a Regional Prediction System to Initial and Lateral Boundary Conditions

Sensitivity of Typhoon Track Predictions in a Regional Prediction System to Initial and Lateral Boundary Conditions

The Analysis of Typhoon Structures Using Advanced Microwave Sounding Unit Data and Its Application to Prediction

Climate Characteristics of the CWB Global Forecast System:Hydrological Processes and Atmospheric Circulation

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