A numerical typhoon track prediction model and its application on the real-time operation

ABSTRACT. Recently a nested numerical model for typhoon track prediction (MTP) with a higher horizontal resolution and a complex physical package has been developed by the National Meteorological Center (NMC, Beijing). For its improvement of initialization, a modified typhoon bogus scheme (Iwasaki 1987) also has been applied. The design of the M1TP had been determined by the end of 1992 and the forecast capability of this model was tested firstly with a series of experiments for the selected typhoon cases in 1993 (Wang and Li 1994). After it was examined in real-time forecast in the next year, further improvements were made in 1995 including a higher horizontal resolution increased from about 100 to 50 km, a package of complex physics instead of the simple one and a scheme for removal of analyzed vortex. With the improved forecast capability, the MTP run in quasi-operation from the date of 1 June 1995. Its products were also used by the forecasters during the past two years and the results were very encouraging.

Impact of Radio Occultation Data on the Prediction of Typhoon Haishen (2020) with WRFDA Hybrid Assimilation

FORMOSAT-7/COSMIC-2 (FS7/C2) satellite was successfully launched in June 2019. The satellite provides about 5000 radio occultation (RO) soundings daily over the tropical and partial subtropical regions. Such plentiful RO soundings with high accuracy and vertical resolution could be used to improve model initial analysis for typhoon prediction. In this study, assimilation experiments with and without the RO data were conducted with the WRFDA hybrid system for the prediction of Typhoon Haishen (2020). The experimental results show a remarkable improvement in typhoon track prediction with RO data assimilation, especially when using a nonlocal refractivity operator. Results in cycling DA and forecast are analyzed and verified for the RO data impact. Diagnostics of potential vorticity (PV) tendency budget helps explain the typhoon translation induced by different physical processes in the budget. The typhoon translation is essentially dominated by horizontal PV advection, but the track deviation can increase due to the vertical PV advection with opposite effects in the absence of RO data. Sensitivity experiments for different model initial times, physics schemes, and RO observation amounts show positive RO data impacts on typhoon prediction, mainly contributed from FS7. Complementary, an improved forecast of Typhoon Hagupit (2020) is also illustrated for the RO data impact.

Distributed Typhoon Track Prediction Based on Complex Features and Multitask Learning

Typhoons are common natural phenomena that often have disastrous aftermaths, particularly in coastal areas. Consequently, typhoon track prediction has always been an important research topic. It chiefly involves predicting the movement of a typhoon according to its history. However, the formation and movement of typhoons is a complex process, which in turn makes accurate prediction more complicated; the potential location of typhoons is related to both historical and future factors. Existing works do not fully consider these factors; thus, there is significant room for improving the accuracy of predictions. To this end, we presented a novel typhoon track prediction framework comprising complex historical features—climatic, geographical, and physical features—as well as a deep-learning network based on multitask learning. We implemented the framework in a distributed system, thereby improving the training efficiency of the network. We verified the efficiency of the proposed framework on real datasets.

Assimilation of FY-3D MWHS-2 Radiances with WRF Hybrid-3DVAR System for the Forecast of Heavy Rainfall Evolution Associated with Typhoon Ampil

A detailed investigation about the effects of the Microwave Humidity Sounder-2 (MWHS-2) radiances on board the Fengyun-3D (FY-3D) satellite is combined with developments within the Weather Research and Forecasting Data Assimilation (WRFDA) system and analyses on the evolution of the heavy rainfall associated with Typhoon Ampil during 23–24 July 2018. In the analysis field, the position of Typhoon Ampil is found out to be distinctly affected by the MWHS-2 assimilation. The experiment that assimilates MWHS-2 radiances through hybrid-3DVAR generates the best analysis with large increments around the typhoon, which contributes to the typhoon moving inland to the southwest. In the forecast fields, the MWHS-2 assimilation improves the rainfall in not only the accumulated amount, but also the evolution characteristics. The hybrid-3DVAR experiment reduces the RMSE of the rainfall amount, and enhances the spatial correlation and the fractions skill score of the rainfall evolution to the greatest extent, followed by the 3DVAR MWHS-2 experiment. As for the cause of the rainfall improvements, analyses suggest that it could be closely connected with the characteristics of the circulation structures related to the typhoon evolution. On one hand, the increases of the rainfall amount and intensities in the MWHS-2 assimilation experiments (previously underestimated) correspond to the strengthened typhoon structures with strong anomalies in both the upper-layer temperature and the lower-layer geopotential height. On the other hand, the better rainfall evolution in the hybrid-3DVAR experiment could be explained by its clearer evolution of the structure of typhoon under the effects of an approaching upper trough, and its smallest typhoon track errors around the middle time period.

An Impact Study of GNSS RO Data on the Prediction of Typhoon Nepartak (2016) Using a Multi-resolution Global Model with 3D-Hybrid Data Assimilation

Conventional soundings are rather limited over the western North Pacific and can be largely compensated by GNSS radio occultation (RO) data. We utilize the GSI hybrid assimilation system to assimilate RO data and the multi-resolution global model (MPAS) to investigate the RO data impact on prediction of Typhoon Nepartak that passed over southern Taiwan in 2016. In this study, the performances of assimilation with local RO refractivity and bending angle operators are compared for the assimilation analysis and typhoon forecast.Assimilations with both RO data have shown similar and comparable temperature and moisture increments after cycling assimilation and largely reduce the RMSEs of the forecast without RO data assimilation at later times. The forecast results at 60-15-km resolution show that RO data assimilation largely improves the typhoon track prediction compared to that without RO data assimilation, and assimilation with bending angle has better performances than assimilation with refractivity, in particular for wind forecast. The improvement in the forecasted track is mainly due to the improved simulation for the translation of the typhoon. Diagnostics of wavenumber-one potential vorticity (PV) tendency budget indicates that the northwestward typhoon translation dominated by PV horizontal advection is slowed down by the southward tendency induced by the stronger differential diabatic heating south of the typhoon center for bending-angle assimilation. Simulations with the enhanced resolution of 3 km in the region of the storm track show further improvements in both typhoon track and intensity prediction with RO data assimilation. Positive RO impacts on track prediction are also illustrated for other two typhoons using the MPAS-GSI system.

Characteristics Analysis of Wind Components according to the Typhoon Track Influenced in the Korean Peninsula Using a Wind Profiler Radar

<p> </p><p> Typhoon is a tropical cyclone accompanied by strong wind and heavy precipitation. It induces high human and property damages depending on typhoon track. The typhoon influenced in the Korean Peninsula mainly passes through Jeju Island and the Southern costal area from northward the East China Sea. In this study, wind components analysis using a wind profiler radar close to the shoreline is conducted. The wind profiler radar observes the three-dimensional wind components for a fixed-point regardless of precipitation and provides high-resolution (10 min., 100 m) data for continuous analysis. The wind characteristics according to the typhoon track was investigated using the Boseong wind profiler radar (34.76 °N, 127.21 °E) located on the south coast in Korea.</p><p> Some cases were selected as typhoons that occurred in 2010 (Dianmu, Kompasu, Malou), 2011 (Meari, Muifa) and 2012 (Khanun). For the horizontal wind analysis, there were distributed the preprocessed zonal (U) and meridional (V) wind components with time. As a result, the shape of the scatter plot and their distribution characteristics were differently shown according to the typhoon track. Dianmu and Malou had circle-shape and distributed similarly over time, however Muifa, Meari, Kompasu and Khanun displayed the line-shape, relatively. Their differences were confirmed through the quadratic regression equations by each typhoon track. In addition, the amount of change in U and V was analyzed in time series.</p><p> These wind components analysis using ground-based observation data are expected to be applied for typhoon track analysis, prediction and natural disaster prevention.</p>