scholarly journals Eddy Energy along the Tropical Storm Track in Association with ENSO

2009 ◽  
Vol 87 (4) ◽  
pp. 687-704 ◽  
Author(s):  
Pang-Chi HSU ◽  
Chih-Hua TSOU ◽  
Huang-Hsiung HSU ◽  
Jui-Hsin CHEN
Keyword(s):  
Storm Track ◽  
Tropical Storm

scholarly journals Sub-seasonal variations of the tropical storm track in the western north Pacific

MAUSAM ◽  
2021 ◽  
Vol 48 (2) ◽  
pp. 189-194
Author(s):  
BIN WANG ◽  
LIGUANG WU
Keyword(s):  
Summer Monsoon ◽  
Seasonal Variations ◽  
North Pacific ◽  
Time Scale ◽  
Western North Pacific ◽  
Storm Track ◽  
Tropical Storm ◽  
Climatological Data ◽  
Seasonal Oscillation ◽  
The Western Pacific

 With 20-year (1975-94) climatological data, we demonstrate that the tropical storm track over the western North Pacific (0° - 40°N, 100 - 180°E) exhibits prominent sub-seasonal variations on a time scale of about 40 days from May to November. The storm track variability is regulated by the conspicuous Climatological Intra Seasonal Oscillation (CISO) in the strength of the western North Pacific summer monsoon and the associated position of the western Pacific Sub-tropical High. The CISO cycle regulates the number of tropical storm formation during the Pre-Onset and Withdraw Cycles but not during the Onset and Peak Monsoon Cycles (from mid-June to mid-September).    

A Simultaneous Multi-scale Data Assimilation using Scale-dependent Localization in GSI-based Hybrid 4DEnVar for NCEP FV3-based GFS

2020 ◽  
Author(s):  
Bo Huang ◽  
Xuguang Wang ◽  
Daryl T. Kleist ◽  
Ting Lei
Keyword(s):  
Data Assimilation ◽  
Sampling Error ◽  
Storm Track ◽  
Single Step ◽  
Tropical Storm ◽  
Lead Times ◽  
Scale Invariant ◽  
Multi Scale ◽  
Experiment Versus ◽  
Cross Experiment

AbstractA scale-dependent localization (SDL) method was formulated and implemented in the Gridpoint Statistical Interpolation (GSI)-based four-dimensional ensemble-variational (4DEnVar) system for NCEP FV3-based Global Forecast System (GFS). SDL applies different localization to different scales of ensemble covariances, while performing a single-step simultaneous assimilation of all available observations. Two SDL variants with (SDL-Cross) and without (SDL-NoCross) considering cross-waveband covariances were examined. The performance of two- and three-waveband SDL experiments (W2 and W3, respectively) was evaluated through one-month cycled data assimilation experiments. SDL improves global forecasts to five days over scale-invariant localization including the operationally-tuned level-dependent scale-invariant localization (W1-Ope). The W3 SDL-Cross experiment shows more accurate tropical storm track forecasts at shorter lead times than W1-Ope. Compared to the W2 SDL experiments, the W3 SDL counterparts applying tighter horizontal localization at medium-scale waveband generally show improved global forecasts below 100 hPa, but degraded global forecasts above 50 hPa. While the outperformance of the W3 SDL-NoCross experiment versus the W2 SDL-NoCross experiment below 100 hPa lasts for five days, that of the W3 SDL-Cross experiment versus the W2 SDL-Cross experiment lasts for three days. Due to local spatial averaging of ensemble covariances that may alleviate sampling error, the SDL-NoCross experiments show slightly better forecasts than the SDL-Cross experiments at shorter lead times. However, the SDL-Cross experiments outperform the SDL-NoCross experiments at longer lead times, likely from retention of more heterogeneity of ensemble covariances and resultant analyses with improved balance. Relative performance of tropical storm track forecasts in the W2 and W3 SDL experiments are generally consistent with that of global forecasts.

scholarly journals Dual-Doppler Observations of Severe Tropical Storm Maggie 1999

2005 ◽  
Vol 20 (1) ◽  
pp. 112-123
Author(s):  
Sai-Choi Tai ◽  
Edwin Wing-Lui Ginn ◽  
Chiu-Ying Lam
Keyword(s):  
Hong Kong ◽  
Storm Track ◽  
Tropical Storm ◽  
Vertical Shear ◽  
Ambient Flow ◽  
Steering Flow ◽  
Nonhydrostatic Model ◽  
Tropical Areas ◽  
Weather Stations ◽  
Experimental Runs

Abstract Severe Tropical Storm Maggie crossed Hong Kong, China, in June 1999. The dual-Doppler winds of Maggie captured by the Hong Kong Observatory's (HKO) S-band Doppler weather radar array were studied. The tracks of Maggie's vorticity centers at 1–3-km levels were analyzed and compared with that at the surface as determined from the wind observations of automatic weather stations. The results indicated that the storm had a vertical tilt toward the west to northwest during the transit over Hong Kong. The tracks also deviated significantly from the deep-layer environmental steering flow. The southward movement and vertical tilt could be partly attributed to the easterly vertical shear in the ambient flow. But the terrain of Hong Kong could have also played a significant role in the lowest 1 km of the atmosphere. The tendency of the storm track to avoid mountains was well illustrated and may serve as a useful forecasting guidance indicator for tropical areas with significant terrain. Experimental runs of a nonhydrostatic model at 5-km resolution were able to simulate the broad west-southwestward movement of Maggie and the vertical tilt of the circulation near the center of the tropical cyclone as revealed by the dual-Doppler observations.

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