MJO modulation and its ability to predict boreal summer tropical cyclone genesis over the northwest Pacific in Met Office Hadley Centre and Beijing Climate Center seasonal prediction systems

2019 ◽  
Vol 145 (720) ◽  
pp. 1089-1101 ◽  
Author(s):  
Chongbo Zhao ◽  
Hong‐Li Ren ◽  
Rosie Eade ◽  
Yujie Wu ◽  
Jie Wu ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Seasonal Prediction ◽  
Boreal Summer ◽  
Tropical Cyclone Genesis ◽  
Northwest Pacific ◽  
Prediction Systems ◽  
Cyclone Genesis ◽  
Hadley Centre

scholarly journals Forecasting the Tropical Cyclone Genesis over the Northwest Pacific through Identifying the Causal Factors in Cyclone–Climate Interactions

2018 ◽  
Vol 35 (2) ◽  
pp. 247-259 ◽  
Author(s):  
Chengzu Bai ◽  
Ren Zhang ◽  
Senliang Bao ◽  
X. San Liang ◽  
Wenbo Guo
Keyword(s):  
Tropical Cyclone ◽  
Southern Oscillation ◽  
Causal Relation ◽  
Western Pacific Subtropical High ◽  
Tropical Cyclone Genesis ◽  
Climate Indices ◽  
Northwest Pacific ◽  
Causality Analysis ◽  
Climate Interactions ◽  
Cyclone Genesis

AbstractHow to extract the causal relations in climate–cyclone interactions is an important problem in atmospheric science. Traditionally, the most commonly used research methodology in this field is time-delayed correlation analysis. This may be not appropriate, since a correlation cannot imply causality, as it lacks the needed asymmetry or directedness between dynamical events. This study introduces a recently developed and very concise but rigorous formula—that is, a formula for information flow (IF)—to fulfill the purpose. A new way to normalize the IF is proposed and then the normalized IF (NIF) is used to detect the causal relation between the tropical cyclone (TC) genesis over the western North Pacific (WNP) and a variety of climate modes. It is shown that El Niño–Southern Oscillation and Pacific decadal oscillation are the dominant factors that modulate the WNP TC genesis. The western Pacific subtropical high and the monsoon trough are also playing important roles in affecting the TCs in the western and eastern regions of the WNP, respectively. With these selected climate indices as predictors, a method of fuzzy graph evolved from a nonparametric Bayesian process (BNP-FG), which is capable of handling situations with insufficient samples, is employed to perform a seasonal TC forecast. A forecast with the classic Poisson regression is also conducted for comparison. The BNP-FG model and the causality analysis are found to provide a satisfactory estimation of the number of TC genesis observed in recent years. Considering its generality, it is expected to be applicable in other climate-related predictions.

scholarly journals How Significant are Low-Level Flow Patterns in Tropical Cyclone Genesis over the Western North Pacific?

2020 ◽  
Vol 148 (2) ◽  
pp. 559-576 ◽  
Author(s):  
Ryuji Yoshida ◽  
Hironori Fudeyasu
Keyword(s):  
Tropical Cyclone ◽  
Flow Pattern ◽  
North Pacific ◽  
Western North Pacific ◽  
Flow Patterns ◽  
Lower Latitude ◽  
Boreal Summer ◽  
Tropical Cyclone Genesis ◽  
Low Level ◽  
Cyclone Genesis

Abstract The low-level flow pattern characteristics of the tropical cyclone genesis (TCG) environment over the western North Pacific (WNP) were investigated not only for the periods during which TCG occurred, but also for the periods during which no TCG occurred. The flow patterns investigated were the shear line (SL), confluence region (CR), and easterly wave (EW) patterns. Although these flow patterns are recognized as favorable environmental conditions for TCG, their general characteristics, such as the climatological horizontal distribution, have not been previously investigated and there has been no comparison of the significance of the TCG cases to the climatological mean. We examined flow patterns using flow pattern indices defined by the modified semiobjective analysis method. SL and CR were broadly distributed over the WNP east of the Philippines during the boreal summer season. There was a peak in the EW from summer to autumn and it was distributed in a band running in an east–west direction at a lower latitude. Flow pattern indices of all three flow patterns gradually intensified until the TCG date was reached. The SL and EW indices became more intense compared to the climatological mean one day before the TCG, while that of the CR did not exceed the climatological mean. TCG occurred at the eastern edge of the area with a high genesis potential index and relative humidity and a weak vertical shear over flow patterns. This determination of the general characteristics of favorable flow pattern conditions improves our understanding of the TCG process.

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