scholarly journals Cluster Analysis of Tropical Cyclone Tracks over the Western North Pacific Using a Self-Organizing Map

2016 ◽  
Vol 29 (10) ◽  
pp. 3731-3751 ◽  
Author(s):  
Han-Kyoung Kim ◽  
Kyong-Hwan Seo
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
The Philippines ◽  
Self Organizing Map ◽  
Central Pacific ◽  
Philippine Sea ◽  
Genesis Frequency ◽  
Sst Anomalies ◽  
Self Organizing

Abstract Tropical cyclone (TC) tracks over the western North Pacific (WNP) in 1979–2013 are classified by a self-organizing map technique. A false detection rate method identifies five optimal TC clusters. Physical mechanisms of the intraseasonal and interannual variations in the TC genesis frequency are investigated for each cluster. The five clusters are separated by genesis location, from the westernmost area (east of the Philippines, C1) to the easternmost (~150°E, C5) onset area over the WNP. The intraseasonal Madden–Julian oscillation (MJO) significantly affects the genesis frequency for all clusters except for C5. In particular, MJO phases 5 and 6 (1 and 2) provide significantly favorable (unfavorable) large-scale conditions for TC genesis. Two types of El Niño–Southern Oscillation influence the interannual variation of the genesis frequency for only C2 (generated over the western Philippine Sea and East China Sea) and C4 (formed near the eastern Philippine Sea). Enhanced eastern Pacific sea surface temperature (SST) anomalies lead to a ~40% decrease in the C2 TC frequency through a reversed Walker circulation with downward motion over the WNP. Conversely, increased central Pacific SST anomalies generate a cyclonic Rossby wave northwest of the forcing, inducing a significant increase (~50%) in the C4 TC frequency. The interannual variability for the C5 TCs is strongly controlled by the variation of the western Pacific subtropical high (WPSH). A positive WPSH variation reduces the C5 TC genesis frequency by 66%, while negative WPSH anomalies enhance the frequency by 50%. A prediction scheme using information from the first four 6-h TC locations demonstrates a skillful determination of TC clusters.

scholarly journals Contributions of SST Anomalies in the Indo-Pacific Ocean to the Interannual Variability of Tropical Cyclone Genesis Frequency over the Western North Pacific

2019 ◽  
Vol 32 (11) ◽  
pp. 3357-3372 ◽  
Author(s):  
Ruifen Zhan ◽  
Yuqing Wang ◽  
Jiuwei Zhao
Keyword(s):  
Pacific Ocean ◽  
Tropical Cyclone ◽  
Statistical Model ◽  
Interannual Variability ◽  
North Pacific ◽  
Western North Pacific ◽  
Southern Oscillation ◽  
Typhoon Season ◽  
Genesis Frequency ◽  
Sst Anomalies

Abstract This study attempts to evaluate quantitatively the contributions of sea surface temperature (SST) anomalies in the Indo-Pacific Ocean to the interannual variability of tropical cyclone (TC) genesis frequency (TCGF) over the western North Pacific (WNP). Three SST factors in the Indo-Pacific Ocean are found to play key roles in modulating the interannual variability of WNP TCGF. They are summer SST anomaly in the east Indian Ocean (EIO), the summer El Niño–Southern Oscillation Modoki index (EMI), and the spring SST gradient (SSTG) between the southwestern Pacific and the western Pacific warm pool. Results show that the three factors together can explain 72% of the total variance of WNP TCGF in the typhoon season for the period 1980–2015. Among them, the spring SSTG and the summer EIO contribute predominantly to the interannual variability of TCGF, followed by the summer EMI, with respective contributions being 39%, 38%, and 23%. Further analysis shows that the summer EMI was affected significantly by the spring SSTG and thus had a relatively lower contribution to the TCGF than the spring SSTG. In addition, a statistical model is constructed to predict the WNP TCGF in the typhoon season by a combination of the May EIO and the spring SSTG. The new model can reproduce well the observed WNP TCGF and shows an overall better skill than the ECMWF Seasonal Forecasting System 5 (SEAS5) hindcasts. This statistical model provides a good tool for seasonal prediction of WNP TCGF.

scholarly journals Characterizing the highest tropical cyclone frequency in the Western North Pacific since 1984

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Joseph Basconcillo ◽  
Eun-Jeong Cha ◽  
Il-Ju Moon
Keyword(s):  
Tropical Cyclone ◽  
Summer Monsoon ◽  
North Pacific ◽  
Western North Pacific ◽  
Tropical Indian Ocean ◽  
Boreal Summer ◽  
Central Pacific ◽  
Impact Reduction ◽  
Cyclone Frequency ◽  
Sst Anomalies

AbstractThe 2018 boreal summer in the Western North Pacific (WNP) is highlighted by 17 tropical cyclones (TC)—the highest record during the reported reliable years of TC observations. We contribute to the existing knowledge pool on this extreme TC frequency record by showing that the simultaneous highest recorded intensity of the WNP summer monsoon prompted the eastward extension of the monsoon trough and enhancement of tropical convective activities, which are both favorable for TC development. Such changes in the WNP summer monsoon environment led to the extreme TC frequency record during the 2018 boreal summer. Meanwhile, the highest record in TC frequency and the intensity of the WNP summer monsoon are both attributed with the combined increase in the anomalous westerlies originating from the cold tropical Indian Ocean sea surface temperature (SST) anomalies drawn towards the convective heat source that is associated with the warm central Pacific SST anomalies. Our results provide additional insights in characterizing above normal tropical cyclone and summer monsoon activities in the WNP in understanding seasonal predictable horizons in the WNP, and in support of disaster risk and impact reduction.

scholarly journals Differences in Western North Pacific Tropical Cyclone Activity among Three El Niño Phases

2020 ◽  
Vol 33 (18) ◽  
pp. 7983-8002
Author(s):  
Jinjie Song ◽  
Philip J. Klotzbach ◽  
Yihong Duan
Keyword(s):  
Tropical Cyclone ◽  
El Niño ◽  
North Pacific ◽  
Western North Pacific ◽  
El Nino ◽  
Walker Circulation ◽  
The Philippines ◽  
Central Pacific El Niño ◽  
Low Level ◽  
Sst Anomalies

AbstractThe impacts of El Niño on tropical cyclone (TC) activity over the western North Pacific (WNP) are examined through investigation of three types of tropical Pacific warming episodes according to where the maximum sea surface temperature (SST) anomalies occur in the equatorial Pacific: the eastern Pacific El Niño (EPE), the central Pacific El Niño (CPE), and the mixed El Niño (ME). More TCs form over the eastern part of the WNP in all three El Niño types, whereas the frequency of TCs over the western part of the WNP increases as the peak SST anomalies migrate from east to west. Although TCs more frequently recurve at higher latitudes during EPE and CPE, the most frequent region for recurving is much closer to the East Asian continent in CPE years than in EPE years. In contrast, more TCs track westward and threaten the Philippines in ME years. The increased TC genesis over the western part of the WNP can be explained by enhanced low-level relative vorticity, reduced vertical wind shear, and increased maximum potential intensity during CPE and increased midlevel moisture during EPE and ME. This increase is further related to updraft anomalies near the date line driven by an anomalous Walker circulation and an anomalous low-level cyclonic circulation over the WNP. The TC track differences among the different El Niño types are linked to the east–west shift of the western Pacific subtropical high, possibly caused by an anomalous Hadley circulation from 120° to 130°E that is strongly coupled with the anomalous Walker circulation.

scholarly journals Contribution of the Interdecadal Pacific Oscillation to the Recent Abrupt Decrease in Tropical Cyclone Genesis Frequency over the Western North Pacific since 1998

2018 ◽  
Vol 31 (20) ◽  
pp. 8211-8224 ◽  
Author(s):  
Jiuwei Zhao ◽  
Ruifen Zhan ◽  
Yuqing Wang ◽  
Haiming Xu
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
General Circulation ◽  
Western North Pacific ◽  
The Philippines ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Interdecadal Pacific Oscillation ◽  
Abrupt Decrease ◽  
Study Results ◽  
Genesis Frequency

Previous studies have documented an abrupt decrease of tropical cyclone (TC) genesis frequency over the western North Pacific (WNP) since 1998. In this study, results from an objective clustering analysis demonstrated that this abrupt decrease is primarily related to the decrease in a cluster of TCs (C1) that mostly formed over the southeastern WNP, south of 15°N and east of the Philippines, and possessed long tracks. Further statistical analyses based on both best track TC data and global reanalysis data during 1980–2015 revealed that the genesis of C1 TCs was significantly modulated by the interdecadal Pacific oscillation (IPO), whose recent negative phase since 1998 corresponded to a La Niña–like sea surface temperature anomaly (SSTA) pattern, which strengthened the Walker circulation in the tropical Pacific and weakened the WNP monsoon trough, suppressing genesis of C1 TCs in the southeastern WNP and predominantly contributing to the decrease in TC genesis frequency over the entire WNP basin. These findings were further confirmed by results from similar analyses based on longer observational datasets and also the outputs from a 500-yr preindustrial general circulation model experiment using the Geophysical Fluid Dynamics Laboratory (GFDL) Coupled Model, version 3. Additional analysis indicates that the decrease in C1 TC genesis frequency in the recent period was dominated during August–October, with the largest decrease in October.

Lightning bursts observed in the tropical cyclone during the genesis over the western north Pacific

2021 ◽  
Author(s):  
Hisayuki Kubota ◽  
Yukihiro Takahashi ◽  
Mitsuteru Sato
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
The Philippines ◽  
Lightning Activity ◽  
The Other ◽  
Tropical Cyclone Intensity ◽  
Cyclone Intensity ◽  
Philippine Sea ◽  
Other Hand

<p>The accuracy of tropical cyclone (TC) track forecast has been improved year by years, on the other hand, the forecast of tropical cyclone intensity still has a difficulty of improvement. Recently the relationship between lightning activity and tropical cyclone intensity has been investigated. Lightning tends to increase during the rapid intensification of the TC. Therefore, monitoring the lightning activity becomes important for a TC intensity forecast. Lightning observation network are deployed over the western north Pacific by five very long frequency events trigger measurements called V-POTEKA at Palau, Guam, Manila, Okinawa Japan and Serpong Indonesia under the ULAT (Understanding Lightning and Thunderstorm) of SATREPS (Science and Technology Research Partnership for Sustainable Development) in the Philippines.</p><p>Tropical storm (TS) Bavi and Maysak were generated over the Philippine Sea on August 2020. We found that lightning activity drastically increased in the TC during the TC genesis stage when the TC reached TS criteria. Numbers of lightning reached the maximum during the life cycle of the TCs. Lightning was concentrated in the convective clouds about 100 to 200 km size. They are located around 400 to 500 km and 100 to 200 km from the TC center respectively and lasted about few hours. We called this phenomenon as “lightning burst”. On the other hand, when TS Haishen and Dolphin were generated over the Philippine Sea in September 2020, they did not observe lightning burst. About half of the TCs observed lightning burst in the Philippine Sea in 2020. We will investigate further what kind of structure occurred during the lightning burst and what kind of mechanism responsible for the lightning burst.</p>

scholarly journals Multi-model Projection of Tropical Cyclone Genesis Frequency over the Western North Pacific: CMIP5 Results

SOLA ◽  
2012 ◽  
Vol 8 (0) ◽  
pp. 137-140 ◽  
Author(s):  
Satoru Yokoi ◽  
Chiharu Takahashi ◽  
Kazuaki Yasunaga ◽  
Ryuichi Shirooka
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Tropical Cyclone Genesis ◽  
Model Projection ◽  
Cyclone Genesis ◽  
Genesis Frequency

scholarly journals Reintensification of the Anomalous Western North Pacific Anticyclone during the El Niño Modoki Decaying Summer: Relative Importance of Tropical Atlantic and Pacific SST Anomalies

2020 ◽  
Vol 33 (8) ◽  
pp. 3271-3288
Author(s):  
Juan Feng ◽  
Wen Chen ◽  
Xiaocong Wang
Keyword(s):  
El Niño ◽  
North Pacific ◽  
General Circulation ◽  
Western North Pacific ◽  
El Nino ◽  
Central Pacific ◽  
El Niño Modoki ◽  
Sst Cooling ◽  
Sst Warming ◽  
Sst Anomalies

AbstractThe El Niño Modoki–induced anomalous western North Pacific anticyclone (WNPAC) undergoes an interesting reintensification process in the El Niño Modoki decaying summer, the period when El Niño Modoki decays but warm sea surface temperature (SST) anomalies over the tropical North Atlantic (TNA) and cold SST anomalies over the central-eastern Pacific (CEP) dominate. In this study, the region (TNA or CEP) in which the SST anomalies exert a relatively important influence on reintensification of the WNPAC is investigated. Observational analysis demonstrates that when only anomalous CEP SST cooling occurs, the WNPAC experiences a weak reintensification. In contrast, when only anomalous TNA SST warming emerges, the WNPAC experiences a remarkable reintensification. Numerical simulation analysis demonstrates that even though the same magnitude of CEP SST cooling and TNA warming is respectively set to force the atmospheric general circulation model, the response of the WNPAC is still much stronger in the TNA warming experiment than in the CEP cooling experiment. Further analysis demonstrates that this difference is caused by the distinct location of the effective tropical forcing between the CEP SST cooling and TNA SST warming for producing a WNPAC. The CEP cooling-induced effective anomalous diabatic cooling is located in the central Pacific, by which the forced anticyclone becomes gradually weak from the central Pacific to the western North Pacific. Thus, a weak WNPAC is produced. In contrast, as the TNA SST warming–induced effective anomalous diabatic cooling is just located in the western North Pacific via a Kelvin wave–induced Ekman divergence process, the forced anticyclone is significant and powerful in the western North Pacific.

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