Rapid weakening of Typhoon Chan-Hom (2015) in a monsoon gyre

2016 ◽  
Vol 121 (16) ◽  
pp. 9508-9520 ◽  
Author(s):  
Jia Liang ◽  
Liguang Wu ◽  
Guojun Gu ◽  
Qingyuan Liu
Keyword(s):  
Monsoon Gyre

scholarly journals Observational Analysis of Tropical Cyclone Formation Associated with Monsoon Gyres

2013 ◽  
Vol 70 (4) ◽  
pp. 1023-1034 ◽  
Author(s):  
Liguang Wu ◽  
Huijun Zong ◽  
Jia Liang
Keyword(s):  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
Western North Pacific ◽  
Large Scale ◽  
Vertical Wind Shear ◽  
Relative Vorticity ◽  
Monsoon Trough ◽  
Cyclonic Circulation ◽  
Tropical Cyclone Formation ◽  
Monsoon Gyre

Abstract Large-scale monsoon gyres and the involved tropical cyclone formation over the western North Pacific have been documented in previous studies. The aim of this study is to understand how monsoon gyres affect tropical cyclone formation. An observational study is conducted on monsoon gyres during the period 2000–10, with a focus on their structures and the associated tropical cyclone formation. A total of 37 monsoon gyres are identified in May–October during 2000–10, among which 31 monsoon gyres are accompanied with the formation of 42 tropical cyclones, accounting for 19.8% of the total tropical cyclone formation. Monsoon gyres are generally located on the poleward side of the composited monsoon trough with a peak occurrence in August–October. Extending about 1000 km outward from the center at lower levels, the cyclonic circulation of the composited monsoon gyre shrinks with height and is replaced with negative relative vorticity above 200 hPa. The maximum winds of the composited monsoon gyre appear 500–800 km away from the gyre center with a magnitude of 6–10 m s−1 at 850 hPa. In agreement with previous studies, the composited monsoon gyre shows enhanced southwesterly flow and convection on the south-southeastern side. Most of the tropical cyclones associated with monsoon gyres are found to form near the centers of monsoon gyres and the northeastern end of the enhanced southwesterly flows, accompanying relatively weak vertical wind shear.

scholarly journals Development of a One-Month-Long, Westward-Propagating Subtropical Low in Boreal Summer

2018 ◽  
Vol 146 (1) ◽  
pp. 231-242 ◽  
Author(s):  
John Molinari ◽  
David Vollaro
Keyword(s):  
Wave Breaking ◽  
Northeast Asia ◽  
Wave Structure ◽  
Boreal Summer ◽  
Central Pacific ◽  
The Pacific ◽  
Monsoon Gyre ◽  
Jet Streak ◽  
Q Vector ◽  
Equatorial Rossby Wave

Abstract A strong MJO event produced an upper-tropospheric jet streak in northeast Asia and repeated wave breaking in the jet exit region along 150°E during July 1988. A midlatitude low moved equatorward and intensified in the presence of bandpass-filtered (15–100 day) Q vector forcing for upward motion associated with the wave breaking. This forced ascent helped to moisten the atmosphere enough to increase the column water vapor to above 55 mm. This value was sufficiently large to support a self-sustaining low even after the upper forcing weakened. The horizontal scale of the Q vector forcing was about 1500 km, consistent with the scale of most favorable convective response to quasigeostrophic forcing in the subtropics described by Nie and Sobel. The low lasted one month as it moved southwestward, then westward, while remaining north of 20°N. Maximum precipitation along the track of the low exceeded 700 mm, with an anomaly more than 400 mm. A climatology of long-lasting lows was carried out for the monsoon gyre cases studied previously. During El Niño, long-lasting lows often began near the equator in the central Pacific, and were likely to have a mixed Rossby–gravity wave or equatorial Rossby wave structure. It is speculated that the quasi-biweekly mode, the submonthly oscillation, the 20–25-day mode, and the Pacific–Japan pattern are each variations on this kind of event. During La Niña, long-lasting lows that originated in midlatitudes were more common. It is argued that these lows from midlatitudes represent a unique disturbance type in boreal summer.

Are Tropical Cyclones Less Effectively Formed by Easterly Waves in the Western North Pacific than in the North Atlantic?

2008 ◽  
Vol 136 (11) ◽  
pp. 4527-4540 ◽  
Author(s):  
Tsing-Chang Chen ◽  
Shih-Yu Wang ◽  
Ming-Cheng Yen ◽  
Adam J. Clark
Keyword(s):  
Tropical Cyclones ◽  
North Atlantic ◽  
North Pacific ◽  
Western North Pacific ◽  
Monsoon Trough ◽  
Easterly Waves ◽  
The North ◽  
Easterly Wave ◽  
Monsoon Gyre ◽  
The North Atlantic

Abstract It has been observed that the percentage of tropical cyclones originating from easterly waves is much higher in the North Atlantic (∼60%) than in the western North Pacific (10%–20%). This disparity between the two ocean basins exists because the majority (71%) of tropical cyclogeneses in the western North Pacific occur in the favorable synoptic environments evolved from monsoon gyres. Because the North Atlantic does not have a monsoon trough similar to the western North Pacific that stimulates monsoon gyre formation, a much larger portion of tropical cyclogeneses than in the western North Pacific are caused directly by easterly waves. This study also analyzed the percentage of easterly waves that form tropical cyclones in the western North Pacific. By carefully separating easterly waves from the lower-tropospheric disturbances generated by upper-level vortices that originate from the tropical upper-tropospheric trough (TUTT), it is observed that 25% of easterly waves form tropical cyclones in this region. Because TUTT-induced lower-tropospheric disturbances often become embedded in the trade easterlies and resemble easterly waves, they have likely been mistakenly identified as easterly waves. Inclusion of these “false” easterly waves in the “true” easterly wave population would result in an underestimation of the percentage of easterly waves that form tropical cyclones, because the TUTT-induced disturbances rarely stimulate tropical cyclogenesis. However, an analysis of monsoon gyre formation mechanisms over the western North Pacific reveals that 82% of monsoon gyres develop through a monsoon trough–easterly wave interaction. Thus, it can be inferred that 58% (i.e., 82% × 71%) of tropical cyclones in this region are an indirect result of easterly waves. Including the percentage of tropical cyclones that form directly from easterly waves (∼25%), it is found that tropical cyclones formed directly and indirectly from easterly waves account for over 80% of tropical cyclogeneses in the western North Pacific. This is more than the percentage that has been documented by previous studies in the North Atlantic.

scholarly journals Sudden Tropical Cyclone Track Changes over the Western North Pacific: A Composite Study

2013 ◽  
Vol 141 (8) ◽  
pp. 2597-2610 ◽  
Author(s):  
Liguang Wu ◽  
Zhongping Ni ◽  
Jingjing Duan ◽  
Huijun Zong
Keyword(s):  
North Pacific ◽  
Time Scale ◽  
Western North Pacific ◽  
Low Frequency ◽  
Monsoon Circulation ◽  
The West ◽  
The North ◽  
Monsoon Gyre ◽  
Forecasting Errors ◽  
Composite Study

Abstract Tropical cyclones (TCs) over the western North Pacific (WNP) are usually embedded in the multitime-scale summer monsoon circulation and occasionally experience sudden track changes, which are currently a challenge in TC forecasting. A composite analysis of 15 sudden north-turning cases and 14 west-turning cases that occurred during the period 2000–10 was conducted with a focus on influences of low-frequency monsoon circulations. It is found that TCs in the two specific categories of track changes are embedded in a monsoon gyre of about 2500 km in diameter on the quasi-biweekly oscillation (QBW) time scale, which is also embedded in a larger-scale cyclonic gyre or monsoon trough on the Madden–Julian oscillation (MJO) time scale. The two types of track changes are closely associated with interaction between low-frequency and synoptic flows. Two different types of asymmetric flow patterns are identified on the synoptic time scale in the vicinity of these TCs. In the north-turning case, enhanced winds lie mainly on the southeast side of TCs due to strong ridging associated with interactions between low-frequency and synoptic flows. In the west-turning case, the westward extension of the subtropical high leads to ridging on the northwest side of TCs and the enhanced winds can largely offset the steering of enhanced southwesterly winds on the synoptic time scale. Thus the north-turning (west turning) sudden track changes are affected primarily by the synoptic-scale (low frequency) steering. This may be one of the reasons for the larger forecasting errors in the north-turning case than in the west-turning case.

scholarly journals Role of the Monsoon Gyre in the Interannual Variation of Tropical Cyclone Formation over the Western North Pacific

2004 ◽  
Vol 19 (4) ◽  
pp. 776-785 ◽  
Author(s):  
Tsing-Chang Chen ◽  
Shih-Yu Wang ◽  
Ming-Cheng Yen ◽  
William A. Gallus
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Interannual Variation ◽  
Tropical Cyclone Formation ◽  
Monsoon Gyre

scholarly journals High-Resolution Initialization and Simulations of Typhoon Morakot (2009)

2011 ◽  
Vol 139 (5) ◽  
pp. 1463-1491 ◽  
Author(s):  
Hiep Van Nguyen ◽  
Yi-Leng Chen
Keyword(s):  
High Resolution ◽  
Large Scale ◽  
Initial Conditions ◽  
Model Simulation ◽  
Global Analysis ◽  
Asymmetric Structure ◽  
Track Forecast ◽  
Typhoon Morakot ◽  
Southern Taiwan ◽  
Monsoon Gyre

A model self-bogus vortex is constructed by cycle runs using the Weather Research and Forecasting (WRF) model to provide high-resolution initial conditions for tropical cyclone (TC) simulations. The vortex after 1 h of model simulation is used to construct the vortex structure for the initial conditions for the next cycle run. After about 80 cycle runs, the TC structure is well adapted to the model employed and well adjusted to the given large-scale conditions. Three separate simulations using three different initial conditions including global analysis (CTRL), the bogus package from WRF (WB), and the new initialization package (NT) are performed for Typhoon Morakot (2009). The NT scheme shows advantages in generating realistic vortex features including sea level pressure, winds, a warm core, and correct TC size with the meteorological fields away from the observed TC center consistent with the global analysis. The NT scheme also shows significant improvements in TC simulations including asymmetric structure, track, intensity, strength of low-level winds, radar reflectivity, and rainfall. For other runs, such as WB and CTRL, the unbalanced initial vortex needs to adjust to the changing environment during the first 2–3 days of model simulations, which is likely to have negative impacts on the track, intensity, and rainfall forecasts in most cases. For all three different types of model initializations, the model is capable of simulating heavy orographic precipitation over southern Taiwan. However, with a better track forecast, only the NT run simulates the high-reflectivity band associated with the convergence zone between Morakot’s circulations and the southwest monsoon off the southeast coast. In addition to Morakot’s slow movement and relatively large size, Typhoons Goni and Etau were embedded within a moist monsoon gyre. The combined circulations associated with the monsoon gyre and tropical storms bring in moisture-laden flows toward the western slopes of southern Taiwan.

The Mid-latitudinal influence on the formation of the monsoon gyre in August 1991

2019 ◽  
Vol 86 ◽  
pp. 52-62
Author(s):  
Xuyang Ge ◽  
Donglei Shi
Keyword(s):  
Monsoon Gyre

Simulated sensitivity of tropical cyclone track to the moisture in an idealized monsoon gyre

2017 ◽  
Vol 80 ◽  
pp. 173-182 ◽  
Author(s):  
Ziyu Yan ◽  
Xuyang Ge ◽  
Bingyao Guo
Keyword(s):  
Tropical Cyclone ◽  
Cyclone Track ◽  
Tropical Cyclone Track ◽  
Monsoon Gyre

scholarly journals Interactions between Typhoon Megi (2010) and a Low-Frequency Monsoon Gyre

2015 ◽  
Vol 72 (7) ◽  
pp. 2682-2702 ◽  
Author(s):  
Mingyu Bi ◽  
Tim Li ◽  
Melinda Peng ◽  
Xinyong Shen
Keyword(s):  
Low Frequency ◽  
Frequency Component ◽  
The Philippines ◽  
Sharp Change ◽  
Budget Analysis ◽  
Before And After ◽  
Arw Model ◽  
Monsoon Gyre ◽  
Scale Motion ◽  
Vorticity Tendency

The ARW Model is used to investigate the sharp northward turn of Super Typhoon Megi (2010) after it moved westward and crossed the Philippines. The NCEP analyzed fields during this period are separated into a slowly varying background-flow component, a 10–60-day low-frequency component representing the monsoon gyre, and a 10-day high-pass-filtered component representing Megi and other synoptic-scale motion. It appears that the low-frequency (10–60 day) monsoon gyre interacted with Megi and affected its track. To investigate the effect of the low-frequency mode on Megi, numerical experiments were designed. In the control experiment, the total fields of the analysis are retained in the initial and boundary conditions, and the model is able to simulate Megi’s sharp northward turn. In the second experiment, the 10–60-day monsoon gyre mode is removed from the initial and lateral boundary fields, and Megi moves westward and slightly northwestward without turning north. Tracks of the relative positions between the Megi and the monsoon gyre centers suggest that a Fujiwhara effect may exist between the monsoon gyre and Megi. The northward turning of both Megi and the monsoon gyre occurred when the two centers were close to each other and the beta drift was enhanced. A vorticity budget analysis was conducted. It is noted that the Megi moves toward the maximum wavenumber-1 vorticity tendency. The sharp change of the maximum vorticity tendency direction before and after the track turning point is primarily attributed to the change of the horizontal vorticity advection. A further diagnosis shows that the steering of the vertically integrated low-frequency flow is crucial for the change of the horizontal advection tendency.

scholarly journals NICAM Predictability of the Monsoon Gyre over the Western North Pacific during August 2016

2019 ◽  
Vol 97 (2) ◽  
pp. 533-540 ◽  
Author(s):  
Takuya JINNO ◽  
Tomoki MIYAKAWA ◽  
Masaki SATOH
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Monsoon Gyre
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