From mid‐May to late June, the eastward propagation of some mid‐tropospheric cyclones (MTCs) originating in the Bay of Bengal (BOB)‐Burma (BUM) region across northern Indochina and southwest China to East Asia are observed. From 1979 to 2016, 137 MTCs were identified for the BOB‐BUM region. Eighty‐eight MTCs were trapped over northern Indochina, but 49 were propagated by the southwesterly flow of the BOB mid‐tropospheric trough to reach East Asia. Thirty‐one moved across Taiwan, but 18 did not. Eventually, all these MTCs moved to Okinawa. The former group of rainstorms produced rainfall ≥100 mm·day−1over Taiwan, while 44 rainstorms generated rainfall ≥50 mm·day−1over Okinawa. The 49 eastward propagating through‐Indochina MTCs exhibited the following salient features: (a) initial formation mostly occurred in the mid‐troposphere ahead/within the BOB trough in the morning over the BOB, but in the afternoon‐evening over BUM. (b) The eastward propagating BOB‐BUM MTCs underwent two descending processes: descending one mandatory level 6 hr after formation, and descending again from 700 to 925 hPa over southeastern China to interact with a low‐level cyclonic shear flow. (c) Intensified (weakened) by dipole anomalous circulation cells, the confluent monsoon southwesterly flow west (east) of Taiwan facilitated the merger of the MTC with a local front. (d) Rainfall produced by rainstorms over Taiwan/Okinawa was maintained by the intensified convergence of water vapour flux toward Taiwan/Okinawa. This hydrological process was stronger toward Taiwan than Okinawa and generated more rainfall in the former region. The impact of the BOB‐BUM MTC on East Asian weather is confirmed by this study.
- Award ID(s):
- 1712290
- NSF-PAR ID:
- 10158499
- Date Published:
- Journal Name:
- Monthly Weather Review
- ISSN:
- 0027-0644
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1175/MWR-D-19-0038.1
