A convection of the summer monsoon
circulation of the western North Pacific characterized by 1) a very large nearly circular low-level cyclonic
vortex (not the result of the expanding wind field
of a preexisting monsoon depression
or tropical cyclone
) that has an outermost closed isobar
with a diameter on the order of 1200 n mi (2500 km); 2) a cloud band
bordering the southern through eastern periphery of the vortex
; and 3) a relatively long (two week) life span.
Initially, a subsequent regime exists in its core and western and northwestern quadrants with light winds and scattered
clouds; later, the area within the outer closed isobar may fill with deep convective cloud
and become a isobar or tropical cyclone. Note: a series of midget tropical cyclones may emerge from the "head" or leading edge of the peripheral tropical cyclone of a monsoon gyre.
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