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Title: Impacts of an Upper-Tropospheric Cold Low on Tropical Cyclone Intensity
Abstract Following a previous study examining the influence of an upper-tropospheric cold low (CL) on the track of a nearby tropical cyclone (TC), this study investigates the impacts of a CL on TC intensity. The results suggest that the relative position and separation distance between the CL and the TC are the key factors affecting TC intensity. When located outside the CL’s radius of maximum winds (RMW) but within its circulation, TCs initially in the northwest quadrant of the CL intensify faster than those in the other quadrants. Theβeffect causes the CL to move northwestward toward the TC and enhances eddy angular momentum flux convergence. Meanwhile, the upper-level TC outflow erodes the CL and reduces the associated vertical wind shear, promoting TC intensification. In contrast, for TCs initially located southeast of the CL, the attraction of the Fujiwhara effect between the two entities counteracts the CL’sβdrift and helps to maintain their separation distance. Moreover, Rossby wave energy dispersion induces an anticyclone southeast of the CL, which transports lower-θeair toward the TC and hinders the TC development. Furthermore, TCs within the CL’s RMW reach a similar intensity due to their PV superposition, irrespective of their relative positions to the CL. For TCs located outside the CL circulation, the CL’s impacts are largely negligible for TCs located northwest of the CL, but TCs located southeast of the CL may still be affected by the CL-induced anticyclone. Significance StatementThis study examines the influence of an upper-tropospheric cold low on tropical cyclone intensity. The results illustrate that the relative position and separation distance between the cold low and tropical cyclone are crucial factors in determining tropical cyclone intensity. Tropical cyclones initially northwest of a cold low intensify faster than those to the southeast when located outside the cold low’s radius of maximum winds but still within its circulation. The main mechanisms are how theβsteering and interactions between the two entities act together. The midlevel intrusion of cold, dry air and Rossby energy dispersion also contribute to their complex interaction. These insights provide a guide for forecasting the tropical cyclone intensity when influenced by a nearby upper-level cold low.  more » « less
Award ID(s):
2116804
PAR ID:
10618669
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
AMS
Date Published:
Journal Name:
Monthly Weather Review
Volume:
152
Issue:
12
ISSN:
0027-0644
Page Range / eLocation ID:
2661 to 2677
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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