摘要
The track of tropical cyclone‘Madi’showed almost 180° turn around,while immediately after recurvature it decayed rapidly in the following 24 hours.Sea surface temperature(SST)analyses rule out confrontation with low SST as cause of weakening.At 0000 UTC of 9 December 2013 diabatic heating(DH),potential vorticity(PV)and vertical wind shear(VWS)were favourable for intensification.However,a dry area close to the system centre at mid-troposphere subsequently engulfed the middle strata and the mid-tropospheric relative humidity(MTH)drastically reduced on 0000 UTC of 10 December 2013.The MTH further reduced on 0000 UTC of 11 December 2013.Lack of moisture in mid-troposphere apparently caused a mutation within the structure causing a sudden decrease in elevation.As the system dried up,reduction in convection above 400 h Pa hindered latent heat release.PV above 400 h Pa decreased significantly.Eventually,there was a spurt of VWS at 1200 UTC of the 10December 2013.The opposite wind flow between lower level and upper level whisked away the top of the system to northeast.Under the influence of the net northeasterly flow in lower to middle troposphere,the miniature vortex recurved southwestward and the vertical distortion due to shear weakened the system into a depression.
The track of tropical cyclone‘Madi’showed almost 180° turn around,while immediately after recurvature it decayed rapidly in the following 24 hours.Sea surface temperature(SST)analyses rule out confrontation with low SST as cause of weakening.At 0000 UTC of 9 December 2013 diabatic heating(DH),potential vorticity(PV)and vertical wind shear(VWS)were favourable for intensification.However,a dry area close to the system centre at mid-troposphere subsequently engulfed the middle strata and the mid-tropospheric relative humidity(MTH)drastically reduced on 0000 UTC of 10 December 2013.The MTH further reduced on 0000 UTC of 11 December 2013.Lack of moisture in mid-troposphere apparently caused a mutation within the structure causing a sudden decrease in elevation.As the system dried up,reduction in convection above 400 h Pa hindered latent heat release.PV above 400 h Pa decreased significantly.Eventually,there was a spurt of VWS at 1200 UTC of the 10December 2013.The opposite wind flow between lower level and upper level whisked away the top of the system to northeast.Under the influence of the net northeasterly flow in lower to middle troposphere,the miniature vortex recurved southwestward and the vertical distortion due to shear weakened the system into a depression.
