An Analysis of Environmental Dynamical Control of Tropical Cyclone Intensity over the Bay of Bengal during 1981-2010 - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 83

4. Effect of Vertical Wind Shear on Intensification

Figure 2(a-f) presents a function fit between maximum intensification and
corresponding VWS for 12 h, 24 h, 36 h, 48 h, 60 h and 72 h intervals
respectively (Dotted line indicates maximum intensity change line and solid
line indicates best-fit line). The figures illustrate that there is an upper boundary
of TC intensification against VWS. The nature of maximum intensification
(MI) of tropical cyclone appears to be linear function of VWS at all the intervals.
To find the nature of relationship between VWS and MI of tropical cyclones,
the range of VWS from 4 ms -1 to 26 ms -1 is divided at 2 ms -1 interval for 12 h,
24 h, 36 h, 48 h, 60 h and 72 h intervals. The higher intensification in the weak
VWS region at all the intervals reconfirms that a weak VWS region is favourable
for intensification of tropical cyclones. The maximum intensity changes were
plotted (Fig. 2(a-f)) against the mid points of each VWS group.
The scattered diagram in Fig. 2(a-f) suggests that maximum intensity is a
linear function of VWS as given below:
dv max(t) = A × VWS + B (2)

where A and B are constants for t = 12, 24, 36, 48, 60 and 72 h, dv max = maximum
intensification (MI) in kt and VWS = Vertical wind shear (ms -1 ).
As weak VWS is a favourable parameter for intensification of tropical
cyclones, it is expected that maximum intensification of tropical cyclones will
increase with the decrease of VWS. This study also shows increase of maximum
intensification of tropical cyclones with decrease of VWS. The nature of
maximum intensification is found to be a linear function of VWS with negative
gradient. The statistical analysis (Fig. 2(a-e)) also shows the intensification of

(b)

(c)

(a)

(e)

(f)

(d)

Fig. 2: Same as Fig. 1 except for vertical wind shear.