Understanding the Properties of Cyclonic Storm ‘Aila’ Using NWP Technique - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 368

and WRF Single-Moment 5 Class (referred WSM5) microphysics schemes
are used in the study. The combinations of KF scheme with FR, KS, LN, WSM3
and WSM5 are also hereafter referred as KFFR, KFKS, KFLN, KFWSM3 and
KFWSM5. The model is integrated from 00 UTC of 21 May to 27 May, 2009.
3. Numerical Experiments and Data Used
The experiment is conducted for KF with the combination of FR, KS, LN,
WSM3 and WSM5 microphysics schemes. Numerous observational and
modelling studies have demonstrated that vorticity, vertical velocity, and vertical
wind shears are main controlling factors on tropical cyclone (TC) intensity
change. Keeping these points in mind surface and upper air pressure, wind,
vorticity, vertical velocity, and vertical wind shears are analyzed quantitatively.
Minimum sea level pressure, maximum wind at 10 m height, minimum and
maximum vorticity, minimum vertical wind shears are searched. Finally the
results are compared with India Meteorological Department (IMD) and Joint
Typhoon Warning Centre (JTWC) archived information.
4. Results and Discussions
The first initial vortex for KFFR, KFKS, KFLN and KFWSM5 are found at 22
UTC of 20 May and for KFWSM3 it is found at 00 UTC of 21 May. But the
clear signature of the vortex at low level for KFFR, KFKS, KFLN, KFWSM3
and KFWSM5 are found at 08 UTC of 24 May, at 06 UTC of 24 May, at 04
UTC of 24 May, at 22 UTC of 24 May, and at 18 UTC of 24 May respectively.
The mean sea level pressure (MSLP) of the system decreased slowly with
the progress of time till 12 UTC of 23 May; then it decreased sharply and
reached minimum value at 00 UTC of 25 May when the system was near the
coast (Fig. 1). The lowest central pressure of 'Aila' for KFFR, KFKS, KFLN,
KFWSM3 and KFWSM5 were 963.0 hPa (at 23 UTC, 24 May), 962.3 hPa (at
12 UTC, 24 May), 958.1 hPa (at 22 UTC, 24 May), 966.6 hPa (at 00 UTC, 25
May) and 957.2 hPa (at 23 UTC, 24 May) respectively. But it increased
afterwards slowly attaining to normal value as it decayed slowly due to some
favourable synoptic conditions on its way of movement after making landfall.
Similarly when the system was nearer the coast the distribution of MSLP
was uniform; isobars were almost circular but the central location of the system
was little far away from each other as illustrated in Fig. 3(a-e). Following the
pressure trend, the trend of maximum wind associated with the system was
very similar to each other till 15 UTC of 22 May but it differed afterwards. It
increased slowly from 7.0 ms -1 to 15.0 ms -1 till 15 UTC of 22 May and remained
steady afterwards till 00 UTC of 23 May and then increased rapidly till it
reached maximum value (Fig. 2). The maximum winds associated with the
system for KFFR, KFKS, KFLN, KFWSM3 and KFWSM5 were 39.2 ms -1
(19 UTC, 24 May), 36.1 ms -1 (04 UTC, 24 May), 44.6 ms -1 (16 UTC, 24