Simulation of Pre-monsoon Cyclones of Two Contrasting Monsoon Years Using Mesoscale Model WRF (ARW) - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 317

convergence and relative vorticity increased gradually over the southeast Bay
of Bengal. It led to the development of the upper air cyclonic circulation
extending up to midtropospheric level on 21 st May over the southeast Bay of
Bengal and associated convective cloud clusters persisted over the region. Under
the influence of the cyclonic circulation, a low pressure area formed over the
southeast Bay of Bengal over 22 nd May morning. It lay over east central and
adjoining west central Bay of Bengal on 22 nd evening. It concentrated into a
depression and lay centered at 1130 hours IST of 23 rd near Lat. 16.5º N/Long
88.0º E about 600 kms south of Sagar Island.
Synoptic Situation of Cyclone Laila
A low pressure area developed over the southeast Bay of Bengal on 15 May
2010. It concentrated into a depression at 0600 UTC of 17 May over the
southeast Bay of Bengal. It moved in a northwesterly direction and intensified
into a severe cyclonic storm 'Laila'. Moving in a west-northwesterly direction
towards Andhra Pradesh coast, it crossed Andhra Pradesh coast near Bapatla
between 1100 and 1200 UTC of 20 May 2010 as a severe cyclonic storm. It
caused moderate damage over Andhra Pradesh with death of six persons.
The special features of the storm are as follows:
(i) It was one of the rarest track in recent years, as the cyclone developed
over southeast Bay of Bengal on 17 May, moved initially in a west-
northwesterly direction towards south Andhra Pradesh and adjoining north
Tamil Nadu coast till 19 May morning and then moved in a northwesterly
to northerly direction and crossed Andhra Pradesh coast near Bapatla
(about 50 km southwest of Machilipatnam) on 20 May evening. It then
recurved north-northeastwards and weakened gradually.
(ii) The cyclone slowed down during landfall period. It lay very close to
coast after landfall maintaining cyclone intensity for about 12 hrs after
landfall.
(iii) It was the first severe cyclone to cross Andhra Pradesh coast after 1990
in the month of May. A very severe cyclone crossed Andhra Pradesh
coast near the same area during May, 1990.
3. Results and Discussion
The evolution of the vortex each for Aila and Laila is described at the mature
stage of the respective cyclones. The mature is designated when the model
attains the minimum central surface pressure in time.
Structure of the Simulated Cyclone Aila
Figure 2 shows the model simulated mean sea level pressure of 972 hPa at 06
UTC on 25 May 2009 at the mature stage with 27 km resolution and 972 hPa
at 03 UTC 25 May 2009 with 9 km resolution while the IMD observed mean