Tropical Cyclones are very intense
characterized by a
low-pressure center, a closed low-level atmospheric circulation,
strong winds, and a spiral arrangement of
thunderstorms that produce heavy rain.important at the coast as they can lead to high waves, storm
surges, inland inundation, and erosion in populated areas resulting in severe economical
and societal damage. Prediction of these events is a challenging task, around
the world various models were used to predict these events. All these models
were very sensitive to forcing fields like wind speed, track and mean sea level
pressure anomalies. A wide variety of tropical cyclone surface wind fields have
been used to drive storm surge prediction models, ranging from parametric wind
models (Holland 1980, 2010), to steady-state dynamic PBL models, to interactive
objective kinematic analysis (Cox et al., 1995), and to sophisticated non-hydrostatic
Numerical Weather Prediction (NWP) models. Though parametric wind models have distinct
operational advantages that maximize the number of hours of forecast utility,
they cannot reproduce a fine scale features such as spiral rain bands. Difficulties
in storm modeling be related to the
smoothness of model simulated/predicted wind fields because of the limitations
of spatial resolution not capturing secondary depression, fronts, and the sting
jet phenomenon (Browning 2004). Improved atmospheric model resolution has been
found to improve the representation of storms, producing sharper Mesoscale
features as well as better representing convective events (Mass et al., 2002). In
India, several earlier works on storm surge modeling based on above methods
concluded that resolving the atmospheric forcing of the cyclone is very
important along with detailed coastal geometry for surge development (
\cite{Sig_enza_Ortiz_2017},
\cite{1977}). Hence, the motivation of this work is to examine
the application of numerical weather prediction model (WRF-ARW) to compute the
realistic maximum wind speed, lower sea level pressure and reduced track error
values by improving the track simulation at high domain resolution towards
application to storm surge simulations. This study mainly focused to explore
the impact of atmospheric model resolution and initial conditions in simulating
the cyclone track, maximum winds and intensity. In these regions several
studies have been carried-out for
prediction of track and intensity of tropical cyclones using numerical weather
prediction (NWP) models (Pattanayak and Mohanty 2008). But those studies are
confined to coarse resolution grids and are not aimed towards applications in
storm surge prediction. Bhaskaran et al., (2013) have used WRF simulated winds
and pressure fields as inputs to ocean model to study the water level rise at
the coast based on ensemble tracks. Their study was confined to coarse domain
resolution at 9 km.
Thus,
one of the primary focuses of the present work was to reconstruct the wind
fields and their forcing under different horizontal resolutions using WRF model
for predicting the cyclone. The results will be implied in future studies towards
track prediction and intensity under various initial conditions and to be used
in the storm surge studies.
The Hudhud cyclone was the very
severe cyclonic storm occurred over the Bay of Bengal during 07-14th October 2014. It developed over low-pressure area near Tenasserim coast and
adjoining North Andaman Sea in the morning of 6th October 2014. It
emerged into Southeast Bay of Bengal and continued to move west-northwestwards
intensifying into a severe cyclonic storm in the morning of 09th October and into a very severe cyclonic storm in the afternoon of 10th October. It crossed north Andhra Pradesh coast over Visakhapatnam (VSP) between
1200 and 1300 hrs IST (0630 – 0730 UTC) of 12th October. IMD
reported the maximum sustained wind speed of 180 kmph at the time of landfall. The
lowest estimated central pressure was 950 hPa from 0000 UTC of 12th to 0600 UTC of 12th October. The maximum estimated wind speed was 185
kmph. The system moved in a west northwestward direction over the sea area and
then northwestward at the time of landfall. The lowest observed pressure of
950.3 hPa was reported by Visakhapatnam station at 0700 UTC (at the time of
landfall) of 12th October and the maximum sustained wind speed of 130
kmph at 0500 UTC. The damage was quite severe and the VSCS, Hudhud mainly
affected North Andhra Pradesh and adjoining south Odisha. In Andhra Pradesh, 46
people lost their lives, and 43 were injured. About 41,269 houses were damaged.
Thousands of animals including poultry/duck perished. 2.3 lakh Hectares of land
was submerged (Medha and Sunitha, 2015). The IMD post cyclonic survey (IMD report
2014) reported maximum of storm surge of 1.4 meters above the astronomical tide
at Visakhapatnam at the landfall.