Wave fields, both measured and forecast during the very severe cyclone Phailin, are discussed in this communication. Waves having maximum height of 13.54 m were recorded at Gopalpur, the landfall point of the cyclone. The forecast and observed significant wave heights matched well at Gopalpur with correlation coefficient of 0.98, RMS error of 0.35 m and scatter index of 14%. Forecasts were also validated in the open ocean and found to be reliable (scatter index &#60; 15%). The study also revealed the presence of Southern Ocean swells with a peak period of 20-22 sec hitting Gopalpur coast along with the cyclone-generated waves

Harikumar, R.

Hithin, N. K.

Jeyakumar, C.

Kaviyazhahu, K.

Kumar, Ramesh M.

Kumar, Sanil V.

Kumari, Rakhi

Nagaraju, C.

Nair, Balakrishnan T. M.

Nayak, Shailesh

Nherakkol, Arun

Prasad, Krishna B.

Remya, P. G.

Sandhya, K. G.

Shenoi, S. S. C.

Sirisha, P.

Srinivas, K.

English

Publications of the IAS Fellows

RESEARCH COMMUNICATIONS 
 
CURRENT SCIENCE, VOL. 106, NO. 8, 25 APRIL 2014 1121 
*For correspondence. (e-mail: bala@incois.gov.in) 
Wave forecasting and monitoring  
during very severe cyclone Phailin in 
the Bay of Bengal 
 
T. M. Balakrishnan Nair1,*, P. G. Remya1,  
R. Harikumar1, K. G. Sandhya1, P. Sirisha1,  
K. Srinivas1, C. Nagaraju1, Arun Nherakkol1,  
B. Krishna Prasad1, C. Jeyakumar1,  
K. Kaviyazhahu1, N. K. Hithin1, Rakhi Kumari1,  
V. Sanil Kumar2, M. Ramesh Kumar1,  
S. S. C. Shenoi1 and Shailesh Nayak3 
1Information Services and Ocean Sciences Group,  
ESSO–Indian National Centre for Ocean Information Services,  
‘Ocean Valley’, Pragathi Nagar (BO), Nizampet (SO),  
Hyderabad 500 090, India 
2CSIR-National Institute of Oceanography, Dona Paula,  
Goa 403 004, India 
3Earth System Science Organization, New Delhi 110 003, India 
 
Wave fields, both measured and forecast during the  
very severe cyclone Phailin, are discussed in this 
communication. Waves having maximum height of 
13.54 m were recorded at Gopalpur, the landfall point 
of the cyclone. The forecast and observed significant 
wave heights matched well at Gopalpur with correla-
tion coefficient of 0.98, RMS error of 0.35 m and scat-
ter index of 14%. Forecasts were also validated in the  
open ocean and found to be reliable (scatter index < 
15%). The study also revealed the presence of South-
ern Ocean swells with a peak period of 20–22 sec  
hitting Gopalpur coast along with the cyclone-genera-
ted waves. 
 
Keywords: Buoys, Phailin, tropical cyclone, swell, 
wave forecast. 
 
PROVIDING accurate ocean state forecasts during tropical 
cyclones is challenging. However, it is also important to 
forewarn the users such as fishermen community, oil and 
shipping industry, ports and harbours, navy, coast guard 
and coastal communities on the possible hazardous condi-
tions during such extreme weather events. The Earth  
System Science Organization (ESSO)–Indian National 
Centre for Ocean Information Services (ESSO–INCOIS), 
Hyderabad started the quantitative Ocean State Forecast 
(OSF) service in 2005 by issuing forecasts of vital ocean 
parameters like significant wave heights, remotely gener-
ated waves (swells) and ocean surface winds, seven days 
in advance and at three hourly intervals, with daily  
updates1. Prediction and evaluation of the wave features 
generated by the very severe cyclonic storm (VSCS) 
Phailin are attempted in the present study.  
 Phailin2 was the only VSCS to hit the east coast of  
India during the last four years. The cyclone lasted for  
6 days from 8 to 14 October 2013 and it made landfall on 
12 October at 1700 UTC in Gopalpur, Odisha (Figure 1). 
During the Odisha super cyclone of 1999, no quantitative 
OSF system was in place for forewarning the coastal 
communities, but for Phailin, the warnings were issued 
five days in advance. This helped the maritime authorities 
and users to take maximum precautions well in advance 
and save lives and properties. Phailin also provided a 
unique opportunity to study instrumentally recorded  
extreme wave data and evaluate the forecast. 
 Monitoring of extreme wave fields and evaluation of 
its forecast (issued from ESSO–INCOIS) have been done 
using data from the directional wave rider buoy3,4 
(DWRB) network of ESSO–INCOIS, including off 
Gopalpur (19.28N, 84.97E at 12 m water depth), the 
landfall location of Phailin. Wave data obtained from 
deep-sea moored buoys BD08 (18.14N, 89.67E), BD11 
(13.49N, 83.98E) and BD14 (7.03N, 87.99E)  
deployed by the ESSO–National Institute of Ocean Tech-
nology (ESSO–NIOT) have also been used for validating 
the forecast wave parameters (Figure 1). 
 The buoy measures horizontal (roll and pitch) and ver-
tical (heave) acceleration using accelerometers and on-
board compasses to give the directional displacement in  
 
 
 
 
Figure 1. Snapshot of forecasted wave fields overlaid by Phailin 
track and location of buoys (Gopalpur (Odisha), BD08, BD11 and 
BD14) in the study area. 
RESEARCH COMMUNICATIONS 
 
CURRENT SCIENCE, VOL. 106, NO. 8, 25 APRIL 2014 1122 
 
 
Figure 2. Real- time comparison between the forecast and observed significant wave heights at Gopalpur, during 
very severe cyclonic storm Phailin. 
 
 
 
Figure 3. a, Path traversed by directional wave rider buoy after detaching from mooring. b, Along- track comparison of significant wave 
height forecast with observed data (time reported is in UTC). 
 
 
 
 
Figure  4. Percentage occurrence of waves in different peak period 
ranges during the cyclone period. 
 
horizontal and vertical axes. The displacements are con-
verted into two-dimensional wave energy spectra, which 
represent distribution of wave energies over different fre-
quencies and directions. Integral wave parameters such as 
significant wave height (Hs), maximum wave height 
(Hmax), peak wave period (Tp) and mean wave period (Tm) 
were derived from the wave spectrum. Hs is the average 
of one-third of the highest waves. Hmax is the maximum 
wave height during a record. Tp (in seconds) is defined as 
the wave period associated with the most energetic waves 
in the total wave spectrum at a specific point. The data 
are received in real-time at INCOIS through the Indian 
National Satellite (INSAT) system. A state-of-the-art 
third-generation spectral wind–wave model (MIKE21 
SW)5,6, based on unstructured meshes, was used for fore-
casting the wave fields. The three-hourly forecast winds 
(0.25  0.25) from European Centre for Medium-Range 
Weather Forecasts (ECMWF) was used for forcing the 
model. A varying resolution mesh ranging from 25 km  
25 km in the open ocean to 4 km  4 km in the coastal  
areas was used for the present study.  
RESEARCH COMMUNICATIONS 
 
CURRENT SCIENCE, VOL. 106, NO. 8, 25 APRIL 2014 1123 
 
 
Figure  5. Model-derived two-dimensional wave energy spectra at (a) BD14 on 10 October 2013 at 1500 UTC, (b) BD08 
on 11 October 2013 at 1800 UTC, (c) BD11 on 11 October 2013 at 1800 UTC and (d) Gopalpur on 12 October 2013 at 
0600 UTC. The time steps are chosen in such a way that the southern swells and cyclone-generated waves are easily dis-
cernib le. 
 
Table 1. Comparison of forecast and observed wave 
parameters at Gopalpur on 12 October 2013 at 0900  
  UTC 
Parameter Observed Forecast 
 
Hs (m) 7.3  7.2  
Hmax (m) 13.5 13.6 
Tp (s) 11.7 11.4  
Tm (s) 8.6  7.8 
 
 
 The wave forecast (issued on 11 October 2013) indi-
cated that high waves of 6.95 m would hit the Gopalpur 
coast by 0600 UTC on 12 October 2013, and the observed 
wave height was 6.84 m (Figure 2). Wave height forecast 
around 0900 UTC at Gopalpur was 7.31 m, while that ob-
served was 7.20 m. The results reveal that the wave fore-
casts were highly accurate. Subsequently, the DWRB got 
drifted in the southwest direction from the deployed  
location due to high currents generated by the cyclone. 
Interestingly, even while drifting, the DWRB was con-
tinuously recording and transmitting wave data through 
INSAT. Figure 3 a shows the buoy’s track during the drift 
and Figure 3  b shows comparison along the track. Table 1 
shows excellent agreement of observed Hs, Hmax, Tp and 
Tm with those forecast at Gopalpur, just before the drift of 
the buoy from the location. It is encouraging to note that 
the system could forecast Hmax as high as 13.5 m to a 
good level of accuracy. The forecasts were compared 
with observations in real-time and published on-line in 
the ESSO–INCOIS website (http://www.incois.gov.in/ 
wrbimage.jsp). The forecasts and alerts were issued in 
English as well as in regional languages and disseminated 
through various electronic media. 
 Figure 4 shows the frequency of occurrence of waves 
in different ranges of peak period at Gopalpur. This 
analysis manifests the presence of long-period swells 
(>12 sec) nearly 80% of the time during the cyclone  
period. It is intriguing to note that about 14% of the time, 
the longer period waves in the range 20–22 sec are ob-
served to be reaching the Gopalpur location from the 
southerly direction. To confirm this, 2D wave spectra  
extracted from the numerical model at the selected buoy 
locations were analysed (Figure 5). The results show the 
presence of long-period Southern Ocean swells in all the 
buoy locations along with the cyclone-generated waves.  
Moreover, a decrease in the wave energy of this swell 
system could be seen as it propagated more towards
RESEARCH COMMUNICATIONS 
 
CURRENT SCIENCE, VOL. 106, NO. 8, 25 APRIL 2014 1124 
 
 
Figure 6 a–d. Comparison of observed and forecast Hs for the selected buoys. Shadows indicate 30% error zone, the acceptable 
error limit for operational wave forecasting. NP, Number of points. 
 
north, i.e. from BD14 to Gopalpur buoy location. Careful 
examination of synoptic maps of the wave fields was car-
ried out to back-track this swell system and this clearly 
showed that these swells were generated in the southern  
ocean around 50S, 44E as a result of a storm in that 
area. The significant impact of Southern Ocean swells on 
the north Indian Ocean wave characteristics is well 
known from the past studies7. In short, the waves ob-
served off Gopalpur were a combination of waves gener-
ated by cyclone Phailin as well as the swells propagating 
from the Southern Ocean (Figure 5  d). 
 Further assessment of the accuracy of the wave fore-
cast was done by computing the model error statistics1 in 
terms of bias, root mean square error (RMSE), scatter in-
dex (SI) and correlation coefficient (R) at buoy locations 
(BD14, BD08, BD11 and Gopalpur) for the period 8–12 
October (Figure 6). Hs is the most commonly used wave 
parameter in almost all the marine applications. Hence, 
we have focused mainly on this parameter for further dis-
cussions.  
 Figure 6  a shows the scatter plot of forecast Hs with 
observations at BD14. The low scatter index of 8% and 
no remarkable bias indicate the high quality of our fore-
cast. High waves were seen at this location during 8–12 
October 2013. The highest observed wave height was 
3.93 m at 1500 UTC on 10 October, which was due to the 
Southern Ocean swells as is clearly seen from the two-
dimensional wave spectrum (Figure 5  a). During this 
time, the eye of the cyclone was at 89.84E, 15.55N and 
the forecast wave height was 3.8 m. Cyclone-generated 
waves did not produce any impact at this location, proba-
bly because it was far south off the cyclone track.  
 Figure 6 b and c shows the scatter plot of forecast wave 
heights with observations at BD08 and BD11 respec-
tively. BD08 lies on the right side of the cyclone tracks 
whereas BD11 lies on the left side. The very high correla-
tion of 0.97, negligible bias and low SI of 13% are indi-
cators of good forecast at BD08. As the cyclone moved in 
the northwest direction, the wave height started to  
increase at BD08 location, the highest observed Hs value 
was 6.27 m at 1200 UTC on 11 October. Southern Ocean 
swells as well as cyclone-generated waves contributed 
towards this, as evident from Figure 5  b. The Southern 
Ocean swells and the cyclone-generated waves appro-
ached the location from the south-southwest direction 
owing to the buoy location being on the right side of the 
track. The wave height at the location thereafter decrea-
sed monotonically as the cyclone moved further north-
westwards towards the east coast. Correlation coefficient 
as high as 0.90 and SI of 15% at BD11 show that the 
model could forecast the waves to a high degree of accu-
racy. As in the case of BD14, wave height started increas-
ing from 8 October onwards due to the impact of 
Southern Ocean swells. The cyclone-generated swells 
RESEARCH COMMUNICATIONS 
 
CURRENT SCIENCE, VOL. 106, NO. 8, 25 APRIL 2014 1125 
*e-mail: ghosenc2008@gmail.com 
started reaching this location from the northeast direction 
as expected, from 11 October at 03:00 UTC onwards. 
This is clear from Figure 5 c. The location of the eye of the 
cyclone at this time was 11.85N, 88.56E (nearly 530 km 
away from BD14). Later, the wave height reached a 
maximum of 3.96 m on 12 October at 0900 UTC, when 
the cyclone reached near Gopalpur, due to the combined 
effect of Southern Ocean swells and cyclone-generated 
swells. As expected, the wave heights at BD08 were 
much higher than at BD11, as it was on the right side of 
the cyclone track. 
 Figure 6 d shows a comparison of measured and fore-
cast wave heights at the Gopalpur location. Error in the 
forecast wave height at this location was only 14%, 
which reveals the reliability of the wave forecast system 
at ESSO–INCOIS. A high degree of correlation of 0.98 
between the measured and forecast Hs was obtained at 
this location. The bias was negligible at this near-shore 
location, similar to the deep-sea buoys.  
 In conclusion, the evaluation once again proves that the 
OSF system at ESSO–INCOIS is fully poised to warn  
the coastal communities and offshore industries along the 
entire Indian coastline well in advance. The present study 
also suggests that the presence of Southern Ocean swells 
during cyclone events may enhance the complexity of the 
wave fields. 
 
1. Balakrishnan Nair, T. M. et al., Performance of the Ocean State 
Forecast system at Indian National Centre for Ocean Information 
Services. Curr. Sci., 2013, 105, 175–181. 
2. IMD, Very severe cyclonic storm, Phailin over the Bay of Bengal 
(8–14 October 2013): A report. India Meteorological Department, 
New Delhi, 2013. 
3. Barstow, S. F. and Kollstad, T., Field trials of the directional wave 
rider. In Proceedings of the First International Offshore and Polar 
Engineering Conference, Edinburgh, 1991, pp. 55–63. 
4. Sanil Kumar, V., Philip, C. S. and Balakrishnan Nair, T. M., Waves 
in shallow water off west coast of India during the onset of summer 
monsoon. Ann. Geophys., 2010, 28, 817–824. 
5. DHI, Mike 21 spectral wave module–scientific documentation. Dan-
ish Hydraulic Institute, 2005. 
6. Sørensen, O. R., Kofoed-Hansen, H., Rugbjerg, M. and Sørensen, L. 
S., A third-generation spectral wave model using an unstructured  
finite volume technique. In Proceedings of the 29th International 
Conference on Coastal Engineering, Lisbon, Portugal, 2004. 
7. Sabique, L., Annapurnaiah, K., Balakrishnan Nair, T. M. and Srini-
vas, K., Contribution of Southern Indian Ocean swells on the wave 
heights in the Northern Indian Ocean – A modeling study. Ocean 
Eng., 2012, 43, 113–120. 
 
ACKNOWLEDGEMENTS. We thank M. Jeyamani, R. Venkat 
Sheshu, N. Kiran Kumar, A. Muralikrishna, Ramakrishna Phani and S. 
P. Vighneshwar (ESSO–INCOIS) for providing support during various 
stages of this work and Jai Singh (CSIR–NIO) for help during wave 
data collection. The moored buoy data for the analysis was provided by 
ESSO–NIOT. We also thank Earth System Science Organization, Min-
istry of Earth Sciences, Government of India for financial support. This  
is ESSO–INCOIS contribution no. 184. 
 
 
Received 27 January 2014; revised accepted 12 March 2014 
Occurrence of native gold and  
gold–silver alloy in the olivine gabbro  
of layered cumulate sequence of Naga 
Hills ophiolite, India 
 
N. C. Ghose* 
G/608, Spruce, Raheja Residency, Koramangala, 3rd Block,  
Bangalore 560 034, India 
 
Occurrence of native gold and gold–silver alloy 
formed in high-temperature olivine gabbro of a laye-
red cumulate body is reported 2 km northwest of 
Sutsu. It lies close to a major fault in the central part 
of Late Cretaceous–Eocene Naga Hills ophiolite 
(NHO). The amphibole-bearing olivine gabbro is 
composed of serpentine (MgO-28.91), anorthite (An93), 
clinopyroxene (En46Fs8Wo46), edenite (Mg# 76), mag-
nesiohornblende (Mg# 78), accessory minerals, viz., 
chlorite (Mg# 75), epidote, sulphides (chalcopyrite and 
millerite) and gold. The formation of noble metals in 
olivine gabbro is re lated to partitioning of Au into in-
tercumulus sulphides and silicates in magma and their 
deposition along grain boundaries and fractures. It 
was carried out by hydrothermal fluids by transporta-
tion and concentration of immiscible sulphide phases, 
and depositing these in suitable locales during final 
stages of crystallization. Gold mineralization in lay-
ered gabbros of cumulate bodies opens a new avenue 
towards primary source of precious metals in NHO. 
Alternative secondary source of precious metals in 
NHO, e.g. (i) basal conglomerate of cover sediments 
derived from ophiolite (Jopi or Pokhphur Formation), 
and (ii) placers of arterial Tizu River in Nagaland, 
may be considered as favourable repository. 
 
Keywords: Anorthite, gold–silver alloy, layered olivine 
gabbro, ophiolite, native gold. 
 
LATE Cretaceous mafic and ultramafic rocks are known 
to occur as dismembered ophiolite bodies of varied  
dimensions along the Trans-Himalayan and the Indo-
Myanmar Ranges (IMR). They demarcate the northwest-
ern, northern and eastern margins of the Indian plate1, 
along which the Indian plate is subducting under the 
Eurasian plate since Late Cretaceous2. These mafic–
ultramafic rocks once constituted a part of the ocean floor 
of Tethyan Sea (Upper Jurassic)3,4, and were preserved as 
accretionary wedge or prism on continental margin. Ex-
humation of such ancient oceanic crust at the eastern In-
dian plate margin along the hill ranges of Nagaland and 
Manipur, bordering Myanmar is known as the Naga Hills 
ophiolite (NHO)1. The northern and southern edges of the 
ophiolite belt extend into Myanmar. The NHO is character-
ized by the presence of ophiolitic melange, olistostrome, 


Wave forecasting and monitoring during very severe cyclone 

Phailin in the Bay of Bengal

http://repository.ias.ac.in/98759/1/1121.pdf

Wave forecasting and monitoring during very severe cyclone Phailin in the Bay of Bengal

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