TROPICAL CYCLONE 'OSCAR' - M. L. Browne and Ram Krishna
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
Weather and Climate (1983) 3: 59-65 59
TROPICAL CYCLONE 'OSCAR'
M. L. Browne and Ram Krishna
Fiji Meteorological Service,
Nandi Airport, Fiji.
ABSTRACT
Hurricane Oscar approached Fiji from the west-northwest on Tuesday
1 March 1983 and was located just south o f Singatoka at about midnight.
It passed between Vatulele and the south coast o f V i t i Levu and, as i t
approached Mbengga about 6 a m . * next morning, i t turned towards the
south-southeast, crossing Kandavu at 10 a.m. on 2 March. By that evening
it was well to the south-southeast of Kandavu and continued to move away.
The lowest pressure recorded during Oscar was 952.7 millibars at Vunisea,
Kandavu at 10 a.m. on 2 March. when the eye of the cyclone lay over the
station. This is certainly one of the lowest pressures ever recorded in Fiji.
The cyclone had estimated maximum sustained winds of 100 knots (gusts
of 140 knots) close to its centre and winds o f hurricane force (sustained
winds over 63 knots) extended t o 30-35 nautical miles (55-65 k m ) from
the centre.
Oscar has been classed as the worst natural disaster i n F i j i since the
cyclone of 1931. I t caused the loss of 9 lives and preliminary estimates of
damage are about $F80 million. High winds, flooding due to heavy rainfall
and storm surge caused widespread devastation i n the west and south o f
Viti Levu and nearby islands o f Mamanuthas, Vatulele, Mbengga and
Kandavu.
HISTORY began t o move i n a south-easterly direction
On 23 February a shallow depression lay towards Fiji. I t was far from certain whether
this movement would be maintained and the
just t o t h e south o f Rotuma. I t deepened
slowly and moved westwards. A t 4 a.m. o n Guam Warning Centre thought i t was likely
25 February the depression was considered to to change direction later towards the west.
have gale force winds near its centre and was By the morning of 28 February the general
classified as a tropical cyclone with the name southeastward movement had continued for 24
Oscar. The cyclone deepened further with a hours and there was every reason to believe
slow movement towards t h e west-northwest
it would b e maintained. A tropical cyclone
away from Fiji. B y midnight on 26 February alert f o r F i j i was issued a t 8 a.m. o n 2 8
the cyclone was estimated t o have hurricane February. This and the subsequent warnings
force winds near its centre (Fig. 1). A t about are described in another section of this article.
this time its position and movement had be-
come rather uncertain, but on 27 February i t Throughout 28 February i t was apparent
from t h e satellite imagery that the cyclone
was increasing i n intensity. A t 3.30 p.m. the
* A l l times are F i j i local time, eye of the cyclone was picked up by the Nandi60 Tropical Cyclone 'Oscar'
175 E180 W
ROTUMA I
Noon 26
•-" ''''''' •••••• Midnight
Noon 25 Midnight
%
Midnight
0 • •
()-----
• 4t,
V Ak
27
v N o r
—15° ---••• 1 15° S
•A# •
• , •,(•!, FIJI METEOROLOGICAL SERVICE
Midnight # #41.'i•Tropical Cyclone 'Oscar' 61
surveillance radar as an annular ring of echoes evening, when it was venting its fury on western
160 nautical miles (250 k m ) distant o n a Viti Levu, i t accelerated t o about 8 knots.
bearing of 287 degrees. Radar data showed that This increase i n speed o f movement would
Oscar had an eye within a larger better defined have been picked u p readily had the radar
almost concentric eye (Fig. 2). The larger eye (which could n o t b e operated again u n t i l
was about 20 nautical miles (35 km) i n radius about midnight) been functioning.
and the inner eye about 5 miles (10 km). The
location o f the cyclone was determined each In t h e early morning o f 2 March as i t
hour b y radar until 5.30 p.m. o n 1 March, approached Mbengga, i t veered towards the
when increasing w i n d s a t N a n d i f o r c e d south-southeast, sparing Suva its worst effects.
abandonment of the radar sweeps. A t this time At about 1 0 a.m, i t crossed Kandavu, t h e
the cyclone was centred 50 nautical miles (90 hurricane force winds dropped almost t o a
km) west-southwest o f Nandi. During t h e calm (sustained winds of 10, 18 and 20 knots
afternoon o f 1 March, Oscar's course tended at 9, 10 and 11 a.m. before returning from the
more easterly towards the southern Viti Levu opposite direction (sustained winds of 65 knots
coast with a speed o f 4 knots. During the at noon). I n the afternoon westerly winds at
INNER EYE
WALL - -
OUTER EYE
WALL
,LNNER t o
,,WALL CLOUD
Fig. 2 : Radar echoes o f tropical cyclone "Oscar" received a t N a n d i between 10.30 p.m. o n 2 8 February a n d
5.30 p.m. o n 1 M a r c h 1983. (Radial rings are i n nautical miles.)62 T r o p i c a l Cyclone 'Oscar'
Kandavu decreased as the cyclone moved away
and b y midnight on 2 March i t had almost
cleared the Fiji Group.
WINDS
The interpretation of satellite imagery plays
a large part in estimating the location of centre
and maximum winds in tropical cyclones. The
American satellite interpretation units at Guam
and Honolulu, particularly the latter, kept the
Nandi Weather Forecasting Centre regularly
supplied with invaluable estimates of the posi-
tion and intensity of the cyclone. The American
units use the same satellites as Nandi, but their
high resolution equipment enables a more
accurate determination than the low resolution
equipment at Nandi. However, when the eye
of a cyclone shows up in satellite pictures as
Oscar's did on the afternoon o f 27 February,
the shortcomings of the low resolution equip-
ment in the estimation o f the location o f the
centre are much reduced.
The tropical cyclone was estimated to have
maximum sustained winds near its centre o f
about 40-45 knots early on 25 February. The
cyclone intensified slowly and the maximum
sustained winds were estimated t o have in-
creased t o 65 knots, o r hurricane force, b y
midnight on the 26th. Fig. 3 : Infra-red satellite picture o f tropical cyclone
"Oscar" a t noon o n 1 M a r c h 1983. T h e eye, which
The cyclone continued t o intensify, w i t h was approaching the southwest coast o f Vi t i Levu a t
estimates o f maximum sustained winds o f 80 that time, can be clearly seen i n the picture.
knots by noon on the 28th and ultimately, on
1 March, i t was estimated that the maximum
sustained winds had reached 100 knots with WEATHER FORECAST CENTRE, N A N D I
momentary gusts up to 140 knots (see satellite As soon as the cyclone alert was issued
picture, Fig. 3). These estimates were in fairly extra staff were brought o n d u t y and t h e
close agreement with those made b y other Tropical Cyclone Warning Centre was activ-
meteorological services. The cyclone appears ated to handle the stream of enquiries. Special
to have weakened quite rapidly after it passed weather bulletins and marine weather bulletins
beyond Kandavu. were issued at regular intervals, six-hourly at
first and later every three hours.
The highest measurements o f sustained
winds and gusts a t weather stations as the During 28 February the winds a t Nandi
cyclone passed are given in Table L increased slowly t o 2 5 knots w i t h overcast
TA B L E L H I G H E S T M E A S U R E D S U S TA I N E D W I N D S A N D GUSTS.
Yasawa-i-rara 9 a.m. 1March 30 knots gust 46 knots
Viwa 3 p.m. 1 „ 50 „ „ 63
Nandi A i r p o r t 8 p.m. 1 „ 68 „ „ 100
Lauthala Bay (Suva) 1 a.m. 2 40 „ „ 67
Nausori 2 a m. 2 38 „ „ 60 93
Vunisea, Kandavu 6 a.m. 2 „ 80 „ 116
Matuku 4 p.m. 2 „ 42 „ „ 50
Ono-i-Lau 1 a.m. 3 26 „ 40Tropical Cyclone 'Oscar' 63
skies and intermittent light rain. Next morning just t o the south o f Singatoka, after having
the winds continued t o increase and reached apparently accelerated during the period of the
40 knots by midday, still with only intermittent radar shut-down.
rain. A t no period did the sky look different
from a stormy day in temperate latitudes and The rain eased t o showers after midnight
there were no thunderstorms. During the after- and by 1 a.m. 2 March the wind was below
noon t h e rain became more persistent and storm force. From early evening on the 1st the
heavier and the north-northeast wind reached direction backed slowly from north-northeast
storm force (sustained winds over 47 knots) to north by 10 p.m. and to northwest by 2 a.m.
about 5 p.m. A t 5.30 p.m. with the wind gusting on the 2nd. Northwest gales and occasional
to 75 knots it was decided to secure the radar showers continued until daybreak.
dish and the satellite antennae, and the Nandi
Weather Forecast Centre was no longer in a WARNINGS
position to monitor the progress of the hurri-
cane. Radio bulletins kept the F i j i public aware
of the presence of a tropical cyclone several
Shortly after 7 p.m. the wind was gusting days before i t actually threatened Fiji, but a
to 95 knots and until 11 p.m. the sustained tropical cyclone alert was not issued until 8
winds ranged between 62 tind 68 knots with a.m., 28 February. A t 10.30 a.m. a gale warn-
the maximum gust of 100 knots at 8.40 p.m. ing was issued for the Yasawa and Mamanutha
Torrential rain was falling and the 6-hourly Groups, western V i t i L e v u , Vatulele a n d
total measured at midnight was no less than Kandavu, and similar warnings were main-
273 mm ( o r nearly 11 inches). The constant tained until the following morning. A t 10.30
roar o f the wind and the whirling sheets o f a.m., 1 March it was apparent that the cyclone
rain will not readily be forgotten. was taking a course closer to Vi t i Levu and a
storm warning was issued for practically the
Communications broke down early i n the same area with a gale warning for the rest of
evening except for a tenuous radio link to the Viti Levu. A t 2.30 p.m. the warning was up-
Post Office Radio Station i n Suva, through graded to a hurricane warning.
whom Nandi were able to pass their bulletins.
Their o w n r a d i o network w i t h observing During the evening of 1 March the hurricane
stations throughout Fiji was not affected and warning was extended to Suva, with a storm
they were able t o receive the hourly station warning t o some islands immediately t o the
reports, practically their only information for east o f Suva, but the hurricane's unexpected
some hours. turning away towards the south-southeast as
A telephone call t o the National Weather it approached Mbengga resulted in only gales
at these places.
Forecasting Centre i n Wellington during the
afternoon had confirmed that the staff there All hurricane and storm warnings specific-
were all prepared to take over the issuing of ally stated the likelihood o f very heavy rain,
warnings, i f necessary. Wellington issued a and very high tides and waves, causing rapid
Fiji bulletin a t 1.30 a.m. 2 March, i n case flooding of low-lying islands and coastal areas.
we had not been in a position to do so. They
also took over Nandi's international respon-
sibilities until overseas communications were EFFECTS
restored several days later. The cyclone produced severely damaging
hurricane and storm force winds ( f o r several
For several hours, when the hurricane was hours o v e r western V i t i L e v u a n d t h e
at its worst, there was little to be done except Mamanuthas), severe flooding due to torrential
watch the barograph and anemometer and mop rain and storm surge (combined effect o f rise
up the water finding its way into the building. of sea level resulting from very l o w atmos-
Towards midnight the pressure was rising and pheric pressure in the vicinity o f the cyclone
the wind dropping, with gusts no longer reach- centre, the physical movement of sea water by
ing 70 knots, and i t was felt safe t o begin high winds a n d phenomenally h i g h waves
radar surveillance again. The image was poor crashing on the shore) over the Mamanutha
but suggested that the hurricane eye now lay Group, western and southwestern V i t i Levu64 Tropical Cyclone 'Oscar'
and Ya n u t h a , * Va t u l e l e , K a n d a v u a n d Storm surge w a s a particularly notable
Mbengga Islands. feature o f the cyclone. Surge inundated and
severely damaged a number o f establishments
Oscar caused the deaths of 9 people. Three and crops i n coastal farmlands, caused con-
of these were by drowning, 2 by falling trees, siderable erosion o f the shoreline i n places,
2 (children) through exposure, 1 b y electro- especially about western Viti Levu where wave
cution, 1 by flying flat piece of iron. action was directed towards the coastline. The
A preliminary estimate of the cost of rations Mamanutha Group, southwestern Viti Levu and
and rehabilitation o f people; repairs to build- the islands t o the south which experienced
ings and structures, communications, roading, storm or hurricane force winds would also have
water and power supply installations, irrigation experienced storm surge but good estimates of
and drainage, port installations, structures a t heights are scanty. Near Nandi Airport storm
sea; damage to pine plantations, natural forests, surge is estimated to have been about 2 metres
crops, livestock, tourist industry; loss of stock above the astronomical tide and eyewitness
through flooding and so on has been put at reports suggest that it was higher (about 3 to
around SF80 million (SNZ120 million). 4 metres) at Momi, about 23 km southwest of
Nandi Airport.
Flooding due to torrential rains (see Table
* Yanutha Island i s just o f f the southwest coast o f 2 and Figs. 4 and 5) was severe in western and
Via Levu, near Singatoka. southwestern Viti Levu. At Nandi Market flood
ND 99
e c ) Y A -IR
W
A
S
0t j a
ONAITALIMBA
tY
KANATHEA
tIKCP.0
OMUNIA
°MANGO
0
THITHIA 0 KATAFANGA
cytAD
LAKEMBA 0
c?MOALA
M I METEOROLOGICAL SERVICE
42Ze
R e i n f O l t Millimetres 10TOYA0 AAMBANAO____
o n l March 1983
0900 TO 0900 NEXT DAY ONO-I-LAIC
CDMATUKU
Fig. 4 : Rainfall distribution f o r the 2 4 hours ending 9 a.m. o n 1 March 1983.Tropical Cyclone 'Oscar' 6 5
TA B L E 2 : 2 4 H O U R R A I N F A L L ( M M ) F R O M The relatively long duration (6-7 hours) o f
9 A . M . T O 9 A . M . T H E N E X T D AY. hurricane a n d storm f o r c e winds i n t h e
28 Feb. Mamanutha Group and western Viti Levu due
28 Feb. 1 M a r. + 1 M a r.
2 M a r. to the slow movement o f the cyclone helped
enhance the damage.
Rotuma 3.7 0.9 4=--
Udu Point 2.9 0.8 3.0 4 Nandi A i r p o r t was closed t o a l l traffic
Lambasa Airfield 46.0 16.0 19.7 62 during the storm and f o r almost 36 hours
Nabouwalu 36.6 8.0 3.6 45
Yasawa-i-Rara 19.5 0.2 afterwards. I t was opened on a restricted basis
Savusavu A i r f i e l d 33.4 9.9 43 upon the restoration of the navigational aids,
Matei A i r f i e l d 30.7 3.2 2.5 34 which had been closed down and secured the
Viwa 81.0 64.7 Nil 146 day before the hurricane struck, as a precau-
Levuka 38.0 20.0 Nil 58
Nandi A i r p o r t 70.7 301.3* 14.1 372 tion against possible damage. T h e A i r p o r t
Nausori A i r p o r t 62.8 54.5 2.5 117 Terminal Building suffered extensive structural
Lauthala B a y 81.2 93.6 18.6 175 damage when a section o f the transit lounge
Lakemba 34.4 1.3 0.5 36 roof was ripped off (Fig. 6). The twisted shapes
Vunisea 74.4 248.3 77.7 323
Matuku 23.5 4.9 6.7 28 of hundreds o f sheets o f galvanised roofing
Ono-i-Lau 16.8 9.3 iron from the walkways and aerobridges littered
Koro-O 108.8 16.4 the ground within a radius o f 500 metres.
Nacocolevu 91.5 However, the Weather Forecasting Centre was
Lautoka 73.2 137.2 17.0 210
Rarawai M i l l 97.6 Nil Nil completely unscathed. Staff housing o n the
Govt. House 116.7 68.6 0.7 185 Airport suffered little, but houses on the way
Mago 25.7 to Nandi and in the town itself sustained much
Colo-i-Suva 69.1 53.7 14.2 123 damage from broken roofs and from flooding.
= Rounded off to nearest whole millimetre.
* A t Nandi A i r p o r t 273 m m between 6 p m . and
midnight o n 1 M a r c h .
Fig. 6: The transit lounge at Nandi Airport Terminal
Building in the wake o f "Oscar". ( C A A F Photo).
CONCLUSION
Fig. 5 : Severe flooding i n the main street o f Nandi
Tropical cyclone Oscar was one of the worst
caused by the cyclone. natural disasters i n Fiji. I t had a somewhat
erratic movement. Oscar moved slowly in an
east-southeast direction just off the south coast
levels reached about 4 metres above the asphalt of Vi t i Levu but turned towards the south-
pavement. I n t h e Singatoka Valley, which southeast unexpectedly sparing t h e heavily
supplies most o f Fiji's vegetables, most crops populated area around Suva its worst effects.
were destroyed a n d flooding reached t h e For more than 24 hours before winds rose
highest levels in living memory, destroying and to storm force i n southwest V i t i Levu, the
washing away homes and cattle.
storm was being closely monitored b y radar
Considerable damage is likely to have been at Nandi Airport, and warnings o n winds,
sustained by shallow reefs, particularly in the flooding and storm surge were substantially
area of hurricane and storm force winds. timely and correct.You can also read
