RA I/TCC-21/Doc. 4.2(1), P. 1
WORLD METEOROLOGICAL ORGANIZATION______
RA I TROPICAL CYCLONE COMMITTEE
FOR THE SOUTH-WEST INDIAN OCEAN
TWENTY-FIRST SESSION
ST DENIS, LA REUNION
28 SEPTEMBER – 2 OCTOBER 2015 / RA I/TCC-21/Doc. 4.2(1)
(25.IX.2015)
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ITEM 4.2
Original: ENGLISH
REVIEW OF THE 2012/2013, 2013/2014 AND 2014/2015 CYCLONE SEASONS
Reports of Members on significant/notable cyclones of the seasons
Report from Mauritius
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1. 2012-2013 TROPICAL CYCLONE SEASON
The Southwest Indian Ocean (SWIO) Tropical Cyclone basin experienced an active Cyclone Season 2012-2013 with 10 named tropical storms/cyclones. Seven of these reached an intensity of tropical cyclone or greater.
The Islands of the Republic of Mauritius were affected directly or indirectly by two of these tropical cyclones, namely: Tropical Cyclone (TC) Dumileand TC Imelda.
1.1Tropical Cyclone Dumile (01-05 January 2013)
Originating from the southwest of Diego Garcia on 28 December 2012 a tropical disturbance moved in the neighbourhood of Agalega Islands on the 31 December 2012 when the system intensified into a tropical depression, and then into a moderate tropical storm on 01 January 2013 at 0400 hours local time. The storm was named Dumile.
Dumile passed at about 130 km to the south southeast of Agalega Island. Active clouds associated with the storm gave heavy precipitation over the Island. Rainfall recorded was 183.1 mm on 31 December 2012, 140.3 mm on 01 January 2013 and 115.4 mm on 02 January.
As Dumile continued to intensify, and considering its forecast southerly track, a cyclone warning class I was issued on 1st January 2013 at 1000 hours for Mauritius. The warningwas upgraded to class II at 1600 hours of the same day. On the following day, the system re-curved towards the south southwest at an accelerated speed of 20 km/h. Dumile maintained this trajectory for the next 24 hours and though it became a tropical cyclone on 03 January 2013, the risk of having cyclonic winds over Mauritius decreased considerably. The Warnings were therefore waived on 03 January at 1600 hours local time. Dumile passed at about 300 km at its closest distance to the west of Mauritius on 03 January 2013 at around mid-day. Highest gusts recorded were 108 km/h at Domaine les Pailles, 97 km/h at Le Morne and 96 km/h at QuatreBornes.
Outer cloud bands associated with Dumile gave some significant rainfall over the Island, especially over the Central Plateau. The 3-day cumulative rainfall at some stations was as follows:
Station name / Rainfall Amount in mmVacoas / 92.3
Trou Aux Cerfs / 149.0
Arnaud / 173.8
Mon Bois / 186.0
Grand Bassin / 181.6
Providence / 153.4
Apart from a few branches of trees being broken and some places suffering from excessive water, the overall effect of Dumile was beneficial to Mauritius in terms of rainfall.
1.2 Tropical Cyclone Imelda (8-15 April 2013)
As the marked low pressure area from the Diego Garcia region moved westward, it reached the moderate tropical storm intensity on08 April 2013 and was named Imelda. The system intensified into a severe tropical storm 24 hours later and then into a tropical cyclone on 10 April. Outer cloud bands of the storm gave heavy rainfall together with strong winds and rough seas at Agalega.
Imelda changed direction and started to move towards the south east on the 11 April 2013. It weakened slightly and became almost stationary later. It re-started to move in a general southerly direction at about 5 km/h while it was located in the vicinity of St Brandon on12 April 2013. Imelda passed at about 15km to the west of Raphael Island in the following night.The lowest pressure recorded at St Brandon was 989.6 hPa on 13 April at 1700 hours and the maximum gust was 158 km/h on the same day at 2100 hours local time. The table underneath gives rainfall amount at St Raphael during the Imelda episode.
Date / 9 / 10 / 11 / 12 / 13 / 14 / 15 / TotalRainfall (mm) / 14.5 / 14.2 / 7.1 / 114.9 / 276.4 / 1.2 / 0.0 / 428.3
Considering the position of Imelda on 13 April, its slow movement towards the south and the risk of further intensification, both Mauritius and Rodrigues went on cyclone warning class I. As the system intensified into a tropical cyclone again, the level of warning was raised to class II for both Islands on Sunday 14 April at 10.30 hours.
Eventually Imelda took a south easterly direction and became a serious threat to Rodrigues. A Class III warning was issued for Rodrigues on 15 April at 10.30 hours. Frequent gusts of 100 -110 km/h were recorded. Pointe Canon registered gusts of 119 km/h and therefore a cyclone warning class IV was issued at 1500 hours. Cyclonic conditions lasted for about 6 hours. All warnings were waived out at 2100 hours on 15 April 2013.
Tropical cyclone Imelda passed at about 75 km at its closest distance to the southwest of Rodrigues at around 1700 hours local time on 15 April 2013. Lowest barometric pressure recorded was 1000.3 hPa at Pointe Canon and 1000.7 hPa at PlaineCorail at 1600 hours. Highest rainfall for the event was at BaieTopaze with 182 mm followed by Baie aux Huitres with 148.8 mm. Highest 24hour rainfall, from 15/1000 to 16/1000 hours, was 95.6 mm at Pointe Canon and 115.2 mm at PlaineCorail. Highest gusts at Pointe Canon were 119 km/h.
2. 2013-2014TROPICALCYCLONE SEASON
Ten named storm/cyclones were observed in cyclone season 2013-14, out of which 5 reached or exceed the tropical cyclone intensity.ITC Amara affected weather at Rodrigues and ITC Bejisa and STS Edilson influenced weather at Mauritius.
2.1 Intense Tropical Cyclone Amara (16-23 December 2013)
The system, originating in the vicinity of Diego Garcia on 13 December 2013, moved in a general west south west direction while intensifying. It reached the moderate tropical storm intensity in the evening of 16 December and was named Amara. As the storm continued to move in this trajectory and intensifying into an intense tropical cyclone, a class I warning was issued for Rodrigues on the 19 December. The warnings were upgraded to a class II and then a class III on 20 December 2013 at 0700 hours in the morning. Rodrigues Island experienced cyclonic conditions on 21 December for over 14 hours. Amara passed at about 50 km at its closest distance to the east of Rodrigues on 21 December 2013 at about 0500 hours in the morning.
Highest gusts and pressure recorded at Rodrigues during Amara
Station / Highest Gusts (km/h) and time / Lowest Pressure (hPa)Pointe Canon / 152 km/h often / 987.6 @ 21 Dec 0500 hours LT
PlaineCorail / 135 km/h @ 0100 hours / 990.1 @ 21 Dec 0500 hours LT
Citronelle / 133 km/h 2230 and 2330 hours
Intense Tropical cyclone Amara did not give much rainfall. Cumulative rainfall from 19 to 21 December was as follows: Pointe Canon 52 mm, PlaineCorail 22 mm and Citronelle 62 mm. The highest rainfall was at Roche Bon Dieu with 78 mm over the the 3 day period
Impacts: Significant damage was reported to agriculture, some trees were uprooted and few houses were damaged and almost 80 % of electric lines were down.
2.2Intense Tropical Cyclone Bejisa (29 Dec 2013 – 04 Jan 2014)
The well-marked low pressure area located to the northeast of Madagascar intensified into a moderate tropical storm and was named Bejisa by Meteo Madagascar on Sunday 29 December 2013 at 2200 hours local time. Moving in a general southerly track, Bejisa intensified rapidly into a Severe Tropical Storm over the following 12 hours and then explosively into a Tropical Cyclone. The system became an intense tropical cyclone on 30 December 2013 at 1600 hours local time. On its southerly trajectory, Bejisa represented a threat to Mauritius and therefore, a cyclone warning class I was issued at 1030 hours on 31 December 2013. The warning was upgraded to class II on Wednesday 01 January 2014 at 1630 hours. Class II warning was maintained for twenty seven and a half hours.
Bejisa crossed the latitude of Mauritius in the morning of 02 January when it was moving in a general south-south-easterly direction at about 14 km/h. The cyclone passed at about 250 km at its closest distance to the west-south-west of Le Morne on Thursday 02 January 2014 at about 1800 hours local time.
Active rain bands associated with the tropical cyclone crossed the Island from North to South and caused severe weather, heavy thundery showers and strong gusts over the country on 02 January 2014. Some of the highest 24-hr rainfalls on 02 January 2014 were 156.3 mm at Sans Souci, 124.0 mm at Bagatelle Dam and 112 mm at Grande Providence. The Lowest atmospheric pressure recorded was 1004.3 hPa at Plaisance. Highest gusts recorded were 94 km/h at Bagatelle Dam, 76 km/h at Beaux Songes and 84 km/h at Nouvelle Découverte.
A mini-tornado was reported in the region of Grand Gaube and Poudre d’Or in the morning of 02 January2014.
2.3Severe Tropical Storm Edilson (5-7 February 2014)
Satellite imagery of 03 February 2014 indicated a marked zone of disturbed weather to the south of Agalega. Evolving in a favourable environment, the tropical disturbance gradually developed into a tropical depression on the following day while moving in general southerly direction. Given that most numerical model output was indicating that the tropical depression will continue to move southward and will intensify further, a cyclone warning class I was issued for Mauritius.
As expected the tropical depression did intensify into a moderate tropical storm and was named Edilson on 05 February 2014 at 0400 hours local time.Edilson was then located in the neighbourhood of St Brandon. The storm gave significant showers at Raphael Island with gusts of 48 km/h. The lowest barometric pressure was 992.2 hPa at 0600 hours local time.
While Edilson was leaving St Brandon, it momentarily took a south easterly direction and therefore the cyclone warning class I was extended to Rodrigues Island as well.Clouds associated with Edilson gave insignificant showers (1.0 to 2.0 mm) at Rodrigues. Highest gust recorded was 85 km/h at Pointe Canon.
A few hours later the storm re-curved towards the south again and thus thelevel of warning for Mauritius was upgraded to Class II and then to class III at 16.30 hours on 05 February 2014. STS Edilson passed at about 70 km off the coast of Blue Bay at its closest distance at around 1100 hours on the following day.
Cloud bands associated with STS Edilson gave scattered showers on the 6th. Highest 24-hour rainfall was 97 mm at Bois Cheri. The other stations recorded between 5 mm and 40 mm. Highest gusts were 94 km/ h at Queen Victoria, 90 km/h at Port Louis and 85 km/h at Plaisance. No severe damage was reported.
3. 2014-2015 TROPICAL CYCLONE SEASON
Eleven named tropical storm/cyclone formations were observed during the 2014-2015 cyclone season, out of which 5 reached or exceeded the tropical cyclone intensity. Two of the formations reached the very intense tropical cyclone stage. VITC Bansi influenced weather at St Brandon, Rodrigues, and Mauritius
1. Very Intense Tropical Cyclone Bansi (11-18 January 2015)
The well-marked low pressure area located in the vicinity of Tromelin Island on 09 January 2015 slowly developed into a moderate tropical storm and was named Bansi on the 11th at 1000 hours local time. Passing off the southeast coast of Tromelin, Bansi started to move in a south-easterly direction and became a threat to Mauritius. A cyclone warning class I was issued for Mauritius. Considering that Bansi continued to intensify rapidly reaching the tropical cyclone strength and the intense tropical cyclone stage on the following day, the cyclone warning was upgraded to class II at 0400 hours.
The cyclone changed its trajectory on the 12th morning moving in a general easterly direction while deepening further into a very intense tropical cyclone. On this new trajectory, St Brandon Islands were under the direct threat of VITC Bansi.
Bansi passed at about 110 km almost to the south of Raphael Island, St-Brandon on January 14. Cyclonic conditions (wind gusts exceeding 120km/h) prevailed over the island for over 28 hours, from 14 January at 0800 hours local time to 15 January 1200 hours local time. Highest gust recorded at Raphael Island was 167 km/h and the lowest barometric pressure was 984.4 hPa
As per reports received from St-Brandon, the sea state was phenomenal and storm surge inundated Raphael Island completely. In fact, the entire island was covered with water of about 1.0 to 1.50 metre high. The meteorological plot of the MMS was completely demolished and the satellite antenna was blown away by strong winds.
On 14 January TC Bansi adopted a general east south-easterly trajectory and represented a threat to Rodrigues Island. The first series of cyclone warnings for the island were issued at 04h10 on 14 January 2015. On this cyclone track since Mauritius was no longer under cyclonic threat the cyclone warnings were waived at 16h10 on the same day. Simultaneously warning for Rodrigues was upgraded to Class II. The following day, Bansi started to accelerate towards the east south east and further approached Rodrigues. A Cyclone warning Class III was issued for the island at 10h10 on the 15th.
Overnight, the island experienced cyclonic conditions (cyclone warning class IV).The lowest pressure recorded at Pointe Canon was 977.6 hPa at 0300 hours on 16 January. In the early morning of 16 January 2015 at 0200 hours local time, gusts exceeding 120 km/h were recorded both at Pointe Canon and PlaineCorail. A cyclone warning class IV was subsequently issued to inform the population that cyclonic conditions were prevailing at Rodrigues. Cyclonic conditions lasted for about 6 hours in the morning of 16 January.Bansi passed at about 100 km at its closest distance to the north east of Rodrigues at about 0400 hours on the same day (16 January 2015).
Highest gusts recorded were 126 km/h at Pointe Canon and PlaineCorail, and 133 km/h at Citronelle. Cumulative rainfall during the Bansi episode, from 10 to 16 January 2015 was 224 mm at Pointe Canon, 258 mm at PlaineCorailand 315 mm at Citronelle.
Active clouds bands associated with this system gave widespread rainfall over Mauritius as well. The VITC Bansi episode accounted for a mean of 99 mm of rainfall over Mauritius amounting to 38% of the normal rainfall for January 2015. Highest gusts recorded were 104 km/h at Port Louis and 101 km/h at Beaux Songes. Lowest barometric pressure was 1000.7 hPa at 14 January at 1600 hours local time. The table underneath gives rainfall statistics over Mauritius:
Rainfall over Mauritius during VITC Bansi episode
S.No / Station / Rainfall (mm),10 - 14 Jan 2015
1 / P. Louis(L. Barracks) / 80.6
2 / Beaux Songes / 72.2
3 / Medine / 50.0
4 / Pamplemousses / 100.5
5 / Plaisance / 51.6
6 / FUEL / 85.3
7 / Belle Mare / 56.4
8 / Sans Souci / 176.1
9 / Vacoas / 128.5
10 / Arnaud / 129.2
11 / G.Bassin / 126.8
12 / QuatreBornes / 109.0