TROPICAL CYCLONE JONI, 3-13 DECEMBER Tropical Cyclone Joni developed from a depression along the convergence zone near Tuvalu on 6 December and progressed southwards to pass over western and southwestern part of the Fiji Group during 10 and 11 December, 1992. The cyclone reached peak intensity with estimated average winds of 90 knots and gusts of 130 knots close to the centre as it approached the Group. Soon after crossing Fiji the system began to lose intensity and degenerated into a depression on the 13th. A relatively smaL but intense tropical cyclone, Joni had a total life-span of about seven days. It had a relatively small eye with very destructive winds confined very close to the centre only. The system displayed no unexpected characteristics and was reasonably simple to track. Fiji suffered damage estimated at around $1.5 million from this cyclone. The areas affected most were the Yasawa and Mamanuca Groups, western and southwestern parts of Viti Levu, Kadavu, Vatulele and nearby smaller islands. Joni also affected Tuvalu during early stages of development causing minor damage. HISTORY A shallow depression persisted along the South Pacific Convergence Zone, in the vicinity of Tuvalu since the beginning of December. However, it was not until the 5th when it began drifting southeast and showed significant development. Over the next two days the depression underwent very slow deepening, with subsequent increase in organization, causing gales over Niulakita and strong squally winds over the rest of Tuvalu. The system was designated a tropical cyclone and named "JONI" early on the 7th, just as it started to curve towards the southwest and passed close to Niulakita, the southern-most island of Tuvalu. It subsequently tracked about 80 miles southwest of Rotuma, meanwhile continuing to develop. By early on the 8th Joni had reached hurricane intensity. For another 24 hours, it moved steadily southwest at about 08 knots, temporarily slowing down to 05 knots, before turning south and heading for Fiji. The centre of Joni passed close to Yasawa and Mamanuca, and about 30 miles west of Viti Levu between midday and midnight (Fiji time) on the 9th. By then Joni had recurved to the southeast with its eye consequently passing over Kadavu in the early afternoon on 11 December. Thereafter, as the system gradually curved towards the south, it accelerated to about 20 kts. It began to weaken as a result of entering into cooler sea waters and also because it encountered strong vertical wind shear. The system finally transformed into a depression on the 13th. The Nadi Tropical Cyclone Warning Centre (TCWC) had the primary responsibility to monitor and issue marine, aviation and public warnings on the system. It obtained useful guidance in the form of advisories/warnings from various other tropical cyclone warning centres, such as the Joint Typhoon Warning Centre in Guam, the Weather Service in Honolulu, the Global Forecast Centre in Bracknell, U.K. and the Brisbane TCWC, Australia. i) International Marine Warnings The first international marine bulletin on the system was issued at 1915 UTC on 5th December 1992. Carrying a gale warning, the bulletin indicated the tropical depression to deepen with average winds close to the centre expected to rise to 35 to 40 knots within the next 12 to 24 hours. The depression was located about 40 miles south of Funafuti in Tuvalu and 450 miles north of Fiji at that time. Subsequent warnings were issued at 6 hourly intervals. The system was upgraded to the status of a tropical cyclone and named at 1851 UTC on the 6th. Immediately following this the warning was upgraded to that of storm as continued development was observed in satellite imagery. At 1200 UTC on the 7th the warning estimated average winds of 50 knots close to the centre and over 35 knots within 100 miles of the centre. The cyclone was forecast to develop further. The formation of an eye became apparent soon afterwards and the warning consequently upgraded to hurricane category in the bulletin issued at 1907 UTC on the 7th. The cyclone was located about 90 miles east-southeast of Rotuma and about 200 miles north of Labasa at that time. Warnings were upgraded accordingly as Joni developed to peak intensity, with estimated average winds of 90 knots close to centre, around 0000 UTC on the 10th (1200 hrs FST) and maintained this intensity for more than 24 hours. Thereafter the cyclone was forecast to commence weakening which was reflected in the 0000 UTC issue of the warning on the 11th. Soon after 1200 UTC on the 12th the cyclone started accelerating to the south-southeast and the final warning was issued by Nadi at 1915 UTC on that day as the system moved out of Nadi's area of responsibility. Further warnings were issued on it by the Regional Meteorological Centre in Wellington which tracked the system until it became absorbed in an approaching mid- latitude trough. ii) Tropical Disturbance Advisories Tropical Disturbance Advisories were issued by Nadi through the entire lifespan of the system to keep meteorological offices within the region, and beyond, informed of developments with respect to its location, movement, intensity, wind distribution and other peculiar characteristics. These were compiled every 12 hours with the first issue at 1930 UTC on 5th December when it was still a depression, located about 40 miles south of Funafuti in Tuvalu. TUVALU The first Special Weather Bulletin for Tuvalu was issued at 1730 UTC on 5th December 1992 when the system was located as a depression about 80 miles north of Niulakita and 60 miles south of Funafuti. It was then moving southeast at about 08 knots. The SWB carried a gale warning for Niulakita and a strong wind warning for the rest of Tuvalu, with forecast of heavy rain. The gale warning for Niulakita was maintained in all of the twelve SWBs that followed at 3 to 6 hourly intervals, until 0500 UTC on the 7th. The depression was expected to pass closest to the island during the night of the 6th or early morning on the 7th. Maximum average winds of 40 knots and momentary gusts upto 65 knots were forecast in SWB Number Ten issued at 2000 UTC on the 6th, just after the system was named Joni. A strong wind warning was maintained for most of Tuvalu during the same period. The final SWB was issued when the system took a definite southward track leaving Tuvalu out of any major direct threat. Wallis and Futuna Both Wallis and Futuna were placed under an "Alert" during early stages when the cyclone was located about 220 miles northwest of Futuna and 260 miles northwest of Wallis and moving slowly southwards. SWB Number One issued at 2130 UTC on 6th mentioned that Joni was likely to cause gales over Futuna in the next 36 hours if it maintained a southward movement and over Wallis if it changed course to a more easterly direction. In the second SWB issued 5 hours later, the "Alert" for Wallis was discontinued as Joni showed signs of maintaining its southward track. By 1900 UTC on the 7th, Joni was confirmed to be moving towards the southwest, away from Futuna. The final SWB (Number Five) was therefore issued cancelling the alert for Futuna. Fiji The first SWB was issued at 1100 hours FST on Monday 7th December (2300 UTC on the 6th), carrying an "Alert" for Rotuma. At this stage Joni was located about 160 miles northeast of Rotuma and was moving south-southwest at 07 knots. Average winds of 40 knots were estimated within 100 miles of the centre. The bulletin indicated that if Joni curved more towards the west, then it was likely to pass close to Rotuma later the next day. In the second SWB compiled at 3.30pm, a gale warning was issued for Rotuma while the rest of the Fiji Group was placed under "Alert". In the next 3 bulletins, gale force winds of 35 to 40 knots with momentary gusts to 60 knots were forecast to affect Rotuma. Joni maintained a general southwestward track and passed within 100 miles east of Rotuma around midnight as it temporarily accelerated. As the cyclone moved away from Rotuma, threat to Fiji increased. Hence a gale warning was first issued for the Yasawa and Mamanuca Group at 11 am on the 8th. It was maintained for almost 30 hours before being upgraded to storm warning in SWB Number Fourteen issued at 1800 hours FST on Wednesday the 9th. At the same time the western half of Viti Levu was placed under a gale warning. By then the centre of Joni lay only about 100 miles north of the Yasawas, with the cyclone moving south-southwest but likely to curve more towards the south. Joni was reaching peak intensity. Winds over the Yasawas were expected to increase the next day to 55 knots with momentary gusts to 80 knots. Twelve hours later, as Joni curved south and headed towards the Yasawa and Mamanuca Groups, the warning for these islands was upgraded to that of a hurricane. The gale warning was now extended to cover the whole of Viti Levu, Kadavu, Beqa and Lomaiviti Group while an alert was maintained for the rest of Fiji. Several hours later as Joni reached peak intensity with estimated average winds of 90 knots and momentary gusts to 130 knots, the hurricane warning was also extended to cover Southwestern Viti Levu and Vatulele in SWB Number Twenty-two. Except for Southern Lau, the entire Fiji Group was placed under either gale, storm or hurricane warning. A 'FLASH' SWB Number Twenty-Four was issued at 10.30 pm on Thursday the 10th when the Nadi-based weather radar successfully located the cyclone about 35 miles west-southwest of Nadi. For the next 6 hours Joni was located by radar until it passed over Vatulele and then headed southeast towards Kadavu and Ono-i-Lau. By Friday morning the remaining islands in the Lau group were also issued with a gale warning. Average winds of 45 knots with momentary gusts upto 70 knots were expected over these areas including the Lomaiviti Group and the northern half of Viti Levu. The last hurricane warning was issued for Kadavu and nearby smaller islands at 3pm on Friday in the SWB Number Thirty. Subsequent warnings were downgraded accordingly as the cyclone Joni accelerated and curved more towards the south, passing about 100 miles west of Ono-i-Lau around 6am Saturday 12th December. The final SWB for the Fiji Group was issued around this time. In total 34 Special Weather Bulletins were issued for Fiji, at 3 to 6 hourly intervals, between 2300 UTC on 6th and 1800 UTC on 11th December. EFFECTS Joni was the first cyclone to affect Fiji and Tuvalu in the 1992/1993 Tropical Cyclone Season. Since Joni was in its early stages of development when it passed Tuvalu, damage over the Group was minor except for Niulakita which experienced damaging gale force winds occasionally rising to destructive storm force in squalls. Over Fiji, the effect was moderate to severe especially in the western and southwestern parts of the Group, with total cost of damage estimated to be around $11.5 million. Survey reports indicate that major damage was caused to crops and vegetation while significant structural damage was confined to areas falling very close to the cyclone path. Heavy rainfall in some areas resulted in severe floods which caused significant loss of livestock. CONCLUSION Joni was a relatively small, but intensive tropical cyclone with the strongest winds confined to a very short distance from its centre. For this reason severe damage was confined to areas close to the cyclone path. Joni was also at its peak intensity when it passed close to Fiji.