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Cyclone Evan
Severe Tropical Cyclone Evan was considered to be the worst tropical cyclone to affect the island nation of Samoa since Cyclone Val in 1991 and was the strongest storm to impact the main South Pacific islands until Winston in 2016. The system was first noted on December 9, 2012, as a weak tropical depression about 700 km (435 mi) to the northeast of Suva, Fiji. Over the next couple of days, the depression gradually developed further before it was named Evan on December 12, as it had fully developed into a tropical cyclone. During that day the system moved toward the Samoan Islands and gradually intensified, before the system slowed and severely affected the Samoan Islands during the next day with wind gusts of up to 210 km/h (130 mph).
The storm moved east and impacted the French islands of Wallis and Futuna before affecting Samoa and American Samoa. On December 16, Evan turned to the south and paralleled western areas of Fiji.
The tropical depression that was to become Severe Tropical Cyclone Evan was first noted by the Fiji Meteorological Service (FMS) on December 9, while it was located within the South Pacific Convergence Zone near the Fijian dependency of Rotuma. At this stage, the system's broad low-level circulation was poorly organised, while the majority of atmospheric convection was fragmented and located over its northeastern quadrant. Over the next day, the system subsequently moved south-eastwards within an area favourable for further development, with low vertical windshear, sea surface temperatures of 29–30 °C (84–86 °F) and favourable outflow. During December 11, the systems low-level circulation centre started to rapidly consolidate, as it passed around 55 km (35 mi) to the southwest of the French Territory of Futuna. Later that day as the depression became equivalent to a tropical storm and develop a small eye on microwave imagery, the United States Joint Typhoon Warning Center initiated advisories on the system and designated it as Tropical Cyclone 04P. This was followed by the FMS naming the system as Evan the following day, after it had become a Category 1 tropical cyclone on the Australian tropical cyclone intensity scale.
After the system was named, the upper-level ridge continued to steer Evan eastward, toward the Samoan islands, as the cyclone quickly intensified. By December 12, as the system started to impact the Samoan Islands with gale and storm force wind speeds, RSMC Nadi reported that the system had become a category 2 tropical cyclone with 10-minute sustained wind speeds of 90 km/h (55 mph). The JTWC also reported that day that the system had become equivalent to a category 1 hurricane on the Saffir-Simpson hurricane scale (SSHS) with 1-minute sustained wind speeds of 120 km/h (75 mph). Over the next 12 hours, the system developed a 17 km (11 mi) cloud-filled eye on visible imagery, while the system's forward motion started to slow down as it entered a weak steering environment with the upper-level ridge of high pressure to the north of the system weakened and a subtropical ridge of high pressure developed to the south of the system.
The system continued to intensify and began to re-curve toward the west on December 16; at 18:00 UTC (07:00 UTC+13, December 17) the JTWC reported that Evan had reached an intensity of 185 km/h (115 mph), which made it equivalent to a category 3 hurricane on the SSHS.
Early on December 17, the JTWC reported that Cyclone Evan had reached its peak intensity with 1-minute windspeeds of 230 km/h (145 mph), which made it equivalent to a category 4 hurricane on the SSHS. During that day Evan started to gradually weaken as it moved around the coast of the Fijian island of Viti Levu. With RSMC Nadi reporting by 18:00 UTC (07:00 UTC+13, December 18) that the system had weakened into a category 3 severe tropical cyclone.
By December 19, wind shear from the northwest had exposed the system's low level circulation center completely, pushing the bulk of convection and thunderstorm activity about 120 km (75 mi) to the southeast of the center. Evan had also moved into cooler sea surface temperatures, below 27 °C (81 °C), so evaporation and thunderstorm development had waned, leading to falling cloud heights because of less moisture.
Later that same day, RSMC Nadi reported that Cyclone Evan had weakened below cyclone intensity and declassified it as a tropical cyclone, before the JTWC issued their final warning later that day as the system started to transition into an extratropical cyclone. Over the next couple of days the remnant low continued moving southwards and moved below 25°S and into the Wellington tropical cyclone warning centre's (TCWC Wellington area of responsibility. During December 21, the system started to move towards the southwest as it directed a moist tropical airmass onto the North Island during the next day. The remnants of Evan were last noted by TCWC Wellington during December 25.
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Cyclone Evan
Severe Tropical Cyclone Evan was considered to be the worst tropical cyclone to affect the island nation of Samoa since Cyclone Val in 1991 and was the strongest storm to impact the main South Pacific islands until Winston in 2016. The system was first noted on December 9, 2012, as a weak tropical depression about 700 km (435 mi) to the northeast of Suva, Fiji. Over the next couple of days, the depression gradually developed further before it was named Evan on December 12, as it had fully developed into a tropical cyclone. During that day the system moved toward the Samoan Islands and gradually intensified, before the system slowed and severely affected the Samoan Islands during the next day with wind gusts of up to 210 km/h (130 mph).
The storm moved east and impacted the French islands of Wallis and Futuna before affecting Samoa and American Samoa. On December 16, Evan turned to the south and paralleled western areas of Fiji.
The tropical depression that was to become Severe Tropical Cyclone Evan was first noted by the Fiji Meteorological Service (FMS) on December 9, while it was located within the South Pacific Convergence Zone near the Fijian dependency of Rotuma. At this stage, the system's broad low-level circulation was poorly organised, while the majority of atmospheric convection was fragmented and located over its northeastern quadrant. Over the next day, the system subsequently moved south-eastwards within an area favourable for further development, with low vertical windshear, sea surface temperatures of 29–30 °C (84–86 °F) and favourable outflow. During December 11, the systems low-level circulation centre started to rapidly consolidate, as it passed around 55 km (35 mi) to the southwest of the French Territory of Futuna. Later that day as the depression became equivalent to a tropical storm and develop a small eye on microwave imagery, the United States Joint Typhoon Warning Center initiated advisories on the system and designated it as Tropical Cyclone 04P. This was followed by the FMS naming the system as Evan the following day, after it had become a Category 1 tropical cyclone on the Australian tropical cyclone intensity scale.
After the system was named, the upper-level ridge continued to steer Evan eastward, toward the Samoan islands, as the cyclone quickly intensified. By December 12, as the system started to impact the Samoan Islands with gale and storm force wind speeds, RSMC Nadi reported that the system had become a category 2 tropical cyclone with 10-minute sustained wind speeds of 90 km/h (55 mph). The JTWC also reported that day that the system had become equivalent to a category 1 hurricane on the Saffir-Simpson hurricane scale (SSHS) with 1-minute sustained wind speeds of 120 km/h (75 mph). Over the next 12 hours, the system developed a 17 km (11 mi) cloud-filled eye on visible imagery, while the system's forward motion started to slow down as it entered a weak steering environment with the upper-level ridge of high pressure to the north of the system weakened and a subtropical ridge of high pressure developed to the south of the system.
The system continued to intensify and began to re-curve toward the west on December 16; at 18:00 UTC (07:00 UTC+13, December 17) the JTWC reported that Evan had reached an intensity of 185 km/h (115 mph), which made it equivalent to a category 3 hurricane on the SSHS.
Early on December 17, the JTWC reported that Cyclone Evan had reached its peak intensity with 1-minute windspeeds of 230 km/h (145 mph), which made it equivalent to a category 4 hurricane on the SSHS. During that day Evan started to gradually weaken as it moved around the coast of the Fijian island of Viti Levu. With RSMC Nadi reporting by 18:00 UTC (07:00 UTC+13, December 18) that the system had weakened into a category 3 severe tropical cyclone.
By December 19, wind shear from the northwest had exposed the system's low level circulation center completely, pushing the bulk of convection and thunderstorm activity about 120 km (75 mi) to the southeast of the center. Evan had also moved into cooler sea surface temperatures, below 27 °C (81 °C), so evaporation and thunderstorm development had waned, leading to falling cloud heights because of less moisture.
Later that same day, RSMC Nadi reported that Cyclone Evan had weakened below cyclone intensity and declassified it as a tropical cyclone, before the JTWC issued their final warning later that day as the system started to transition into an extratropical cyclone. Over the next couple of days the remnant low continued moving southwards and moved below 25°S and into the Wellington tropical cyclone warning centre's (TCWC Wellington area of responsibility. During December 21, the system started to move towards the southwest as it directed a moist tropical airmass onto the North Island during the next day. The remnants of Evan were last noted by TCWC Wellington during December 25.