Tag Archives: 01S

Rare Late Season Tropical Cyclone Forms over South Indian Ocean

A rare late season tropical cyclone formed over the South Indian Ocean on Thursday. At 5:00 p.m. EDT on Thursday the center of Tropical Cyclone 01S was located at latitude 10.7°S and longitude 95.0°E which put it about 170 miles (275 km) west-northwest of Cocos Island. Tropical Cyclone 01S was moving toward the southeast at 7 m.p.h. (11 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 1002 mb.

The circulation around a low pressure system over the South Indian Ocean west-northwest of Cocos Island strengthened on Thursday and the Joint Typhoon Warning Center and the Australian Bureau of Meteorology both designated the system as a tropical cyclone. It is unusual for a tropical cyclone to form this late in the season in the southern hemisphere. It is the equivalent of a tropical cyclone forming in late January in the northern hemisphere.

The distribution of thunderstorms around Tropical Cyclone 01S was asymmetrical. The strongest thunderstorms were occurring in bands in the southern half of the tropical cyclone. Bands in the northern half of Tropical Cyclone 01S consisted primarily of showers and lower clouds. Tropical Cyclone 01S was under the southwestern part of an upper level ridge centered northwest of Australia. The upper level ridge was producing northerly winds that were blowing toward the top of the tropical cyclone’s circulation. Those winds were causing moderate vertical wind shear. The wind shear was causing the asymmetrical distribution of thunderstorms. Winds to tropical storm force extended out 170 miles (275 km) in the southeastern quadrant of Tropical Cyclone 01S. Winds in the other parts of the tropical cyclone were blowing at less than tropical storm force.

Tropical Cyclone 01S will move through an environment somewhat favorable for intensification during the next 24 hours. The tropical cyclone will move over water where the Sea Surface Temperatures are near 28˚C. However, the upper level ridge northwest of Australia will continue to cause moderate vertical wind shear. Tropical Cyclone 01S could strengthen a little more during the next 24 hours, but the moderate vertical wind shear will limit intensification.

Tropical Cyclone 01S will move north of a high pressure system over the South Indian Ocean during the next several days. The high pressure system will steer the tropical cyclone toward the west. On its anticipated track Tropical Cyclone 01S will begin to move farther away from Cocos Island.

Tropical Cyclone Paddy Weakens South of Christmas Island

Tropical Cyclone Paddy weakened over the South Indian Ocean south of Christmas Island on Wednesday. At 10:00 a.m. EST on Wednesday the center of Tropical Cyclone Paddy was located at latitude 14.5°S and longitude 105.5°E which put it about 270 miles (440 km) south of Christmas Island. Paddy was moving toward the southwest at 6 m.p.h. (10 km/h). The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h). The minimum surface pressure was 1003 mb.

An upper level trough over the South Indian Ocean west of Australia was producing strong northwesterly winds that were blowing toward the top of Tropical Cyclone Paddy’s circulation. Those winds were causing strong vertical wind shear and the upper level winds were blowing the tops off of many of the thunderstorms around Paddy’s circulation. The strongest thunderstorms were occurring in bands on the southeastern side of Tropical Cyclone Paddy. Bands in the other parts of the tropical cyclone consisted primarily of showers and lower clouds. The strong vertical wind shear was causing Paddy to weaken.

Tropical Cyclone Paddy will move through an environment unfavorable for a tropical cyclone during the next several days. Paddy will move over water where the Sea Surface Temperatures are near 26˚C. However, the upper level trough west of Australia will continue to cause strong vertical wind shear. The strong wind shear will blow the tops off of any new thunderstorms that develop. The winds around Tropical Cyclone Paddy will decrease gradually during the next 48 hours.

Tropical Cyclone Paddy will move south of a high pressure system over the South Indian Ocean. The high pressure system will steer Paddy toward the west during the next several days as the tropical cyclone weakens gradually. On its anticipated track Tropical Cyclone Paddy will remain well to the south of Christmas Island.

Tropical Cyclone Paddy Develops Southeast of Christmas Island

Tropical Cyclone Paddy developed over the South Indian Ocean southeast of Christmas Island on Monday. At 10:00 a.m. EST on Monday the center of Tropical Cyclone Paddy was located at latitude 13.8°S and longitude 108.0°E which put it about 275 miles (440 km) southeast of Christmas, Island. Paddy was moving toward the southwest at 5 m.p.h. (8 km/h). The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h). The minimum surface pressure was 997 mb.

A low pressure system over the South Indian Ocean south of Java strengthened on Monday and the Australian Bureau of Meteorology designated the system as Tropical Cyclone Paddy. The strongest thunderstorms in Paddy’s circulation were occurring in bands that were southeast and northwest of the center of circulation. Bands in the northeastern and southwestern parts of the circulation consisted primarily of showers and lower clouds. Storms near the center of circulation generated upper level divergence that pumped mass away from the tropical cyclone. Winds to tropical storm force extended out 75 miles (120 km) from the center of Tropical Cyclone Paddy.

Tropical Cyclone Paddy will move through an environment somewhat favorable for intensification during the next 12 hours. Paddy will move over water where the Sea Surface Temperatures are near 27˚C. It will move through a region where the upper level winds are weak and there will be little vertical wind shear. Tropical Cyclone Paddy could get a little stronger during the next 12 hours. Paddy will move under an area where there are strong northwesterly winds in the upper levels on Tuesday. Those winds will create strong vertical wind shear and the shear will cause Tropical Cyclone Paddy to weaken.

Tropical Cyclone Paddy will move around the northern side of a high pressure system over the South Indian Ocean. The high pressure system will steer Paddy toward the southwest during the next 12 to 24 hours. When Tropical Cyclone Paddy starts to weaken on Tuesday, it will be steered by winds in the lower levels of the atmosphere. Those winds will steer Paddy toward the west during the middle of this week. On its anticipated track Tropical Cyclone Paddy will remain well to the south of Christmas Island.

Tropical Cyclone Alicia Develops East of Diego Garcia

Tropical Cyclone Alicia developed east of Diego Garcia on Friday. At 10:00 p.m. EST on Friday the center of Tropical Cyclone Alicia was located at latitude 7.8°N and longitude 79.1°E which put it about 495 miles (795 km) east of Diego Garcia. Alicia was moving toward the west-southwest at 23 m.p.h. (37 km/h). The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h). The minimum surface pressure was 991 mb.

The circulation around a low pressure system east of Diego Garcia exhibited more organization on Friday and the system was designated as Tropical Cyclone Alicia. The inner end of a rainband wrapped around the western and northern sides of the center of circulation. Other bands of showers and thunderstorms were revolving around the center of Alicia. Storms near the center generated upper level divergence which pumped mass away from the tropical storm. Winds to tropical storm force extended out 130 miles (210 km) from the center of circulation.

Tropical Cyclone Alicia will move through an environment that will be favorable for intensification during the next 36 hours. Alicia will move over water where the Sea Surface Temperature is near 29°C. Alicia will be under an upper level ridge where the winds are weaker and there will be little vertical wind shear. Tropical Cyclone Alicia could strengthen into the equivalent of a hurricane/typhoon within 36 hours.

Tropical Cyclone Alicia will move around the western end of a high pressure system over the southeastern Indian Ocean. The high will steer Alicia toward the south-southwest during the next several days. On its anticipated track Tropical Cyclone Alicia will pass southeast of Diego Garcia and east of Rodrigues.

Tropical Cyclone Abela Forms over the South Indian Ocean in the Middle of Winter

Tropical Cyclone Abela formed over the South Indian Ocean in the middle of winter on Sunday.  At 5:00 p.m. EDT on Sunday the center of Tropical Cyclone Abela was located at latitude 12.9°S and longitude 62.4°E which put it about 640 miles (1030 km) northeast of Port Louis, Mauritius.  Abela was moving toward the west-southwest at 18 m.p.h. (29 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 989 mb.

Enough spiral banding developed in a low pressure system over the South Indian Ocean to allow the system to be classified as Tropical Cyclone Abela.  The circulation is not well organized.  Most of the thunderstorms were located in a thin primary rainband that wrapped around the western side of the center of circulation.  The other rainbands contained shallower clouds.  There was enough convection to produce some upper level divergence.  Winds to tropical storm force extend out about 150 miles (240 km) from the center of circulation.

The environment around Tropical Cyclone Abela is only marginal for further intensification.  It is moving over water where the Sea Surface Temperature (SST) is near 26°C.  Northeasterly winds in the upper levels are creating a moderate amount of vertical wind shear.  The wind shear will limit the potential for intensification during the short term.  In about a day or so Abela will move over cooler SSTs and it should start to weaken.

A ridge of high pressure located east of Abela is steering the tropical cyclone toward the west-southwest and that general motion is expected to continue for another day or two.  On its anticipated track Tropical Cyclone Abela will pass north of Mauritius and La Reunion.  Abela is expected to reach the western end of the ridge and recurve toward the south as it nears the east coast of Madagascar.