Monthly Archives: February 2018

Former Tropical Cyclone Gita Speeds Toward New Zealand

After causing flooding in Samoa, significant damage in Tonga, and passing southeast of Vanuatu and New Caledonia, former Tropical Cyclone Gita sped toward New Zealand on Monday.  At 4:00 p.m. EST on Monday the center of former Tropical Cyclone Gita was located at latitude 36.6°S and longitude 168.1°E, which put it about 575 miles (930 km) northwest of Wellington, New Zealand.  Gita was moving toward the southeast at 32 m.p.h. (52 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 979 mb.

An upper level trough near the east coast of Australia was generating strong northwesterly winds which were blowing across the top of former Tropical Cyclone Gita.  Those winds were causing significant vertical wind shear.  In addition, former Tropical Cyclone Gita has moved over water where the Sea Surface Temperature is near 23°C.  A combination of strong wind shear and colder water caused the structure of former Tropical Cyclone Gita to evolve into a powerful extratropical cyclone.  It has lost its warm core and a cold front appears to have formed.  The low level circulation has elongated in a north to south orientation.  Even though Gita is now an extratropical cyclone, it is still a powerful low pressure system.  The low is producing winds to 65 m.p.h.  (105 km/h).  Winds to tropical storm force extend out about 230 miles (370 km) from the center of circulation.

The upper level trough is steering former Tropical Cyclone Gita quickly toward the southeast.  On its anticipated track the extratropical cyclone will reach the northern end of the South Island of New Zealand in 12 to 18 hours.  It will produce strong gusty winds capable of toppling trees and bringing down power lines.  The extratropical cyclone will also drop locally heavy rain and it could contribute to flash flooding.

Stronger Tropical Cyclone Kelvin Makes Landfall in Western Australia

A stronger Tropical Cyclone Kelvin made landfall on the coast of Western Australia near Anna Plains on Saturday night.  At 10:00 p.m. EST on Saturday the center of Tropical Cyclone Kelvin was located at latitude 19.4°S and longitude 121.9°E which put it about 60 miles (95 km) east-northeast of Sandfire, Australia.  Kelvin was moving toward the east-southeast at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 95 m.p.h. (155 km/h).  The minimum surface pressure was 975 mb.  The Australian Bureau of Meteorology issued a Warning for the portion of the coast from Broome to Wallal Downs and the Warning extends inland to include Telfer.

Tropical Cyclone Kelvin intensified very rapidly before it made landfall on the coast of Western Australia.  Kelvin strengthened in a few hours from a minimal tropical storm to the equivalent of a hurricane/typhoon.  A small circular eye developed at the center of circulation.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in the ring of storms.  Bands of showers and thunderstorms were revolving around the core of the circulation.  Kelvin was a small tropical cyclone.  Winds to tropical storm force only extended out about 60 miles (95 km) from the center of circulation.

Tropical Cyclone Kelvin intensified enough to be capable of causing wind damage, but locally heavy rain is the greater risk.  The small size of Kelvin will limit the area of heavy rain, but there could be enough rain in some areas to create the potential for floods.  The Australian Bureau of Meteorology issued Flood Warnings for the North Kimberly District, the West Kimberly District, and the Sandy Desert.  Flood Watches were issued for the De Grey Rivers and the Salt Lake District Rivers.  Tropical Cyclone Kelvin will weaken as it moves farther inland, but Kelvin will take longer to spin down because it strengthened so much before landfall.

Tropical Cyclone Kelvin Develops Near Western Australia

Tropical Cyclone Kelvin developed near the coast of Western Australia on Saturday.  At 1:00 p.m. EST on Saturday the center of Tropical Cyclone Kelvin was located at latitude 19.2°S and longitude 120.9°E which put it about 60 miles (95 km) north-northeast of Wallal Downs, Australia.  Kelvin was moving toward the east at 4 m.p.h. (6 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 988 mb.  The Australian Bureau of Meteorology issued a Warning for the portion of the coast from Broome to Pardoo Roadhouse and the Warning extended inland to include Telfer.

A Tropical Low meandered near the coast of Western Australia during the past several days.  The Tropical Low moved off the coast and strengthened into Tropical Cyclone Kelvin on Saturday.  The circulation of Kelvin is small.  Winds to tropical storm force only extend out about 60 miles (95 km) from the center of circulation.  Even though it is small, the circulation of Tropical Cyclone Kelvin is well organized.  There is a distinct low level center of circulation.  Thunderstorms are occurring near the center of circulation.  Additional bands of showers and thunderstorms are revolving around the core of Tropical Cyclone Kelvin.  The storms in the core are generating upper level divergence which is pumping away mass.

Tropical Cyclone Kelvin will move through an environment favorable for intensification during the next few hours.  Kelvin will move over water where the Sea Surface Temperature is near 30°C.  It is moving near the southwestern end of an upper level ridge and the upper level winds are weak.  There is little vertical wind shear.  The only factor inhibiting intensification is the proximity to the coast of Western Australia.  Tropical Cyclone Kelvin is likely to intensify until it makes landfall on the coast of Western Australia.  Kelvin should gradually weaken when it moves inland.

The upper level ridge is steering Tropical Cyclone Kelvin slowly toward the east.  That general motion is forecast to continue for several more hours.  Kelvin is likely to move more toward the southeast when it nears the coast.  On its anticipated track Tropical Cyclone Kelvin could make landfall on the coast of Western Australia between Bidyadanga and Wallal Downs within the next 12 hours.  Kelvin will bring gusty winds to the coast, but locally heavy rain and flooding are greater risks.  The Australian Bureau of Meteorology has issued Flood Warnings for the North Kimberly District and the West Kimberly District,  Flood Watches have been issued for the Kimberly and North Pilbara District catchments.  An Initial Flood Warning has been issued for the Sandy Desert.

Strong Tropical Cyclone Gita Moves Toward New Caledonia

Strong Tropical Cyclone Gita moved toward New Caledonia on Wednesday.  At 10:00 p.m. EST on Wednesday the center of Tropical Cyclone Gita was located at latitude 21.6°S and longitude 173.7°E which put it about 510 miles (825 km) east of Noumea, New Caledonia.  Gita was moving toward the west at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 120 m.p.h (195 km/h) and there were wind gusts to 150 m.p.h. (240 km/h).  The minimum surface pressure was 949 mb.  Tropical Cyclone Gita was the equivalent of a major hurricane.

The structure of Tropical Cyclone Gita is similar to that of an annular hurricane.  There is a large eye at the center of circulation.  The eye is surrounded by a ring of strong thunderstorms and the strongest winds are occurring in that ring.  The circulation is symmetrical and several rainbands are revolving around the core of the circulation.  Storms in the core are generating strong upper level divergence which is pumping mass away from the tropical cyclone.  Winds to hurricane/typhoon force extend out about 60 miles (95 km) from the center of circulation.  Winds to tropical storm force extend out about 165 miles (270 km) from the center.

Tropical Cyclone Gita will be moving through an environment that is favorable for strong tropical cyclone for several more days.  Gita will move over water where the Sea Surface Temperature is near 28°C.  Tropical Cyclone Gita is moving under the western end of an upper level ridge and the upper level winds are weak.  There is little vertical wind shear.  Tropical cyclones with a symmetrical annular structure often are able to maintain their intensity and Tropical Cyclone Gita could stay strong or weaken very slowly during the next 24 hours.  Gita will get close to the western end of the upper level ridge in a day or so and stronger upper level winds could cause more vertical wind shear at that time.

The ridge is steering Tropical Cyclone Gita toward the west.  Gita is likely to move more toward the southwest when it approaches the western end of the ridge.  It is likely to reach the western end of the ridge in about 48 hours, and Gita will turn more toward the south at that time.  On its anticipated track Tropical Cyclone Gita is expected to pass south of Vanuatu.  Gita could approach the Iles Loyaute and New Caledonia in about 36 hours.

Powerful Tropical Cyclone Gita Hits Tonga, Threatens Southern Fiji

Powerful Tropical Cyclone Gita hit the most populated islands in Tonga on Monday and moved west to threaten the southernmost islands of Fiji.  Gita brought strong winds and very heavy rain to Tongapatu and Eau on Monday and there were reports of damage from Tonga.  At 10:00 p.m. EST on Monday the center of Tropical Cyclone Gita was located at latitude 21.1°S and longitude 178.9°W which put it about 300 miles (480 km) southeast of Suva, Fiji.  Gita was moving toward the west at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 140 m.p.h. (220 km/h) and there were wind gusts to 165 m.p.h. (270 km/h).  The minimum surface pressure was 935 mb.  Tropical Cyclone Gita was the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale.

Gita remains a powerful tropical cyclone.  There is a circular eye at the center of circulation.  The eye is surrounded by a ring of strong thunderstorms and the strongest winds are occurring in that ring.  A rainband has wrapped most of the way around the core of Tropical Cyclone Gita and there are indications that a second, concentric eyewall is forming.  Other rainbands are revolving around the core of the circulation.  Storms in the core are producing strong upper level divergence which is pumping away mass and is allowing the tropical cyclone to remain very strong.  Winds to hurricane/typhoon force extend out about 60 miles (95 km) from the center of circulation.  Winds to tropical storm force extend out about 200 miles (320 km) from the center.

The Hurricane Intensity Index (HII) for Tropical Cyclone Gita is 28.3.  The Hurricane Size Index (HSI) is 20.5 and the Hurricane Wind Intensity Size Index (HWISI) is 48.8.  Those indices indicate that Tropical Cyclone Gita is capable of causing significant damage.

Tropical Cyclone Gita will remain in an environment favorable for strong tropical cyclones for another 24 to 36 hours.  Gita will move over water where the Sea Surface Temperature is near 30°C.  The upper level winds are weak and there is not much vertical wind shear.  If a second concentric eyewall forms, then an eyewall replacement cycle could produce a fluctuation in intensity.  Gita could weaken when the inner eyewall dissipates.  The circulation could strengthen again if the outer eyewall remains intact and starts to contract around the center of circulation.

Tropical Cyclone Gita is moving north of a subtropical ridge which is steering the tropical cyclone toward the west.  A general motion toward the west is expected to continue for another 48 to 72 hours.  On its anticipated track Tropical Cyclone Gita could move over the southernmost islands of Fiji on Tuesday.  The strongest part of Gita could affect Vatoa, Ono-i-lau, Tuvana-i-colo and Tuvana-i-ra.  Gita could bring destructive winds, locally heavy rain and storm surges to the southernmost parts of Fiji.  Tropical Cyclone Gita could approach southern Vanuatu and New Caledonia in about three days.

Tropical Storm Sanba Brings Rain to the Southern Philippines

Tropical Storm Sanba brought rain to the southern Philippines on Monday.  At 10:00 p.m. EST on Monday the center of Tropical Storm Sanba located at latitude 9.9°N and longitude 125.1°E which put it about 100 miles (160 km) east of Cebu, Philippines.  Sanba was moving toward the west-northwest at 19 m.p.h. (31 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1000 mb.

Tropical Storm Sanba dropped locally heavy rain on parts of northern Mindanao, Siriagao Island, Dinegat Island, Leyte, southern Samar, Bohol and Cebu on Monday.  The circulation of Tropical Storm Sanba was not well organized.  Bands of showers and thunderstorms were occurring to the north and west of the center of circulation.  There were thin bands of showers and low clouds to the south and east of the center.  An upper level ridge to the north of Sanba was producing easterly winds which were blowing over the top of the circulation.  Those winds were causing moderate vertical wind shear which was the primary reason for the asymmetrical distribution of thunderstorms.

Tropical Storm Sanba will move through an environment marginal for intensification.  Sanba will move over water where the Sea Surface Temperature is near 28°C.  The upper level ridge will continue to produce moderate vertical wind shear, which will inhibit intensification.  In addition, the center of circulation will move across Cebu and Negros.  Increased friction caused by the and could weaken Tropical Storm Sanba.  Sanba could intensify a little when the center moves over the Sulu Sea.

A ridge north of Sanba is steering the tropical storm toward the west.  A general motion toward the west is expected to continue for another 24 to 36 hours.  After that time Sanba could move a little more toward the west-northwest.  On its anticipated track Tropical Storm Sanba is forecast to move over Cebu and Negros during the next 12 to 18 hours.  Sanba will move across the Sulu Sea toward Palawan and over the South China Sea.  Tropical Storm Sanba could drop locally heavy rain over Cebu, Negros, Panay and Palawan.  Prolonged heavy rain could cause flooding in some places.

Powerful Tropical Cyclone Gita Threatens Tonga

Powerful Tropical Cyclone Gita posed an increasing threat to Tonga on Sunday night.  At 10:00 p.m. EST the center of Tropical Cyclone Gita was located at latitude 21.7°S and longitude 173.2°W which put it about 120 miles (195 km) east of Nuku’Alofa, Tonga.  Gita was moving toward the west at 13 m.p.h. (21 km/h).  The maximum sustained wind speed was 125 m.p.h. (200 km/h) and there were wind gusts to 155 m.p.h. (205 km/h).  The minimum surface pressure was 944 mb.  Tropical Cyclone Gita was the equivalent of a major hurricane.

The circulation of Tropical Cyclone Gita is very well organized.  There is a circular eye at the center of circulation.  A ring of strong thunderstorms surrounds the eye and the strongest winds are occurring in that eye.  Bands of showers and thunderstorms are revolving around the core of Tropical Cyclone Gita.  Storms in the core are generating strong upper level divergence which is pumping mass away in all directions.  Winds to hurricane/typhoon force extend out about 50 miles (80 km) from the center of circulation.  Winds to tropical storm force extend out about 165 miles (270 km) from the center.

The Hurricane Intensity Index (HII) for Tropical Cyclone Gita is 23.6.  The Hurricane Size Index (HSI) is 16.0 and the Hurricane Wind Intensity Size Index (HWISI) is 39.6.  Those indices indicate that Gita will be capable of causing major damage when it moves over Tonga on Monday.

Tropical Cyclone Gita will be moving through an environment favorable for strong tropical cyclones during the next 24 to 48 hours.  Gita will move over water where the Sea Surface Temperature is near 30°C.  The upper level winds are weak and there is little vertical wind shear.  The favorable environment could allow Tropical Cyclone Gita to intensify more before it reaches Tonga.

Tropical Cyclone Gita is moving north of a subtropical ridge which is steering the tropical cyclone toward the west.  A general motion toward the west is expected to continue for another two or three days.  On its anticipated track the center of Tropical Cyclone Gita could reach Tonga within 12 hours.  Tropical Cyclone Gita will be capable of causing major wind damage when it reaches Tonga.  Gita will also drop heavy rain and flooding is possible.  Winds blowing the wind toward the coast could also produce significant storm surges in some locations.

Tropical Storm Sanba Develops Near Palau

Tropical Storm Sanba developed near Palau on Sunday.  At 10:00 a.m. EST on Sunday the center of Tropical Storm Sanba was located at latitude 7.2°N and longitude 133.5°E which put it about 20 miles (35 km) south-southwest of Koror, Palau.  Sanba was moving toward the west at 19 m.p.h. (31 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1000 mb.

Thunderstorms developed closer to the center of circulation of former Tropical Depression 02W and the Japan Meteorological Agency classified the system as Tropical Storm Sanba.  The distribution of storms was asymmetrical.  The stronger thunderstorms were occurring in bands west of the center of circulation.  The bands in the eastern half of the circulation consisted primarily of showers and lower clouds.  Sanba is moving south of a strong upper level ridge.  The ridge is producing easterly winds which are causing moderate vertical wind shear.  The wind shear is causing the asymmetrical distribution of thunderstorms.

Tropical Storm Sanba will move through an environment marginally favorable for intensification.  Sanba will move over water where the Sea Surface Temperature is near 29°C.  So, there is sufficient energy in the upper ocean to support intensification.  However, the upper level ridge will continue to generate moderate vertical wind shear which will inhibit intensification.  Tropical Storm Sanba could get a little stronger during the next 24 to 36 hours.

The ridge is steering Tropical Storm Sanba toward the west and a general westerly motion is expected to continue.  On its anticipated track Tropical Storm Sanba could approach Mindanao in the southern Philippines in about 36 hours.  Sanba could bring gusty winds and locally heavy rain to parts of the southern Philippines.  Locally heavy rain could cause flash floods.

Tropical Cyclone Gita Strengthens Near Niue

Tropical Cyclone Gita strengthened on Saturday as it passed just to the east of Niue.  Outer rainbands on the western side of Gita were bringing gusty winds and heavy rain to Niue.  At 4:00 p.m. EST on Saturday the center of Tropical Cyclone Gita was located at latitude 19.2°S and longitude 168.8°W which put it about 85 miles (135 km) east-southeast of Niue.  Gita was moving toward the south at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 85 m.p.h. (135 km/h) and there were wind gusts to 105 m.p.h. (165 km/h).  The minimum surface pressure was 969 mb.  Tropical Cyclone Gita was the equivalent of a hurricane/typhoon.

The circulation of Tropical Cyclone Gita became more symmetrical on Saturday.  Several rainbands wrapped completely around the center of circulation.  A clear area appeared at the center of circulation on visible satellite images, which indicated that an eye was forming.  A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in the ring.  Storms in the core of the circulation were generating upper level divergence which was pumping mass away from the tropical cyclone.  Other rainbands were revolving around the core of Tropical Cyclone Gita.

Tropical Cyclone Gita will move through an area favorable for intensification during the next 24 to 48 hours.  Gita will move over water where the Sea Surface Temperature is near 30°C.  Tropical Cyclone Gita is moving around the eastern end of an upper level low, but the upper level winds are weak and there is not much vertical wind shear.  There is drier air to the southwest of Gita, but it does not seem to be entering the circulation of the tropical cyclone.  Tropical Cyclone Gita will continue to intensify and it could strengthen rapidly.  Gita could strengthen into the equivalent of a major hurricane.

The upper level low is steering Tropical Cyclone Gita toward the south.  Gita will turn toward the southeast in about 12 to 24 hours.  When Gita reaches the southern side of the upper low, it will move toward the west.  On its anticipated track Tropical Cyclone Gita will pass just to the southeast of Niue.  Gita could approach Tonga in about 36 hours and it could the equivalent of a major hurricane at that time.

Tropical Cyclone Gita Forms Near Samoa

Tropical Cyclone Gita formed near Samoa on Friday.  At 10:00 a.m. EST on Friday the center of Tropical Cyclone Gita was located at latitude 14.8°N and longitude 172.3°E which put it about 155 miles (250 km) west of Pago Pago, Samoa.  Gita was moving toward the east 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.

Tropical Cyclone Gita was bringing gusty winds and heavy rain to Samoa.  The strongest rainbands were north and east of the center of circulation.  The bands south of the center consisted primarily of showers and low clouds.  There appeared to be drier air in the southern half of the circulation which was inhibiting the development of taller clouds and stronger storms in that part of Gita.  Thunderstorms in the rainbands north of the center of circulation were generating upper level divergence which was pumping mass away to the east of the tropical cyclone.

Tropical Cyclone Gita will be moving through an environment favorable for intensification.  Gita will move over water where the Sea Surface Temperature is near 30°C.  An upper level low south of Gita is producing easterly winds which are blowing toward the top of the circulation.  Those winds are causing some vertical wind shear, but the shear does not appear to be strong enough to prevent intensification.  The drier air in southern half of the circulation will inhibit intensification.  However, if some of the rainbands north of the center wrap around the southern side of the center, then they could reduce the effects of the drier air.  Tropical Cyclone Gita is likely to intensify into the equivalent of a hurricane/typhoon during the weekend.

The upper low south of Gita is currently steering the tropical cyclone toward the east.  Gita will approach the eastern end of the upper low during the next 24 hours and it will move more toward the south.  Tropical cyclone Gita will turn back toward the west when it moves south of the upper low.  On its anticipated track Tropical Cyclone Gita will continue to bring gusty winds and heavy rain to Samoa for another 12 to 24 hours.  Gita could pass near Niue in 24 to 48 hours and it could move near Tonga in about three days.