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Tropical Cyclone Wasi Brings Wind and Rain to Samoa

Tropical Cyclone Wasi brought wind and rain to Samoa  on Saturday.  At 10:00 p.m. EST on Saturday the center of Tropical Cyclone Wasi was located at latitude 16.7°S and longitude 171.3°W which put it about 140 miles (225 km) south-southwest of Pago Pago, American Samoa.  Wasi was moving toward the south-southeast at 14 m.p.h. (22 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 996 mb.

The eastern side of Tropical Cyclone Wasi brought wind and rain to parts of Samoa on Saturday.  A weather station in Pago Pago, American Samoa reported a sustained wind speed of 25 m.p.h. (40 km/h) and a wind gust of 43 m.p.h. (69 km/h).  Several inches of rain also fell on parts of Samoa.

Tropical Cyclone Wasi moved under the western side of an upper level ridge over the South Pacific Ocean.  The ridge produce strong northerly winds which blew across the top of Wasi.  Those winds caused strong vertical wind shear and Tropical Cyclone Wasi began to weaken.  Many of the taller thunderstorms dissipated.  Some storms were still occurring in a band south and east of the center of circulation.  Bands in other parts of the circulation consisted primarily of showers and lower clouds.  Winds to tropical storm force extended out 75 miles (120 km) from the center of Wasi.

Tropical Cyclone Wasi will move through an environment unfavorable for intensification.  Wasi will move over water where the Sea Surface Temperature is near 28°C.  However, the upper level ridge will continue to cause strong vertical wind shear.  The shear will be strong enough to prevent significant intensification and Tropical Cyclone Wasi could continue to weaken since it has a small circulation.

Tropical Cyclone Wasi will move around the western end of a high pressure system over the South Pacific Ocean.  The high will steer Wasi toward the south.  On its anticipated track Tropical Cyclone Wasi could pass near Niue in about 18 hours.  Wasi will bring gustier winds and rain showers to Niue on Sunday.

Elsewhere over the South Pacific Ocean, Tropical Cyclone Vicky was dissipating south of Niue.  At 10:00 p.m. EST on Saturday the center of Tropical Cyclone Vicky was located at latitude 22.6°S and longitude 168.6°W which put it about 250 miles (400 km) south-southeast of Niue.  Vicky was moving toward the south at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1004 mb.

Tropical Cyclone Wasi Develops Near Samoa

Tropical Cyclone Wasi developed near Samoa on Friday night.  At 10:00 p.m. EST on Friday the center of Tropical Cyclone Wasi was located at latitude 13.6°S and longitude 172.9°W which put it about 20 miles (35 km) west of Falealupo, Samoa and about 185 miles (300 km) west-northwest of Pago Pago, American Samoa.  Wasi was moving toward the southeast at 11 m.p.h. (17 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 993 mb.

Tropical Cyclone Wasi spun up out of the same elongated trough of low pressure near Samoa that produced Tropical Cyclone Vicky on Thursday.  A small center of low pressure developed west-northwest of Samoa on Friday.  More thunderstorms formed near the center of circulation and the system was classified as Tropical Cyclone Wasi.  Microwave satellite imagery indicated that there was a tight inner core in the tropical cyclone.  Storms near the core were generating upper level divergence which was pumping mass away from Tropical Cyclone Wasi.  The circulation around Wasi was even smaller than the circulation around Tropical Cyclone Vicky.  Winds to tropical storm force only extended out about 50 miles (80 km) from the center of Tropical Cyclone Wasi.

Tropical Cyclone Wasi will move into an environment somewhat favorable for intensification during the next 24 to 36 hours.  Wasi will move over water where the Sea Surface Temperature is near 28°C.  It will move under the western end of an upper level ridge over the South Pacific Ocean.  The ridge will produce northwesterly winds which will blow toward the top of the tropical cyclone.  Those winds will cause moderate vertical wind shear, but the winds may not be strong enough to prevent intensification.  Tropical Cyclone Wasi could strengthen during the next 24 to 36 hours.  Since the circulation around Wasi is so small, if the tropical cyclone moves into an area where the upper level winds are stronger, it could weaken quickly.

Tropical Cyclone Wasi will move around the western end of a high pressure system over the South Pacific Ocean.  The high will steer Wasi toward the southeast during the next 12 hours.  Wasi will move more toward the south later in the weekend.  On its anticipated track Tropical Cyclone Wasi will bring gust winds and locally heavy rain to portions of Samoa during the next 24 hours.

Elsewhere over the South Pacific Ocean, Tropical Cyclone Vicky weakened as it passed near Niue on Friday.  At 10:00 p.m. EST on Friday the center of Tropical Cyclone Vicky was located at latitude 19.7°S and longitude 168.7°W which put oit about 95 miles (150 km) southeast of Niue.  Vicky was moving toward the south-southeast at 13 m.p.h. (20 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 1001 mb.

Tropical Cyclone Iris Redevelops East of Queensland.

Tropical Cyclone Iris redeveloped east of Queensland on Sunday night.  At 11:00 p.m. EDT on Sunday the center of Tropical Cyclone Iris was located at latitude 16.9°S and longitude 148.7°E which put it about 190 miles (310 km) east of Cairns, Australia.  Iris was moving toward the southwest at 8 m.p.h. (13 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 995 mb.

Tropical Cyclone Iris formed over the Coral Sea last week but wind strong vertical shear quickly weakened Iris into an area of low pressure.  The low pressure system meandered over the Coral Sea east of Australia during the past few days.  More thunderstorms developed near the center of circulation on Sunday and the Australian Bureau of Meteorology designated the system as Tropical Cyclone Iris again.

The circulation around Tropical Cyclone Iris was still reorganizing on Sunday night.  A distinct low level center of circulation was evident on visible satellite images.  More thunderstorms were developing near the center.  A primary rainband wrapped around the northern, eastern and southern sides of the center of circulation.  Bands northwest of the center consisted mainly of showers and low clouds.  Storms near the core of the circulation generated upper level divergence which was pumping mass away to the east of the tropical cyclone.

Tropical Cyclone Iris will move through an environment somewhat favorable for intensification on Monday.  Iris will move over water where the Sea Surface Temperature is 29°C.  It is moving around the western end of an upper level ridge.  The ridge is producing northwesterly winds which were blowing toward the top of the circulation.  Those winds were causing moderate vertical wind shear and they may have been the reason for the lack of strong rainbands northwest of the center of circulation.  The wind shear is likely to inhibit intensification, but it probably won’t prevent Tropical Cyclone Iris from intensifying on Monday.

Tropical Cyclone Iris was moving around the western end of a subtropical ridge which was steering Iris toward the southwest.  Iris will likely move more toward the south and then southeast as it rounds the western end of the ridge.  On its anticipated track Tropical Cyclone Iris is expected to remain east of Queensland.

Elsewhere over the South Pacific Ocean Tropical Cyclone Josie was swirling south of Fiji.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Josie was located at latitude 21.1°S and longitude 178.1°E which put it about 185 miles (300 km) south of Suva, Fiji.  Josie was moving toward the south-southeast at 14 m.p.h. (22 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 999 mb.

Tropical Cyclone Josie Brings Wind and Rain to Fiji

Tropical Cyclone Josie brought wind and rain to Fiji on Saturday.  At 5:00 p.m. EDT on Saturday the center of Tropical Cyclone Josie was located at latitude 19.2°S and longitude 177.4°E which put it about 105 miles (170 km) southwest of Suva, Fiji.  Josie was moving toward the east-southeast at 14 m.p.h. (22 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 998 mb.

Tropical Cyclone Josie formed within an area of thunderstorms that had persisted west of Fiji for several days.  A center of circulation developed within the area of thunderstorms and the Fiji Meteorological Service designated the system as Tropical Cyclone Josie.  The circulation of Tropical Cyclone Josie was somewhat asymmetrical.  Most of the stronger thunderstorms were occurring in the eastern half of the circulation.  The strongest winds were occurring in a primary rainband east of the center of circulation,  The bands in the western half of the circulation consisted primarily of showers and lower clouds.  Winds to tropical storm force extended out about 160 miles (260 km) east of the center of circulation.

Tropical Cyclone Josie will move through an area somewhat favorable for intensification during the next day or two.  Josie will move over water where the Sea Surface Temperature is near 28°C.  It will move near an area where westerly winds are blowing in the upper levels and those winds may already be responsible for the asymmetrical distribution of stronger storms.  The upper level winds will cause moderate vertical wind shear, but the shear may not be strong enough to prevent some intensification.  Tropical Cyclone Josie could intensify slowly during the next 24 to 48 hours.

Tropical Cyclone Josie is moving near the eastern end of a ridge which is steering Josie toward the east-southeast.  The westerly winds in the middle troposphere will continue to steer Tropical Cyclone Josie toward the southeast during the next several days.  On its anticipated track the center of Josie will pass south of Viti Levu.  The center of Tropical Cyclone Josie will move near Kadavu and Ono in about 12 hours.  Even though the center of circulation will pass south of Viti Levu, Tropical Cyclone Josie will drop heavy rain there and the potential for flash floods will exist.  Josie will also bring gusty winds and heavy rain to Kadavu and Ono.

Tropical Cyclone Donna Brings Wind and Rain to New Caledonia

Tropical Cyclone Donna brought wind and rain to New Caledonia as it moved over that region.  At 11:00 p.m. EDT on Monday the center of Tropical Cyclone Donna was located at latitude 19.9°S and longitude 166.8°E which put it about 185 miles (295 km) north of Noumea, New Caledonia.  Donna was moving toward the south-southeast at 11 m.p.h. (17 km/h).  The maximum sustained wind speed was 110 m.p.h. (175 km/h) and there were wind gusts to 130 m.p.h. (215 km/h).  The minimum surface pressure was 962 mb.

The inner core of Tropical Cyclone Donna remained intact despite increased vertical wind shear on Monday.  A well formed circular eye with a diameter of 30 miles (50 km) was evident on microwave satellite images.  A ring of strong thunderstorms wrapped around the eye.  Additional bands of showers and thunderstorms were revolving around the core of the circulation.  The size of the circulation of Tropical Cyclone Donna increased on Monday.  Winds to hurricane/typhoon force extend out about 80 miles (130 km) on the eastern side of the center and about 45 miles (75 km) on the western side.  Winds to tropical storm force extended out about 200 miles (320 km) from the center.

The Hurricane Intensity Index (HII) for Tropical Cyclone Donna was 19.2.  The Hurricane Size Index (HSI) was 23.3 and the Hurricane Wind Intensity Size Index was 42.5.  These indices suggest that Tropical Cyclone Donna is very similar in size and intensity to Hurricane Gustav in 2008 just before Gustav made landfall in Louisiana.

Tropical Cyclone Donna will weaken during the next several days.  An upper level trough is approaching it from the west.  The upper level trough is generating northwesterly winds which are blowing toward the top of the circulation.  The northwesterly winds are inhibiting upper level divergence to the west of Donna and moderate vertical wind shear will continue to weaken the tropical cyclone.  In addition Tropical Cyclone Donna will move over cooler SSTs when it moves farther south.

The winds in the upper level trough are pushing Tropical Cyclone Donna toward the south-southeast.  That general motion is expected to continue during the next several days.  On its anticipated track the core of Tropical Cyclone Donna will move over the Iles Loyaute (Loyalty Islands).  Donna will bring strong gusty winds winds to those islands.  In addition rainbands will bring wind and heavy rain to parts of New Caledonia.  Tropical Cyclone Donna is capable of causing widespread serious damage.

Powerful Tropical Cyclone Donna Moves Toward New Caledonia

Powerful Tropical Cyclone Donna moved toward New Caledonia on Sunday.  At 11:00 p.m. EDT on Sunday the center of Tropical Cyclone Donna was located at latitude 17.2°S and longitude 164.9°E which put it about 340 miles (550 km) north of Noumea, New Caledonia.  Donna was moving toward the south at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 135 m.p.h. (220 km/h) and there were wind gusts to 160 m.p.h. (260 km/h).  The minimum surface pressure was 942 mb.

Tropical Cyclone Donna intensified rapidly into the equivalent of a major hurricane on Sunday.  The core of Donna is very well organized.  A ring of strong thunderstorms surrounds a circular eye which has a diameter of 35 miles (55 km).  Additional bands of showers and thunderstorms are occurring in the eastern half of the circulation.  Thunderstorms around the eye are generating strong upper level divergence which is pumping out mass.  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 200 miles (320 km) from the center.

The Hurricane Intensity Index (HII) for Tropical Cyclone Donna was 26.7.  The Hurricane Size Index (HSI) was 17.5 and the Hurricane Wind Intensity Size Index (HWISI) was 44.2.

Tropical Cyclone Donna will move through an environment that will become less favorable for intensification during the next several days.  Donna will move over water where the Sea Surface Temperature is near 27°C.  It is currently in an area where upper level winds are weak and there is little vertical wind shear.  However, an upper level trough is approaching from the west.  Stronger northwesterly winds associated with the upper level trough will increase the vertical shear during the next several days and Tropical Cyclone Donna will weaken when the shear increases.

Donna is at the western end of a subtropical ridge which is steering the tropical cyclone slowly toward the south.  The approaching upper level trough will turn Tropical Cyclone Donna more toward the southeast in 12 to 24 hours.  On its anticipated track the center of Tropical Cyclone Donna could approach the Iles Loyaute in about 24 hours.  Donna could move near the southern portion of New Caledonia within 36 hours.

Tropical Cyclone Donna could bring strong gusty winds and locally heavy rains to portions of New Caledonia.  Donna could also generate a storm surge on the Iles Loyaute and on parts of the southern coast of New Caledonia.

Tropical Cyclone Donna Turns South As Eye Forms

An eye formed at the center of Tropical Cyclone Donna as it turned southward on Saturday.  At 11:00 p.m. EDT on Saturday the center of Tropical Cyclone Donna was located at latitude 14.1°S and longitude 164.1°E which put it about 390 miles (625 km) northwest of Port Vila, Vanuatu.  Donna was moving toward the south at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 105 m.p.h. (170 km/h) and there were wind gusts to 120 m.p.h. (205 km/h).  The minimum surface pressure was 965 mb.

A primary rainband finally wrapped around the center of circulation on Saturday and a circular eye appeared on visible satellite imagery.  Additional bands of showers and thunderstorms revolved around the core of Tropical Cyclone Donna.  Thunderstorms in the core of the tropical cyclone generated strong upper level divergence which pumped out mass.  Winds to hurricane/typhoon force extended out about 30 miles (50 km) from the center of circulation.  Winds to tropical storm force extended out about 185 miles (295 km) from the center.

The Hurricane Intensity Index (HII) for Tropical Cyclone Donna was 17.8.  The Hurricane Size Index (HSI) was 14.4 and the Hurricane Wind Intensity Size Index (HWISI) was 32.2.

Tropical Cyclone Donna will move through an environment favorable for intensification for another 24 to 36 hours.  Donna will move over water where the Sea Surface Temperature is near 29°C.  Donna is moving near the western end of a upper level ridge and there are light northerly winds blowing toward the top of the circulation.  There is little vertical wind shear.  Tropical Cyclone Donna is likely to intensify during the next 24 hours.  The formation of an eye and a more organized inner core could allow Tropical Cyclone Donna to convert energy more efficiently and a period of rapid intensification is possible.  Tropical Cyclone Donna is likely to intensify into the equivalent of a major hurricane during the next day or so.

Tropical Cyclone Donna moved slowly westward as it neared the western end of a subtropical ridge.  Donna appears to have reached the end of the ridge and it has turned southward.  The tropical cyclone is likely to move south for another 24 hours.  A upper level trough will approach Donna from the west in about a day and northwesterly winds in the leading side of the trough are likely to push Donna southeast at a faster speed.  The westward movement of Tropical Cyclone Donna during the past several days reduced the potential threat to Vanuatu.  However, that same motion increased the potential threat to New Caledonia.

Rainbands in the eastern half of Tropical Cyclone Donna are likely to bring gusty winds and locally heavy rain to Vanuatu, but the core and strongest winds are likely to stay west of those islands.  On its anticipated track Tropical Cyclone Donna could approach New Caledonia in 36 to 48 hours.  The core of Tropical Cyclone Donna could pass over the Iles Loyaute.

Stronger Tropical Cyclone Donna Moves North of Vanuatu

Tropical Cyclone Donna strengthened on Thursday as it moved north of Vanuatu.  The center of Donna passed near the Banks Islands and the Torres Islands and it is currently located northwest of Espiritu Santo.  At 11:00 p.m. EDT on Thursday the center of Tropical Cyclone Donna was located at latitude 13.2°S and longitude 166.0°E which put it about 350 miles (560 km) north-northwest of Port Vila, Vanuatu.  Donna was moving toward the west-southwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 100 m.p.h. (160 km/h) and there were wind gusts to 120 m.p.h. (195 km/h).  The minimum surface pressure was 967 mb.

A partial eyewall continued to wrap around the center of circulation, but a well defined eye did not form.  A band of thunderstorms extended about two thirds of the way around the center.  Other bands of showers and thunderstorms were revolving around the core of the circulation.  Thunderstorms near the core of the circulation generated upper level divergence that pumped out mass to the southeast of Tropical Cyclone Donna.

Winds to hurricane/typhoon force extend out about 40 miles (65 km) from the center of circulation and winds to tropical storm force extend out about 140 miles (225 km) from the center.  The Hurricane Intensity Index (HII) is 16.5.  The Hurricane Size Index (HSI) is 13.4 and the Hurricane Wind Intensity Size Index (HWISI) is 29.9.

Tropical Cyclone Donna will move through an area that will be somewhat favorable for intensification.  Donna will move over water where the Sea Surface Temperature is near 30°C.  An upper level ridge east of Donna is producing northerly winds which are blowing toward the top of the tropical cyclone.  The upper level winds are generating moderate vertical wind shear and the shear seems to have slowed the intensification of Donna.  The strength of the upper level winds could decrease and intensification could resume on Friday.  Tropical Cyclone Donna could intensify into the equivalent of a major hurricane during the next 24 to 48 hours.

A subtropical ridge to the south of Donna is steering the tropical cyclone toward the west-southwest and that general motion is expected to continue for about another 24 hours.  Tropical Cyclone Donna will reach the western end of the ridge in about a day or so and it will turn toward the south.  On its anticipated track the center of Tropical Cyclone Donna will pass west of Espiritu Santo.  Guidance from the numerical models suggests the center of Donna could pass between Vanuatu and New Caledonia, but different models are predicting different tracks and so there is more uncertainty in the track at that time.

Tropical Cyclone Donna Moves Toward Vanuatu and Strengthens

Tropical Cyclone Donna moved toward Vanuatu and strengthened into the equivalent of a hurricane/typhoon on Wednesday.  At 8:00 p.m. EDT on Wednesday the center of Tropical Cyclone Donna was located at latitude 12.4°S and longitude 168.2°E which put it about 270 miles (435 km) north-northeast of Port Vila, Vanuatu.  Donna was moving toward the west at 11 m.p.h. (17 km/h).  The maximum sustained wind speed was 85 m.p.h. (135 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 976 mb.

The circulation of Tropical Cyclone Donna organized further on Wednesday.  An eyelike feature appeared on some microwave satellite images.  An eyewall wrapped about two thirds of the way around the western side of the center of circulation.  A primary rainband curled around the southern and western portions of the core of Tropical Cyclone Donna.  Additional bands of showers and thunderstorms formed and revolved around the core of Donna.  Thunderstorms around the core generated strong upper level divergence which pumped out mass and allowed the pressure to decrease quickly.  A stronger pressure gradient force accelerated the air and resulted in faster wind speeds.

Tropical Cyclone Donna will continue to move through a favorable environment during the next several days.  Donna will move over water where the Sea Surface Temperature is near 30°C.  It is currently in an area where the upper level winds are weak and there is little vertical wind shear.  The combination of warm water and little shear will produce further strengthening and Tropical Cyclone Donna could continue to intensify rapidly.  Donna could intensify into the equivalent of a major hurricane within 24 to 48 hours.

Donna is moving around the northern side of a subtropical ridge which is steering the tropical cyclone toward the west.  A general westerly motion is expected to continue for another 24 hours.  After that time Tropical Cyclone Donna will approach the western end of the ridge and it will turn more toward the south.  Guidance from numerical models differs on the timing and location of the turn toward the south.  On its anticipated track the center of Tropical Cyclone Donna could approach some of the islands of northern Vanuatu in about 24 hours.  It could be a significant tropical cyclone at that time.

Tropical Cyclone 18P Develops Northeast of Vanuatu

Tropical Cyclone 18P developed quickly northeast of Vanuatu on Tuesday.  At 8:00 p.m. EDT on Tuesday the center of Tropical Cyclone 18P was located at latitude 12.7°S and longitude 171.7°E which put it about 695 miles (1120 km) north-northeast of Port Vila, Vanuatu.  The tropical cyclone was moving toward the east at 4 m.p.h. (6 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 992 mb.

The circulation of Tropical Cyclone 18P organized quickly on Tuesday.  More thunderstorms formed near the center of circulation and a  primary rainband wrapped around the eastern side of the center.  Additional bands of showers and thunderstorms developed in the outer regions of the circulation.  Thunderstorms near the core of the circulation generated upper level divergence which pumped out mass and allowed the surface pressure to decrease.

Tropical Cyclone 18P will be moving through an environment that will be very favorable for intensification.  It will move over water where the Sea Surface Temperature is near 30°C.  Tropical Cyclone 18P is centered underneath an upper level ridge and the upper level winds are light.  There is little vertical wind shear.  Tropical Cyclone 18P is likely to intensify rapidly and it could become the equivalent of a hurricane/typhoon within 24 hours.  Once an eye and eyewall form, Tropical Cyclone 18P could intensify very rapidly and it could become the equivalent of a major hurricane within 48 to 72 hours.

Tropical Cyclone 18P is moving through an area where the winds are the steering level are weak.  It has been moving slowly toward the east.  A subtropical ridge to the south of Tropical Cyclone 18P is expected to strengthen and it will turn the tropical cyclone toward the west for about 48 to 72 hours.  When Tropical Cyclone 18P nears the western end of the ridge, it will turn toward the south.  On its anticipated track, Tropical Cyclone 18P could approach Vanuatu in about three days and it could be a significant tropical cyclone at that time.