Tag Archives: New Zealand

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.

Tropical Cyclone Winston Stalls Between Vanuatu and Fiji

Steering currents weakened on Sunday and Tropical Cyclone Winston stalled about half way between Vanuatu and Fiji.  At 10:00 p.m. EST on Sunday the center of Tropical Cyclone Winston was located at latitude 18.0°S and longitude 172.5°E which put it about 300 miles (480 km) east of Port Vila, Vanuatu.  Winston was moving toward the west-southwest at 3 m.p.h. (5 km/h).  The maximum sustained wind speed was 110 m.p.h. (175 km/h) and there were wind gusts to 135 m.p.h. (215 km/h).  The minimum surface pressure was 952 mb.

Vertical wind shear over Winston decreased on Sunday and the organization of the tropical cyclone improved.  The eye has become more visible on satellite images and thunderstorms surrounding the eye are generating more upper level divergence.  Easterly winds which were blowing over the top of Winston diminished and the upper level divergence is again flowing out in all directions.

Tropical Cyclone Winston is in an environment that favors intensification.  It is over water where the Sea Surface Temperature is near 30°C.  There is not much vertical wind shear and Winston is likely to intensify during the next 24 hours.

Winston has moved into an area that is between two subtropical ridges.  As a result, it is in an area where the steering winds are not very strong.  The forward motion of Winston has slowed and there is some indication that it may be turning southward.  The guidance from numerical models is forecasting a southerly or southeasterly motion during the next 24 to 48 hours.  On its anticipated track Tropical Cyclone Winston is predicted to stay east of Vanuatu.  However, a more westerly track could bring it closer to that country.

Tropical Cyclone Victor Moves Toward Tonga

Tropical Cyclone Victor moved slowly westward toward Tonga as it passed south of Niue on Wednesday.  At 4:00 p.m. EST on Wednesday the center of Tropical Cyclone Victor was located at latitude 21.5°S and longitude 169.8°W which put it about 155 miles (250 km) south of Niue and about 370 miles (595 km) east of Tonga.  Victor was moving toward the west at 4 m.p.h. (6 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 977 mb.

Tropical Cyclone Victor still looks like the equivalent of a hurricane on satellite images.  It has a well formed eye which is surrounded by a ring of thunderstorms.  The thunderstorms near the center of Victor are generating a large area of upper level divergence.  Convection outside of the core of Victor is somewhat asymmetrical.  Most of the stronger thunderstorms are located in bands south and east of the center of circulation.  There are few tall thunderstorms in the northwestern part of Victor.

Tropical Cyclone Victor continues to be in an environment that is favorable for intensification.  Victor is moving over water where the Sea Surface Temperature is near 27°C.  The upper level winds near Victor are light and there is no appreciable vertical wind shear.  Tropical Cyclone Victor has the potential to intensify during the next 24 hours.

A subtropical ridge south of Victor is steering the tropical cyclone slowly toward the west.  The ridge is expected to continue to steer Victor toward the west, but at a faster speed, during the next day or two.  On its anticipated track Tropical Cyclone Victor could be approaching Tonga in about 36 hours.

Tropical Cyclone Victor passed far enough south of Niue that the stronger winds and heavy rain did not affect the island.  Large waves and surf may have affected some of the coastal areas.  Tropical Cyclone Victor could bring wind and rain to Tonga in two or three days.

Tropical Cyclone Ula Equivalent of Cat. 4 Hurricane

Tropical Cyclone continued to intensify steadily on Saturday and it is now the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale.  At 8:00 p.m. EDT on Saturday the center of Tropical Cyclone Ula was located at latitude 19.8°S and longitude 171.4°E which put it about 400 miles (640 km) east-northeast of Noumea, New Caledonia.  Ula was moving toward the southwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 140 m.p.h. (225 km/h) and there were wind gusts to 165 m.p.h. (270 km/h).  The minimum surface pressure was 933 mb.

Tropical Cyclone Ula has circular eye with a diameter of 24 miles (38 km).  The eye is surrounded by a closed ring of thunderstorms.  Other spiral bands are rotating around the center of circulation.

Tropical Cyclone Ula is moving through an environment that is almost perfect for intensification.  The upper level winds are very light and there is almost no vertical wind shear.  Ula is over water where the Sea Surface Temperature (SST) is near 28°C.  It intensified quickly on Saturday and it has the potential to intensify a little more before it moves over cooler SSTs.

Tropical Cyclone Ula is moving around the western end of a subtropical ridge which is steering it toward the southwest.  That general motion is expected to continue for another 12 to 24 hours.  As Ula reaches the western end of the ridge it will start moving more toward the south.  Eventually the mid-latitude westerlies will start to steer Ula toward the southeast.

On its anticipated track Tropical Cyclone Ula could pass near the extreme southeastern islands of Vanuatu.  The greatest risk is to Aneityum and Futuna.  Ula could also bring wind and rain to Tanna, Aniwa, and Erromango.  The core with the strongest winds should pass southeast of Vanuatu, but Ula could bring wind and rain to some of those islands.  The center of Ula is expected to pass east of New Caledonia early next week, but it could also bring wind and rain to the Iles Loyaute.

Intense Tropical Cyclone Pam Moving Over Southeastern Vanuatu

Very intense Tropical Cyclone Pam has been moving over some of the southeastern islands of Vanuatu  during Friday.  At 5:00 p.m. EDT on Friday the center of Tropical Cyclone Pam was located at latitude 19.3°S and longitude 169.1°E which put ti about 10 miles northwest of Tanna, Vanuatu and about 120 miles northeast of Noumea, New Caledonia.  Pam was moving toward the south at 12 m.p.h.  The maximum sustained wind speed was 155 m.p.h. and it was estimated that there were wind gusts to 190 m.p.h.  The minimum surface pressure was 922 mb.

The center of Pam moved very close to the islands of Efate, Erromango and Tanna.  Given the size and intensity of the circulation, it is likely that it caused significant damage on those islands.  Pam may have reached its peak intensity and there are some indications that it could be undergoing an eyewall replacement cycle.  Some fluctuation or decrease in intensity is likely during the next 24 hours.

The center of Pam is projected to pass east of New Caledonia.  However, it may get close enough to cause significant damage, especially to the islands of Ouvea, Lifou and Mare, which will be closer to the center of circulation.  Pam should begin to weaken more quickly as it moves farther south in the general direction of New Zealand.