Category Archives: Tropical Cyclones

Information about tropical cyclones

Tropical Storm Bavi Nearing Guam

Tropical Storm Bavi is moving rapidly toward Guam.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Bavi was located at latitude 13.8°N and longitude 148.7°E which put it about 100 miles east-northeast of Guam.  Bavi was moving toward the west at 18 m.p.h.  The maximum sustained wind speed was 50 m.p.h. and there were gusts to 65 m.p.h.  The minimum surface pressure was 989 mb.

Bavi is moving over water where the Sea Surface Temperatures are around 27.5°C.  So, there is sufficient energy to support intensification.  Moderate easterly winds in the upper levels are generating vertical wind shear over the circulation.  Most of the thunderstorms have been located in the western half of the circulation.  However, recent satellite imagery indicates that there may be more thunderstorms forming near the core of the circulation.  The rapid movement of the storm and the wind shear are likely to limit potential intensification.

A subtropical ridge to the north of Bavi is steering it rapidly to the west and that motion is expected to continue.  Bavi will move  near Guam within a few hours and the core of the circulation could pass near Rota, Tinian and Saipan.  It is likely to bring gusty winds and locally heavy rains as it passes.  The subtropical ridge is expected to steer Bavi or its remnants toward the Philippines during the next few days.

Tropical Cyclone Pam Weakening North of New Zealand

Tropical Cyclone Pam is on a weakening trend as it moves north of New Zealand.  At 11:00 p.m. EDT on Saturday the center of Tropical Cyclone Pam was located at latitude 29.3°S and longitude 175.0°E which put it about 500 miles north of Auckland, New Zealand.  Pam was moving toward the south-southeast at 33 m.p.h.  The maximum sustained wind speed was 115 m.p.h. and there were gusts to 135 m.p.h.  The minimum surface pressure was 948 mb.

Pam has moved over water where the Sea Surface Temperature is 25°C and it is no longer able to extract sufficient energy from the ocean to maintain its intensity.  Stronger winds in the upper levels are increasing the vertical wind shear over the circulation and the weakening trend should continue.  The steering flow should carry Pam east of New Zealand and farther out into the South Pacific Ocean.

Tropical Cyclone Nathan Moving Away From Queensland

Tropical Cyclone Nathan started moving eastward away from Queensland on Saturday.  At 10:00 p.m. EDT on Saturday the center of Tropical Cyclone Nathan was located at latitude 13.4°S and longitude 148.5°E which put it about 400 miles northeast of Townsville, Australia.  Nathan was moving toward the east at 10 m.p.h.  The maximum sustained wind speed was 50 m.p.h. and there were wind gusts to 65 m.p.h.  The minimum surface pressure was 989 mb.

The circulation around Nathan showed signs of increasing organization with a long spiral band beginning to wrap around the center.  It is possible that the long period of time Nathan was stationary caused it to upwell cooler water.  As it moves eastward, the center of circulation is moving back over warmer Sea Surface Temperatures which are supplying more energy to the system.  Nathan is in an area where the upper level winds are relatively light and it has the potential to intensify during the next day or two.

A ridge located north of Nathan is steering it toward the east.  The steering currents are expected to weaken in 24 to 48 hours and Nathan could stall again.  Numerical guidance is providing conflicting indications about the longer term track.  Some guidance turns the tropical cyclone back to the southwest, while other guidance pushes the system farther to the east.

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.

 

Tropical Storm Bavi Moving Toward Guam

Tropical Storm Bavi continued to move rapidly toward the west-northwest toward Guam on Friday.  At 5:00 p.m. EDT on Friday the center of Tropical Storm Bavi was located at latitude 10.7°N and longitude 157.6°E which put it about 880 miles east-southeast of Guam.  Bavi was moving toward the west-northwest at 17 m.p.h.  The maximum sustained wind speed was 45 m.p.h. and there were gusts to 60 m.p.h.  The minimum surface pressure was 989 mb.

Strong easterly winds in the upper levels are creating vertical wind shear and are inhibiting intensification of Bavi.  The wind shear is also causing most of the thunderstorms to be located on the western side of the circulation.  Thus, Bavi is not well organized at the current time.  However, Bavi is moving over warm Sea Surface Temperatures and it could strengthen slowly as it moves farther west, if the wind shear decreases.

A strong subtropical ridge to the north of Bavi is steering it rapidly westward.  Bavi could be in the vicinity of Guam in about 48 hours.  The ridge is expected to continue to steer Bavi westward after it moves past Guam and it could approach the Philippines in a few days.

Tropical Cyclone Olwyn Near Carnarvon, Australia

The center of Tropical Cyclone Olwyn has been moving roughly parallel to the coast of Western Australia and it is near Carnarvon.  At 11:00 p.m. EDT on Thursday the center of Tropical Cyclone Olwyn was located at latitude 24.6°S and longitude 113.4°E which put it about 20 miles northwest of Carnarvon and about 100 miles north of Denham, Australia.  Olwyn was moving toward the south-southwest at 15 m.p.h.  The maximum sustained wind speed was 100 m.p.h. and there were gusts to 120 m.p.h.  The minimum surface pressure was 959 mb.  Earlier on Thursday the airport at Learmonth measured sustained winds to 84 m.p.h. and a pressure of 970 mb when the center of Olwyn passed just to its west.

Olwyn is being steered southward by a subtropical ridge to its east.  The projected path takes the center of circulation inland and then moves it parallel to the coast.  When Olwyn moves inland it will start to weaken.  However, if there is a slight deviation of the track to the west which keeps the center of circulation over water for a longer period of time, it would keep the circulation stronger.  The latter possibility would extend the risk for wind damage farther south along the coast.  In either case, the clockwise rotation around the center and the shape of the coast could produce a significant storm surge in Shark Bay.  There is also a potential for locally heavy rainfall and flooding near the coast.

Pam Reaches Equivalent of Category 5 Hurricane

Tropical Cyclone Pam continued to intensify on Thursday and it has attained an intensity equivalent to a Category 5 hurricane on the Saffir-Simpson Scale.  At 5:00 p.m. the center of Tropical Cyclone Pam was located at latitude 15.0°S and longitude 169.6°E which put it about 100 miles east of Maewo, Vanuatu and about 560 miles northwest of Fiji.  Pam was moving toward the west-southwest at 10 m.p.h.  The maximum sustained wind speed was 160 m.p.h. and it was estimated that there could be wind gusts to 200 m.p.h.  The minimum surface pressure was 918 mb.

Pam is in an almost ideal environment for a tropical cyclone.  The Sea Surface Temperatures are warm and the upper level winds are very light.  It has a well developed circulation with a tight inner core.  Upper level divergence is pumping out mass in all directions.  Some further intensification is possible during the shorter term.  Eventually, when Pam moves farther south in a couple of days, it will move over cooler Sea Surface Temperatures and into a region where the upper level winds are stronger.  At that time it should start a steady weakening trend.  In the interim eyewall replacement cycles could produce fluctuations in intensity, but Pam is likely to be a big strong tropical cyclone for several more days.

An upper level ridge to the east of Pam is steering it generally toward the south.  It has moved a little west of due south today and that has brought the western part of the circulation closer to Vanuatu.  Any further westward movement could bring strong winds very close to Maewo, Pentecote, Ambrym, Epi, Efate and numerous smaller islands in southeastern Vanuatu.  Pam is a large, strong tropical cyclone and it is capable of causing serious damage on any island it crosses.

 

Tropical Cyclone Olwyn Intensifying near Western Australia

An eye appears to be forming in the center of Tropical Cyclone Olwyn and it is near hurricane intensity.  At 11:00 p.m. EDT on Wednesday the center of Tropical Cyclone Olwyn was located at latitude 18.5°S and longitude 114.8°E which put it about 210 miles northwest of Karratha and about 250 miles north-northeast of Exmouth, Australia.  Olwyn was moving toward the south-southwest at 9 m.p.h.  The maximum sustained wind speed was 70 m.p.h. and there were gusts to 90 m.p.h.  The minimum surface pressure was 978 mb.

The circulation around Olwyn became increasingly well organized on Wednesday and and eye appeared to develop.  The stronger thunderstorms are on the western side of the eye and the circulation could be pulling in a little drier air on the eastern side.  Olwyn is over warm Sea Surface Temperatures and the upper level winds are light.  So, further intensification is possible before Olwyn makes landfall.

A subtropical ridge is steering Olwyn in a generally southerly direction and that steering pattern is expected to continue.  The projected track brings the center of Olwyn near Exmouth on the coast of Western Australia in about 18 to 24 hours.  Owlyn has the potential to bring strong winds and a significant storm surge near the point of landfall.  In addition it could bring locally heavy rainfall and the potential for floods as it moves inland.

Tropical Storm Bavi Forms South of Kwajalein

A fourth tropical cyclone formed in the active region over the western Pacific and Australian region.  A low level circulation center developed in an elongated area of thunderstorms south of Kwajalein and the system was classified as Tropical Storm Bavi.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Bavi was located at latitude 7.2°N and longitude 166.7°E which put it about 40 miles southwest of Kwajaein, about 410 miles east-southeast of Ujelang and about 1470 miles east of Guam.  Bavi was moving toward the west at 18 m.p.h.  The maximum sustained wind speed was 40 m.p.h. and there were gusts to 50 m.p.h.  The minimum surface pressure was 996 mb.

The circulation around Bavi is stretched out in the east to west direction and most of the convection and stronger winds are on the northern side of the circulation.  The rapid forward speed is generating vertical wind shear and it is inhibiting the organization around the center of circulation.  Brisk easterly winds in the upper levels are adding to the wind shear.  Bavi is moving over warm Sea Surface Temperatures and it could intensify if the forward motion slows and the wind shear decreases.

A subtropical ridge is steering Bavi in a westerly direction.  The ridge is expected to continue to steer Bavi toward the west or west-northwest over the next several days.   The projected track of Bavi could bring it near Guam in about four days.

Tropical Cyclone Nathan Lingering Off Coast of Queensland

Tropical Cyclone Nathan moved slowly toward the northern coast of Queensland on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Tropical Cyclone Nathan was located at latitude 13.5°S and longitude 145.3°E which put it about 110 miles north of Cooktown, Australia and about 70 miles east of Cape Flattery.  Nathan was moving toward the west at 4 m.p.h.  The maximum sustained wind speed was 65 m.p.h. and there were gusts to 85 m.p.h.  The minimum surface pressure was 982 mb.

The eastern half of the circulation around Nathan was being affected by some of the upper level outflow from large Tropical Cyclone Pam to the east.  The outflow from Pam was creating vertical wind shear over the eastern half of Nathan and inhibiting convection on that side of the circulation.  In addition, Nathan is close enough to the coast of Queensland that interaction with land could be affecting some of the circulation on the western side of the storm.  Despite those negative influences, Nathan is over warm Sea Surface Temperatures and the wind speeds increased slightly on Wednesday.

Numerical guidance continues to suggest that a near equatorial ridge will build north of Nathan and stop its westward motion.  The ridge is projected to eventually push Nathan back toward the east later this week.  The center of Nathan is within 70 miles of the coast of Queensland, and even if it turns back toward the east it could bring high winds and a storm surge to a portion of the coast near Cape Flattery.