Monthly Archives: January 2019

Tropical Cyclone Riley Strengthens to Equivalent of Hurricane/Typhoon

Tropical Cyclone Riley strengthened into the equivalent of a hurricane/typhoon on Friday.  At 4:00 p.m. EST on Friday the center of Tropical Cyclone Riley was located at latitude 17.2°S and longitude 116.9°E which put it about 415 miles (675 km) north-northeast of Learmonth, Australia.  Riley was moving toward the west at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 976 mb.

Tropical Cyclone Riley strengthened, but the distribution of thunderstorms was asymmetrical.  The strongest winds were occurring in a band the curled around the northern half of the center of circulation.  Storms in the band were generating upper level divergence which was pumping mass away from the tropical cyclone.  Other bands of showers and thunderstorms were present in the western half of the circulation, but the bands in the eastern half of Tropical Cyclone Riley consisted primarily of showers and lower clouds.  Winds to hurricane/typhoon force extended out about 35 miles (55 km) from the center of circulation and they were occurring mainly north of the center of Riley.  Winds to tropical storm force extended out about 130 miles (215 km) from the center.

Tropical Cyclone Riley was moving around the northwestern part of an upper level ridge.  The ridge was producing easterly winds which were blowing toward the top of the circulation.  Those winds appeared to converge with the upper level divergence on the east side of Riley to produce sinking motion in that part of the tropical cyclone.  The sinking motion was bringing drier air to the lower levels and it appeared to suppressing convection in that region.

Tropical Cyclone Riley may be close to its peak intensity.  Riley is currently over water where the Sea Surface Temperature is near 28°C, but it will move over cooler water during the next few days.  The upper level ridge will continue to produce easterly winds which will blow toward the top of the circulation.  Those winds could strengthen which would cause more vertical wind shear.  Riley could intensify during the next 24 hours, but it is more likely to gradually weaken during the next two or three days.

The ridge will steer Tropical Cyclone Riley toward the west-southwest during the next few days.  On its anticipated track Riley will remain north of the coast of Western Australia,  However, watches and warnings are in effect for portions of the coast in case the Tropical Cyclone Riley moves more toward the south.  A Tropical Cyclone Warning is in effect for the portion of the coast from Whim Creek to Onslow including Karratha and Dampier.  A Tropical Cyclone Watch is in effect from Onslow to Exmouth.

Elsewhere around Australia, a Tropical Low was dropping heavy rain over portions of northern Queensland.  At 1:00 p.m. EST the center of the Tropical Low was located at latitude 13.8°S and longitude 141.3°E which put it about 80 miles (125 km) north-northwest of Pormpuraaw, Australia.  It was moving toward the southeast 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 1002 mb.  Locally heavy rain could cause floods in parts of northern Queensland.

Tropical Low Prompts Warning for Northern Queensland

A tropical low over the Gulf of Carpentaria prompted the issuance of warnings and watches for northern Queensland on Thursday.  A Tropical Cyclone Warning was in effect for the portion of the coast from Mapoon to Karumba.  A Tropical Cyclone Watch was in effect for the portion of the coast from Karumba to the border between Queensland and the Northern Territory including Mornington Island.

At 7:00 p.m. EST on Thursday the center of the tropical low was located at latitude 13.0°S and longitude 139.9°E which put it about 135 miles (220 km) west of Weipa, Australia.  It was moving toward the north at 5 m.p.h. (8 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 1002 mb.

The circulation around the tropical low exhibited more organization on Thursday.  A band of showers and thunderstorms wrapped around the western and northern sides of the center of circulation.  Other bands of showers and thunderstorms were developing over the Gulf of Carpentaria.  Storms near the center of circulation began to generate upper level divergence which was pumping mass away in outflow channels to the northwest and southeast of the tropical low.

The tropical low will move through an environment favorable for intensification.  It will move over water where the Sea Surface Temperature is near 30°C.  The tropical low will be in an area where the upper level winds are weaker and the vertical wind shear will be limited.  The tropical low is likely to intensify during the next 24 to 36 hours and it is forecast to become a named tropical cyclone.

The tropical low is under the northeastern portion of an upper level low.  It is in a small region where the steering winds are weaker and the tropical low meandered over the eastern Gulf of Carpentaria on Thursday.  Northerly winds blowing around the upper level low are forecast to steer the tropical low toward the south during the next day or two.  On its anticipated path the tropical low is expected to move over the eastern Gulf of Carpentaria near the coast of Queensland.  If the tropical low follow its anticipated track, it will make landfall on the south coast of the Gulf of Carpentaria in about 48 hours.  However, any eastward deviation would bring the tropical low inland over Queensland much sooner.

Elsewhere, Tropical Cyclone Riley strengthened northwest of Australia.  At 7:00 p.m. EST on Thursday the center of Tropical Cyclone Riley was located at latitude 16.5°S and longitude 118.8°E which put it about 265 miles (425 km) north of Port Hedland, Australia.  Riley was moving toward the west 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 985 mb.  A Tropical Cyclone Watch was in effect for the portion of the coast from Whim Creek to Onslow, Australia including Karratha and Dampier.

Tropical Cyclone Riley Forms West of Australia

Tropical Cyclone Riley formed west of Australia on Wednesday.  At 4:00 p.m. EST on Wednesday the center of Tropical Cyclone Riley was located at latitude 16.7°S and longitude 121.2°E which put it about 110 miles (175 km) northwest of Broome, Australia.  Riley was moving toward the west-southwest 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 997 mb.

The circulation around a tropical low off the coast of Western Australia strengthened on Wednesday and the Australian Bureau of Meteorology designated the system as Tropical Cyclone Riley.  A band of thunderstorms wrapped clockwise from northwest to southeast around the center of circulation.  Additional bands of showers and thunderstorms were developing around the western side of the circulation which was over the open water of the south Indian Ocean.  The bands on the eastern side of the circulation were weaker, but portions of those bands were still over Western Australia.  Thunderstorms around the center of circulation were generating upper level divergence which was pumping mass away from the tropical cyclone.

Tropical Cyclone Riley will move through an environment favorable for intensification during the next several days.  Riley will move over water where the Sea Surface Temperature is near 30°C.  It will move through an area where the upper level winds are weak and there will not be much vertical wind shear.  Tropical Cyclone Riley is likely to intensify steadily and it could intensify rapidly once an eye forms and the inner core is well developed.  Tropical Cyclone Riley is likely to strengthen into the equivalent of a hurricane/typhoon within 24 to 36 hours.

Tropical Cyclone Riley will move along the northwestern edge of a subtropical ridge during the next 48 to 72 hours.  The ridge will steer Riley in a general west-southwesterly direction.  On its anticipated track Tropical Cyclone Riley will move parallel to the coast of Western Australia.  However, a southward deviation of the track could bring Riley closer to the coast.

Tropical Cyclone Desmond Brings Wind and Rain to Mozambique

Tropical Cyclone Desmond brought wind and rain to Mozambique on Monday.  At 4:00 p.m. EST on Sunday the center of Tropical Cyclone Desmond was located at latitude 18.8°S and longitude 36.3°E which put it about 25 miles (40 km) west of Conceicao, Mozambique.  Desmond was moving toward the west-northwest at 12 m.p.h. (19 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 Cyclone Desmond made landfall in Mozambique near Ponta Timbue on Monday.  Thunderstorms developed on the western side of the circulation where the winds were blowing toward the land.  Those thunderstorms were dropping heavy rain over parts of Mozambique.  The strongest winds were occurring along the coast of Mozambique and over the Mozambique Channel.  Winds to tropical storm force extended out about 100 miles (160 km) on the eastern side of Tropical Cyclone Desmond.  Wind speeds were slower over land.

Tropical Cyclone Desmond will move around the eastern end of a subtropical high pressure system over southern Africa.  The high will steer Desmond toward the north-northwest.  On its anticipated track Tropical Cyclone Desmond will move farther inland over the Zambezi River toward southern Malawi.  Desmond will drop locally heavy rain over parts of the lower Zambezi River basin and flooding could occur in some locations.

Tropical Cyclone Desmond Forms Over Mozambique Channel

Tropical Cyclone Desmond formed over the Mozambique Channel on Sunday.  At 4:00 p.m. EST on Sunday the center of Tropical Cyclone Desmond was located at latitude 21.3°S and longitude 39.0°E which put it about 250 miles (400 km) south-southeast of Quelimane, Mozambique.  Desmond was moving toward the north at 6 m.p.h. (10 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.

Thunderstorms developed closer to the center of a low pressure system over the Mozambique Channel on Sunday and the system was designated Tropical Cyclone Desmond.  The distribution of thunderstorms around Desmond was very asymmetrical.  Most of the stronger thunderstorms were occurring in bands southeast of the center of circulation.  Bands in other parts of the circulation consisted of showers and lower clouds.  An upper level trough just southeast of Africa was producing northwesterly winds which were blowing toward the top of Tropical Cyclone Desmond.   Those winds were causing moderate vertical wind shear and they were probably the reason for the asymmetrical distribution of thunderstorms.

Tropical Cyclone Desmond will move through an environment somewhat favorable for intensification during the next 24 to 36 hours.  Desmond will move over water where the Sea Surface Temperature is near 29°C.  The upper level trough is forecast to move eastward and the vertical wind shear could decrease.  Tropical Cyclone Desmond could strengthen when the shear decreases, if it is still over water.

Tropical Cyclone Desmond will move around the eastern end of a subtropical ridge in the middle levels over southern Africa.  The ridge should steer Desmond in a north-northwesterly direction.  On its anticipated track Tropical Cyclone Desmond will move toward Mozambique and it could make landfall within 36 hours.  However, there is another low pressure system near northern Madagascar.  If the circulations of the two low pressure systems interact, then Desmond could be pulled farther to the north.

Tropical Cyclone Mona Turns Back Toward Fiji

Tropical Cyclone Mona turned back toward Fiji on Saturday.  At 10:00 p.m. EST on Saturday the center of Tropical Cyclone Mona was located at latitude 14.9°S and longitude 179.2°E which put it about 250 miles (400 km) north of Suva, Fiji.  Mona was moving toward the east-southeast at 16 m.p.h. (26 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 1002 mb.

After being strongly sheared and making a slow clockwise loop on Friday, Tropical Cyclone Mona resumed a course toward Fiji on Saturday.  An upper level trough west of Fiji was producing northwesterly winds which were blowing toward the top of Tropical Cyclone Mona.  Those winds were causing moderate vertical wind shear and they were also causing the distribution of thunderstorms around Mona to be asymmetrical.  The strongest thunderstorms and winds were occurring in bands southeast of the center of circulation.  Bands in the other parts of the circulation consisted primarily of showers and lower clouds.

Tropical Cyclone Mona will move through an environment marginally favorable for intensification during the next 24 hours.  Mona will move over water where the Sea Surface Temperature is near 28°C.  The upper level trough west of Fiji will continue to cause moderate vertical wind shear which will inhibit development.  Tropical Cyclone Mona could strengthen a little bit on Sunday, but it is likely to remain close to its current intensity.

The upper trough will steer Tropical Cyclone Mona toward the south-southeast during the next 12 hours.  The trough is forecast to cutoff and make a transition to an upper low.  The low will steer Mona more toward the south between 12 and 36 hours into the future.  Tropical Cyclone Mona will turn more toward the southwest on Monday.  On its anticipated track the center of Mona will pass near the northeastern end of Vanua Levu in about 12 hours.

Tropical Cyclone Mona will bring wind and rain to Vanua Levu and the eastern islands of Fiji.  Locally heavy rain could cause flash floods in some locations.

Elsewhere, Tropical Cyclone Penny was moving over the Coral Sea back toward Queensland.  At 10:00 p.m. EST on Saturday the center of Tropical Cyclone Penny was located at latitude 17.2°S and longitude 154.8°E which put it about 605 miles (980 km) east of Cairns.  Penny was moving toward the southwest 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.

Tropical Cyclone Mona Stalls North of Fiji

Tropical Cyclone Mona stalled north of Fiji on Friday.  At 4:00 p.m. EST on Friday the center of Tropical Cyclone Mona was located at latitude 13.3°S and longitude 176.3°E which put it about 365 miles (590 km) north-northwest of Suva, Fiji.  Mona was moving toward the north-northeast 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 1000 mb.

Northerly winds blowing around the western end of an upper level ridge over the South Pacific Ocean strengthened on Friday.  Those upper level winds blew across the top of Tropical Cyclone Mona and they caused strong vertical wind shear.  The wind shear blew the upper portion of the circulation south of the circulation in the lower and middle levels of Tropical Cyclone Mona.  As a result, Mona was steered by the winds lower in the atmosphere, which caused it to stall.

New thunderstorms were redeveloping near the center of Tropical Cyclone Mona.  However, many of the bands revolving around the center of Mona still consisted primarily of showers and lower clouds.  The strong upper level winds were shearing the tops off of many of the thunderstorms that developed.  The upper level winds were also preventing the storms near the center of circulation from generating upper level divergence.

Tropical Cyclone Mona could intensify if the upper level winds weaken.  Mona will move over water where the Sea Surface Temperature is near 29°C.  The upper level ridge will continue to produce northerly winds, but those winds are forecast to weaken a little during the weekend.  If the upper level winds weaken and the vertical wind shear lessens, the Tropical Cyclone Mona could strengthen.  However, if the stronger upper level winds persist, then Mona could weaken further.

Tropical Cyclone Mona will meander north of Fiji as long as the wind shear prevents the development of a core of taller thunderstorms.  If Mona strengthens as forecast, then the upper level ridge will steer the tropical cyclone toward the south.  On its anticipated track Tropical Cyclone Mona could approach Fiji in about 48 hours.  Some guidance is suggesting the Mona could be the equivalent of a hurricane/typhoon at that time.

Elsewhere over the South Pacific Ocean, Tropical Cyclone Penny was meandering over the Coral Sea.  At 4:00 p.m. EST on Friday the center of Tropical Cyclone Penny was located at latitude 15.9°S and longitude 155.8°E which put it about 670 miles (1080 km) east of Cairns,, Australia.  Penny was moving toward the north at 2 m.p.h. (3 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 Storm Pabuk Brings Wind and Rain to Southern Thailand

Tropical Storm Pabuk brought wind and rain to southern Thailand on Friday.  At 5:00 p.m. EST on Friday the center of Tropical Storm Pabuk was located at latitude 8.7°N and longitude 98.5°E which put it about 60 miles (95 km) northeast of Phuket, Thailand.  Pabuk was moving toward the west-northwest at 10 m.p.h. (16 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.

Tropical Storm Pabuk made landfall near Sichon in southern Thailand.  Pabuk brought gusty winds to much of the Isthmus of Kra.  It also dropped heavy rain over parts of southern Thailand.  Tropical Storm Pabuk weakened when it crossed the Isthmus of Kra, but the core of the circulation appears to have remained intact.  Pabuk is moving over the Andaman Sea and it still has a well defined low level center of circulation.  Several bands of showers and thunderstorms are revolving around the core of the tropical storm.  Additional bands of showers and thunderstorms are located in the northeastern part of the circulation which is over the Gulf of Thailand.

Tropical Storm Pabuk will move into an environment favorable for intensification during the next 24 to 36 hours.  Pabuk will move over water where the Sea Surface Temperature is near 28°C.  An upper level ridge over the Western North Pacific Ocean will produce southeasterly winds which will blow toward the top of the circulation.  Those winds will cause moderate vertical wind shear, which will inhibit intensification.  However, the wind shear may not be strong enough to prevent Tropical Storm Pabuk from strengthening.

Tropical Storm Pabuk will continue to move around the western end of the ridge over the Western North Pacific Ocean.  The ridge will steer Pabuk toward the west-northwest for another 24 to 36 hours.  Pabuk will turn more toward the north when it reaches the western end of the ridge.  On its anticipated track Tropical Storm Pabuk will reach the Andaman Islands in about 36 hours.

Elsewhere over the Western North Pacific Ocean, Tropical Depression 01W formed southeast of the Marshall Islands.  At 4:00 p.m. EST on Friday the center of Tropical Depression 01W was located at latitude 4.9°N and longitude 174.0°E which put it about 250 miles (400 km) southeast of Majuro, Marshall Islands.  It was moving toward the northwest at 15 m.p.h. (24 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 Depression 01W is forecast to move toward the west-northwest and strengthen.  On its anticipated track it could move toward Majuro, Kwajalein, Ujelang, and the Marianas.

Tropical Storm Pabuk Nears Southern Thailand

Tropical Storm Pabuk neared southern Thailand late on Thursday.  At 10:00 p.m. EST on Thursday the center of Tropical Storm Pabuk was located at latitude 8.0°N and longitude 101.0°E which put it about 110 miles (170 km) southeast of Sichon, Thailand.  Pabuk was moving toward the west-northwest at 16 m.p.h. (26 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 988 mb.

Tropical Storm Pabuk exhibited more organization on Thursday.  A broken ring of showers and thunderstorms surrounded the center of circulation.  Stronger thunderstorms were occurring in the western part of the ring, while weaker storms and showers comprised the rest of the ring.  Several bands of thunderstorms were on the western side of Tropical Storm Pabuk.  Bands of showers and thunderstorms were also on the eastern side of the circulation.  Storms near the center of circulation were generating upper level divergence which was pumping mass away to the northwest of the tropical storm.  Winds to tropical storm force extended out about 100 miles (160 km) from the center.

Tropical Storm Pabuk will move through an environment favorable for intensification for the next six to twelve hours.  Pabuk will move over water where the Sea Surface Temperature is near 28°C.  It will move around the western end of a subtropical ridge over the Western North Pacific Ocean.  The ridge will produce southeasterly winds which will blow toward the top of the circulation.  Those winds will cause moderate vertical wind shear which will inhibit intensification.  Pabuk could intensify during the short term.  It will reach the coast of southern Thailand in less than 12 hours.  Tropical Storm Pabuk will weaken when it moves across the Isthmus of Kra.  Pabuk could strengthen again when it moves over the Andaman Sea in a day or so.

Tropical Storm Pabuk will move around the western end of the subtropical ridge, which will steer the tropical storm in a northwesterly direction.  On its anticipated track Tropical Storm Pabuk will make landfall on the coast of southern Thailand near Sichon in a few hours.  Pabuk will move across the Isthmus of Kra and into the Andaman Sea in a day or so.  Tropical Storm Pabuk could reach the Andaman Islands within 60 hours.

Tropical Storm Pabuk will bring gusty winds and heavy rain to southern Thailand.  Heavy rain could cause flash floods, especially in areas of steeper terrain.

Unusual Development Possible Southwest of Baja California

Unusual development of a tropical or subtropical cyclone is possible southwest of Baja California during the next few days.  The National Hurricane Center (NHC) issued a special Tropical Weather Outlook on Thursday afternoon for a weather system southwest of Baja California.  NHC indicated that there is a 50% probability of development of a tropical or subtropical cyclone during the next five days.  No tropical cyclone or subtropical cyclone is known to have developed over the Eastern North Pacific Ocean in January.  The record extends back to 1949, but it is most complete for the era of Geostationary Operational Environmental Satellites (GOES) which extends from 1970 to the present.

A broad area of low pressure was located about 1300 miles (2100 km) southwest of the southern tip of Baja California.  Clusters of showers and thunderstorms were occurring in parts of the low pressure system.  Visible satellite images were not showing evidence that the showers and thunderstorms were forming into rainbands.  There was a broad area of low pressure, but there was no evidence of a distinct low level center of circulation.

The broad area of low pressure will move through an environment somewhat favorable for the formation of a tropical or subtropical cyclone during the next few days.  It will move over water where the Sea Surface Temperature is near 27°C, which means that there will be enough energy in the ocean to support a tropical cyclone.  An upper level low is northwest of the broad surface low pressure system.  The upper level low is producing strong southwesterly winds which are blowing across the top of the broad low pressure system.  Those winds will cause moderate vertical wind shear, which will inhibit the formation of a tropical cyclone.  If the winds weaken, a tropical cyclone could form, but if the wind shear remains stronger, a subtropical cyclone could develop.  As mentioned above, the National Hurricane Center indicates that there is a 50% probability of development of a tropical or subtropical cyclone.

The broad area of low pressure is forecast to move slowly toward the north during the next several days.  If a tropical or subtropical cyclone develops with taller thunderstorms, then the southwesterly winds blowing around the upper low will steer the cyclone toward Baja California.  The system could bring gusty winds and heavy rain to Baja California and northern Mexico in a few days.