Subtropical Storm Oscar Develops East of Bermuda

Subtropical Storm Oscar developed east of Bermuda on Friday night.  At 11:00 p.m. EDT on Friday the center of Subtropical Storm Oscar was located at latitude 26.7°N and longitude 45.7°W which put it about 1210 miles (1940 km) east-southeast of Bermuda.  Oscar was moving toward the north-northwest at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gust to 60 m.p.h. (95 km/h).  The minimum surface temperature was 1005 mb.

More thunderstorms developed closer to the center of a low pressure system east-southeast of Bermuda on Friday night and the National Hurricane Center designated the system as Subtropical Storm Oscar.  The strongest winds were occurring in a band of showers and thunderstorms about 80 to 100 miles (130 to 160 km) east of the center of the low pressure system.  Several other bands were forming southeast of the center of circulation.  Bands in other parts of Subtropical Storm Oscar consisted primarily of showers and low clouds.

Subtropical Storm Oscar will move through an area somewhat favorable for intensification.  Oscar will move over water where the Sea Surface Temperature is near 27°C.  An upper level low will move just to the south of Subtropical Storm Oscar.  The upper level low will produce easterly winds which will blow toward the top of the subtropical storm.  Those winds will cause moderate vertical wind shear which will inhibit intensification on Saturday.  In a day or so Oscar will move northwest of the upper level low and the vertical wind shear will decrease.

The upper level low will steer Subtropical Storm Oscar toward the north-northwest on Saturday.  When Oscar moves farther way from the upper level low, it will move south of a ridge of high pressure over the Atlantic Ocean.  The ridge will steer Subtropical Storm Oscar toward the west on Sunday and into early next week.  On its anticipated track Subtropical Storm Oscar could be southeast of Bermuda by Monday night.

Powerful Typhoon Yutu Churns Toward Northern Luzon

Powerful Typhoon Yutu churned toward northern Luzon on Friday.  At 5:00 p.m. EDT on Friday the center of Typhoon Yutu was located at latitude 17.7°N and longitude 135.9°E which put it about 900 miles (1450 km) east of Cape Engano, Philippines.  Yutu was moving toward the west-northwest at 17 m.p.h. (28 km/h).  The maximum sustained wind speed was 160 m.p.h. (260 km/h) and there were wind gusts to 195 m.p.h. (315 km/h).  The minimum surface pressure was 920 mb.

After completing an eyewall replacement cycle Typhoon Yutu strengthened again on Friday.  Yutu is once again the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale.  The eyewall replacement cycle also caused an increase in the size of Typhoon Yutu’s circulation.  Winds to typhoon force extend out about 80 miles (130 km) from the center of circulation.  Winds to tropical storm force extend out about 260 miles (420 km) from the center.  The Hurricane Intensity Index (HII) is 35.0.  The Hurricane Size Index (HSI) is 28.9 and the Hurricane Wind Intensity Size Index (HWISI) is 63.9.

Typhoon Yutu has a large, very well organized circulation and it will remain in an environment capable of supporting a powerful typhoon for several more days.  Yutu will move over water where the Sea Surface Temperature is near 31°C.  It will move through an area where the upper level winds are weak and there will be little vertical wind shear.  Typhoon Yutu could strengthen a little more during the next 12 to 24 hours.  At some point another rainband is likely to wrap around the existing eye and eyewall, and another eyewall replacement cycle could occur.  If there is another eyewall replacement cycle, then Yutu would weaken, at least temporarily.

Typhoon Yutu will move south of a ridge of high pressure over the Western North Pacific Ocean.  The ridge will steer Yutu in a generally westward direction.  On its anticipated track Typhoon Yutu could reach northern Luzon in about four days.  Yutu is very likely to be a strong typhoon when it approaches Luzon.

Dangerous Typhoon Yutu Slams Tinian and Saipan

Dangerous Typhoon Yutu slammed Tinian and Saipan on Wednesday.  At 5:00 p.m. EDT on Wednesday the center of Typhoon Yutu was located at latitude 15.5°N and longitude 144.8°E which put it about 35 miles (55 km) west-northwest of Saipan.  Yutu was moving toward the northwest at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 175 m.p.h. (280 km/h) and there were wind gusts to 205 m.p.h. (330 km/h).  The minimum surface pressure was 908 mb.

Typhoon Warnings were in effect for Rota, Tinian and Saipan.  Tropical Storm Warnings were in effect for Guam, Alamagan, Pagan and Agrihan.

The eye of Typhoon Yutu passed directly over Tinian on Wednesday and the northern side of the eyewall moved over Saipan.  So, they would have experienced the strongest parts of Typhoon Yutu.  The Hurricane Intensity Index (HII) for Typhoon Yutu is 40.4.  The Hurricane Size Index (HSI) is 26.7 and the Hurricane Wind Intensity Size Index (HWISI) is 67.1.  Typhoon Yutu was capable of causing widespread catastrophic damage when it passed over Tinian and Saipan.

Yutu is still a very powerful typhoon, but an eyewall replacement cycle appears to have started.  A rainband has wrapped around the original eye and eyewall.  The inner eye and eyewall are still intact and the strongest winds are occurring in the ring of thunderstorms that surround the original eye.  The imminent formation of a second, outer eyewall increased the size of the circulation around Typhoon Yutu.  Winds to typhoon force extend out about 70 miles (110 km) from the center of circulation.  Winds to tropical storm force extend out about 240 miles (390 km) from the center.

Typhoon Yutu will remain in an environment capable of supporting a very strong typhoon for several more days.  Yutu will move over water where the Sea Surface Temperature is near 31°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  The incipient eyewall replacement cycle will cause Typhoon Yutu to weaken when the inner eyewall dissipates.  However, Yutu could strengthen again, if it remains in a favorable environment and the outer eyewall contracts closer to the center of circulation.  Typhoon Yutu is likely to remain a powerful typhoon during the next 48 hours.

Typhoon Yutu will move southwest of a ridge of high pressure over the Western North Pacific Ocean.  The ridge will steer Yutu toward the west-northwest during the next several days.  On its anticipated track Typhoon Yutu will move away from the Northern Marianas, and conditions should gradually improve there.  Yutu could be south of Okinawa in four or five days.

Typhoon Yutu Intensifies Rapidly to Equivalent of Cat. 4 Hurricane, Imminent Threat to Marianas

Typhoon Yutu intensified rapidly on Tuesday into the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale and Yutu posed an imminent threat to the Marianas.  At 11:00 p.m. EDT on Tuesday the center of Typhoon Yutu was located at latitude 13.6°N and longitude 147.5°E which put it about 155 miles (255 km) east-southeast of Rota.  Yutu was moving toward the northwest at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 150 m.p.h. (240 km/h) and there were wind gusts to 185 m.p.h. (295 km/h).  The minimum surface pressure was 935 mb.

Typhoon Warnings are in effect for Rota, Saipan and Tinian.  Tropical Storm Warnings are in effect for Guam, Alamagan, Pagan and Agrihan.

Typhoon Yutu intensified rapidly during the past 24 hours.  A circular eye developed at the center of Yutu.  The eye is surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Numerous bands of showers and thunderstorms were revolving around the core of Typhoon Yutu.  Storms near the core were generating strong upper level divergence which was pumping mass away from the typhoon in all directions.  The removal of mass allowed the surface pressure to decrease rapidly.

Typhoon Yutu has a large circulation.  Winds to typhoon force extend out about 65 miles (105 km) from the center of circulation.  Winds to tropical storm force extend out about 210 miles (335 km) from the center.  The Hurricane Intensity Index (HII) for Typhoon Yutu is 31.6.  The Hurricane Size Index (HSI) is 20.8 and the Hurricane Wind Intensity Size index (HWISI) is 52.4.  Typhoon Yutu is capable of causing widespread extensive damage.

Typhoon Yutu will move through an environment favorable for further intensification during the next several days.  Yutu will move over water where the Sea Surface Temperature is near 31°C.  It will move through a region where the upper level winds are weak and there is little vertical wind shear.  Typhoon Yutu could intensify into the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale.  At some point a rainband will wrap around the existing eye and eyewall, and an eyewall replacement cycle will occur.  Yutu will weaken during the eyewall replacement cycle, but the typhoon could strengthen afterwards if it remains in an environment favorable for intensification.

Typhoon Yutu will move around the southwestern portion of a ridge of high pressure over the Western North Pacific Ocean.  The ridge will steer Yutu in a general west-northwesterly direction.  On its anticipated track Typhoon Yutu will reach the Northern Marianas in about 12 hours.  The core of Yutu will pass between Rota and Tinian.  Rota, Tinian and Saipan are likly to have winds to typhoon force.  Typhoon Yutu will be capable of causing extensive damage in those locations.  Guam, Alamagan, Pagan and Agrihan are likely to receive winds to tropical storm force.  Wind speeds will be stronger on the northern part of Guam and the damage potential is greater there than it is for the southern part of Guam.

Major Hurricane Willa Makes Landfall in Mexico

Major Hurricane Willa made landfall on the coast of Mexico between Teacapan and Mazatlan on Tuesday evening.  At 8:00 p.m. EDT on Tuesday the center of Hurricane Willa was located at latitude 22.6°N and longitude 106.0°W which put it about 50 miles (80 km) south-southeast of Mazatlan, Mexico.  Willa was moving toward the north-northeast at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 140 m.p.h. (220 km/h).  The minimum surface pressure was 965 mb.

A Hurricane Warning is in effect for the portion of the coast from San Blas to Mazatlan, Mexico.  Tropical Storm Warnings were in effect for the portions of the coast from Playa Perula to San Blas and from Mazatlan to Bahia Tempehuaya, Mexico.

An eyewall replacement cycle occurred in the core of Hurricane Willa on Tuesday.  When the original inner eyewall dissipated, the core of Willa was larger even though the maximum sustained wind speed was slower.  Winds to hurricane force extend out about 35 miles from the the center of Hurricane Willa.  Winds to tropical storm force extend out about 100 miles from the center of circulation.  The Hurricane Intensity Index (HII) for Hurricane Willa is 22.1.  The Hurricane Size Index (HSI) is 12.7 and the Hurricane Wind Intensity Size Index (HWISI) s 34.8.  Hurricane Willa is capable of causing regional major damage.

Hurricane Willa will produce hurricane force winds along the coast between Tecuala and Mazatlan.  Those winds will be capable of causing major damage.  The winds will also push water toward the coast and a storm surge of 10 to 12 feet (3 to 4 meters) is possible.  Hurricane Willa will dissipate fairly quickly when it moves over the Sierra Madre Occidental Mountains.  However, Willa will drop locally heavy rain over the southern part of Sinaloa and over Durango.  The locally heavy rain is likely to cause flash floods in some locations.

Yutu Strengthens Into a Typhoon East of the Marianas

Former Tropical Storm Yutu strengthened into a typhoon east of the Marianas on Monday evening.  At 11:00 p.m. EDT on Monday the center of Typhoon Yutu was located at latitude 11.8°N and longitude 151.2°E which put it about 475 miles (770 km) east-southeast of Guam.  Yutu was moving toward the west-northwest at 14 m.p.h. (22 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 975 mb.

A Typhoon Warning was in effect for Tinian and Saipan.  A Tropical Storm Warning was in effect for Rota.  Tropical Storm Watches were in effect for Guam, Alamagan, Pagan and Agrihan.

The circulation around Typhoon Yutu became better organized on Monday.  An inner rainband wrapped around the northern and western sides of the center of circulation.  A partial eyewall appeared to be forming.  Several bands of showers and thunderstorms were revolving around the center of Typhoon Yutu.  The strongest thunderstorms were developing in the bands in the eastern half of the circulation.  There were thunderstorms in bands in the western side of Typhoon Yutu, but those bands consisted primarily of showers and lower clouds.  Winds to typhoon force extended out about 60 miles (95 km) from center center of circulation.  Winds to tropical storm force extended out about 160 miles (260 km) from the center.

Typhoon Yutu will move through an environment favorable for intensification during the next two or three days.  Yutu will move over water where the Sea Surface Temperature is near 30°C.  It will move through an environment where the upper level winds are weak and there will be little vertical wind shear.  Yutu will continue to intensify and it could strengthen into the equivalent of a major hurricane in a day or two.

Typhoon Yutu will move around the southwestern portion of an ridge of high pressure over the Western North Pacific Ocean.  The ridge will steer Typhoon Yutu toward the west-northwest during the next few days.  On its anticipated track Typhoon Yutu will move over the Northern Marianas in about 36 to 48 hours.  Yutu will be a typhoon when it reaches the Marianas.  It will bring strong winds and it could be capable of causing major damage.

Hurricane Willa Strengthens to Cat. 5, Poses Imminent Threat to Mexico

Hurricane Willa strengthened Monday morning to Category 5 on the Saffir-Simpson Scale and Willa poses an imminent threat to Mexico.  At 11:00 a.m. EDT on Monday the center of Hurricane Willa was located at latitude 19.1°N and longitude 107.2°W which put it about 135 miles (215 km) southwest of Cabo Corrientes.  Willa was moving toward the north at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 160 m.p.h. (260 km/h) and there were wind gusts to 190 m.p.h. (305 km/h).  The minimum surface pressure was 925 mb.

A Hurricane Warning was in effect for the portion of the coast from San Blas to Mazatlan, Mexico.  Tropical Storm Warnings were in effect for the portion of the coast from Playa Perula to San Blas and from Mazatlan to Bahia Tempehuaya, Mexico.

Hurricane Willa strengthened from a tropical storm to a Category 5 hurricane in 36 hours.  Willa is a small, very well organized hurricane.  There is a small 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 of storms.  Several bands of showers and thunderstorms are revolving around the core of Hurricane Willa.  Storms near the core are generating strong upper level divergence which is pumping mass away from the hurricane.

Hurricane Willa is a small hurricane.  Winds to hurricane force extend out about 30 miles ( 50 km) from the center of Willa.  Winds to tropical storm force extend out about 100 miles (160 km) from the center of circulation.  The Hurricane Intensity Index (HII) for Hurricane Willa is 35.0.  The Hurricane Size Index (HSI) is 9.7 and the Hurricane Wind Intensity Size Index (HWISI) is 44.7.  The core of Hurricane Willa is capable of causing catastrophic damage.

Hurricane Willa will remain in an environment capable of supporting strong hurricanes for about another 24 hours.  Willa will move over water where the Sea Surface Temperature is near 29°C.  It will move through an environment where the upper level winds are weak and there will be little vertical wind shear.  If an outer rainband wraps around the existing eye and eyewall, then an eyewall replacement cycle could cause Hurricane Willa to weaken.  An upper level trough near the West Coast of the U.S. will produce southwesterly winds which will blow toward the top of Hurricane Willa on Tuesday.  Those winds will cause vertical wind shear and the shear will start to weaken Willa.  Since Willa is a small hurricane, it will weaken faster than a larger hurricane would weaken.

Hurricane Willa will move around the western end of a ridge of high pressure over Mexico.  The ridge will steer Willa toward the north for another 12 hours or so.  Then the upper level trough will turn Hurricane Willa toward the northeast.  On its anticipated track Hurricane Willa will move over the Islas Marias on Tuesday morning.  Willa will reach the coast of Mexico between San Blas and Mazatlan on Tuesday afternoon or evening.

Hurricane Willa could still be a major hurricane when it reaches the coast of Mexico.   Willa will be capable of causing major damage.  The core of Hurricane Willa will bring damaging winds.  It will also produce a storm surge of 10 to 13 feet (3 to 4 meters) near where core of Willa makes landfall.  Hurricane Willa will drop heavy rain over Nayarit, Sinaloa and Durango.  The heavy rain could cause flash floods in some locations.

Elsewhere over the Eastern North Pacific Ocean, upper level divergence from Hurricane Willa appeared to be causing wind shear which was weakening Tropical Storm Vicente.  At 11:00 a.m. EDT on Monday the center of Tropical Storm Vicente was located at latitude 14.9°N and longitude 100.8°W which put it about 365 miles (590 km) southeast of Manzanillo, Mexico.  Vicente was moving toward the west-northwest at 12 m.p.h. (19 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 1004 mb.

Willa Rapidly Intensifies Into a Major Hurricane, Warnings Issued for Mexico

Hurricane Willa intensified rapidly into a major hurricane on Sunday and Warnings were issued for Mexico.  At 11: 00 p.m. EDT on Sunday the center of Hurricane Willa was located at latitude 17.7°N and longitude 107.2°W which put it about 210 miles (340 km) south-southwest of Cabo Corrientes, Mexico.  Willa was moving toward the north-northwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 145 m.p.h. (230 km/h) and there were wind gusts to 170 m.p.h. (275 km/h).  The minimum surface pressure was 941 mb.  Hurricane Willa was a Category 4 hurricane on the Saffir-Simpson Scale.

A Hurricane Warning was in effect for the portion of the coast from San Blas to Mazatlan, Mexico.  A Tropical Storm Warning was in effect for the portion of the coast from Playa Perula to San Blas.  A Tropical Storm Warning was also in effect for the portion of the coast from Mazatlan to Bahia Tempehuaya.

Hurricane Willa intensified from a tropical storm to a Category 4 hurricane in 24 hours.  A small circular eye formed at the center of Hurricane Willa.  The eye was surround by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Several bands of showers and thunderstorms were revolving around the core of Hurricane Willa.  Storms near the core were generating strong upper level divergence which was pumping large quantities of mass away from the hurricane.  The strong divergence allowed the surface pressure to decrease quickly and that caused the wind speeds to increase rapidly.

Willa is a small hurricane.  Winds to hurricane force only extend out about 25 miles (40 km) from the center of Hurricane Willa.  Winds to tropical storm force only extend out about 90 miles (145 km) from the center of circulation.  The Hurricane Intensity Index (HII) for Hurricane Willa is 29.9.  The Hurricane Size Index (HSI) is 8.2 and the Hurricane Wind Intensity Size Index (HWISI) is 38.1.

Hurricane Willa will move through an environment favorable for intensification during the next 12 to 24 hours.  Willa will move over water where the Sea Surface Temperature is near 29°C.  It will move through a region where the upper level winds are weak and there will not be much vertical wind shear.  Hurricane Willa could strengthen to a Category 5 hurricane on the Saffir-Simpson Scale during the next 12 hours.  An upper level trough near the west coast of the U.S. will produce southwesterly winds which will start to affect Hurricane Willa in about 24 hours.  Those winds will cause vertical wind shear, which will cause Willa to start to weaken.

Hurricane Willa will move around the western end of a ridge of high pressure over Mexico.  The ridge will steer Willa toward the north on Monday.  The upper level trough near the west coast of the U.S. will turn Hurricane Willa toward the northeast on Tuesday.  On its anticipated track Hurricane Willa could make landfall on the coast of Mexico on Tuesday night.  Willa could be a major hurricane when it approaches the coast.  It will be capable of causing major wind damage and a significant storm surge along the coast.  Willa will also drop locally heavy rain and it could flash floods when it moves inland over Mexico.

Elsewhere over the Eastern North Pacific Ocean Tropical Storm Vicente was moving near the southeastern periphery of Hurricane Willa.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Vicente was located at latitude 13.9°N and longitude 98.7°W which put it about 220 miles (355 km) south-southeast of Acapulco, Mexico.  Vicente was moving toward the west at 10 m.p.h. (16 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 1005 mb.

Tropical Storm Yutu Forms Southeast of the Marianas

Tropical Storm Yutu formed southeast of the Marianas on Sunday.  At 5:00 p.m. EDT on Sunday the center of Tropical Storm Yutu was located at latitude 8.7°N and longitude 156.4°E which put it about 880 miles (1420 km) east-southeast of Guam.  Yutu was moving toward the west-northwest at 10 m.p.h. (16 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.

A distinct low level center of circulation developed in an area or thunderstorms northeast of Chuuk and the Japan Meteorological Agency designated the system as Tropical Storm Yutu.  The circulation around Yutu was organizing quickly.  An inner band of showers and thunderstorms was wrapping around the center of circulation.  Other bands of showers and thunderstorms were forming and they were starting to revolving around the center.  Storms near the center were producing upper level divergence which was pumping mass away from the tropical storm.

Tropical Storm Yutu will be moving through an environment that is very favorable for intensification.  Yutu will move over water where the Sea Surface Temperature is near 30°C.  It will move through an environment where the upper level winds are weak and there will little vertical wind shear.  Tropical Storm Yutu could strengthen into a typhoon within 36 hours and it could rapidly intensify into the equivalent of a major hurricane within three or four days.

Tropical Storm Yutu will move around the western end of a subtropical ridge over the Western North Pacific Ocean during the next few days.  The ridge will steer Yutu toward the northwest during the next two or three days.  On its anticipated track Yutu will approach the Marianas in about three days.  It will likely be a typhoon by that time.

Tropical Storm Willa Strengthens Quickly Southwest of Mexico

Only one day after the formation of Tropical Storm Vicente, Tropical Storm Willa strengthened quickly southwest of Mexico.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Willa was located at latitude 15.2°N and longitude 105.8°W which put it about 280 miles (450 km) south-southwest of Manzanillo, Mexico.  Will was moving toward the west-northwest at 6 m.p.h. (10 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 999 mb.

Several bands of showers and thunderstorms wrapped tightly around a distinct low level center of circulation on Saturday and the National Hurricane Center designated the system as Tropical Storm Willa.  Willa continued to organize quickly on Saturday afternoon.  Bands of showers and thunderstorms formed and began to revolve around the core of Tropical Storm Willa.  Storms near the core started to generate upper level divergence which pumped mass away from the tropical storm.  The circulation around Tropical Storm Willa was still compact.  Winds to tropical storm force only extended out about 35 miles (55 km) from the center of circulation.

Tropical Storm Willa will move through an environment favorable for intensification.  Willa will move over water where the Sea Surface Temperature is near 29°C.  It will move through an area where the upper level winds are weak and there will be little vertical wind shear.  Willa is likely to intensify into a hurricane during the next 24 hours.  It could intensify rapidly and there is a chance Tropical Storm Will could strengthen into a major hurricane during the next two or three days.

Tropical Storm Willa will move around the western end of a ridge of high pressure over Mexico during the next two or three days.  The ridge will steer Willa toward the northwest during the next 24 to 48 hours.  An upper level trough west of California will turn Willa toward the northeast in about 48 hours.  On its anticipated track Willa could approach the coast of Mexico in about fours.  Willa could be a hurricane when it nears the coast.

Elsewhere over the Eastern North Pacific Ocean, Tropical Storm Vicente also strengthened on Saturday.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Vicente was located at latitude 14.6°N and longitude 94.3°W which put it about 120 miles (200 km) south-southeast of Salina Cruz, Mexico.  Vicente was moving toward the west at 9 m.p.h. (15 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 1002 mb.