Monthly Archives: June 2019

Tropical Storm Barbara Forms South of Baja California

Tropical Storm Barbara formed south of Baja California on Sunday as the remnants of former Hurricane Alvin were dissipating over the Eastern North Pacific Ocean.  At 11:00 a.m. EDT on Sunday the center of Tropical Storm Barbara was located at latitude 10.6°N and longitude 110.4°W which put it about 850 miles (1370 km) south of the southern tip of Baja California.  Barbara was moving toward the west-northwest 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 1006 mb.

More thunderstorms developed near the center of a low pressure system south of Baja California on Sunday and the National Hurricane Center designated the system as Tropical Storm Barbara.  Bands of showers and thunderstorms were revolving around the center of circulation.  Storms near the center were generating upper level divergence which was pumping mass away from the tropical storm.  Tropical Storm Barbara was larger than former Hurricane Alvin.  Winds to tropical storms force extended out about 80 miles (130 km) from the center of circulation.

Tropical Storm Barbara will move through an environment favorable for intensification during the next several days.  Barbara 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.  Tropical Storm Barbara will continue to intensify and it is likely to strengthen into a hurricane by the middle of the week.  Barbara could intensify rapidly when the inner core is more developed.

Tropical Storm Barbara will move south of a subtropical ridge over the Eastern North Pacific Ocean.  The ridge will steer Barbara toward the west-northwest.  On its anticipated track Tropical Storm Barbara will move away from Baja California and the rest of Mexico.

Alvin Strengthens Into a Hurricane Southwest of Baja California

Former Tropical Storm Alvin strengthened into a hurricane southwest of Baja California on Thursday evening.  At 11:00 p.m. EDT on Thursday the center of Hurricane Alvin was located at latitude 17.4°N and longitude 115.4°W which put it about 520 miles (840 km) southwest of the southern tip of Baja California.  Alvin was moving toward the northwest at 16 m.p.h. (26 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 992 mb.

The circulation around Hurricane Alvin exhibited much greater organization on Wednesday.  A small circular eye with a diameter of 10 miles (15 km) appeared at the center of circulation.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  The circulation around Hurricane Alvin was very small.  Winds to hurricane force extended out only 10 miles (15 km) from the center of circulation.  Winds to tropical storm force extended out about 50 miles (80 km) from the center.

Hurricane Alvin may be near its maximum intensity.  Alvin was moving over water where the Sea Surface Temperature was near 27°C.  However, it will move over cooler water on Friday.  The small size of the circulation around Hurricane Alvin could allow it to weaken quickly once it moves over the cooler water.

Hurricane Alvin will move near the western end of a subtropical ridge over Eastern North Pacific Ocean.  The ridge will steer Alvin toward the west-northwest during the next several days.  On its anticipated track Hurricane Alvin is forecast to weaken when it moves over colder water between Baja California and Hawaii.

Tropical Storm Sepat Forms Near Honshu

Tropical Storm Sepat formed near Honshu on Thursday.  More thunderstorms formed near the center of a low pressure system near the southeast coast of Honshu on Thursday and the Japan Meteorological Agency designated the system as Tropical Storm Sepat.  At 8:00 a.m. EDT on Thursday the center of Tropical Storm Sepat was located at latitude 32.6°N and longitude 134.7°E which put it about 100 miles (160 km) southwest of Susami, Japan.  Sepat was moving toward the northeast at 32 m.p.h. (50 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 998 mb.

The distribution of thunderstorms around Tropical Storm Sepat was asymmetrical.  The strongest thunderstorms were in several bands south and east of the center of circulation.  Bands in the other parts of the circulation consisted primarily of showers and lower clouds.  Storms southeast of the center of Sepat were generating upper level divergence which was pumping mass away to the northeast of the tropical storm.  Winds to tropical storm force extended out about 150 miles (240 km) to the east of the center of circulation.

Tropical Storm Sepat will move through an environment marginally favorable for intensification during the next 12 to 24 hours.  Sepat will move over water where the Sea Surface Temperature is near 24°C.  An upper level trough west of Japan will produce strong southwesterly winds which will blow toward the top of the circulation.  Those winds will cause moderate vertical wind shear, which is the primary reason for the asymmetrical distribution of thunderstorms.  Moderate vertical wind shear and cooler water will cause the structure of Tropical Storm Sepat to change to that of an extratropical cyclone.  Sepat could strengthen during the extratropical transition because upper level divergence will cause the surface pressure to decrease.

The upper level trough will steer Tropical Storm Sepat rapidly toward the northeast.  On its anticipated track the center of Tropical Storm Sepat will pass near the coast of Honshu.  Sepat will bring gusty winds and it could drop locally heavy rain.

Tropical Storm Alvin Develops South of Baja California

Tropical Storm Alvin developed south of Baja California on Wednesday morning, when former Tropical Depression One-E strengthened to a tropical storm.  At 11:00 a.m. EDT on Wednesday the center of Tropical Storm Alvin was located at latitude 14.7°N and longitude 109.4°W which put it about 565 miles (915 km) south of the southern tip of Baja California.  Alvin was moving toward the west 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 1005 mb.

The circulation around Tropical Storm Alvin exhibited greater organization on Wednesday morning.  A band of thunderstorms wrapped around the eastern side of the center of circulation.  Other bands of showers and thunderstorms were organizing in the eastern half of the circulation.  Winds to tropical storm force extended out about 35 miles (55 km) from the center on the eastern side of the circulation.  Bands in the western half of the circulation consisted primarily of showers and lower clouds.  Storms near the center were generating upper level divergence which was pumping mass away from the tropical storm.

Tropical Storm Alvin will move through an environment favorable for intensification during the next 24 to 36 hours.  Alvin will move over water where the Sea Surface Temperature is near 28°C.  Tropical Storm Alvin will move south of an upper level ridge.  The ridge will produce northeasterly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear, but the shear will not be strong enough to prevent intensification.  Tropical Storm Alvin will intensify during the next day or two and it could strengthen into a hurricane.

The upper level ridge will steer Tropical Storm Alvin toward the west during the next several days.  Alvin could move a little to the south of due west during the next 24 hours.  On its anticipated track Tropical Storm Alvin will move steadily farther away from Mexico.

Tropical Depression One-E Forms West of Mexico

Tropical Depression One-E formed west of Mexico on Tuesday afternoon.  More thunderstorms developed close to the center of a low pressure system over the Eastern North Pacific Ocean and the National Hurricane Center designated the system as Tropical Depression One-E.  At 5:00 p.m. EDT on Tuesday the center of Tropical Depression One-E was located at latitude 15.2°N and longitude 105.7°W which put it about 280 miles (450 km) south-southwest of Manzanillo, Mexico.  The depression was moving toward the west-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 1007 mb.

The circulation around Tropical Depression One-E exhibited greater organization on Tuesday afternoon.  Several short bands of showers and thunderstorms were developing near the center of circulation.  One band was north of the center, another was west of the center and a third band was south of the center of circulation.  Bands east of the center consisted primarily of showers and lower clouds.  Thunderstorms near the center of circulation were beginning to generate upper level divergence which was pumping mass away from the tropical depression.

Tropical Depression One-E will move through an environment favorable for intensification during the next day or two.  The depression will move over water where the Sea Surface Temperature is near 28°C.  It will move south of an upper level ridge over Mexico and the Eastern North Pacific Ocean.  The ridge will produce northeasterly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear which will slow the rate of intensification, but the shear will not be strong enough to prevent intensification.  Tropical Depression One-E is likely to intensify into a tropical storm during the next 24 to 36 hours.

A subtropical ridge north of Tropical Depression One-E will steer the depression toward the west-northwest.  On its anticipated track Tropical Depression One-E will move away from Mexico.  It is forecast to pass south of Baja California.

Tropical Cyclone Vayu Weakens South of Pakistan

Tropical Cyclone Vayu weakened over the Arabian Sea south of Pakistan on Saturday.  At 11:00 p.m. EDT on Saturday the center of Tropical Cyclone Vayu was located at latitude 24.2°N and longitude 65.3°E which put it about 275 miles (445 km) south-southwest of Karachi, Pakistan.  Vayu was moving toward the northwest at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 985 mb.

The low level circulation around Tropical Cyclone Vayu remained well organized on Saturday, but the distribution of thunderstorms was asymmetrical.  The stronger thunderstorms were occurring in the southern half of the former eyewall and in several rainbands in the southern half of the circulation.  The strongest winds were occurring in the remaining portion of the eyewall.  Bands in the northern half of the circulation consisted primarily of showers and lower clouds.  Winds to tropical storm force extended out about 150 miles (240 km) from the center of circulation.

The circulation around Tropical Cyclone Vayu continued to draw drier air into the northern half of the tropical cyclone on Saturday.  An upper level ridge north of Vayu was producing strong northeasterly winds which were blowing toward the top of the circulation.  Those winds were causing moderate vertical wind shear.  The drier air and wind shear were the primary factors causing the asymmetrical distribution of thunderstorms.

Tropical Cyclone Vayu will move through an environment unfavorable for intensification during the next 24 hours.  Even though Vayu will move over water where the Sea Surface Temperature is near 30°C, the combined effects of the drier air and the wind shear are likely to cause the tropical cyclone to continue to weaken on Sunday.  If the upper level winds get stronger, they could blow the upper half of the circulation southwest of the lower part of Tropical Cyclone Vayu.  In that case Vayu will weaken more quickly.

The future track of Tropical Cyclone Vayu will also depend on the vertical wind shear.  If the wind shear is not too strong and the circulation remains vertically intact, then the ridge north of Vayu will steer the tropical cyclone slowly toward the northwest on Sunday.  If the upper level winds blow the upper half of the circulation away from the lower portion of Tropical Cyclone Vayu, then southwesterly winds in the lower atmosphere will blow the shallower system toward the northeast.  Guidance from numerical models suggest this second scenario is more likely and the anticipated track takes Tropical Cyclone Vayu toward the northeast.

Tropical Cyclone Vayu Stalls, Weakens Southwest of Gujarat

Tropical Storm Vayu stalled and weakened southwest of Gujarat on Friday.  At 11:00 p.m. EDT on Friday the center of Tropical Cyclone Vayu was located at latitude 20.6°N and longitude 67.4°E which put it about 170 miles (275 km) southwest of Dwarka, India.  Vayu was moving toward the west at 4 m.p.h. (6 km/h).  The maximum sustained wind speed was 90 m.p.h. (150 km/h) and there were wind gusts to 115 m.p.h. (185 km/h).  The minimum surface pressure was 969 mb.

The structure of the inner core of Tropical Cyclone Vayu changed significantly on Friday.  The previous small eye disappeared and a large new eye with a diameter of 50 miles (80 km) developed at the center of Vayu.  The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms.  The strongest rainbands were located in the southern half of the circulation.  Bands in the northern half of the circulation consisted primarily of showers and lower clouds.  Winds to hurricane/typhoon force extended out about 35 miles (55 km) from the center of circulation.  Winds to tropical storm extended out about 150 miles (240 km) from the center.

The environment around Tropical Cyclone Vayu will become less favorable for a tropical cyclone on Saturday.  An upper level ridge north of Vayu will strengthen.  The ridge will produce stronger northeasterly winds which will blow toward the top of the circulation.  Those winds will cause more vertical wind shear.  Tropical Cyclone Vayu will also continue to pull drier air into the northern half of the circulation.  Vayu will move over water where the Sea Surface Temperature is near 30°C.  Even though Tropical Cyclone Vayu will be over very warm water, the combined effects of stronger wind shear and drier air are likely to cause it to weaken on Saturday.

The ridge north of Vayu will block the tropical cyclone from moving toward the north on Saturday.  The ridge is likely to continue to steer Tropical Cyclone Vayu slowly toward the west over the northeastern Arabian Sea during the next 24 hours.  On its anticipated track Vayu will move farther away from Gujarat and Pakistan on Saturday.

Tropical Cyclone Vayu Turns West Over Northeast Arabian Sea

Tropical Cyclone Vayu turned west over the northeastern Arabian Sea on Thursday.  At 11:00 p.m. EDT on Thursday the center of Tropical Cyclone Vayu was located at latitude 20.9°N and longitude 68.4°E which put it about 80 miles (130 km) southwest of Porbandar, India.  Vayu was moving toward the west-northwest at 4 m.p.h. (6 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. (195 km/h).  The minimum surface pressure was 960 mb.

Tropical Cyclone Vayu maintained its intensity on Thursday, but the circulation exhibited slightly less organization.  A small eye continued to mark the center of circulation.  A ring of strong thunderstorms surrounded the eye, but there was a break in the northeastern portion of the ring.  The circulation continued to pull drier air into the northern part of the tropical cyclone.  Many of the stronger thunderstorms were occurring in bands in the southern half of the circulation.  Rainbands in the northern half of the circulation were weaker.  Winds to hurricane/typhoon force extended out about 40 miles (65 km) from the center of circulation.  Winds to tropical storm force extended out about 125 miles (200 km) from the center.

Tropical Cyclone Vayu will continue to move through an environment capable of sustaining a tropical cyclone on Friday.  Vayu will move under the axis of an upper level ridge where the winds are weaker and there will be little vertical wind shear.  The Sea Surface Temperature in the northeastern Arabian Sea is near 30°C.  However, Tropical Cyclone Vayu moved slowly on Thursday and it may have stirred some cooler water to the surface.  In addition, the circulation around Vayu will continue to draw in drier air from over south Asia.  Tropical Cyclone Vayu could start to weaken slowly on Friday, although it could maintain its intensity if it moves away from the upwelled cooler water.

Tropical Cyclone Vayu will be south of a strengthening ridge of high pressure over south Asia.  The ridge will block Vayu and prevent it from moving farther toward the north.  The ridge will steer Vayu slowly toward the west during the next 24 to 48 hours.  On its anticipated track Tropical Cyclone Vayu will remain southwest of Gujarat and south of Pakistan during the next two days.

Tropical Cyclone Vayu Slows Near Gujarat Coast

Tropical Cyclone Vayu slowed near the coast of Gujarat on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Tropical Cyclone Vayu was located at latitude 20.4°N and longitude 69.1°E which put it about 85 miles (135 km) south-southwest of Porbandar, India.  Vayu was moving toward the north-northwest at 8 m.p.h. (13 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 962 mb.

The circulation around Tropical Cyclone Vayu weakened slightly on Wednesday, although the inner core appeared to remain mostly intact.  The circulation seemed to pull some drier air over India into the eastern and northern portions of Vayu.  Outer rainbands weakened in those parts of the tropical cyclone.  The drier air did not appear to have penetrated the inner core of the circulation.  A tiny eye remained at the center of circulation.  A ring of showers and thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Bands of strong thunderstorms in the southern half of the circulation were revolving around the core of Tropical Cyclone Vayu.  Winds to hurricane/typhoon force extended out about 35 miles (55 km) from the center of circulation.  Winds to tropical storm force extended out about 120 miles (195 km) from the center.

Tropical Cyclone Vayu will move through an environment that will be mainly favorable for a tropical cyclone during the next 24 to 48 hours.  Vayu will move over water where the Sea Surface Temperature is near 30°C.  It will move near the axis of an upper level ridge where winds are weaker and there will be less vertical wind shear.  The drier air being pulled into the circulation from over India will be a factor that could inhibit any additional strengthening of Tropical Cyclone Vayu.  Vayu could strengthen during the next 24 hours, but it is more likely to maintain its intensity or weaken slightly.  If drier air mixes into the inner core of the circulation, then Tropical Cyclone Vayu could weaken more quickly.

Tropical Cyclone Vayu will move around the western end of a ridge over India during the next 12 to 24 hours.  The ridge will steer Vayu toward the north-northwest on Thursday.  A second ridge will develop north of Tropical Cyclone Vayu.  The second ridge will block the northward movement of Vayu and force the tropical cyclone to move more toward the west.  On its anticipated track the core of Tropical Cyclone Vayu will remain west of the coast of Gujarat.  Bands on the eastern side of the circulation could drop rain over Gujarat but the strongest part of the circulation is likely to remain offshore.

Tropical Cyclone Vayu Strengthens to Equivalent of Hurricane/Typhoon

Tropical Cyclone Vayu strengthened into the equivalent of a hurricane/typhoon over the eastern Arabian Sea on Tuesday.  At 11:00 a.m. EDT on Tuesday the center of Tropical Cyclone Vayu was located at latitude 16.4°N and longitude 70.8°E which put it about 200 miles (320 km) southwest of Mumbai, India.  Vayu was moving toward the north at 10 m.p.h. (16 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. (150 km/h).  The minimum surface pressure was 974 mb.

Microwave satellite imagery indicated that an inner rainband had wrapped completely around the center of circulation and a small eye had formed at the center of Tropical Cyclone Vayu.  The core of Vayu was relatively small.  Winds to hurricane/typhoon force only extended out about 20 miles (30 km) from the center of circulation.  Winds to tropical storm force extended out about 100 miles (160 km) from the center.  Storms around the core of Tropical Cyclone Vayu were generating upper level divergence which was pumping mass to the west of the tropical cyclone.  Additional bands of showers and thunderstorms were revolving around the core of Vayu.

Tropical Cyclone Vayu will move through an environment favorable for intensification during the next 24 to 36 hours.  Vayu will move over water where the Sea Surface Temperature is near 30°C.  Tropical Cyclone Vayu will move near the southwestern portion of an upper level ridge.  The ridge will produce southeasterly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear, but the shear will not be strong enough to prevent intensification.  Tropical Cyclone Vayu will intensify during the next 24 to 36 hours.  It could intensify rapidly once the eye and eyewall are fully formed.  Vayu could strengthen into the equivalent of a major hurricane.

Tropical Cyclone Vayu will move around the western end of a ridge over India.  The ridge will steer Vayu toward the north.  On its anticipated track Tropical Cyclone Vayu could approach the coast of Gujarat within 36 hours.  Vayu could be the equivalent of a major hurricane by that time.  It could bring strong winds and locally heavy rain to Gujarat.  Heavy rain could cause flash floods.  Tropical Cyclone Vayu could also generate a significant storm surge along the coast of Gujarat.