Category Archives: Eastern and Central Pacific

TCs between Mexico and Hawaii

Tropical Storm Cosme Forms Southwest of Baja California

Tropical Storm Cosme formed southwest of Baja California on Saturday.  At 11:00 a.m. EDT on Saturday the center of Tropical Storm Cosme was located at latitude 15.6°N and longitude 115.7°W which put it about 630 miles (1015 km) southwest of the southern tip of Baja California.  Cosme was moving toward the west-northwest at 14 m.p.h. (22 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 1001 mb.

The National Hurricane Center (NHC) determined on Saturday that a distinct center of circulation had developed in a broader area of lower pressure and NHC designated the system as Tropical Storm Cosme.  The distribution of thunderstorms around Tropical Storm Cosme was asymmetrical.  The stronger thunderstorms were occurring in bands in the eastern half of the circulation.  Bands in the western half of the circulation consisted primarily of showers and lower clouds.  An upper level trough near Baja California was producing strong southwesterly winds which were blowing across the top of the circulation.  Those winds were causing strong vertical wind shear and they were probably the reason for the asymmetrical distribution of thunderstorms.  Winds to tropical storm force extended out about 150 miles (240 km) from the center of circulation.

Tropical Storm Cosme will move through an environment that is not favorable for significant intensification.  Cosme will move over water where the Sea Surface Temperature is near 26°C.  The upper level trough will continue to produce southwesterly winds that will blow toward the top of Tropical Storm Cosme.  The upper level winds are likely to weaken somewhat, but they will continue to cause vertical wind shear.  Tropical Storm Cosme could intensify a little during the next 24 hours, but it is not likely to strengthen significantly.

Tropical Storm Cosme will move south of a subtropical high pressure system over Eastern North Pacific Ocean.  The high will steer Cosme toward the west-northwest.  On its anticipated track Tropical Storm Cosme is forecast to remain well to the west of Baja California.

Elsewhere over the Eastern North Pacific Ocean, Tropical Storm Barbara continued to weaken as it moved toward Hawaii.  At 11:00 a.m. EDT on Saturday the center of Tropical Storm Barbara was located at latitude 18.7°N and longitude 139.2°W which put it about 1040 miles (1670 km) east of Hilo, Hawaii.  Barbara was moving toward the west at 17 m.p.h. (28 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.

Barbara Weakens to a Tropical Storm

Former Hurricane Barbara weakened to a tropical storm on Friday.  At 5:00 p.m. EDT on Friday the center of Tropical Storm Barbara was located at latitude 18.6°N and longitude 134.7°W which put it about 1330 miles (2145 km) east of Hilo, Hawaii.  Barbara was moving toward the west-northwest at 13 m.p.h. (20 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 997 mb.

The effects of vertical wind shear and cooler Sea Surface Temperatures caused former Hurricane Barbara to weaken quickly to a tropical storm on Friday.  An upper level trough northeast of Hawaii produced strong southwesterly winds which blew the upper portion of the circulation north of the remainder of the tropical storm.  In addition, Tropical Storm Barbara moved over water where the Sea Surface Temperature was near 25°C which meant there was less energy to support the development of taller thunderstorms.  Tropical Storm Barbara still had a well formed circulation in the lower levels of the atmosphere.  However, as a result of the strong shear and cooler water, bands consisted primarily of showers and lower clouds.  Winds to tropical storm force extended out about 140 miles (220 km) from the center of circulation.

Tropical Storm Barbara will continue to move over cooler water and through a region of strong vertical wind shear during the next several days.  Barbara will continue to weaken and it could be a tropical depression on Saturday.

Since Tropical Storm Barbara contains few tall thunderstorms, it is being steered by winds closer to the surface.  A subtropical high pressure system north of Barbara will steer the tropical storm toward the west.  On its anticipated track Tropical Storm Barbara will move toward Hawaii.

Hurricane Barbara Starts to Weaken

Hurricane Barbara started to weaken on Wednesday when it moved over cooler water well to the east of Hawaii.  At 5:00 p.m. EDT on Wednesday the center of Hurricane Barbara was located at latitude 14.3°N and longitude 127.5°W which put it about 1860 miles (2990 km) east of Hilo, Hawaii.  Barbara was moving toward the west-northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 140 m.p.h. (220 km/h) and there were wind gusts to 170 m.p.h. (275 km/h).  The minimum surface pressure was 941 mb.

The circulation around Hurricane Barbara remained very well organized.  There was a circular eye 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.  Several bands of showers and thunderstorms were revolving around the core of Hurricane Barbara.  Storms near the core of the circulation were generating strong upper level divergence which was pumping mass away from the hurricane.  Winds to hurricane force extended out about 45 miles (75 km) from the center of circulation.  Winds to tropical storm force extended out about 185 miles (295 km) from the center.

Hurricane Barbara still rated at Category 4 on the Saffir-Simpson Scale.  The Hurricane Intensity Index (HII) for Barbara was 28.3.  The Hurricane Size Index (HSI) was 16.5 and the Hurricane Wind Intensity Size Index (HWISI) was 44.8.

Hurricane Barbara will gradually move into an environment less capable of supporting a strong hurricane during the next few days.  Barbara will move over water where the Sea Surface Temperature is near 26°C.  As a result, Hurricane Barbara will extract less energy from the upper ocean and it will gradually weaken.  Barbara will move closer to an upper level trough located northeast of Hawaii.  When Hurricane Barbara gets closer to the trough later this week, stronger upper level southwesterly winds will create more vertical wind shear and the hurricane will weaken more quickly.

Hurricane Barbara will move south of a subtropical ridge over the Eastern North Pacific Ocean.  The ridge will steer Barbara toward the west-northwest during the next 24 to 36 hours.  The ridge is forecast to strengthen on Friday and it will steer Hurricane Barbara more toward the west when that happens.  On its anticipated track Barbara could approach Hawaii in about five days.  It will be much weaker by that time.

Barbara Rapidly Intensifies Into a Major Hurricane

Hurricane Barbara rapidly intensified into a major hurricane on Tuesday as it moved over the Eastern North Pacific Ocean between Baja California and Hawaii.  At 11:00 a.m. EDT on Tuesday the center of Hurricane Barbara was located at latitude 12.5°N and longitude 122.2°W which put it about 1080 miles (1740 km) southwest of the southern tip of Baja California.  Barbara was moving toward the west-northwest at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 130 m.p.h. (215 km/h) and there were wind gusts to 150 m.p.h. (240 km/h).  The minimum surface pressure was 948 mb.

Hurricane Barbara continued to intensify rapidly on Tuesday.  A circular eye became more evident on satellite imagery.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Storms near the core of Barbara were generating strong upper level divergence which was pumping mass away from the hurricane in all directions.  Multiple bands of showers and thunderstorms were revolving around the core of Hurricane Barbara.  Winds to hurricane force extended out about 25 miles (40 km) from the center of circulation.  Winds to tropical storm force extended out about 200 miles (320 km) in the southeastern quadrant of the circulation.  Tropical storm force winds extended out about 120 miles (195 km) from the center in the other three quadrants.

Hurricane Barbara was at Category 4 on the Saffir-Simpson Scale.  The Hurricane Intensity Index (HII) for Barbara was 25.1.  The Hurricane Size Index (HSI) was 11.0 and the Hurricane Wind Intensity Size Index (HWISI) was 36.1.

Hurricane Barbara will move through an environment very favorable for strong hurricanes for another 12 to 24 hours.  Barbara will move over water where the Sea Surface Temperature is near 28°C.  It will move through an area where the upper level winds are weak and there will be little vertical wind shear.  Hurricane Barbara is likely to intensify further during the next 12 hours.  If a rainband wraps around the existing eye and eyewall, then an eyewall replacement cycle could cause Barbara to weaken.  Hurricane Barbara will approach cooler water on Wednesday and it is likely to start to weaken by that time.  Barbara will move into an area where the upper level winds are stronger later this week and it could weaken more quickly when the wind shear increases.

Hurricane Barbara will move south of a subtropical ridge over the Eastern North Pacific Ocean.  The ridge will steer Barbara in a west-northwesterly direction during the next several days.  On its anticipated track Hurricane Barbara will move in the general direction of Hawaii.

Barbara Rapidly Intensifies Into a Hurricane

Former Tropical Storm Barbara rapidly intensified into a hurricane over the Eastern North Pacific Ocean on Monday.  At 5:00 p.m. EDT on Monday the center of Hurricane Barbara was located at latitude 11.5°N and longitude 118.5°W which put it about 970 miles (1560 km) southwest of the southern tip of Baja California.  Barbara was moving toward the west at 16 m.p.h. (26 km/h).  The maximum sustained wind speed was 85 m.p.h. (135 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure  was 983 mb.

Hurricane Barbara intensified rapidly on Monday.  An eye formed at the center of circulation and a ring of strong thunderstorms surrounded the eye.  The strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of the circulation.  Storm near the core of Barbara were generating strong upper level divergence which was pumping mass away from the hurricane.  Winds to hurricane force extended out about 25 miles (40 km) from the center of circulation.  Winds to tropical storm force extended out about 160 miles (260 km) from the center.

Hurricane Barbara will move through an environment very favorable for intensification during the next 36 to 48 hours.  Barbara 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 be little vertical wind shear.  Hurricane Barbara will continue to intensify rapidly and it is expected to strengthen into a major hurricane on Tuesday.

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

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 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.

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.