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Tropical Storm Bud Forms South of Mexico, Aletta Weakens

Tropical Storm Bud formed south of Mexico on Saturday while former Hurricane Aletta weakened rapidly to a tropical storm.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Bud was located at latitude 12.9°N and longitude 102.0°W which put it about 575 miles (920 km) south-southeast of Cabo Corrientes, Mexico.  Bud was moving toward the 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 1003 mb.

The circulation of Tropical Storm Bud organized quickly on Saturday.  A distinct low level center of circulation formed.  Several bands of showers and thunderstorms formed in all parts of the circulation.  Storms near the center of circulation generated upper level divergence which pumped mass away from the tropical storm.  Winds to tropical storms force extended out about 60 miles (95 km) from the center of circulation.

Tropical Storm Bud will move through an environment favorable for intensification during the next several days.  Bud 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 be little vertical wind shear.  Tropical Storm Bud is likely to intensify steadily during the next day or two and it could intensify rapidly once an eye forms.

Tropical Storm Bud is being steered to the northwest by a ridge over Mexico.  That general motion is expected to continue for several more days.  On its anticipated track Tropical Storm Bud will move roughly parallel to the west coast of Mexico.  Bud could be near the southern tip of Baja California in about five days.

Former Hurricane Aletta moved over cooler water and it weakened rapidly on Saturday.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Aletta was located at latitude 15.9°N and longitude 114.3°W which put it about 560 miles (905 km) south-southwest of the southern tip of Baja California.  Aletta was moving toward the west at 7 m.p.h. (11 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.

Hurricane Aletta Rapidly Intensifies to Category 4

Hurricane Aletta rapidly intensified Friday morning to Category 4 on the Saffir-Simpson Scale.  At 11:00 a.m. EDT on Friday the center of Hurricane Aletta was located at latitude 15.8°N and longitude 111.2°W which put it about 505 miles (815 km) west-southwest of Manzanillo, Mexico.  Aletta was moving toward the west at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 140 m.p.h. (220 km/h) and there were wind gusts to 165 m.p.h. (265 km/h).  The minimum surface pressure was 943 mb.

An environment with warm Sea Surface Temperatures and little vertical wind shear allowed Hurricane Aletta to intensify rapidly during Thursday night and Friday morning.  A small circular eye was evident at the center of circulation.  A tight ring of strong thunderstorms completely surrounded the eye and the strongest winds were occurring in that ring of storms.  Several bands of strong storms were revolving around the eastern and northern sides of the core of Hurricane Aletta.  Storms around the core were generating very strong upper level divergence which was pumping away large quantities of mass from the hurricane.  The removal of mass allowed the pressure to decrease rapidly and a stronger pressure gradient force generated much stronger winds.

Hurricane Aletta has a relatively small circulation.  Winds to hurricane force extended out about 30 miles (50 km) from the center of circulation.  Winds to tropical storm force extended out about 100 miles (160 km) from the center.  The Hurricane Intensity Index (HII) was 28.3.  The Hurricane Size Index (HSI) was 10.8 and the Hurricane Wind Intensity Size Index (HWISI) was 39.1.  Hurricane Aletta is very similar in intensity and size to Hurricane Charley in 2004 when Charley hit southwest Florida.

Hurricane Aletta will remain in a favorable environment of warm water and little vertical wind shear for another 12 to 24 hours.  So, it could strengthen more in the short term.  Aletta will start to move over cooler water during the next day or so.  There will be less energy in the upper ocean to support the intense hurricane.  In addition, a upper level trough to the northwest of Aletta will produce southwesterly winds which will blow toward the top of the circulation.  Increased vertical wind shear will speed up the rate of weakening.  Since the circulation of Hurricane Aletta is relatively small, it could weaken fairly quickly.

Hurricane Aletta is moving around the southwestern part of a ridge over Mexico.  The ridge has been steering Aletta toward the west.  A turn more toward the northwest is expected when Hurricane Aletta nears the western end of the ridge.  On its anticipated track Hurricane Aletta is forecast to move farther away from the west coast of Mexico.

Aletta Strengthens Into a Hurricane

Former Tropical Storm Aletta strengthened into a hurricane on Thursday.  At 5:00 p.m. EDT on Thursday the center of Hurricane Aletta was located at latitude 15.3°N and longitude 110.0°W which put it about 455 miles (730 km) west-southwest of Manzanillo, Mexico.  Aletta was moving toward the west-northwest at 6 m.p.h. (10 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 987 mb.

A circular eye developed at the center of Hurricane Aletta on Thursday afternoon.  The inner ends of several rainbands wrapped part of the way around the eye and a broken ring of thunderstorms surrounded the eye.  The strongest winds were occurring in the broken ring of storms.  Several other bands of showers and thunderstorms were revolving around the core of Hurricane Aletta.  Storm near the core 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 90 miles (150 km) from the center.

Hurricane Aletta will move through an environment favorable for intensification during the next 24 to 36 hours.  Aletta 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.  Hurricane Aletta is likely to strengthen during the next day or two and it could intensify rapidly if the ring of storms completely encircles the eye.

Hurricane Aletta is moving southwest of a ridge over Mexico which is steering the hurricane toward the west-northwest.  Aletta could move a little more toward the northwest when it reaches the western end of the ridge.  On its anticipated track Hurricane Aletta will move farther away from the west coast of Mexico.

Tropical Storm Aletta Forms West of Mexico

Tropical Storm Aletta formed west of Mexico on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Aletta was located at latitude 14.3°N and longitude 108.4°W which put it about 425 miles (680 km) southwest of Manzanillo, Mexico.  Aletta was moving toward the west at 7 m.p.h. (11 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 999 mb.

A distinct low level center of circulation developed within a large area of showers and thunderstorms over the eastern North Pacific Ocean west of Mexico on Wednesday and the National Hurricane Center designated the system as Tropical Storm Aletta.  The circulation of Aletta was still organizing.  Several bands of showers and thunderstorms developed east of the center of circulation.  The bands in the western half of the circulation consisted primarily of showers and low clouds.  Storms near the center of circulation were generating upper level divergence which was pumping mass away from Tropical Storm Aletta.

Tropical Storm Aletta will move through an environment favorable for intensification during the next 48 hours.  Aletta will move over water where the Sea Surface Temperature is near 29°C.  An upper level trough located northwest of Tropical Storm Aletta will produce southwesterly 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.  Aletta will likely strengthen into a hurricane during the next several days.

Tropical Storm Aletta is moving south of a ridge over Mexico.  The ridge is steering Aletta toward the west.  A general motion toward the west-northwest is forecast for the next several days.  On its anticipated track Tropical Storm Aletta will move farther away from the west coast of Mexico.

Tropical Depression 01E Forms Southwest of Baja California

Tropical Depression 01E formed southwest of Baja California on Thursday afternoon.  A distinct low level center of circulation formed inside a larger area of low pressure that was previously designated as Invest 90E.  The National Hurricane Center (NHC) determined that the system possessed sufficient organization and NHC designated it as Tropical Depression 01E.  At 5:00 p.m. EDT on Thursday the center of Tropical Depression 01E was located at latitude 12.4°N and longitude 126.5°W which put it about 1310 miles (2105 km) west-southwest of the southern tip of Baja California.  Tropical Depression 01E was moving toward the west-northwest at 5 m.p.h. (8 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 1007 mb.

Tropical Depression 01E formed in a larger area of low pressure that was moving slowly westward over the Eastern North Pacific Ocean.  More thunderstorms formed near the center of the low pressure system and a distinct low level center became apparent on visible satellite images.  An upper level trough located west of the depression was producing southwesterly winds which are blowing toward the top of the circulation.  Those winds were causing moderate vertical wind shear and the shear was limiting the development of thunderstorms in the western half of the depression.  Most of the stronger thunderstorms were occurring east of the center of circulation.  The bands in the western half of the depression consisted mostly of lower clouds and showers.  Storms east of the center were producing some upper level divergence which was pumping mass away to the east of the depression.

Tropical Depression 01E will move through an environment only marginally favorable for intensification.  It will move over water where the Sea Surface Temperature is near 27°C.  So, there is enough energy in the upper ocean to support intensification.  However, the upper level trough will continue to produce moderate vertical wind shear.  The upper level winds could be strong enough to prevent further intensification.  If the upper level winds slow, then there is a chance the depression could strengthen into a tropical storm during the next day or two.

Tropical Depression 01E is moving south of a subtropical ridge which is steering the depression toward the west-northwest.  The subtropical ridge is forecast to steer the depression in a general westerly direction during the next several days.  On its anticipated track Tropical Depression 01E poses no immediate threat to any land areas.

Tropical Storm Norma Drifts Near Baja California, Otis Rapidly Intensifies to Cat. 2 Hurricane

Tropical Storm Norma drifted near Baja California on Sunday, while Hurricane Otis rapidly strengthened into a Category 2 hurricane on the Saffir-Simpson Scale.  At 8:00 p.m. EDT on Sunday the center of Tropical Storm Norma was located at latitude 21.3°N and longitude 111.2°W which put it about 140 miles (220 km) south-southwest of Cabo San Lucas, Mexico.  Norma was moving toward the northwest at 6 m.p.h. (9 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.

A Tropical Storm Watch was in effect for the portion of the coast from Los Barriles to Todos Santos, Mexico.

Tropical Storm Norma retains some of the structural features that it had when it was a hurricane.  The remnants of a large circular eye form the center of circulation.  A broken ring of strong thunderstorms surrounds the remnants of the eye and the strongest winds are occurring in that ring.  Bands of showers and weaker thunderstorms are revolving around the core of Tropical Storm Norma.  Some of the outer rainbands of Norma are already dropping heavy rain over parts of the southern end of Baja California.

Tropical Storm Norma will move through an environment that will be only marginally favorable for intensification during the next day or so.  Norma will move over water where the Sea Surface Temperature is near 28°C.  An upper level trough west of North America is producing southwesterly winds which are blowing toward the top of the circulation.  Those winds are causing moderate vertical wind shear.  The circulation of Norma may also be drawing some cooler more stable air into the western part of the tropical storm.  Tropical Storm Norma could intensify somewhat during the next 24 hours, but it will eventually move over cooler water and weaken.

A ridge in the middle troposphere located east of Norma is steering the tropical storm toward the northwest and that general motion is expected to continue for another day or so.  When Norma weakens, it will be steered by the winds in the lower levels of the atmosphere.  Those winds will push Tropical Storm Norma more toward the west during the middle of the weak.  On its anticipated track the center of Tropical Storm Norma is forecast to remain west of Baja California.

Hurricane Otis intensified very rapidly on Sunday from a weak tropical storm to a Category 2 hurricane on the Saffir-Simpson Scale.  At 5:00 p.m. EDT on Sunday the center of Hurricane Otis was located at latitude 17.0°N and longitude 127.3°W which put it about 1200 miles (1930 km) west-southwest of the southern tip of Baja California.  Otis was moving toward the north at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 105 m.p.h. (165 km/h) and there were wind gusts to 125 m.p.h. (200 km/h).  The minimum surface pressure was 973 mb.

Hurricane Otis has a very small circulation, which allowed to strengthen very rapidly when the environment became more favorable.  A small eye formed at the center of Hurricane Otis and a tight ring of very strong thunderstorms surrounded the eye.  Those storms began generating upper level divergence which pumped mass away from the center of circulation.  The pressure decreased quickly and the wind speed increased very rapidly.  Hurricane Otis still has a small circulation.  Winds to tropical storm force only extend out about 70 miles (110 km) from the center.

Hurricane Otis may be near its peak intensity.  Otis is still moving over water where the Sea Surface Temperature is near 27°C, but it will soon move over cooler water.  Hurricane Otis will move nearer to the upper level trough west of North America and the hurricane will encounter stronger vertical wind shear.  Because Otis is a small hurricane, it could weaken almost as fast as it intensified.

A small midlevel ridge east of Otis is steering the hurricane toward the north.  Much like Tropical Storm Norma, Otis will be steered by winds lower in the atmosphere when it weakens.  Those winds are forecast to steer Otis more toward the west-southwest later this week.

Tropical Depression 16E Forms, Flood Risk for Mexico

Tropical Depression Sixteen-E formed south of Mexico on Wednesday morning.  At 11:00 a.m. EDT on Wednesday the center of Tropical Depression Sixteen-E was located at latitude 16.2°N and longitude 101.7°W which put it about 105 miles (165 km) south of Zihuatanejo, Mexico.  It was moving toward the north-northeast at 5 m.p.h. (8 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 1006 mb.

A Tropical Storm Watch was issued for the portion of the coast from Zihuatanejo to Punta Maldonado, Mexico.

A distinct center of circulation formed in a cluster of thunderstorms south of Mexico and that National Hurricane Center designated the system as Tropical Depression Sixteen-E on Wednesday morning.  The circulation of the depression was still organizing.  Several bands of showers and thunderstorms were developing south and east of the center of circulation.  There were fewer showers and thunderstorms in the northwestern quadrant of the circulation and the depression may have been pulling in drier air from Mexico.

The depression has 12 to 18 hours to strengthen before it makes landfall on the coast of Mexico.  It will move over water where the Sea Surface Temperature is near 30°C.  An upper level trough extends from the eastern U.S. to Mexico.  The trough is producing westerly winds which are blowing toward the top of the circulation.  Those winds are generating moderate wind vertical shear, which will inhibit intensification.  Tropical Depression Sixteen-E could strengthen into a tropical storm before it reaches the coast of Mexico.

The upper level trough is forecast to steer Tropical Depression Sixteen-E toward the east.  On its anticipated track the depression could make landfall east of Zihuatanejo in less than 24 hours.  The depression will bring gusty winds, but heavy rain poses a greater threat.  Heavy rain falling in steeper terrain could cause flash floods.

Elsewhere over the Eastern North Pacific Ocean, Tropical Depression Fifteen-E was moving farther away from Mexico.  Tropical Depression Fifteen-E formed when momentum from the upper half of the circulation of former Hurricane Katia spun up a new surface circulation over the Eastern North Pacific.  At 11:00 a.m. EDT on Wednesday the center of Tropical Depression Fifteen-E was located at latitude 14.9°N and longitude 120.6°W which put it about 890 miles (1435 km) southwest of the southern tip of Baja California.  It was moving toward the west at 9 m.p.h. (15 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 1004 mb.

Kenneth Rapidly Intensifies Into a Hurricane

One time Tropical Storm Kenneth rapidly intensified into a hurricane on Sunday.  At 5:00 p.m. EDT on Sunday the center of Hurricane Kenneth was located at latitude 16.2°N and longitude 128.4°W which put it about 1290 miles (2075 km) west-southwest of the southern tip of Baja California.  Kenneth was moving toward the west at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 90 m.p.h. (150 km/h) and there were wind gusts to 105 m.p.h. (170 km/h).  The minimum surface pressure was 980 mb.

The structure of Hurricane Kenneth improved significantly during the past few hours.  A small circular eye emerged at the center of circulation.  A ring of strong thunderstorms surrounded the eye and the strongest winds are occurring in this ring of thunderstorms.  Additional bands of showers and thunderstorms intensified south and east of the center.  Thunderstorms near the core of Kenneth were generating strong upper level divergence which was pumping mass away from the hurricane.

Hurricane Kenneth will continue to move through an environment favorable for intensification on Monday.  Kenneth will move over water where the Sea Surface Temperature (SST) is near 28.5°C.  Hurricane Kenneth is moving through a region where the winds in the upper levels are weak and there is not much vertical wind shear.  Hurricane Kenneth could continue to intensify for another 12 to 24 hours.  The speed of the upper level winds could increase in a day or so, and more vertical wind shear would inhibit intensification.  Eventually Hurricane Kenneth will move over cooler SSTs and start to weaken.

Kenneth if moving south of a subtropical ridge which is steering the hurricane toward the west.  The ridge is forecast to continue to steer Kenneth westward for another 12 to 24 hours.  Hurricane Kenneth will turn toward the north when it reaches the western end of the ridge.  On its anticipated track Hurricane Kenneth would pose no direct threat to land.

Tropical Storm Kenneth Develops Southwest of Baja California

Tropical Storm Kenneth developed southwest of Baja California on Friday.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Kenneth was located at latitude 15.0°N and longitude 119.1°W which put it about 810 miles (1305 km) southwest of the southern tip of Baja California.  Kenneth was moving toward the west at 15 m.p.h. (24 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.

A distinct center of circulation developed in a tropical wave southwest of Baja California on Friday.  Thunderstorms began to form near the center and the National Hurricane Center designated the system as Tropical Storm Kenneth, which was the 11th named tropical storm to form over the Eastern North Pacific during 2017.

A cluster of thunderstorms formed near the core of Tropical Storm Kenneth on Friday.  Even after thunderstorms formed near the core, the circulation of Tropical Storm Kenneth was asymmetrical.  Bands of showers and thunderstorms developed in the western half of the circulation.  The bands in the eastern half of the circulation consisted primarily of showers and low clouds.  Thunderstorms near the core of Kenneth were generating upper level divergence which was pumping mass away to the west of the tropical storm.

Tropical Storm Kenneth will move through an environment that will be favorable for intensification during the next several days.  Kenneth will move over water where the Sea Surface Temperature is near 28.5°C.  An upper level ridge to the north of Tropical Storm Kenneth is producing easterly winds which are blowing toward the top of the circulation.  Those winds are producing moderate vertical wind shear which is probably the cause of the asymmetrical circulation of the tropical storm.  Even though there is moderate vertical wind shear, Tropical Storm Kenneth is likely to intensify and it could become a hurricane in a couple of days.

Tropical Storm Kenneth is begin steered toward the west by a subtropical ridge to the north of the tropical storm.  The subtropical ridge will continue to steer Tropical Storm Kenneth toward the west-northwest for another day or two.  When Tropical Storm Kenneth reaches the western end of the subtropical ridge, it will turn more toward the north.

Tropical Storms Hilary and Irwin Interact As They Weaken

Tropical Storms Hilary and Irwin started to interact on Thursday as both storms began to weaken.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Hilary was located at latitude 18.3°N and longitude 117.3°W which put it about 575 miles (925 km) west-southwest of the southern tip of Baja California.  Hilary was moving toward the west-northwest at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were gust to 85 m.p.h. (140 m.p.h.).  The minimum surface pressure was 992 mb.

At 11:00 p.m. EDT on Thursday the center of Tropical Storm Irwin was located at latitude 14.9°N and longitude 124.6°W which put it about 1105 miles (1780 km) west-southwest of the southern tip of Baja California.  Irwin was moving toward the west at 2 m.p.h. (3 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 1000 mb.

Hilary weakened below hurricane intensity on Thursday.  It appeared that the circulation drew in drier more stable air around the northwestern side of the circulation.  The drier air reduced the formation of showers and thunderstorms and the core of the circulation weakened.  At the same time upper level divergence from Tropical Storm Hilary increased the vertical wind shear over Tropical Storm Irwin.  Irwin was over water where the Sea Surface Temperature is near 28.5°C and it was able to extract enough energy from the ocean to maintain most of its intensity.

Tropical Storms Hilary and Irwin will move over water where the Sea Surface Temperature is near 28°C on Friday.  However, the combination of drier, more stable air and vertical wind shear is likely to keep both of the storms from strengthening.  Hilary and Irwin will move over cooler water during the weekend and both tropical storms are likely to weaken when that occurs.

Tropical Storm Hilary is being steering toward the west-northwest by a subtropical high pressure system to the north of the tropical storm.  Hilary is forecast to continue moving toward the west-northwest.  Tropical Storm Hilary is larger than Irwin.  Winds to tropical storm force extend out about 110 miles (180 km) in Tropical Storm Hilary.  Winds to tropical storm force extend out about 70 miles (110 km) in Tropical Storm Irwin.

The centers of the two tropical storms are only about 540 miles (870 km) apart.  When Tropical Storm Hilary passes north of Irwin, Tropical Storm Irwin is forecast to start to revolve around the larger Tropical Storm Hilary.  Irwin is expected to turn toward the north after Tropical Storm Hilary passes by.  Some models are forecasting the that the centers of the two tropical storms will approach each other and the larger Tropical Storm Hilary will eventually absorb Tropical Storm Irwin.