Monthly Archives: June 2018

Tropical Storm Prapiroon Moves Toward Okinawa

Tropical Storm Prapiroon moved closer to Okinawa on Saturday.  At 11:00 a.m. EDT on Saturday the center of Tropical Storm Prapiroon was located at latitude 22.4°N and longitude 128.3°E which put it about 315 miles (510 km) south of Okinawa.  Prapiroon was moving toward the northwest at 8 m.p.h. (13 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 992 mb.

There was a distinct center of circulation in the middle of Tropical Storm Prapiroon, but the distribution of thunderstorms was asymmetrical.  The stronger thunderstorms were occurring in bands south and east of the center of circulation.  The bands north and west of the center consisted primarily of showers and low clouds.  A large upper level ridge over Asia was producing northerly winds which were blowing toward the top of Tropical Storm Prapiroon.  Those winds were causing moderate vertical wind shear and they were probably the reason for the asymmetric distribution of thunderstorms.  Those winds were also blocking upper level divergence to the north and west of Prapiroon.

Tropical Storm Prapiroon will move through an area marginally favorable for intensification during the next 24 to 36 hours.  Prapiroon will move over water where the Sea Surface Temperature is near 29°C.  So, there will be enough energy in the upper ocean to support intensification.  The upper level ridge will continue to cause some vertical wind shear, but Tropical Storm Prapiroon could move into an area where the upper level winds are a little weaker on Sunday.  If the wind shear decreases, then Tropical Storm Prapiroon will intensify.  There is still a chance that Prapiroon could strengthen into a typhoon when it passes near Okinawa.

Tropical Storm Prapiroon is moving around the western end of a subtropical ridge over the Pacific Ocean which is steering the tropical storm toward the northwest.  Prapiroon is forecast to move more toward the north when it reaches the western end of the ridge in 12 to 24 hours.  On its anticipated track the center of Tropical Storm Prapiroon could approach Okinawa in 12 to 18 hours.  The center of Prapiroon will likely pass west of Okinawa which would bring the strongest winds and heaviest rain over Okinawa.

Tropical Storm Prapiroon Forms South-Southeast of Okinawa

A distinct center of circulation formed within an area of thunderstorms south-southeast of Okinawa on Thursday night and the Japan Meteorological Agency designated the system as Tropical Storm Prapiroon.  At 8:00 p.m. EDT on Thursday the center of Tropical Storm Prapiroon was located at latitude 20.0°N and longitude 130.2°E which put it about 500 miles (800 km) south-southeast of Okinawa.  Prapiroon was moving toward the west at 7 m.p.h. (11 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 circulation of Tropical Storm Prapiroon was still organizing.  More thunderstorms were forming close to the center of circulation.  There were more thunderstorms west of the center than there were east of the center.  Several bands of showers and thunderstorms in the outer part of the circulation were revolving around the core of Tropical Storm Prapiroon.  The storms in the core were generating upper level divergence which was pumping mass away from the tropical storm.

Tropical Storm Prapiroon formed beneath an upper level ridge that developed between an upper level low northwest of the Philippines and a much larger upper low east of the Marianas.  The winds in the upper ridge will be weak and there will be little vertical wind shear.  Prapiroon will move over water where the Sea Surface Temperature is near 29°C.  Tropical Storm Prapiroon will move through an environment very favorable for intensification.  Prapiroon will strengthen and it could intensify rapidly once the inner core organizes.  Tropical Storm Prapiroon could strengthen into a typhoon in 24 to 48 hours.

Tropical Storm Prapiroon was moving around the southwestern part of a subtropical ridge which was steering the tropical storm toward the west.  Prapiroon will turn toward the north in 12 to 24 hours when it reaches the western end of the ridge.  On its anticipated track Tropical Storm Prapiroon could approach Okinawa in about 36 hours.  Prapiroon could be a typhoon when it nears Okinawa.

Tropical Storm Emilia Develops South of Baja California

Tropical Storm Emilia developed south of Baja California on Thursday morning.  At 11:00 a.m. EDT on Thursday the center of Tropical Storm Emilia was located at latitude 14.4°N and longitude 112.4°W which put it about 610 miles (980 km) south-southwest of the southern tip of Baja California.  Emilia was moving toward the west-northwest 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 distribution of thunderstorms around Tropical Storm Emilia was asymmetrical.  Most of the showers and thunderstorms were occurring in bands west and north of the center of circulation.  The center was located near the eastern edge of a cluster of thunderstorms.  Bands east of the center consisted of showers and low clouds.  The cluster of storms west of the center of circulation was generating upper level divergence which was pumping mass away to the west and north of the tropical storm.

Tropical Storm Emilia will move through an environment somewhat favorable for intensification during the next day or two.  Emilia will move over water where the Sea Surface Temperature is near 28°C.  An upper level ridge centered near the southern tip of Baja California was producing northeasterly winds which were blowing toward the top of the circulation.  Those winds were causing moderate vertical wind shear and they were probably the reason why most of the thunderstorms were located west and north of the center of circulation.  The vertical shear is likely to limit intensification during the next 24 hours.  The shear is forecast to decrease on Friday and Tropical Storm Emilia could strengthen faster if that occurs.

The portion of the ridge in the middle troposphere was steering Tropical Storm Emilia toward the west-northwest and that general motion is expected to continue for several more days.  On its anticipated track Emilia will move farther away from the west coast of Mexico.

Tropical Storm Daniel Develops Southwest of Baja California

Tropical Storm Daniel developed southwest of Baja California on Sunday after a relatively quiet week in the tropics.  At 11:00 a.m. EDT on Sunday the center of Tropical Storm Daniel was located at latitude 16.0°N and longitude 115.9°W which put it about 615 miles (990 km) southwest of the southern tip of Baja California.  Daniel was moving toward the north 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 1006 mb.

Microwave satellite data indicated that a better organized center of circulation was present inside former Tropical Depression Five-E and the National Hurricane Center designated the system as Tropical Storm Daniel on Sunday morning.  A band of showers and thunderstorms wrapped around the south and east sides of a small tight center of circulation.  Several bands of showers and thunderstorms were revolving around the center.  Bands northwest of the center of circulation consisted primarily of showers and lower clouds.  Storms near the center began to generate upper level divergence which pumped mass away from the tropical storm.

Tropical Storm Daniel will move through an environment favorable for intensification for about another 24 hours.  Daniel is moving over water where the Sea Surface Temperature is near 27°C.  Tropical Storm Daniel will move over cooler water in about a day or so.  There is an upper level low northwest of Daniel.  The low is generating southerly winds which are blowing toward the top of the tropical storm.  Those winds are causing moderate vertical wind shear, but the shear will not be strong enough to prevent intensification.  Tropical Storm Daniel could intensify a little more during the next 24 hours, but Daniel is likely to weaken when it moves over cooler water.

The upper low northwest of Tropical Storm Daniel was steering the tropical storm toward the north.  The upper low is moving toward the west.  Tropical Storm Daniel if forecast to turn more toward the northwest on Monday as it moves around the western side of the upper low.  When Daniel moves over cooler water the clouds will not grow as tall and the tropical storm will be steered by the winds lower in the atmosphere.  The subtropical high over the Pacific Ocean is forecast to steer Daniel more toward the west later next week after the tropical storm weakens.

Stronger Tropical Storm Carlotta Nears Acapulco

A stronger Tropical Storm Carlotta moved near Acapulco, Mexico on Saturday night.  At 11:00 p.m. EDT the center of Tropical Storm Carlotta was located at latitude 16.6°N and longitude 99.9°W which put it 20 miles (35 km) south of Acapulco.  Carlotta was moving toward the northwest at 6 m.p.h. (10 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 997 mb.  A Tropical Storm Warning was in effect for the portion of the coast from Punta Maldonado to Tecpan de Galeana.

The center of Tropical Storm Carlotta remained over water on Saturday and the circulation strengthened.  A small eye formed 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 the circulation.  Storms in the core were generating upper level divergence which pumped mass away from the tropical storm.

The future intensity of Tropical Storm Carlotta will depend on whether or not the center remains over water.  The Sea Surface Temperature of the water south of Mexico is near 30°C.  Carlotta will move through an area where the upper level winds are weak.  If the center of Carlotta remains over water, then it could intensify more on Sunday.  However, if the center moves inland, then Tropical Storm Carlotta will weaken quickly when the circulation is disrupted by the Sierra Madre del Sur mountains.

Tropical Storm Carlotta moved near the western end of a ridge over Mexico.  The ridge steered Carlotta slowly toward the northwest on Saturday and that general motion is forecast to continue on Sunday.  On its forecast track the center of Tropical Storm Carlotta will move almost parallel to the coast of Mexico west of Acapulco.  A small deviation to the left of the anticipated track will keep the center over water.  A small deviation to the right of the anticipated track will bring Tropical Storm Carlotta inland.  Carlotta will cause gusty winds near the coast.  Heavy rain will fall north of the center and over the south slopes of the Sierra Madre del Sur Mountains.  Flash floods are likely because of the slow movement of Tropical Storm Carlotta.

Tropical Storm Gaemi Brings Wind and Rain to Okinawa

Tropical Storm Gaemi brought wind and rain to Okinawa late on Friday.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Gaemi was located at latitude 26.7°N and longitude 127.9°E which put it near Okinawa.  Gaemi was moving toward the east-northeast at 19 m.p.h (30 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 990 mb.

Tropical Storm Gaemi became better organized after it moved across southern Taiwan early on Friday.  The center of circulation was more evident on microwave satellite images.  A primary band of showers and thunderstorms formed in the eastern side of circulation.  Other showers and thunderstorms were located farther to the northeast of the center of Tropical Storm Gaemi.  An upper level trough west of Gaemi was producing string southwesterly winds which were blowing toward the top of the tropical storm.  Those winds were causing moderate vertical wind shear and they were likely the reason why most of the heavier rain was occurring northeast of the center of circulation.

The upper level trough was also steering Tropical Storm Gaemi quickly toward the east-northeast.  On its anticipated track Gaemi will move over the middle Ryukyu Islands including Amami-O-Shima during the next 12 hours.  Tropical Storm Gaemi will continue to produce gusty winds and locally heavy rain.  Most of the rain will fall before the center of circulation reaches a location.  Gaemi is likely to make a transition to an extratropical cyclone when it moves south of the larger islands of Japan during the weekend.

TD 4E Strengthens to Tropical Storm Carlotta

Tropical Depression Four-E strengthened to Tropical Storm Carlotta south of Mexico on Friday afternoon.  At 2:00 p.m. EDT on Friday the center of Tropical Storm Carlotta was located at latitude 16.0°N and longitude 99.4°W which put it about 60 miles (95 km) south-southeast of Acapulco, Mexico.  Carlotta was moving toward the northeast at 5 m.p.h. (8 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.  A Tropical Storm Warning was in effect for the portion of the coast from Tecpan de Galeana to Lagunas de Chacahua, Mexico.

A single, distinct center of circulation developed in Tropical Depression Four-E on Friday afternoon and the National Hurricane Center designated the system as Tropical Storm Carlotta.  It is possible that the mountains in Mexico deflected the circulation in the lower levels and contributed to the improved organization of Tropical Storm Carlotta.  Stronger thunderstorms were forming near the center of circulation.  A primary band of showers and thunderstorms developed east and south of the core of Carlotta.  Other rainbands were revolving around the core of the tropical storm.  Storms in the core were generating upper level divergence and Carlotta looked like a tropical storm on satellite images.

Tropical Storm Carlotta will remain in an environment favorable for intensification while the center is over water.  The Sea Surface Temperature of the water south of Mexico is near 30°C.  The upper level winds are weak in that area and there is little vertical wind shear.  Carlotta could strengthen further during the next 12 hours.  When the center nears the coast of Mexico, the circulation could begin to pull in drier air from over the land.  If that happens, then Tropical Storm Carlotta could start to weaken even before the center officially makes landfall.

The steering winds are weak around Tropical Storm Carlotta.  A trough in the lower levels is moving across the southwestern Gulf of Mexico and it appears to be pulling Carlotta slowly toward the northeast.  On its anticipated track the center of Tropical Storm Carlotta will reach the coast of Mexico in 12 to 18 hours.  Tropical Storm Carlotta is expected to make landfall east of Acapulco.  Carlotta will produce some gusty winds but the greater risks are heavy rain and flash floods.

Elsewhere, Tropical Depression Bud is moving over the Gulf of California.  At 11:00 a.m. EDT on Friday the center of Tropical Depression Bud was located at latitude 25.3°N and longitude 110.0°W which put it about 70 miles (110 km) west of Los Mochis, Mexico.  Bud was moving toward the north at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 1002 mb.  Bud could drop heavy rain and cause flash floods in the states of Sinaloa, Sonora and Chihuahua.

Tropical Storm Gaemi Forms Near Southwest Taiwan

Tropical Storm Gaemi formed near Kaohsiung on the southwest coast of Taiwan late on Thursday.  At 8:00 p.m. EDT on Thursday the center of Tropical Storm Gaemi was located at latitude 22.8°N and longitude 120.2°E which put it near Kaohsiung, Taiwan.  Gaemi was moving toward the northeast at 5 m.p.h. (8 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 992 mb.

A distinct low level center of circulation developed in an area of showers and thunderstorms southwest of Taiwan on Thursday and the Japan Meteorological Agency designated the system as Tropical Storm Gaemi.  Thunderstorms developed near the core of the circulation.  Several short bands of showers and thunderstorms were revolving around the core.  Mountains in eastern Taiwan may have deflected the flow in the lower levels and contributed to the organization of a center of circulation.  Storms around the center were generating some upper level divergence which was pumping mass away to the east of the tropical storm.

Tropical Storm Gaemi is likely to weaken during the next few hours while the center of circulation moves across southern Taiwan.  Mountains in eastern Taiwan could disrupt the lower portions of the circulation when it moves over them.  If the circulation still exists when it moves east of Taiwan in a few hours, then Tropical Storm Gaemi will move into a more favorable environment for intensification.  Gaemi will move over water where the Sea Surface Temperature is near 29°C.  An upper level trough over eastern Asia is producing southwesterly winds which are blowing toward the top of the circulation.  Those winds will cause some vertical wind shear, but the shear will probably not be strong enough to tear the circulation apart.  Gaemi could remain a tropical storm for another 24 to 36 hours.  When Tropical Storm Gaemi moves farther north in a day or two, it will move over colder water and into an area with stronger vertical wind shear.  Gaemi will likely make a transition to an extratropical cyclone at that time.

The upper level trough is forecast to steer Tropical Storm Gaemi toward the northeast.  Gaemi will move across southern Taiwan during the next few hours.  It will cause gusty winds, but the greater risks will be heavy rain and flash floods.  On its anticipated track Tropical Storm Gaemi will move near the southern Ryukyu Islands of Japan.  It could pass near Ishigaki Jima and Miyako Jima in the next 12 to 18 hours.  Gaemi could be near Okinawa later on Friday.

Tropical Storm Bud Brings Wind & Rain to Baja California, New Depression Forms South of Acapulco

Tropical Storm Bud brought wind and rain to the southern part of Baja Calfornia on Tuesday while a new tropical depression formed south of Acapulco, Mexico.  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Bud was located at latitude 22.2°N and longitude 109.8°W which put it about 50 miles (80 km) south of Cabo San Lucas, Mexico.  Bud was moving toward the north-northwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 1000 mb.

A Tropical Storm Warning remained in effect for the portion of the coast from Santa Fe to La Paz, Mexico including Cabo San Lucas.  The government of Mexico issued new Tropical Storm Watches for the portions of the coast from La Paz to San Evaristo and from Altata to Huatabampito, Mexico.

Rainbands on the northern side of the circulation of Tropical Storm Bud were producing winds to tropical storm force over the southern end of Baja California.  New thunderstorms began to form when a band north and east of the center of circulation moved over the southern part of the Gulf of California.  The Sea Surface Temperature of the water in the Gulf is near 27°C which is warmer than the water of the Eastern North Pacific Ocean south of Baja California.  The additional energy from the ocean may have contributed to the formation of the new storms.

A trough in the upper levels is forecast to steer Tropical Storm Bud toward the north-northeast during the next several days,  Bud could maintain its intensity for another 24 hours if the center of circulation passes southeast of Baja California.  If the center passes over Baja, the mountains would disrupt the circulation in the lower levels and Tropical Storm Bud would weaken.  In either case Tropical Storm Bud will bring gusty winds and heavy rain to the southern end of Baja California for another day or so.  Bud will bring gusty winds and heavy rain to the west coast of Mexico later on Friday.  Heavy rain could cause flash flooding in some locations.

Tropical Depression Four-E formed south of Acapulco on Thursday afternoon.  At 5:00 p.m. EDT on Thursday the center of Tropical Depression Four-E was located at latitude 15.5°N and longitude 100.1°W which put it about 100 miles (155 km) south of Acapulco, Mexico.  It was moving toward the northwest at 6 m.p.h. (10 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 1008 mb.  Because of the proximity to the coast the government of Mexico issued a Tropical Storm Watch for the portion of the coast from Tecpan de Galeana to Punta Maldonado.

A center of circulation developed in a cluster of thunderstorms south of Mexico and the National Hurricane Center designated the system as Tropical Depression Four-E.  The circulation was still organizing.  Several fragmented bands of showers and thunderstorms formed in the outer portions of the circulation.  The center of circulation was broad and there were several smaller cyclonic rotations swirling around inside the broader center.

Tropical Depression Four-E will move through an environment that will be favorable for intensification.  It will move over water where the Sea Surface Temperature is near 30°C.  The upper level winds will be weak and there will be little vertical wind shear.  The proximity to the coast will be the primary factor inhibiting intensification.  The circulation could pull in drier air from Mexico.  Tropical Depression Four-E is expected to strengthen into a tropical storm on Friday.

Tropical Depression Four-E will move around the western end of a subtropical ridge, but the steering currents are likely to be weak.  The depression is expected to move slowly toward the north-northwest during the next day or two.  On its anticipated track the center of the depression could move near the coast during the weekend.  It could bring gusty winds and locally heavy rain.  The rain could cause flash floods.

Hurricane Bud Weakens, Watch Issued for Baja California

Hurricane Bud weakened significantly on Tuesday, but it prompted the issuance of a Tropical Storm Watch for the southern portion of Baja California.  At 11:00 p.m. EDT on Tuesday the center of Hurricane Bud was located at latitude 18.7°N and longitude 108.6°W which put it about 300 miles (485 km) south-southeast of Cabo San Lucas, Mexico.  Bud was moving toward the north-northwest at 3 m.p.h. (5 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 973 mb.  The government of Mexico issued a Tropical Storm Watch for the portion of the coast from Santa Fe to La Paz, Mexico including Cabo San Lucas.

Hurricane Bud weakened to a Category 1 hurricane on the Saffir-Simpson Scale on Tuesday.  The center of Hurricane Bud was over water where the Sea Surface Temperature was near 27°C, but much of the northern half of the circulation was over cooler water.  The slow movement of Bud may have also allowed the winds to mix cooler water to the surface.  Thunderstorms were not as tall and the bands in the northern half of the circulation consisted primarily of showers and low clouds.  The stronger thunderstorms were occurring mainly south and east of the center of Hurricane Bud.

Hurricane Bud is forecast to spin down slowly during the next several days.  Cooler water at the surface of the ocean is not likely to supply sufficient energy to maintain the circulation.  The upper level winds are weak and there is little vertical wind shear, but the lack of shear will be less important than effects of the cooler water.  The lack of stronger thunderstorms in the northern half of the circulation will limit the downdrafts that could transport stronger winds to the surface.  Hurricane Bud could weaken to a tropical storm on Wednesday if new thunderstorms do not form in the core of the circulation.

A ridge in the middle troposphere over the southwestern U.S. almost blocked the forward motion of Hurricane Bud on Tuesday.  Bud moved slowly toward the north-northwest.  A slow motion toward the north-northwest is forecast to continue for another 24 to 36 hours.  After that time a trough over the Pacific Ocean is forecast to push the ridge eastward.  When the trough approaches, stronger southerly winds will steer Bud northward more quickly.  On its anticipated track Bud is forecast to approach the southern tip of Baja California in 36 to 48 hours.

Hurricane Bud is likely to be a tropical storm when it nears Baja California.  Bud will bring gusty winds, but the bigger risk will be locally heavy rain.  Heavy rain falling on steep terrain could cause flash floods.  Bud or its remnants could also bring rain to parts of the southwestern U.S.