Tropical Storm Tina Forms West of Manzanillo

More thunderstorms formed near the center of a low pressure system west of Mexico on Sunday and the National Hurricane Center classified the system as Tropical Storm Tina.  At 10:00 p.m. EDT on Sunday the center of Tropical Storm Tina was located at latitude 18.5°N and longitude 107.1°W which put it about 185 miles (300 km) west of Manzanillo, Mexico.  Tina was moving toward the north at 3 m.p.h. (5 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 of Tropical Storm Tina is not well organized.  Although there is a definite center of circulation in the lower levels, most of the thunderstorms are developing north and east of the center of circulation.  An upper level trough southwest of California is generating southwesterly winds which are blowing across the top of Tropical Storm Tina.  The strong vertical wind shear is tilting the circulation and it is causing the thunderstorms to be concentrated in the northeastern quadrant of the circulation.  The upper level winds are also inhibiting upper level divergence.

Although Tropical Storm Tina is moving over water where the Sea Surface Temperature is near 30°C, the atmospheric environment is unfavorable for intensification.  The strong vertical wind shear will prevent any significant intensification.  In fact, if the upper level winds get much stronger, the shear could blow the top half of the circulation northeast of the bottom half.  In that case the low level circulation will quickly spin down and dissipate.

If the vertical integrity of the circulation is maintained, then the upper level trough will steer Tropical Storm Tina toward the northeast and into Mexico.  However, if the circulation shears apart, a surface high pressure system could steer it slowly toward the west.  In either case the upper level winds could transport some moist air over Jalisco and Colima, where it could enhance rainfall.

Tropical Storm Ma-On Forms East of the Northern Marianas

Tropical Depression 27W intensified into Tropical Storm Ma-On east of the Northern Marianas on Thursday.  At 10:00 a.m. EDT on Thursday the center of Tropical Storm Ma-On was located at latitude 17.7°N and longitude 153.7°E which put it about 405 miles (655 km) south-southeast of Minami Tori Shima.  Ma-On 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 1003 mb.

More thunderstorms developed near the center of a system originally designated Tropical Depression 27W and the Japan Meteorological Agency named it Tropical Storm Ma-On on Thursday.  Although many of the thunderstorms are still developing east of the center of circulation, a few stronger thunderstorms are forming around the center.  The thunderstorms around the center are beginning to generate upper level divergence which is pumping out mass.  Some additional rainbands appear to be forming in the eastern half of the circulation.

Tropical Storm Ma-On is moving through an environment that is favorable for intensification.  Ma-On is moving over water where the Sea Surface Temperature is near 30°C.  Ma-On is moving under the western end of an upper level ridge.  The upper level winds in that part of the ridge are not too strong and the ridge may be enhancing upper level divergence.  Tropical Storm Ma-On could intensify during the next day or so.  When Ma-On gets farther west, it will approach an upper level trough moving off of Asia.  There are stronger southwesterly winds on the eastern side of the trough and the vertical wind shear will increase at that time.

Tropical Storm Ma-On is moving along the southwestern end of a subtropical high pressure system.  The subtropical high is expected to steer Ma-On in a general west-northwesterly direction during the next two or three days.  On its anticipated track Tropical Storm Ma-On could approach the northernmost Marianas in about 36 hours.  It could bring gusty winds and locally heavy rain.

Typhoon Meari Passing Northwest of the Marianas

Typhoon Meari moved northwest of the Marianas on Saturday.  At 11:00 p.m. EDT on Saturday the center of Typhoon Meari was located at latitude 20.2°N and longitude 143.2°E which put it about 240 miles (390 km) west-northwest of Agrihan.  Meari was moving toward the northeast at 13 m.p.h. (21 km/h).  The maximum sustained wind speed was 105 m.p.h. (170 km/h) and there were wind gusts to 125 m.p.h. (205 km/h).  The minimum surface pressure was 963 mb.

Typhoon Meari strengthened on Saturday.  An eye appeared on visible satellite imagery.  The eyewall is thicker on the southwestern side and thinner on the northeastern side.  There are also more rainbands in the southwestern part of the circulation.  Winds to typhoon force extend out about 70 miles (110 km) from the center of circulation.  Thunderstorms around the core of Typhoon Meari are generating upper level divergence which is pumping out mass.

Typhoon Meari will be moving through a favorable environment for another 12 to 24 hours.  Meari is moving over water where the Sea Surface Temperature is near 30°C.  The typhoon is moving along the transition zone between an upper level trough to its west and an upper level ridge to its east.  There are southwesterly winds blowing across the western side of Typhoon Meari, but those winds are actually enhancing the upper level divergence.  Vertical wind shear will increase when the upper level trough moves closer to the typhoon and Meari will start to weaken early next week.

The upper level trough is steering Typhoon Meari toward the northeast and that general motion is expected to continue for the next several days.  On its anticipated track the center of Typhoon Meari will pass northwest of the northernmost Marianas.  Meari will pass southeast of Iwo To as it moves toward the northern Pacific.

Tropical Storm Meari Intensifies Into a Typhoon

A well organized core developed at the center of Tropical Storm Meari on Friday and it intensified into a typhoon.  At 5:00 p.m. EDT on Friday the center of Typhoon Meari was located at latitude 17.0°N and longitude 140.0°E which put it about 425 miles (685 km) west-northwest of Saipan.  Meari was moving toward the north-northeast 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. (145 km/h).  The minimum surface pressure was 979 mb.

A strong center of circulation finally developed within a broader area of low pressure that contained Tropical Storm Meari.  An inner rainband wrapped around the center and an eye appeared on microwave satellite imagery.  The formation of a tight inner core allowed Meari to strengthen into a typhoon.  There are some rainbands east of the center of Typhoon Meari, but most of the stronger thunderstorms are occurring in bands south and west of the center.  Thunderstorms in the core of Typhoon Meari are now generating upper level divergence which is pumping out mass.  Typhoon Meari is now a well organized tropical cyclone.

Typhoon Meari is moving through an environment that is favorable for intensification.  It is moving over water where the Sea Surface Temperature is near 30°C.  An upper level ridge is over Meari which is resulting in light winds in the upper levels and little vertical wind shear.  In fact the upper level ridge is enhancing the divergence generated by the typhoon.  Typhoon Meari should continue to strengthen during the next 24 hours.  Since a well formed core now exists at the center, a period of rapid intensification is quite possible.

Typhoon Meari is moving around the western end of a subtropical ridge which is steering it toward the north-northeast.  That general motion is expected to continue for another day or so.  When Typhoon Meari gets farther north, westerly winds from the middle latitudes will push it toward the northeast more quickly.  On its anticipated track, Typhoon Meari could be near the northernmost Marianas in about 36 hours.  Meari could be a strong typhoon at that time.  Although no warnings are currently in effect, people on Alamagan, Pagan and Agrihan need to monitor the movement of Typhoon Meari.

Tropical Storm Meari Reorganizes West of Guam

The circulation designated as Tropical Storm Meari reorganized west of Guam on Thursday.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Meari was located at latitude 15.0°N and longitude 139.0°E which put it about 415 miles (670 km) west of Guam.  Meari was moving toward the north-northeast at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 990 mb.

Tropical Storm Meari initially formed as a smaller counterclockwise circulation within a much broader cyclonic circulation that stretched from the Northern Mariana Islands toward the Philippines.  The initial surface center weakened on Thursday and a new center of circulation organized northeast of the original center.  A primary rainband began to wrap around the southern and east side of the low level center.  Numerous other bands of showers and thunderstorms were forming within the broader cyclonic circulation.  More bands of showers and thunderstorms were developing southwest of the new center and fewer bands were northeast of the center.  The new center of circulation is still consolidating and Tropical Storm Meari still does not have a well developed core.

Although Meari is still not well organized, the tropical storm is moving through an environment that is favorable for intensification.  Tropical Storm Meari is moving over water where the Sea Surface Temperature is near 30°C.  An upper level ridge is located over Tropical Storm Meari and the upper level winds are weak.  So, there is little vertical wind shear.  Warm water and little shear should allow Tropical Storm Meari to continue to intensify.  The lack of a well formed inner core and the large broad cyclonic circulation will slow the rate of strengthening.

The reformation of the center of circulation farther toward the northeast caused the forecast track guidance from numerical models to shift to a more northeasterly track.  If the current center of Tropical Storm Meari persists, it is located near the western end of a subtropical ridge.  Meari is expected to move toward the northeast around the western end of the ridge.  When Meari moves farther north, westerly winds in the middle latitudes will accelerate the tropical storm toward the northeast.

Tropical Storm Meari Forms East of the Philippines

Tropical Storm Meari formed east of the Philippines on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Meari was located at latitude 13.0°N and longitude 136.4°E which put it about 1045 miles (1685 km) east of Manila, Philippines.  Meari was moving toward the west at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 996 mb.

A distinct center of circulation began to consolidate inside a broad area of low pressure located between Guam and the Philippines on Wednesday.  The center acquired enough characteristics of a tropical cyclone to be classified as Tropical Storm Meari by the Japan Meteorological Agency.  The low level center is still consolidating, but multiple spiral rainbands are forming.  More thunderstorms are forming south and west of the center and there are fewer storms north and east of center.

Tropical Storm Meari formed in an environment that is favorable for further intensification.  It is moving over water where the Sea Surface Temperature is near 30°C.  Meari is organizing beneath an upper level ridge which is an area of weaker winds.  There is little vertical wind shear and the upper level ridge is providing some upper level divergence.  Meari is likely to strengthen slowly while the core of the circulation organizes, but it could intensify more quickly once a well formed center exists.  Tropical Storm Meari could eventually strengthen into a typhoon.

A subtropical ridge located north of Meari is slowly steering the tropical storm toward the west.  That general motion is expected to continue during the next few days.  On its anticipated track Tropical Storm Meari will move gradually closer to the Philippines.

Seymour Strengthens Into a Cat. 4 Hurricane

Hurricane Seymour strengthened into a small but very powerful Category 4 hurricane on the Saffir-Simpson Scale on Tuesday.  At 11:00 p.m. EDT on Tuesday the center of Hurricane Seymour was located at latitude 16.1°N and longitude 117.7°W which put it about 690 miles (1110 km) southwest of the southern tip of Baja California.   Seymour was moving toward the west-northwest at 15 m.p.h.  The maximum sustained wind speed was 150 m.p.h. (240 km/h) and there were wind gusts to 175 m.p.h. (280 km/h).  The minimum surface pressure was 943 mb.

The circulation of Hurricane Seymour is very small, but it is very well organized.  There is a circular eye with a diameter of 10 miles (12 km) which is surrounded by a ring of strong thunderstorms.  Winds to hurricane force only extend out about 18 miles (29 km) from the center of circulation.  Winds to tropical storm force extend out about 80 miles (130 km) from the center.  The Hurricane Intensity Index (HII) is 31.6, but the Hurricane Size Index (HSI) is only 7.1.  The Hurricane Wind Intensity Size Index is 38.7.  Hurricane Seymour is not as strong as Hurricane Patricia was in 2015 and Seymour is smaller than Patricia was.  When Hurricane Patricia had maximum sustained winds of 200 m.p.h. (320 km) its HSI ranged between 11.3 and 13.8.

Hurricane Seymour will remain in a very favorable environment for another 6 to 12 hours.  It will move over water where the Sea Surface Temperature (SST) is near 28°C.  The upper level winds will be light and there will be little vertical wind shear.  Later on Wednesday the upper level winds will increase and Hurricane Seymour will begin to move over cooler SSTs.  The increasingly unfavorable environment will cause Seymour to weaken.  Because of the small size of Seymour’s circulation, wind shear could cause the hurricane to weaken quickly.

Hurricane Seymour is moving around the western end of a ridge that is steering the hurricane toward the west-northwest.  When Seymour reaches the western end of the ridge, the hurricane will begin to move more toward the north.  On its anticipated track Hurricane Seymour will weaken well to the west of Baja California.  An upper level trough moving over the Northern Pacific Ocean could eventually transport some of the moisture from Hurricane Seymour over the western U.S.

Tropical Cyclone Kyant Forms Over Bay of Bengal

Tropical Cyclone Kyant formed over the Bay of Bengal on Tuesday.  At 11:00 a.m. EDT on Tuesday the center of Tropical Cyclone Kyant was located at latitude 16.6°N and longitude 90.4°E which put it about 480 miles (770 km) east of Vishakhapatnam, India.  Kyant 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 994 mb.

A cluster of thunderstorms persisted over the eastern Bay of Bengal during the past few days, but strong upper level easterly winds prevented the development of the system.  The upper level winds began to diminish on Monday and a low level circulation center began to develop on the eastern edge of the area of thunderstorms.  When the upper level winds became weaker, then thunderstorms were able to develop closer to the center of circulation.  The system acquired the structural characteristics associated with a tropical cyclone and the India Meteorological Department named it Kyant.

The circulation of Tropical Cyclone Kyant is still organizing.  Some vertical wind shear continues because of easterly upper level winds being generated by a ridge northeast of the tropical cyclone.  The shear is causing more of the thunderstorms to form in the western half of the circulation.  However, additional thunderstorms have developed closer to the center in recent hours and some spiral rainbands have formed.  The thunderstorms near the center are generating upper level divergence which is starting to pump out mass in all directions.

Tropical Cyclone Kyant will be moving through a favorable environment during the next several days.  It will move over water where the Sea Surface Temperature is near 30°C.  The upper level winds should remain weaker, and the vertical wind shear will not be strong enough to prevent strengthening.  Tropical Cyclone Kyant is likely to intensify and it could undergo a period of rapid intensification.

The upper level ridge is steering Tropical Cyclone Kyant toward the west and that general motion is expected to continue.  On its anticipated track Tropical Cyclone Kyant could approach the east coast of India in about 48 hours.  It could bring strong winds and very heavy rain to portions of eastern India later this week.

Seymour Rapidly Intensifies into a Cat. 2 Hurricane

Tropical Storm Seymour rapidly intensified into a Category 2 hurricane on the Saffir-Simpson Scale on Monday as it moved farther away from Mexico.  At 11:00 p.m. EDT on Monday the center of Hurricane Seymour was located at latitude 15.5°N and longitude 112.6°W which put it about 540 miles (870 km) south-southwest of the southern tip of Baja California.  Seymour was moving toward the west at 16 m.p.h. (26 km/h).  The maximum sustained wind speed was 105 m.p.h. (165 km/h) and there wind gusts to 125 m.p.h. (200 km/h).  The minimum surface pressure was 976 mb.

Hurricane Seymour intensified very rapidly on Monday.  The maximum sustained wind speed increased from 50 m.p.h. (80 km/h) to 105 m.p.h. (165 km/h) in a 24 hour period.  The circulation contracted and the primary rainband wrapped tightly around a small eye.  Seymour is a very small hurricane and hurricane force winds only extend out about 12 miles (19 km) from the center of circulation.  Winds to tropical storm force only extend out about 70 miles (130 km) from the center.  Although Seymour is a small hurricane, the circulation is well organized.  The small eye is surrounded by an almost continuous ring of thunderstorms.  Several other spiral bands are rotating around the core of Hurricane Seymour.  Thunderstorms in the core are generating upper level divergence which is pumping out mass in all directions.

Hurricane Seymour will remain in a favorable environment on Tuesday.  It is moving over water where the Sea Surface Temperature is near 30°C.  The upper level winds are light and there is little vertical wind shear.  Hurricane Seymour is likely to intensify on Tuesday and it could become a major hurricane.  When Seymour moves farther to the west, it will be nearer to an upper level trough which will produce southwesterly winds over the hurricane.  Increased vertical wind shear will begin to weaken Hurricane Seymour.

A ridge over Mexico is steering Hurricane Seymour toward the west and that general motion will occur for another 24 to 36 hours.  Hurricane Seymour will approach the western end of the ridge on Wednesday, and the hurricane will turn more toward the north when that happens.  On its anticipated track this turn will occur well to the west of Baja California.

Tropical Storm Seymour Develops Quickly West of Mexico

Tropical Storm Seymour developed quickly west of Mexico on Sunday and it brought to an end a stretch of three quiet weeks over the Eastern North Pacific Ocean.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Seymour was located at latitude 14.4°N and longitude 107.1°W which put it about 370 miles (590 km) south-southwest of Manzanillo, Mexico.  Seymour was moving toward the west-northwest at 15 m.p.h. (24 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 1002 mb.

The circulation in a cluster of thunderstorms organized quickly on Sunday afternoon.  A primary rainband around the northern and western sides of the circulation wrapped almost entirely around the center and an eye appeared to be forming on microwave satellite images.  Additional bands of thunderstorms were developing.  Thunderstorms in the core of Seymour were beginning to generate upper level divergence.

Tropical Storm Seymour will be moving through a very favorable environment.  It is moving over water where the Sea Surface Temperature is near 31°C.  The upper level winds are relatively weak and there is little vertical wind shear.  Tropical Storm Seymour will continue to intensify and it could intensify rapidly.  Seymour will become a hurricane and it could become a major hurricane.

A ridge over Mexico is steering Tropical Storm Seymour toward the west-northwest and that general motion is expected to continue for several more days.  When Seymour reaches the western end of the ridge, it will turn toward the north.  On its anticipated track Tropical Storm Seymour will make the northward turn well to the southwest of Baja California.