Monthly Archives: November 2016

Possible Tropical Development Over the Southwest Caribbean Sea

A weak trough of low pressure over the Southwestern Caribbean Sea has the potential to develop into a tropical cyclone during the next few days.  The National Hurricane Center is stating that there is a 70% probability of the formation of a tropical cyclone during the next five days.  A broad trough of low pressure stretches from near Panama to east of Nicaragua.  There is not a well defined center of low pressure within the broader trough.  There were more thunderstorms earlier today, but many of them weakened on Monday evening.  A few more thunderstorms developed north of Panama during the past several hours.

The environment over the southwestern Caribbean Sea is favorable for intensification.  The Sea Surface Temperature of water in that part of the Caribbean Sea is around 29°C.  There is an upper level ridge over the area.  The winds are weaker in the center of the ridge and there is little vertical wind shear in that part of the atmosphere.  The ridge providing a source of upper level divergence which is allowing the surface pressure to decrease slowly.

Several numerical models are suggesting that a tropical cyclone could develop during the next few days.  The models do differ on exactly when and where the tropical cyclone could form.  The probability of development will be higher if the area of lower pressure remains over the water.  However, if the trough of low pressure drifts closer to the coast of Nicaragua, then the interaction of the circulation with land could inhibit the formation of a tropical cyclone.  Even if a tropical cyclone does not form, the trough could produce locally heavy rain over parts of Panama, Nicaragua and Honduras.

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.