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Tropical Storm Merbok Moves Closer to China

Tropical Depression 04W intensified into Tropical Storm Merbok on Sunday as it moved closer to the coast of China.  At 5:00 p.m. EDT on Sunday the center of Tropical Storm Merbok was located at latitude 19.9°N and longitude 115.7°E which put it about 220 miles (360 km) south-southeast of Hong Kong.  Merbok was moving toward the north-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 999 mb.

The structure of Tropical Storm Merbok is asymmetrical.  Most of the thunderstorms are occurring east and south of the center of circulation.  A primary rainband curves about halfway around the southeastern side of the center.  Additional bands of showers and thunderstorms exist outside the core in southeastern half of Merbok.  There are bands in the northwestern half of the circulation but they consists primarily of low clouds and showers.  The thunderstorms in the primary rainband are producing upper level divergence which is pumping out mass to the south of Tropical Storm Merbok.

Tropical Storm Merbok is moving through an environment that is marginally favorable for intensification.  It is moving over water where the Sea Surface Temperature is near 29°C.  Merbok is moving under the eastern end of an upper level ridge which is producing northerly winds which are blowing toward the top of the tropical storm.  Those northerly winds are creating moderate vertical wind shear, but they are also enhancing the upper level divergence to the south of Merbok.  Tropical Storm Merbok appears to be pulling some drier air from China into the northwestern part of the circulation.  The combination of moderate vertical wind shear and drier air could be the reason for the asymmetrical distribution of thunderstorms.

Tropical Storm Merbok has a chance to intensify a little more before it makes landfall.  The effects of the moderate vertical wind shear and drier air should limit any intensification and Merbok is likely to remain a tropical storm until it makes landfall.

Merbok is moving around the western end of a subtropical ridge which is steering the tropical storm toward the north-northwest.  That general motion is expected to continue for another day or so.  On its anticipated track the center of Tropical Storm Merbok will reach the coast of China between Hong Kong and Shantou in 12 to 18 hours.  Tropical Storm Merbok will bring gust winds and locally heavy rain.  When Merbok moves inland over eastern China, it will reach the westerly winds in the middle latitudes and those winds will turn the tropical storm toward the east.

Tropical Depression 04W Forms West of Luzon

Tropical Depression 04W formed west of Luzon on Saturday.  At 11:00 p.m. EDT on Saturday the center of Tropical Depression 04W was located at latitude 16.6°N and longitude 116.8°E which put it about 430 miles (690 km) south-southeast of Hong Kong.  The depression was moving toward the northwest at 10 m.p.h. (16 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.

An area of thunderstorms moved west-northwestward across the Philippines and a circulation slowly consolidated around a distinct center.  The center of circulation became well enough defined on Saturday to cause the system to be classified as Tropical Depression 04W.  The inner core of the depression is still organizing.  A band of thunderstorms wrapped around the western and southern sides of the center of circulation.  Additional bands of showers and thunderstorms developed in other parts of the depression.  The area of showers and thunderstorms southwest of the center began to generate upper level divergence which pumped mass away from the depression.

Tropical Depression 04W will be moving through an environment that is favorable for intensification.  The depression will move over water where the Sea Surface Temperature is near 30°C.  The depression is moving under the eastern end of an upper level ridge.  The ridge is producing northerly winds which are blowing toward the top of the circulation.  The vertical wind shear may be part of the reason why there are more thunderstorms south of the center of circulation, but the shear is not strong enough to prevent intensification.  Tropical Depression 04W is expected to intensify into a tropical storm during the next 24 hours.

Tropical Depression 04W is moving around the western end of a subtropical ridge which is steering it toward the northwest.  A general northwesterly motion is expected for another 36 to 48 hours.  A turn toward the east will occur after that time.  On its anticipated track Tropical Depression 04W could be near Hong Kong in about 36 hours.  Tropical Depression 04W will have strengthened into a tropical storm by that time and there is a chance it could intensify into a typhoon by the time it nears the coast of China.

Tropical Storm Beatriz Brings Heavy Rain to Southern Mexico

Tropical Depression Two-E intensified into Tropical Storm Beatriz on Thursday and Beatriz brought heavy rain to parts of southern Mexico.  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Beatriz was located at latitude 15.5°N and longitude 96.8°W which put it about 25 miles (40 km) southwest of Puerto Angel, Mexico.  Beatriz was moving toward the north-northeast at 5 m.p.h. (8 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 1004 mb.  A Tropical Storm Warning was in effect for the portion of the coast from Salina Cruz to Puerto Escondido.

Tropical Depression Two-E intensified into Tropical Storm Beatriz on Thursday even though its structure evolved into a more asymmetrical system.  Tropical Storm Beatriz appeared to consist of a larger low pressure system which was centered just off the coast of Mexico.  The weather radar from Puerto Angel confirmed that the center of circulation was still offshore.  There were several smaller (mesoscale) counterclockwise rotating circulations that were revolving around the center of the larger low.  At least one of the smaller circulations was already over southern Mexico.  Many of the thunderstorms were occurring in a broad band that wrapped around the eastern and northern portions of the larger low pressure system.  The strongest winds were occurring within this primary rainband.  There were far fewer thunderstorms in the western half of the circulation.  It seemed that after air descended from mountains in Mexico then the air was drawn into the western side of Tropical Storm Beatriz.  The warmer drier air was inhibiting the formation of thunderstorms in the western half of Beatriz.

Although Tropical Storm Beatriz is over water where the Sea Surface Temperature is near 30°C, other environmental factors are unfavorable for intensification.  The proximity to land and the apparent ingestion of drier air are both negative factors.  A narrow upper level ridge oriented from the south-southwest to the north-northeast and a upper level trough to the west of Beatriz are producing brisk southerly winds that are blowing toward the top of the circulation.  Those upper level winds are causing moderate vertical wind shear.  Therefore, Tropical Storm Beatriz is unlike to intensify further during the next several days.

The future track of Tropical Storm Beatriz is uncertain.  If the circulation of Beatriz remains intact then the upper level trough and upper level ridge are likely to steer it toward the north-northeast.  Tropical Storm Beatriz would dissipate over the mountains of Mexico if that scenario occurs.  If the upper level winds are strong enough, the vertical shear could detach the upper portion of the circulation from the low level circulation.  That scenario sometimes occurs when slow moving storms approach the south coast of Mexico.  If that happens, the upper half of the circulation could be transported across Mexico and move over the southern Gulf of Mexico.  Some models are suggesting that a new surface low could form over the southern Gulf in several days, but the wind shear would have to decrease in order for that to occur.  The lower level circulation could be left behind near the coast of Mexico where it would drift slowly near the coast.

Tropical Storm Beatriz is bringing heavy rains to parts of southern Mexico and the heavy rain will continue to fall on Friday.  Locally heavy rain in the more mountainous portions of Oaxaca could create the potential for dangerous flash floods.

Tropical Depression 2E Prompts Tropical Storm Watch By Mexico

The National Hurricane Center designated former Invest 91E as Tropical Depression 2E and the government of Mexico issued a Tropical Storm Watch for the portion of the coast from Salina Cruz to Puerto Escondido.  At 11:00 a.m. EDT on Wednesday the center of Tropical Depression 2E was located at latitude 13.9°N and longitude 97.8°W which put it about 250 miles (400 km) southeast of Acapulco, Mexico.  The depression was moving toward the northeast at 3 m.p.h. (5 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.

Bands of showers and thunderstorms developed closer to the center of a broad area of low pressure previously designated as Invest 91E on Wednesday morning.  The improved organization prompted the National Hurricane Center to classify the system as Tropical Depression 2E.  Several bands of showers and thunderstorms were revolving around a tighter center of circulation.  Additional bands of showers and thunderstorms were strengthening in the outer portions of the circulation.  Thunderstorms in the inner part of the circulation were beginning to generate upper level divergence which was pumping out mass to the north and west of the depression.

Tropical Depression 2E will be moving through an environment that will be favorable for intensification.  It will be moving over water where the Sea Surface Temperature is 30°C to 31°C.  An upper level ridge centered east of the depression will generate southerly winds which will blow toward the top of the circulation.  Those winds will generate some vertical wind shear, but the shear will not be strong enough to prevent strengthening.  The circulation around the upper level ridge could actually enhance upper level divergence to the north of the depression.  Tropical Depression 2E is likely to intensify into a tropical storm during the next several days.

A subtropical high east of the depression is steering the system slowly toward the northeast.  A slow northerly motion is forecast for the next day or two.  Forecast guidance from the numerical models diverges when the system approaches Mexico.  Some models continue to move the depression inland over Mexico.  Other models suggest that the steering winds will weaken and that the system will stall before it reaches the coast.  The official forecast from the National Hurricane Center has the depression stalling very near the coast and then turning westward during the weekend.

Bands of rain in the outer part of the circulation are already moving over the coast.  Tropical Depression 2E will produce locally heavy rainfall over parts of southern Mexico and there is the potential for dangerous flash floods.

Invest 91E Slowly Organizing South of Mexico

A broad area of low pressure designated as Invest 91E slowly organized south of Mexico on Tuesday.  At 8:00 p.m. EDT on Tuesday the center of Invest 91E was located at latitude 13.7°N and longitude 97.9°W which put it about 220 miles (350 km) south-southeast of Acapulco, Mexico.  Invest 91E was moving toward the north-northeast at 6 m.p.h. (10 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.

Invest 91E consisted of a broad area of low pressure located south of Mexico.  The Invest did not have a well organized center of circulation.  Instead there was a broad area of counterclockwise rotation.  Many of the thunderstorms were in bands in the outer periphery of the circulation.  A few thunderstorms were beginning to form closer to the center and there were signs that some bands of showers were beginning to organize nearer to the core of the system.

Invest 91E will be moving through an area that will be favorable for development of a tropical cyclone.  It will move over water where the Sea Surface Temperature is near 30°C.  Invest 91E will be moving underneath the western portion of an upper level ridge.  The ridge will produce southerly winds which will blow toward the top of the circulation.  The southerly winds will cause some vertical wind shear.  However, the effects of the shear could be offset by upper level divergence created by the upper level ridge.  Invest 91E has a good chance to develop into a tropical depression and the National Hurricane Center is indicating that there is a 70% probability of a depression forming during the next 48 hours.

A subtropical ridge east of Invest 91E is steering the system slowly toward the north-northeast.  A general northerly motion is expected to continue for another 24 to 48 hours.  On its anticipated track Invest 91E will approach the southern coast of Mexico.  It could bring locally heavy rain when the outer bands on the northern side of the circulation move over land.

Stronger Tropical Cyclone Mora Near Landfall in Bangladesh

A stronger Tropical Cyclone Mora neared landfall between Cox’s Bazar and Chittagong, Bangladesh.  At 11:00 p.m. EDT on Monday the center of Tropical Cyclone Mora was located at latitude 21.8°N and longitude 91.9°E which put it about 90 miles (145 km) south of Chittagong, Bangladesh.  Mora was moving toward the north at 18 m.p.h. (29 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 974 mb.  Tropical Cyclone Mora was the equivalent of a hurricane/typhoon.

The inner core of Tropical Cyclone Mora organized quickly on Monday.  The primary rainband wrapped entirely around the center of circulation and an eye formed.  Additional bands of showers and thunderstorms were revolving around the core Tropical Cyclone Mora.  Thunderstorms near the core of Mora generated strong upper level divergence which pumped out mass and allowed the surface pressure to decrease.  The decrease of pressure caused the surface winds to increase to hurricane/typhoon intensity.  Winds to hurricane/typhoon strength extended out about 25 miles (40 km) from the center.  Winds to tropical storm force extended out about 150 miles (240 km) from the center.  The strongest winds were occurring in the eyewall and over the Bay of Bengal.

Tropical Cyclone Mora is moving around the western end of a subtropical ridge.  The ridge is steering Mora toward the north and that general motion is expected to continue for another 12 to 18 hours.  On its anticipated track the center of Tropical Cyclone Mora will move near the coast of Bangladesh between Cox’s Bazar and Chittagong.  The center is likely to make landfall near Chittagong during the next few hours.

The recent intensification of Tropical Cyclone Mora has made it a more dangerous storm.  The increased wind speed will increase the potential for wind damage.  In addition, stronger winds will increase the height of the storm surge along the coast.  A storm surge of 6 to 9 feet (2 to 3 meters) will be possible along the coast between Cox’s Bazar and Chittagong.  The increase in organization of the core has also created the potential for heavier rain and greater fresh water flooding of rivers and streams.

Tropical Cyclone Mora will start to weaken after the center makes landfall.  However, it will continue to generate areas of heavy rain while it moves inland over Bangladesh and northeastern India.

 

Tropical Cyclone Mora Intensifies As It Nears Bangladesh

Tropical Cyclone Mora intensified on Sunday as it moved closer to Bangladesh.  At 11:00 p.m. EDT on Sunday the center of Tropical Cyclone Mora was located at latitude 17.4°N and longitude 90.9°E which put it about 370 miles (595 km/h) south of Chittagong, Bangladesh.  Mora was moving toward the north at 9 m.p.h. (15 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 988 mb.

The structure of Tropical Cyclone Mora exhibited more organization on Sunday.  A primary rainband wrapped about two thirds of the way around northern and western sides of the circulation.  A tighter center of circulation was evident at the core of Tropical Cyclone Mora.  There were few thunderstorms east of the center of circulation.  The thunderstorms in the primary rainband were generating more upper level divergence which was pumping out mass to the west and north of the tropical cyclone.  The divergence was causing the surface pressure to decrease and was contributing the increase in wind speed.

Tropical Cyclone Mora will move through an environment that will be favorable for additional strengthening during the next 24 hours.  Mora will move over water where the Sea Surface Temperature is near 30°C.  An upper level ridge east of Mora is generating easterly winds that are blowing toward the top of the circulation.  The easterly winds are generating moderate vertical wind shear and they are probably responsible for the location of the primary rainband north and west of the center of circulation.  The vertical shear will slow the rate of intensification, but it will not prevent Tropical Cyclone Mora from intensifying further.  Mora could intensify into the equivalent of a hurricane/typhoon before it makes landfall.

Mora was being steered toward the north by a subtropical ridge located to the east of the tropical cyclone.  A general northward motion is expected to continue for another 24 to 36 hours.  On its anticipated track Tropical Cyclone Mora will approach the coast of Bangladesh in 18 to 24 hours.

Tropical Cyclone Mora could make landfall near Chittagong, Bangladesh.  Mora will bring gusty winds to Bangladesh and northwestern Myanmar.  It will produce locally heavy rain and create a risk for fresh water flooding.  Counterclockwise rotation will push water toward the coast and there could be a storm surge near and to the east of where the center makes landfall.  The surge could increase the water level at the coast by 6 to 8 feet (2 to 3 meters).

Tropical Cyclone 02B Forms Over the Bay of Bengal

A surface circulation formed over the Bay of Bengal on Saturday and the system was designated Tropical Cyclone 02B.  At 8:00 p.m. EDT on Saturday the center of Tropical Cyclone 02B was located at latitude 14.2°N and longitude 88.9°E which put it about 640 miles (1030 km) south-southwest of Chittagong, Bangladesh.  The tropical cyclone was moving toward the north-northeast at 4 m.p.h. (6 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.

A low level center of circulation consolidated over the Bay of Bengal on Saturday.  The distribution of thunderstorms was asymmetrical.  Most of the thunderstorms in the inner part of the circulation developed west of the center.  There were some thunderstorms in outer bands northeast of the center, but there were few thunderstorms closer to the core of the circulation in the eastern half of the tropical cyclone.  The thunderstorms west of the center were producing upper level divergence which was pumping away mass to the west of the tropical cyclone.

Tropical Cyclone 02B will be moving through an environment that will be favorable for intensification.  It will move over water where the Sea Surface Temperature is near 30°C.  An upper level ridge east of the tropical cyclone is generating southeasterly winds which are blowing toward the top of the circulation.  Those winds are creating moderate vertical wind shear and the shear may be the reason why the thunderstorms were developing west of the center.  The shear will be strong enough to slow intensification, but it will not prevent intensification.  Tropical Cyclone 02B will intensify during the next two days and it could become the equivalent of a hurricane/typhoon.

A subtropical ridge located east of Tropical Cyclone 02B is steering it slowly toward the north-northeast.  A general north-northeasterly motion is expected to continue during the next several days.  On its anticipated track the center of Tropical Cyclone 02B could approach the coast of Bangladesh and northwestern Burma in about 48 hours.  Tropical Cyclone 02B could be the equivalent of a hurricane/typhoon by that time.  It could bring gusty winds and locally heavy rain when it makes landfall.  Heavy rain could cause fresh water flooding of rivers.  In addition the winds on the eastern side of Tropical Cyclone 02B will push water in the Bay of Bengal toward the coast.  A serious storm surge could occur along the coast east and near where the center makes landfall.

Possible Tropical Cyclone Developing Over Bay of Bengal

Satellite imagery indicates that a possible tropical cyclone may be developing over the Bay of Bengal.  Thunderstorms have increased and the system has been designated as Invest 94B.  At 8:00 p.m. EDT on Thursday the center of Invest 94B was located at latitude 11.8°N and longitude 88.7°E which put it about 575 miles (930 km) east of Chennai, India.  The invest was not moving much.  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 1002 mb.

A circulation began to consolidate in an area of thunderstorms over the Bay of Bengal on Thursday.  Many more thunderstorms formed in the western half of the circulation.  Although there was still not a well defined center of circulation, some curved bands began to form.  A broad cyclonic circulation began to rotate counterclockwise.

Invest 94B was organizing in area that was favorable for further intensification.  It was moving over water where the Sea Surface Temperature was near 30°C.  An upper level ridge centered to the east of the invest was generating easterly winds that were blowing toward the top of the circulation.  The winds were producing some vertical wind shear and the shear may have contributed to the asymmetrical distribution of thunderstorms.  The shear could slow the development, but it is probably not strong enough to prevent the formation of a tropical cyclone.

Invest 94B did not move much during Thursday.  The is some uncertainty about the future track of the system.  Some numerical models are forecasting that the subtropical ridge to the east of Invest 94B will steer it toward the northern Bay of Bengal.

 

Weaker Tropical Cyclone Ella Passing North of Fiji

Tropical Cyclone Ella weakened on Saturday as passed north of Fiji.  At 11:00 p.m. EDT on Saturday the center of Tropical Cyclone Ella was located at latitude 12.9°S and longitude 178.9°E which put it about 365 miles (585 km) north-northeast of Nadi, Fiji.  Ella was moving toward the west at 5 m.p.h. (8 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.

Tropical Cyclone Ella moved underneath an area of stronger upper level westerly winds on Saturday.  Stronger vertical wind shear pushed the upper part of the circulation east of the lower level circulation.  The center of the lower level circulation was completely exposed by late Saturday.  It consisted of a tight swirl of low clouds and showers.  Some thunderstorms were occurring in bands east of the low level center.

The small size of Tropical Cyclone Ella made it very vulnerable to increased vertical wind shear.  Tropical Cyclone Ella is forecast to continue to move under the upper level westerly winds.  Shear is likely to weaken Ella further even though it will move over water where the Sea Surface Temperature is near 30°C.

A subtropical ridge south of Ella is steering the tropical cyclone toward the west and that general motion is expected to continue.  Tropical Cyclone Ella is forecast to move through Tuvalu, but it will pass north of Fiji.