Monthly Archives: May 2017

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.

Tropical Cyclone Ella Strengthens To Equivalent of a Hurricane Near Wallis & Futuna

Tropical Cyclone Ella strengthened into the equivalent of a hurricane/typhoon as it moved near Wallis and Futuna on Thursday.  Ella brought gusty winds and locally heavy rain to those islands.  At 11:00 p.m. EDT on Thursday the center of Tropical Cyclone Ella was located at latitude 14.0°S and longitude 178.2°W which put it about 20 miles (30 km) north of Wallis and Futuna.  Ella was moving toward the northwest at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 85 m.p.h. (135 km/h) and there were wind gusts to 105 m.p.h. (170 km/h).  The minimum surface pressure was 979 mb.

Tropical Cyclone Ella has a very small circulation, but that circulation is well organized.  There is a very tight inner core.  A ring of strong thunderstorms surrounds a tiny pinhole eye.  The strongest winds are occurring in the tight eyewall.  Additional bands of thunderstorms are forming in the eastern half of the circulation.  There are bands of showers in the western half of the circulation.  Winds to hurricane/typhoon force extend out only about 10 miles (15 km) from the center of circulation.  Winds to tropical storm force extend out about 80 miles (130 km) from the center.

Tropical Cyclone Ella is moving through an environment favorable for intensification.  Ella is moving over water where the Sea Surface Temperature is near 30°C.  It is in an area where the upper level winds are weak and there is little vertical wind shear.  Tropical Cyclone Ella could continue to intensify as long as it is in an area where the upper level winds are weak.  However, there are much strong upper level westerly winds flowing just to the south of the tropical cyclone.  If Tropical Cyclone Ella moves into an area where the upper level winds are strong, vertical wind shear could weaken it very quickly because of Ella’s small size.

A subtropical ridge south of Ella is steering the tropical cyclone toward the west and a general westerly motion is expected to continue for several more days.  On its anticipated path Tropical Cyclone Ella will move away from Wallis and Futuna.  Ella could move near the northeastern portion of Fiji in 24 to 36 hours.

Tropical Cyclone Ella Strengthens As It Nears Wallis and Futuna

Tropical Cyclone Ella strengthened on Wednesday as it moved closer to Wallis and Futuna.  At 11:00 p.m. EDT on Wednesday the center of Tropical Cyclone Ella was located at latitude 14.4°S and longitude 177.0°W which put it about 75 miles (120 km) east of Wallis and Futuna.  Ella was moving toward the west at 3 m.p.h. (5 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 989 mb.

The circulation of Tropical Cyclone Ella exhibited better organization on Wednesday.  A circular eye with a diameter of 25 miles (40 km) was evident on some microwave satellite images.  A ring of thunderstorms surrounded the eye.  Additional bands of showers and thunderstorms developed in the eastern half of the circulation.  Storms in the core of the circulation generated upper level divergence which pumped out mass and allowed the surface pressure to decrease.  The size of the circulation of Tropical Cyclone Ella is small.  Winds to tropical storm force only extend out about 100 miles (160 km) fro the center of circulation.

Tropical Cyclone Ella will move through an area that will be favorable for intensification.  Ella will move over water where the Sea Surface Temperature is near 30°C.  The upper level winds are weak and there is little vertical wind shear.  Tropical Cyclone Ella could intensify into the equivalent of a hurricane/typhoon on Thursday.  However, because the size of the circulation is small, any future increase in the vertical wind shear could quickly weaken Tropical Cyclone Ella.

Ella is moving around the northern side of a subtropical ridge, which is steering the tropical cyclone toward the west.  Ella is currently moving north of a weaker section of the ridge and the steering winds are weaker.  So, Ella is moving more slowly.  The ridge is expected to steer Tropical Cyclone Ella in a general westerly direction during the next several days.  On its anticipated track Tropical Cyclone Ella could pass near Wallis and Futuna in 12 to 18 hours.  It could be near hurricane/typhoon strength at that time.  Ella could approach the northeastern part of Fiji in two or three days.

Strong Shear Weakens Adrian to a Tropical Depression

Strong vertical wind shear weakened Tropical Storm Adrian to a tropical depression on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Tropical Depression Adrian was located at latitude 10.5°N and longitude 93.1°W which put it about 420 miles (675 km) south-southeast of Salina Cruz, Mexico.  Adrian was moving toward the northwest at 5 m.p.h. (7 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.

An upper level ridge east of Adrian generated strong southeasterly winds which produced strong vertical wind shear and literally blew the top off of the tropical storm.  The upper half of the circulation was carried well to the northwest of low level circulation.  The low level circulation consists low clouds and weak showers.  No new thunderstorms have formed in the low level circulation since it decoupled from the upper half of the circulation.

Strong upper level winds are likely to continue to create strong vertical wind shear on Thursday.  Tropical Depression Adrian is likely to remain weak on Thursday.  If the low level circulation persists for several more days, then the upper level winds could weaken.  The Sea Surface Temperature is near 30°C.  So, if there is still a low level circulation, some strengthening could occur when the upper level winds diminish.