Monthly Archives: November 2017

Tropical Cyclone Ockhi Strengthens Quickly Southwest of India

Tropical Cyclone Ockhi strengthened quickly southwest of India on Thursday.  At 7:00 a.m. EST on Thursday the center of Tropical Cyclone Ockhi was located at latitude 8.0°N and longitude 76.2°E which put it about 810 miles (1305 km) south-southeast of Mumbai, India.  Ockhi was moving toward the west-northwest at 10 m.p.h. (16 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 core of the circulation of a tropical depression that developed near Sri Lanka on Wednesday organized quickly on Thursday.  A primary rainband wrapped most of the way around the center of circulation and an eye began to appear on some satellite imagery.  The storms in the eyewall were strongest west of the eye and weakest north of the eye.  Additional bands of showers and thunderstorms formed outside the core of the circulation.  Thunderstorms in the core of Ockhi generated strong upper level divergence which was pumping mass away to the north and west of the tropical cyclone.  The divergence was allowing the surface pressure to decrease and the wind speeds to increase.

Tropical Cyclone Ockhi will be moving through an environment favorable for intensification during the next several days.  Ockhi will move over water where the Sea Surface Temperature is near 29°C.  Tropical Cyclone Ockhi is near the western end of an upper level ridge.  The ridge is producing southeasterly winds which are blowing toward the top of the circulation.  Those winds are causing some vertical wind shear, but they are also enhancing the upper level divergence to the north and west of Tropical Cyclone Ockhi.  The positive effects of enhanced divergence will exceed the negative effects of the vertical wind shear.  Tropical Cyclone Ockhi will continue to intensify and it could intensify rapidly.  Ockhi will likely become the equivalent of a hurricane/typhoon within the next 24 hours.

The upper level ridge is currently steering Tropical Cyclone Ockhi toward the west-northwest.  Ockhi will turn more toward the north in a day or two when it reaches the western end of the ridge.   On its anticipated track Tropical Cyclone Ockhi will move farther away from the coast of India during the next 24 to 48 hours.  The outer rainbands on the eastern side of Ockhi will drop locally heavy rain over portions of southern India and flash floods could occur in some places.  Tropical Cyclone Ockhi is likely to turn toward the northeast in three or four days and it could eventually make landfall in western India.

Tropical Depression Forms Near Southern Tip of Sri Lanka

A tropical depression formed near the southern tip of Sri Lanka on Wednesday.  At 7:00 a.m. EST on Wednesday the center of Tropical Depression 96S was located at latitude 6.2°N and longitude 80.0°E which put it about 20 miles (30 km) northwest of Galle, Sri Lanka.  It was moving toward the west-southwest at 4 m.p.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 1004 mb.

A center of circulation formed within a cluster of thunderstorms also designated as Invest 91B and the Indian Meteorological Department classified the system as a Depression.  The circulation in the tropical depression was still organizing.  A large, primary rainband wrapped around the southern and western sides of the center of circulation.  Additional bands of showers and strong thunderstorms were forming in the western half of the circulation.  Bands of showers and isolated thunderstorms were developing in the eastern half of the circulation.  Thunderstorms in the primary rainband were generating upper level divergence which was pumping away mass to the west of the depression.

The depression will move through an environment favorable for intensification during the next several days.  It will move over water where the Sea Surface Temperature is near 29°C.  An upper level ridge over India is generating easterly winds which are blowing toward the top of the circulation.  Those winds are causing moderate vertical wind shear which is probably the reason why most of the stronger thunderstorms are occurring in the western half of the depression.  The vertical wind shear will inhibit intensification, but it is not likely to prevent strengthening.  The depression is likely to intensify into a stronger tropical cyclone during the next several days.

The ridge over India is steering the tropical depression toward the west-southwest.  The ridge is forecast to steer the depression in a generally westerly direction during the next several days.  On its anticipated track the depression will move away from Sri Lanka and the center will pass south of India.  The depression could cause locally heavy rain and flash floods in parts of Sri Lanka and southern India.

Tropical Cyclone Dahlia Forms Southwest of Indonesia

Tropical Cyclone Dahlia formed southwest of Indonesia on Wednesday.  At 10:00 a.m. EST on Wednesday the center of Tropical Cyclone Dahlia was located at latitude 8.4°S and longitude 101.5°E which put it about 320 miles (520 km) west-northwest of Christmas Island.  Dahlia was moving toward the east 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 999 mb.

A center of circulation developed in a cluster of thunderstorms previously designated as Invest 96S and the Australian Bureau of Meteorology named the system Tropical Cyclone Dahlia.  The circulation of Dahlia is still organizing.  A primary rainband wrapped around the southern and western sides of the center.  Additional bands of showers and thunderstorms formed in the western half of the circulation.  Fewer thunderstorms formed in the eastern half of Dahlia.  The thunderstorms near and to the west of the center were generating upper level divergence which was pumping mass away to the west of the tropical cyclone.

Tropical Cyclone Dahlia will be moving through an environment favorable for intensification during the next several days.  Dahlia will move over water where the Sea Surface Temperature is near 29°C.  Dahlia is underneath the northern part of an upper level ridge.  The ridge is producing easterly winds which are blowing toward the top of the circulation.  Those winds are causing moderate vertical wind shear, which may be the reason why most of the thunderstorms are west of the center of circulation.  The shear is strong enough to slow the intensification of Dahlia, but it is not strong enough to prevent the tropical cyclone from strengthening.  Tropical Cyclone Dahlia is likely to likely to intensify during the next 24 to 48 hours.

The steering winds around Dahlia are relatively weak and the tropical cyclone is moving slowly toward the east.  The upper level ridge is forecast to shift north and stronger westerly winds are likely to steer Tropical Cyclone Dahlia toward the east at a faster speed.  When Dahlia reaches the southern portion of the upper level ridge in a couple of days, northerly winds diverging from the ridge are likely to steer the tropical cyclone toward the south.

Tropical Cyclone Cempaka Develops South of Java

The organization of a small area of low pressure (also known as Invest 95S) south of Java increased early on Monday and the Badan Meteorologi Klimatologi Dan Geofisika (BMKG) Tropical Cyclone Warning Center in Jakarta designated the system as Tropical Cyclone Cempaka.  At 7:00 a.m. EST on Monday the center of Tropical Cyclone Cempaka was located at latitude 8.8°S and longitude 110.8°E which put it about 70 miles (115 km) south-southeast of Yokyakarta, Indonesia.  Cempaka was moving toward the east- 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 997 mb.

Tropical Cyclone Cempaka has a small but well developed center of circulation.  Radar images from BKMG showed an eyelike feature at the center of circulation.  The strongest winds are occurring in a ring of showers and thunderstorms that surrounds the center.  The stronger storms are in the eastern half of the ring.  Other narrow rainbands are developing outside the core of Cempaka.  Thunderstorms around the center are generating some upper level divergence which is pumping mass away from the tropical cyclone.  Winds to tropical storm force extend out about 40 miles (65 km) from the center of circulation.

Tropical Cyclone Cempaka will be in an environment somewhat favorable for intensification during the next 24 to 48 hours.  Cempaka will move over water where the Sea Surface Temperature is near 29°C.  Tropical Cyclone Cempaka is under an upper level ridge and the upper level winds are weak.  There is little vertical wind shear over the tropical cyclone.  The core of Tropical Cyclone Cempaka is near Java.  Part of the circulation is flowing over Java and nearby islands and friction from those islands is slowing the winds.  Interaction with land is the primary factor inhibiting intensification.  If the center of Tropical Cyclone Cempaka remains south of Java, then it has a chance to intensify.  If Cempaka moves closer to Java, then it could weaken.  Also, since Cempaka is a very small tropical cyclone, an increase in the speed of the upper level winds could blow the top off of the circulation.

Since Tropical Cyclone Cempaka is underneath an upper level ridge, the steering winds are weak.  Cempaka is south of the center of the ridge and weak westerly winds are steering the tropical cyclone slowly toward the east-northeast.  Tropical Cyclone Cempaka is forecast to meander south of Java for several more days because of the weak stearing winds.

Tropical Cyclone Cempaka is producing locally heavy rain over parts of Java, Bali and nearby islands.  The locally heavy rain could cause flash floods as Cempaka meanders south of Java during the next day or two.

Low Pressure System Forms South of Java

A small, but well organized area of low pressure developed just to the south of Java on Sunday.  The low pressure system is currently designated as Invest 95S, but it could become a tropical cyclone during the next several days.  At 10:00 p.m. EST on Sunday the center of Invest 95S was located at latitude 8.9°S and longitude 109.8°E which put it about 100 miles (160 km) southwest of Yogyakarta, Indonesia.  It was moving toward the northeast at 4 m.p.h. (6 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 998 mb.

The circulation of Invest 95S is small but well formed.  There is a distinct low level center of circulation.  Two well formed narrow rainbands wrapped around the southern and northeastern sides of the center.  Other rainbands developed just outside the core of the circulation.  Storms near the center of circulation were generating some upper level divergence which was pumping out mass and allowing the surface pressure to decrease.

Invest 95S will move through an environment that is mostly favorable for intensification.  It will move over water where the Sea Surface Temperature is near 29°C.  Invest 95S is near the center of an upper level ridge.  The upper level winds blowing over the top of the low pressure system are weak and there is not a lot of vertical wind shear.  The proximity of the circulation to Java is the only factor likely to inhibit intensification.  If the center of circulation remains south of Java, then there is a good chance it could intensify into a tropical cyclone.

The ridge north of Invest 95S is steering the system slowly toward the northeast and a general easterly motion is expected to continue during the next 24 hours.  Guidance from numerical models diverges in a day or so.  Some models to suggest the northeasterly motion will continue and the low pressure system will move across Java.  Other models predict a turn toward the south in a day or so.  There is a high degree of uncertainty about the future track of Invest 95S.

Tropical Storm Kirogi Brings Rain to Southern Vietnam

Tropical Storm Kirogi brought locally heavy rain to southern Vietnam on Saturday night.  At 10:00 p.m. EST on Saturday night the center of Tropical Storm Kirogi was located at latitude 10.4°N and longitude 109.8°E which put it about 220 miles (355 km) east of Ho Chi Minh City, Vietnam.  Kirogi was moving toward the west at 13 m.p.h. (21 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 1001 mb.

Kirogi is a small tropical storm.  Winds to tropical storm force extend out about 90 miles (145 km) from the center of circulation.  The circulation is compact and circular.  Most of the strong storms are in the western half of the circulation.  There are numerous bands of lighter showers in eastern half of the circulation.  An upper level ridge north of Kirogi is producing easterly winds which are blowing toward the top of the circulation.  The vertical wind shear is causing the asymmetrical distribution of the stronger storms.

The ridge is steering Tropical Storm Kirogi toward the west.  The center of Tropical Storm Kirogi will make landfall on the coast of Vietnam near Ham Thuan Nam in a few hours.  Kirogi will continue moving west toward Ho Chi Minh City and then over southeastern Cambodia.  Tropical Storm Kirogi will drop locally heavy rain along the coast from Nha Trang to the Mouths of the Mekong River.  Kirogi will also be capable of producing heavy heavy over parts of the southern Cambodia.  The rainfall could be heavy enough to cause flooding in some locations.

Tropical Storm Kirogi Forms West of the Philippines

Tropical Storm Kirogi formed west of the Philippines on Friday.  At 4:00 p.m. EST on Friday the center of Tropical Storm Kirogi was located at latitude 10.9°N and longitude 115.7°E which put it about 465 miles (745 km) east of Nha Trang, Vietnam.  Kirogi was moving toward the west-northwest at 18 m.p.h. (30 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 1000 mb.

A low level center of circulation developed near the eastern edge of an area of showers and thunderstorms west of the Philippines on Friday and the Japan Meteorological Agency designated the system as Tropical Storm Kirogi.  The distribution of showers and thunderstorms in Kirogi was asymmetrical.  A primary rainband wrapped around the western side of the center of circulations and most of the stronger storms were west of the center.  There were only bands of low clouds and showers east of the center of Kirogi.  An upper level ridge north of Kirogi was producing easterly winds which were blowing across the top of the tropical storm.  The vertical wind shear created by those winds was causing the asymmetrical distribution of showers and thunderstorms.

Tropical Storm Kirogi will move through an environment that will be somewhat favorable for intensification.  Kirogi will move over water where the Sea Surface Temperature is near 29°C.  The upper level ridge will continue to cause vertical wind shear.  The shear may be strong enough to slow intensification, but it may not strong enough to prevent Tropical Storm Kirogi from strengthening.  The forecast is for Tropical Storm Kirogi to intensify during the next 24 to 36 hours.

The ridge is steering Tropical Storm Kirogi toward the west-northwest and a general westerly motion is expected to continue.  On its anticipated track Tropical Storm Kirogi will move across the South China Sea toward Vietnam.  Kirogi could reach the coast of Vietnam near Nha Trang in about 36 hours.  Kirogi will bring gusty winds and locally heavy rain when it reaches the coast.  The locally heavy rain could cause flash floods.  There could also be a storm surge of 3 to 6 feet (1 to 2 meters) where the wind blows water toward the coast of Vietnam.

Tropical Depression Forms Over Bay of Bengal

A tropical depression formed over the Bay of Bengal on Wednesday.  At 10:00 a.m. EST on Wednesday the center of the tropical depression was located at latitude 16.2°N and longitude 83.3°E which put it about 105 miles (170 km) south of Visakhapatnam, India.  The depression was moving toward the north-northeast at 9 m.p.h. (15 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 1003 mb.

A low level center of circulation developed on the southwestern edge of a cluster of showers and thunderstorms over the Bay of Bengal and the Indian Meteorological Department classified the system as a depression.  The circulation is not particularly well organized.  As noted above, the low level center is on the southwestern side of showers and thunderstorms.  Several bands of showers and storms formed northeast of the center.  There were not many thunderstorms near the center of circulation.  There were bands of showers and lower clouds in the western half of the circulation.  An upper level trough over India is producing southwesterly winds which are blowing over the top of the depression.  Those winds are causing moderate vertical wind shear, which is tilting the upper part of the depression to the northeast of the low level center of circulation.  The depression also appears to be pulling drier air from India around the western side of the circulation.  The combination of wind shear and drier air is probably responsible for the asymmetrical distribution of thunderstorms.

The depression will move through an environment that is marginally favorable for intensification.  It will move over water there the Sea Surface Temperature is near 28.5°C.  So, there is enough energy in the upper ocean to support intensification.  However, the upper level trough over India will continue to cause moderate vertical wind shear, which will inhibit the consolidation of the low level circulation.  The depression is also likely to continue to draw in drier air from over India into the western part of the circulation.  The depression could strengthen, but it could also weaken if the upper level winds get stronger.

The trough over India is steering the depression slowly toward the north-northeast and that general motion is expected to continue.  On its anticipated track the depression is expected to move toward the northern Bay of Bengal during the next several days.  The depression could make landfall over northeastern India or Bangladesh later this week.

The primary risk from the depression will be locally heavy rain, which could cause flash floods in parts of eastern India and Bangladesh.  The wind will push water toward the north coast of the Bay of Bengal and the depression could cause a storm surge of several feet (approximately one meter).

Remnants of Tropical Storm Haikui Make Landfall in Vietnam

The remnants of Tropical Storm Haikui made landfall near Da Nang, Vietnam late on Monday.  At 10:00 p.m. EDT on Monday the center of Tropical Depression Haikui were located at latitude 17.0°N and longitude 108.2°E which put it about 20 miles (30 km/h) north of Da Nang, Vietnam.  Haikui was moving toward the west at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 25 m.p.h. (40 km/h) and there were wind gusts to 35 m.p.h. (55 km/h).  The minimum surface pressure was 1003 mb.

The remnants of Tropical Storm Haikui consists of primarily of a low level counterclockwise circulation.  There are several thin bands of low clouds and showers.  Stronger thunderstorms were forming near the core of the circulation.  It appeared that winds blowing toward the coast were converging due to increased friction caused by the land.  The convergence was causing stronger rising motion which was contributing to the development of strong thunderstorms near and to the west of the center of circulation.

The remnants of Tropical Storm Haikui will move inland before significant intensification can occur.  The remnants of Haikui could drop locally heavy rainfall over portions of Vietnam, southern Laos and northeastern Thailand.  Locally heavy rainfall could cause flooding in some places.

Tropical Storm Haikui Weakens Southeast of Hainan Island

Tropical Storm Haikui weakened as it moved southeast of Hainan Island on Saturday.  At 10:00 p.m. EST on Saturday the center of Tropical Storm Haikui was located at latitude 17.6°N and longitude 112.6°E which put it about 290 miles (470 km) east of Da Nang, Vietnam.  Haikui was moving toward the west-southwest at 6 m.p.h. (10 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.

A combination of drier air and strong vertical wind shear weakened Tropical Storm Haikui on Saturday.  Strong northeasterly winds transported colder drier air from eastern Asia into the circulation of Tropical Storm Haikui.  The drier air reached the core of the circulation and it prevented the formation of new thunderstorms around the center of circulation.  Strong westerly winds in the upper levels were blowing over the top of the circulation.  The combination of northeasterly winds in the lower levels and westerly winds in the upper levels produced strong vertical wind shear.  The wind shear blew the upper portion of the circulation to the east of the low level core of Tropical Storm Haikui.  The core of Tropical Storm Haikui consists of a circular rotation of showers and low clouds.  The only thunderstorms are occurring in a rainband on the northeastern periphery of the circulation.

The strong wind vertical wind shear and drier air should continue to weaken Tropical Storm Haikui.  Haikui is likely to weaken to a tropical depression on Sunday.  Since the circulation exists primarily in the lower levels, it will be steered by the winds closer to the surface of the Earth.  The northeasterly winds in the lower levels will steer Tropical Storm Haikui toward the west- southwest.  On its anticipated track Tropical Storm Haikui will pass south of Hainan Island.  Haikui or its remnants could reach the coast of Vietnam in 36 to 48 hours.