Monthly Archives: December 2017

Tropical Storm Kai-tak Weakens Over the Philippines

Tropical Storm Kai-tak weakened as it passed over the Philippines.   Kai-tak dropped heavy rain which caused floods and mudslides before it weakened.  At 10:00 p.m. EST on Sunday the center of Tropical Storm Kai-tak was located at latitude 10.5°N and longitude 119.1°E which put it about 75 miles (120 km) northeast of Puerto Princesa, Philippines.  Kai-tak was moving toward the west-southwest 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 1000 mb.

Moving over islands of the central Philippines disrupted parts of the circulation of Tropical Storm Kai-tak.  In addition an upper level ridge produced strong easterly winds which blew across the top of the circulation.  Those winds caused moderate vertical wind shear.  The strong upper level winds periodically weakened the thunderstorms near the core of the circulation.  The upper level winds slowed at times and more storms developed near the center of Tropical Storm Kai-tak.  The persistent vertical wind shear weakened the low level circulation.

More thunderstorms developed near the center of Tropical Storm Kai-tak during recent hours, but the circulation remains asymmetrical.  The new storms were forming west of the center of circulation.  There were only a few thin bands of showers in the eastern half of the circulation.  The strongest winds were occurring in the thunderstorms west of the center of Tropical Storm Kai-tak.  The Japan Meteorological Agency was maintaining a classification of a tropical storm.

Tropical Storm Kai-tak will move through an environment only marginally favorable for intensification.  Kai-tak will move over water where the Sea Surface Temperature is near 29°C.  The upper level ridge will continue to produce strong easterly winds and there will continue to be moderate vertical wind shear.  Tropical Storm Kai-tak could maintain its intensify, if the wind shear does not increase.  However, if the upper level winds get stronger, then they could blow the top off of the circulation.

Tropical Storm Kai-tak is moving south of a subtropical ridge which is steering the tropical storm toward the west-southwest.  The west-southwesterly motion is forecast to continue for another day or two.  On its anticipated track Tropical Storm Kai-tak will move across Palawan and over the South China Sea.

Tropical Storm Kai-tak Drops Heavy Rain on Philippines

Tropical Storm Kai-tak dropped heavy rain on places in the Philippines during the past several days.  At 4:00 p.m. EST on Friday the center of Tropical Storm Kai-tak was located at latitude 12.1°N and longitude 126.8°E which put it about 150 miles (240 km) east-northeast of Tacloban, Philippines.  Kai-tak was moving toward the northwest at 10 m.p.h. (16 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 996 mb.

The distribution of thunderstorms around Tropical Storm Kai-Tak remains asymmetrical.  Kai-tak is south of an upper level ridge which is producing easterly winds which are blowing toward the top of the tropical storm.  Those winds are causing moderate vertical wind shear and most of the thunderstorms are developing in the western half of the circulation.  The magnitude of the vertical wind shear fluctuates as the speed of the upper level winds increases or decreases.  Changes in the magnitude of the wind shear contributes to fluctuations in the intensity of the thunderstorms.  When the shear is stronger, most of the storms develop in the outer portion of the circulation of Kai-tak.  When the upper level winds slow, thunderstorms are able to develop closer to the western core of the tropical storm.  Daytime warming of the surface of some of the islands in the Philippines may increase the local instability, which also contributes to the formation of storms over those islands.

Tropical Storm Kai-tak moved very little during the past two days.  As a result, heavy rain fell repeatedly over portions of Samar, Leyte, Bohol, Cebu, Negros, Panay, Masbate and southeastern Luzon.  The heavy rain is creating the potential for floods and mudslides in those areas.

Tropical Storm Kaitak will move through an environment that is only marginally favorable for development.  Kai-tak will move over water where the Sea Surface Temperature is near 29°C.  However, the upper level ridge will continue to cause moderate vertical wind shear.  Tropical Storm Kai-tak could intensify a little during the next 24 hours, but the wind shear will limit the potential for strengthening.  Tropical Storm Kai-tak is likely to weaken when the center of circulation passes over islands in the Philippines.

The subtropical ridge north of Kai-tak is steering the tropical storm toward the northwest.  The ridge is forecast to strengthen during the weekend and it is likely to steer Tropical Storm Kai-tak more toward the west during the next 24 to 36 hours.  On its anticipated track the center of Kai-tak could reach Samar in the next 12 to 18 hours.  The center could then move near Masbate and Panay.

Tropical Storm Kai-tak will continue to drop locally heavy rain on places in Samar, Leyte, Bohol, Cebu, Panay, Negros, Masbate and southern Luzon for several more days.  The heaviest rain will fall in locations where the wind pushes air up the slopes of mountains.  The potential for floods and mudslides will increase as more rain falls.

Tropical Storm Kai-tak Develops East of the Philippines

A tropical depression east of the Philippines strengthened on Wednesday and the Japan Meteorological Agency designated the system as Tropical Storm Kai-tak.  At 10:00 p.m. EST on Wednesday the center of Tropical Storm Kai-tak was located at latitude 11.2°N and longitude 127.2°E which put it about 150 miles (240 km) east of Tacloban, Philippines.  Kai-tak was moving toward the west-northwest 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 1000 mb.

The circulation of Tropical Storm Kai-tak strengthened on Wednesday, but the distribution of thunderstorms was still asymmetrical.  Most of the stronger storms were occurring in bands in the western half of the circulation.  There were few thunderstorms in the eastern half of Kai-tak.  The center of circulation was located near the eastern edge of the strong thunderstorms.  The storms in the western half of the circulation were generating upper level divergence which was pumping mass away to the west of the tropical storm.

Tropical Storm Kai-tak will move through an environment that is marginally favorable for intensification.  Kai-tak will move over water where the Sea Surface Temperature is near 29°C.  So, there is enough energy in the upper ocean to support intensification.  However an upper level ridge east of the Philippines is producing easterly winds which are blowing toward the top of the circulation.  Those winds are causing moderate vertical wind shear and the shear is probably the reason for the asymmetrical distribution of thunderstorms.  The moderate shear will limit the intensification of Tropical Storma Kai-tak.  Kai-tak could intensify slowly during the next day or two.  The center of Kai-tak will pass over some of the Philippines and the interaction with those islands will weaken the tropical storm.

The winds at the steering levels are weaker than the upper level easterlies.  Tropical Storm Kai-tak is forecast to move slowly toward the west-northwest during the next several days, but it could be nearly stationary at times.  On its anticipated track the center of Tropical Storm Kai-tak could move very near Samar during the next 24 to 48 hours.

Tropical Storm Kai-tak is already dropping heavy rain over parts of Samar and Leyte.  The slow movement of Kai-tak could result in prolonged periods of heavy rain in that region.  The heavy rain has the potential to cause serious floods and mudslides.

Tropical Cyclone 04B Develops Over Northern Bay of Bengal

Tropical Cyclone 04B developed over the northern Bay of Bengal on Friday.  The circulation around an area of low pressure southeast of India strengthened on Friday and the Joint Typhoon Warning Center (JTWC) designated the system as Tropical Cyclone 04B.  Data from a scatterometer on a satellite indicated there were winds to 45 m.p.h. (75 km/h) in the western part of the circulation.  The Indian Meteorological Department was classifying the low pressure system as a depression and that was why it did not have a name.

At 4:00 p.m. EDT on Friday the center of Tropical Cyclone 04B was located at latitude 18.7°N and longitude 86.9°E which put it about 340 miles (550 km) southwest of Kolkata, India.  It was moving toward the north at 18 m.p.h. (29 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 994 mb.

Although there was a well defined low level center of circulation, the rest of the circulation of Tropical Cyclone 04B was not particularly well organized.  There were no strong thunderstorms near the center of circulation.  The stronger thunderstorms were occurring in a rainband 80 miles (130 km) northeast of the center of circulation.  Other bands revolving around the center consisted primarily of low clouds and showers.

Tropical Cyclone 04B is moving through an environment that is only marginally favorable for intensification.  It is moving over water where the Sea Surface Temperature is near 28°C.  So, there is enough energy in the upper ocean to support intensification, but that is about the only factor favorable for intensification.  Tropical Cyclone 04B is moving underneath the western end of an upper level ridge.  The ridge is producing southeasterly winds which are blowing across the top of the circulation.  Those winds are also causing moderate vertical wind shear and the shear is probably the reason why the band of thunderstorms is displaced northeast of the center of circulation.  It also appears that the western side of the circulation of Tropical Cyclone 04B is also pulling some drier air from over India into the system.  Tropical Cyclone 04B is unlikely to intensify due to the effects of moderate wind shear and drier air.

The upper level ridge is steering Tropical Cyclone 04B toward the north.  On its anticipated track Tropical Cyclone 04B could make landfall near Kolkata in 24 to 30 hours.  The primary risk is locally heavy rain which could cause flooding.  The rain is likely to reach northeastern India a few hours before the center of circulation makes landfall.

Tropical Cyclone Ockhi Moves Closer to India

Tropical Cyclone Ockhi moved closer to India on Monday.  At 10:00 p.m. EST on Monday the center to Tropical Cyclone Ockhi was located at latitude 17.9°N and longitude 70.7°E which put it about 170 miles (270 km) west-southwest of Mumbai, India and about 250 miles (400 km) southwest of Surat.  Ockhi was moving toward the northeast at 11 m.p.h. (17 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 983 mb.

An upper level trough over the northern Arabian Sea was producing strong southwesterly winds which were blowing across the top of Tropical Cyclone Ockhi.  Those winds were causing significant vertical wind shear.  Microwave satellite imagery was indicating that the shear may be strong enough to push the upper part of Ockhi’s circulation to the northeast of the lower part of the tropical cyclone’s circulation.  The circulation in the middle and upper levels continued to show evidence of an eye surrounded by a ring of strong storms.  Several bands of strong storms were occurring north of the center of circulation.

The upper level trough is steering Tropical Cyclone Ockhi toward the northeast and that general motion is expected to continue for several more days.  On its anticipated track Ockhi will make landfall in Gujarat along the coast of the Gulf of Khambhat within 24 hours.  Strong vertical wind shear will continue to weaken Tropical Cyclone Ockhi.  Ockhi is likely to make landfall as the equivalent of a tropical storm.  Drier air is wrapping around the southern side of the circulation.  The heavy rain will fall over parts of Gujarat before the center of circulation reaches the coast.  Locally heavy rainfall could create the potential for flash floods in some places.

Tropical Cyclone Ockhi Turns Back Toward India

Tropical Cyclone Ockhi turned back toward India on Sunday night as it moved over the eastern Arabian Sea.  At 10:00 p.m. EST on Sunday the center of Tropical Cyclone Ockhi was located at latitude 14.6°N and longitude 68.9°E which put it about 405 miles (650 km) southwest of Mumbai, India.  Ockhi was moving toward the north-northeast at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 976 mb.

Tropical Cyclone Ockhi started to weaken on Sunday.  An upper level trough over the northern Arabian Sea was producing southwesterly winds which were causing moderate vertical wind shear.  In spite of the weakening trend, the structure of Tropical Cyclone Ockhi remained well organized.  There was a circular eye at the center of Ockhi.  A ring of strong storms surrounded the eye, but the ring was broken east of the center of circulation.  Several bands of showers and thunderstorms were occurring north of the core of Tropical Cyclone Ockhi.  The bands in the other parts of the circulation consisted primarily of low clouds and showers.  It appeared that some drier air might be wrapping around the southern and western parts of the circulation.  Winds to hurricane/typhoon force extended out about 50 miles (80 km) from the center or circulation.  Winds to tropical storm force extended out about 180 miles (290 km) from the center.

Tropical Cyclone Ockhi is likely to continue to weaken.  The upper level trough will continue to produce significant vertical wind shear over Ockhi.  The wind shear and drier air will weaken Ockhi to the equivalent of a tropical storm on Monday.  Some models dissipate the circulation of Ockhi before it makes a landfall in India, while other models move a weakened Tropical Cyclone inland before it dissipates.

The trough over the northern Arabian Sea will steer tropical cyclone Ockhi toward the northeast during the next several days.  On its anticipated track the center of Tropical Cyclone Ockhi could make a landfall on the coast of India between Mumbai and Veraval in 36 to 48 hours.  Ockhi could bring gusty winds and heavy rain to the Gulf of Khambhat and surrounding land areas in Gujarat.

Powerful Tropical Cyclone Ockhi Churns West of India

Powerful Tropical Cyclone Ockhi churned over the Arabian Sea west of India on Saturday night.  At 10:00 p.m. EST on Saturday the center of Tropical Cyclone Ockhi was located at latitude 12.1°N and longitude 69.1°E which put it about 535 miles (860 km) south-southwest of Mumbai, India.  Ockhi was moving toward the northwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 110 m.p.h. (175 km/h) and there were wind gusts to 130 m.p.h. (210 km/h).  The minimum surface pressure was 963 mb.

Tropical Cyclone Ockhi intensified again on Saturday and it was the equivalent of a strong Category 2 hurricane on the Saffir-Simpson Scale.  There was an elliptical eye at the center of circulation.  A ring of strong thunderstorms surrounded the eye, but there was a weaker area in the eastern side of the ring.  Bands of showers and thunderstorms were revolving around the core of the circulation.  The storms around the center of circulation were generating strong upper level divergence which was pumping mass away to the northeast of Tropical Cyclone Ockhi.  Winds to hurricane/typhoon force extended out about 45 miles (75 km) from the center of circulation.  Winds to tropical storm force extended out about 160 miles (260 km) from the center.

Tropical Cyclone Ockhi has been moving through an environment favorable for intensification, but it will move into a less favorable environment on Sunday.  Ockhi will continue to move over water where the Sea Surface Temperature is near 29°C.  So, there will be enough energy in the upper ocean to support a strong tropical cyclone.  Tropical Cyclone Ockhi could intensify a little more during the next 12 hours.  However, an upper level trough over Saudi Arabia will approach Ockhi from the west.  Southwesterly winds ahead of the trough will increase the vertical wind shear over Tropical Cyclone Ockhi and the increased shear is likely to cause the tropical cyclone to start to weaken later on Sunday.

Tropical Cyclone Ockhi is moving around the western end of a ridge centered over the Bay of Bengal.  The ridge is steering Ockhi toward the northwest.  Tropical Cyclone Ockhi will turn more toward the north on Sunday when it moves around the western end of the ridge.  The upper level trough approaching Ockhi from Saudi Arabia will steer the tropical cyclone toward the northeast in about 24 hours.  On its anticipated track the center of Tropical Cyclone Ockhi will approach the west coast of India north of Mumbai in about 60 hours.

Tropical Cyclone Ockhi Strengthens to Hurricane Equivalent

Tropical Cyclone Ockhi strengthened to the equivalent of a hurricane/typhoon on Friday as it moved over the Arabian Sea west of India.  At 4:00 p.m. EST on Friday the center of Tropical Cyclone Ockhi was located at latitude 9.4°N and longitude 71.7°E which put it about 655 miles (1055 km) south of Mumbai, India.  Ockhi was moving toward the west-northwest at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 90 m.p.h. (145 km/h) and there were wind gusts to 115 m.p.h. (185 km/h).  The minimum surface pressure was 969 mb.

Tropical Cyclone Ockhi continued to intensify on Friday and it is now the equivalent of a hurricane or typhoon.  An eye has appeared intermittently on satellite imagery.  A ring of strong storms surrounded the eye, although there have been occasional breaks in the northeastern segment of the ring.  Additional bands of showers and thunderstorms were occurring outside the core of the circulation.  There were more showers and thunderstorms in the western half of the circulation.  Storms near the core of Tropical Cyclone Ockhi were generating strong upper level divergence which was pumping mass away to the west and north of the cyclone.

Tropical Cyclone Ockhi will continue to be in an environment favorable for intensification for another 24 to 48 hours.  Ockhi will move over water where the Sea Surface Temperature is near 29°C.  An upper level ridge east of Ockhi is producing southeasterly winds which are blowing toward the top of the circulation.  Those winds may be the reason why more of the stronger rainbands are in the western half of the circulation.  The winds are also causing some vertical wind shear, but the shear is not strong enough to prevent intensification.  Tropical Cyclone Ockhi is likely to continue to intensify for another 24 to 36 hours and it could become the equivalent of a major hurricane during the weekend.

The upper level ridge is steering Tropical Cyclone Ockhi toward the west-northwest.  Ockhi will move more toward the north when it reaches the western end of the upper level ridge.  Tropical Cyclone Ockhi will approach the midlatitude westerly winds in two or three days and those winds will start to steer Ockhi more toward the northeast.  On its anticipated track Tropical Cyclone Ockhi could approach the west coast of India in three or four days.