Tropical Cyclone Chedza Crossing Madagascar

Tropical Cyclone Chedza is moving across the central portion of Madagascar.  At 3:00 p.m. EST the center of Chedza was located at latitude 20.4°N and longitude 44.7°E which put it near Belo Tsiribihina.  It was moving toward the east-southeast at 10 m.p.h.  The maximum sustained wind speed was 45 m.p.h. and there were gusts to 55 m.p.h.  The minimum surface pressure was 996 mb.

Low vertical wind shear and warm Sea Surface Temperatures created an environment favorable for intensification and Chedza strengthened prior to making landfall in western Madagascar.  Satellite imagery indicated an eyelike feature formed and it is possible that Chedza may have reached hurricane intensity before landfall.  The terrain of Madagascar is weakening the lower portions of the circulation and that trend should continue while the center is over land.  It is possible that Chedza could strengthen after the center moves back over water east of Madagascar.

Tropical Storm Chedza Forms West of Madagascar

The tropical cyclone closest to land is Tropical Cyclone Chedza.  A cluster of thunderstorms meandering over the Mozambique Channel organized rapidly on Thursday and developed into Tropical Cyclone Chedza.  At 9:00 p.m. EST on Thursday the center of Chedza was located at latitude 19.1°S and longitude 42.4°E which put it about 140 miles west-northwest of Belo Tsiribihina, Madagascar.  It was moving toward the east at 6 m.p.h.  The maximum sustained wind speed was 45 m.p.h. and there were gusts to 55 m.p.h.  The minimum surface pressure was 996 mb.

Chedza is over warm Sea Surface Temperatures and the upper level winds are relatively light.  Further intensification is likely until Chedza makes landfall on Friday.  It is expected to weaken as it crosses Madagascar.  Some re-intensification may be possible after the center emerges over the Indian Ocean east of Madagascar.  Potential risks include locally heavy rainfall and flooding.

A near equatorial ridge is steering Chedza eastward.  It is expected to make landfall in 12 to 18 hours.  The ridge is expected to steer Chedza toward the east-southeast as it crosses Madagascar.

 

Tropical Storm Mekkhala Intensifies Slightly As It Moves Toward the Philippines

At 9:00 p.m. EST on Thursday the center of Tropical Storm Mekkhala was located at 11.6°N and longitude 131.1°E which put it about 540 miles east of Tacloban and about 710 miles east-southeast of Manila, Philippines.  Mekkhala was moving toward the west at 9 m.p.h.  The maximum sustained wind speed was 45 m.p.h. and there were wind gusts to 60 m.p.h.  The minimum surface pressure was 993 mb.

East-southeasterly winds in the upper levels continue to cause moderate wind shear over the top of Mekkhala.  It has a well developed low level circulation, but most of the thunderstorm formation is still in the western half of the storm.  Although Mekkhala is over warm Sea Surface Temperatures, the wind shear is inhibiting intensification.  Further intensification is possible, but it will likely be limited.

A subtropical ridge north of Mekkhala is extending westward and the ridge should continue to steer it westward.  The projected path would bring Mekkhala near the central Philippines in 24 to 36 hours.  Potential risks include locally heavy rain, flooding and mudslides.

 

Tropical Cyclone Bansi Moving Away from Mauritius

At 9:00 p.m. EST on Thursday the center of Tropical Cyclone Bansi was located at latitude 19.0°S and longitude 64.1°E which put it about 385 miles east-northeast of Port Louis, Mauritius.  Bansi was moving toward the east-southeast at 12 m.p.h.  The maximum sustained wind speed was 130 m.p.h. and it was estimated there were wind gusts to 160 m.p.h..  The minimum surface pressure was estimated to be 937 mb.

Bansi was in an environment of low vertical wind shear and warm Sea Surface Temperatures for much of Thursday and intensified slightly.  The speed of the upper level winds is increasing and the cloud pattern is showing signs of more wind shear.  A subtropical high pressure system is likely to move Bansi toward the southeast at a faster speed.  Bansi is likely to continue to move toward higher latitudes which will move it over colder water.  The speed of the upper level winds will also increase and so Bansi should weaken during the next few days.

 

Tropical Storm Mekkhala Develops East of the Philippines

Tropical Depression 01W intensified into Tropical Storm Mekkhala on Wednesday.  At 11:00 p.m. EST on Wednesday the center of Tropical Storm Mekkhala was located at latitude 11.5°N and longitude 133.8°E which put it about 370 miles north-northwest of Palau and about 820 miles east of Manila, Philippines.  Mekkhala was moving toward the west at 16 m.p.h.  The maximum sustained wind speed was 40 m.p.h. and there were gusts to 60 m.p.h.   The minimum surface pressure was 1000 mb.

Although there are still moderate wind speeds in the upper levels, the wind shear decreased slightly.  That allowed more thunderstorms to develop closer to the center of circulation and the system became more organized.  A subtropical ridge northeast of Mekkhala will continue to produce southeasterly winds over the top of the circulation.  Moderate wind shear will limit intensification.  However, Mekkhala will be moving over Warm Sea Surface Temperatures and so some intensification is possible during the next several days.

The subtropical ridge is expected to strengthen and steer Mekkhala westward toward the Philippines.  The tropical storm could be approaching the central and northern Philippines in 48 to 72 hours.  The main threats appear to be locally heavy rainfall, flooding and mudslides.

 

Tropical Cyclone Bansi Maintaining Intensity Northeast of Mauritius

At 11:00 p.m. EST on Wednesday the center of Tropical Cyclone Bansi was located at latitude 17.6°S and longitude 60.3°E which put it about 270 miles northeast of Port Louis, Mauritius.  Bansi was moving toward the east-southeast at 8 m.p.h.  The maximum sustained wind was 105 m.p.h. and it was estimated there were wind gusts to 125 m.p.h.  The minimum surface pressure was estimated to be 954 mb.

An eyewall replacement cycle altered the structure of Tropical Cyclone Bansi.  It previously had a small eye which had a diameter of 10-15 miles.  The outer eyewall has not contracted significantly since the inner eye dissipated.  Thus, Bansi is now a tropical cyclone with a large circular eye with a diameter of about 60 miles.  The circulation around Bansi seems to have achieved a rough equilibrium  with its surrounding environment and the intensity did not change much on Wednesday.  Bansi remains over warm Sea Surface Temperatures and in an area of light upper level winds.  So, it is still possible that some intensification could occur in the short term.  When Bansi moves to a higher latitude it will encounter cooler water and more wind shear and start to weaken.

A subtropical ridge near Bansi is expected to start to exert a greater influence and start to accelerate it toward the southeast at a faster speed in about 24 hours.

 

Tropical Depression 01W Forms East of Yap

The first tropical depression of 2015 over the Western North Pacific Ocean formed east of Yap on Tuesday.  At 7:00 p.m. EST on Tuesday the center of Tropical Depression 01W (TD01W) was located at latitude 10.1°N and longitude 139.9°E which put it about 130 miles east-northeast of Yap and about 1250 miles east-southeast of Manila, Philippines.  TD01W was moving toward the northwest at 13 m.p.h.  The maximum sustained wind speed was 35 m.p.h. and there were gusts to 45 m.p.h.  The minimum surface pressure was estimated to be 1000 mb.

A subtropical ridge is generating southeasterly winds over the top of TD01W and producing moderate wind shear.  The wind shear is causing much of the thunderstorm activity to be located in the northwestern part of the circulation around TD01W.  The lack of thunderstorms in the southern portion of the circulation is limiting the intensification of the tropical depression.  TD01W is over Sea Surface Temperatures that are around 30°C and so the potential for intensification exists if the speed of the upper level winds diminish.

The subtropical ridge is expected to continue to steer the tropical depression in a general west or west-northwesterly direction during the next few days.  This projected path could bring the tropical cyclone near the Philippines later this week.

 

Eyewall Replacement Cycle Weakens Tropical Cyclone Bansi

At 7:00 p.m. EST on Tuesday the center of Tropical Cyclone Bansi was located at latitude 17.4°S and longitude 58.2°E which put it about 200 miles north-northeast of Port Louis, Mauritius.  Bansi was moving toward the east-southeast at 3 m.p.h.  The maximum sustained wind speed was 130 m.p.h. and it was estimated there could be wind gusts to 160 m.p.h.  The estimated minimum surface pressure was 944 mb.

An outer rain band wrapped completely around the existing eyewall of Tropical Cyclone Bansi to create concentric eyewalls.  As the low level convergence became concentrated on the outer eyewall, the inner eyewall began to weaken.  This resulted in a reduction of the maximum sustained wind speed and a rise in the minimum surface pressure.  Satellite imagery indicates that most of the inner eyewall has dissipated, but some of it still remains.  The strongest winds are now occurring in the outer eyewall.  The eyewall replacement cycle also resulted in a larger circulation.  Bansi is still over warm Sea Surface Temperatures and the upper level winds are relatively weak.  So, some reintensification is possible during the next 24 hours, but it is always challenging to predict intensity changes after an eyewall replacement cycle.  As Bansi moves to higher latitudes, the Sea Surface Temperature will decrease and wind shear will increase.  So, Bansi is expected to weaken later this week.

Bansi remains in an area of weak steering winds.  As a result, it is moving slowly toward the east-southeast.  A subtropical ridge is expected to strengthen in about 24 hours and begin to steer Bansi southeastward at an increasing speed.  The projected track is expected to keep the core of Bansi northeast of Mauritius.

 

Bansi Now a Powerful Tropical Cyclone North of Mauritius

Tropical Cyclone Bansi continued to intensify rapidly on Monday and it is now the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale.  At 4:00 p.m. EST on Monday the center of Tropical Cyclone Bansi was located at latitude 17.6°S and longitude 57.2°E which put it about 175 miles north of Port Louis, Mauritius and about 225 miles north-northeast of Saint Denis, La Réunion.  Bansi was moving toward the east-southeast at 4 m.p.h.  The maximum sustained wind speed was 150 m.p.h. and it was estimated that there could be wind gusts to 185 m.p.h.  The minimum surface pressure was estimated to be 926 mb.

Bansi has been in a nearly perfect environment for rapid intensification of a tropical cyclone.  The Sea Surface Temperature is near 30°C, which means there is plenty of energy in the upper ocean.  The upper level winds are light and that has allowed convection near the center of circulation to drive strong upper level divergence.  The upper level divergence has pumped out mass and the pressure has fallen rapidly.  The circulation around Bansi is very symmetrical and there is a well developed eye that is visible on satellite imagery.  The environment around Bansi is expected to remain favorable for intensification and it is possible that it could reach the equivalent of a Category 5 hurricane.  Eyewall replacement cycles are common in strong hurricanes and if they develop they can cause periodic fluctuations in intensity.  Eventually,when Bansi moves toward higher latitudes, wind shear will increase and it will begin to weaken.

As the upper level winds around Bansi have diminished, the steering currents have weakened.  Bansi is expected to move slowly in a generally east-southeasterly direction for the next 24 to 48 hours.  The projected path would take the center northeast of Mauritius.  Eventually, a subtropical ridge is expected to strengthen and accelerate Bansi toward the southeast.  If a sharper southeasterly turn occurs, that would bring the center of Bansi closer to Mauritius.

 

Tropical Cyclone Bansi Intensifying Rapidly North of La Reunion

A tropical cyclone has intensified rapidly north of La Réunion during the past 24 hours.  At 1:00 p.m. EST on Sunday the center of Tropical Cyclone Bansi was located at latitude 17.1°N and longitude 55.1°E which put it about 300 miles north of Saint Denis, La Réunion and about 250 miles northwest of Port Louis, Mauritius.  Bansi was moving toward the south-southeast at 5 m.p.h.  The maximum sustained wind speed was 75 m.p.h. and there were wind gusts to 90 m.p.h.  The minimum surface pressure was estimated to be 974 mb.

The circulation around Bansi organized rapidly on Sunday and it exhibits a symmetrical shape with a well developed eye at its center.  The circulation is small, but it has well developed upper level outflow to pump out mass.  Bansi is over Sea Surface Temperatures that are warmer than 30°C which provide plenty of energy to intensify the circulation further.  Bansi could intensify rapidly for another 24 hours and become a very strong tropical cyclone as it passes near Mauritius.

Bansi is being steered to the south-southeast by a ridge of high pressure.  The ridge is expected to continue to steer Bansi in a general southeasterly direction, although there could be short-term jogs to the east-southeast or south-southeast.  The anticipated track could bring Bansi near Mauritius in 48-72 hours.