Monthly Archives: December 2015

Tropical Depression 09C Forms Near Equator

Sufficient evidence of a surface center of circulation within a broad area of thunderstorms near the Equator prompted the Central Pacific Hurricane Center to classify the system as Tropical Depression 09C.  At 10:00 p.m. EST on Wednesday the center of Tropical Depression 09C (TD09C) was located at latitude 2.8°N and longitude 177.8°W which put it about 1850 miles (2975 km) southwest of Honolulu, Hawaii.  TD09C was moving toward the west-northwest at 8 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 1001 mb.

The circulation of Tropical Depression 09C is not particularly well organized and there may be multiple small centers inside the larger circulation of the system.  One small center of circulation is near a cluster of thunderstorms in the northern half of the circulation and that center is currently being designated as the center of TD09C.  Another circulation center is near latitude 1.0°N and longitude 174.6°W, but there are no thunderstorms near that center.  The main area of thunderstorms is north of the official center of circulation.  There are a few partial spiral bands northeast of the center of the depression.

The environment around TD09C is only marginal for intensification.  The depression is moving over water where the Sea Surface Temperatures are near 30°C.  So, there is plenty of energy in the upper ocean to support intensification.  However, a strong upper level ridge east of TD09C is generating strong southeasterly winds over the top of the depression.  The strong vertical wind shear is contributing to the poor organization of TD09C.  The wind shear is likely to inhibit intensification during the next several days.

A subtropical ridge east of TD09C is expected to steer the depression slowly toward the west-northwest during the next few days.  The actual track of TD09C could be somewhat erratic, especially if some of the small centers of circulation dissipate and additional centers form in clusters of thunderstorms that develop.  On its anticipated track Tropical Depression 09C could approach Tarawa in about three days and it could be approaching the Marshall Islands this weekend.

The most remarkable thing about Tropical Depression 09C is that is developed so close to the Equator.  Conventional wisdom often says that tropical cyclones cannot form near the Equator because the Coriolis effect is too small.  However, although tropical cyclones are rare near the Equator, Tropical Depression 09C is another example that they can form in that region.

Tropical Cyclone Ula Forms East of Samoa

A well-defined center of circulation consolidated within a very large area of thunderstorms straddling the Equator near the International Date Line and the system was classified as Tropical Cyclone Ula (06P).  At 5:00 a.m. EST on Wednesday the center of Tropical Cyclone Ula was located at latitude 12.5°S and longitude 166.6°W which put it about 325 miles (525 km) east-northeast of Pago Pago, Samoa.  Ula was moving toward the south-southeast at 15 m.p.h. (24 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 991 mb.

Thunderstorms in a spiral rainband are wrapping around the center of circulation and microwave satellite imagery has suggested that an eye may be forming in Tropical Cyclone Ula.  Additional spiral bands are developing in the outer portion of the circulation.  The thunderstorms near the center of circulation are generating upper level divergence which is pumping out mass, especially to the east of the center of Ula.

Tropical Cyclone Ula is in an environment that is favorable for intensification.  It is over water where the Sea Surface Temperatures are between 28°C and 29°C.  The upper level winds are light and there is not much vertical wind shear.  Ula is likely to continue to intensify as the core of the circulation consolidates and it could become the equivalent of a hurricane within 24 to 36 hours.

Ula is currently being steered to the south-southeast by a subtropical ridge which is located east of the tropical cyclone.  The ridge is expected to intensify and extend westward.  If it does so, then the building ridge will cause Tropical Cyclone Ula to turn toward the southwest.  On its anticipated track the center of Tropical Cyclone could pass south of Samoa in 24 to 48 hours and it could approach Fiji in four or five days.

Tropical Cyclone Ula could bring strong winds and heavy rain to any island it passes near.

Tropical Low Forms Over Northern Australia

A distinct center of circulation consolidated within a broader area of low pressure near the northern coast of Australia.  The Australian Bureau of Meteorology designated the system as a Tropical Low.  At 10:00 p.m. EST on Saturday the center of the Tropical Low was located at latitude 14.7°N and longitude 132.7°E which put it about 35 miles (55 km) east-southeast of Katherine, Australia and about 135 miles (220 km) west of Ngukurr.  The Tropical Low was moving toward the east at 3 m.p.h. (5 km).  The maximum sustained wind speed was 30 m.p.h. (45 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1005 mb.

The atmospheric environment around the Tropical Low would be favorable for the development of a tropical cyclone.  The upper level winds are light and there is not much vertical wind shear.  An upper level anticyclone over the Tropical Low is providing a source of upper level divergence, which is pumping out mass.  However, the Tropical Low is over land which is preventing the development of a tropical cyclone.  As long as the Tropical Low remains over land, it will not develop into a tropical cyclone.  However, if the Tropical Low emerges over the Gulf of Carpentaria in a day or so, it could develop into a tropical cyclone.

A ridge in the middle levels of the atmosphere is steering the tropical low toward the east and that general motion is expected to continue for another 24 to 48 hours.  On its anticipated track the Tropical Low could emerge over the southwestern Gulf of Carpentaria south of Port Roper in 24 to 36 hours.

Although the Tropical Low is moving over land, it will still draw in enough moisture to be capable of producing locally heavy rain.  Flooding may be possible in some locations.

Typhoon Melor Making Landfall on Mindoro as Equivalent of Cat. 4 Hurricane

Typhoon Melor intensified on Monday and it is making landfall on Mindoro in the Philippines as the equivalent of a Category 4 Hurricane on the Saffir-Simpson Scale.  At 10:00 p.m. EST on Monday the center of Typhoon Melor was located at latitude 13.0°N and longitude 121.5°E which put it about 20 miles (32 km) southeast of Calapan and about 125 miles (205 km) south-southeast of Manila, Philippines.  Melor was moving toward the west at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 140 m.p.h. (230 km/h) and there were wind gusts to 170 m.p.h. (270 km/h).  The minimum surface pressure was 939 mb.

The core of Typhoon Melor passed just north of Samar and it quickly moved over the southeastern tip of Luzon.  Since the core stayed mainly over water, the circulation was not seriously disrupted by the increased friction that would have occurred if it had moved over land.  As a result, the core Typhoon Melor was intact when it moved over the Sibuyan Sea.  The circulation was able to extract energy from the warm water of Sibuyan Sea.  Melor was in an area where the upper level winds were light and there was little vertical wind shear.  The favorable environment allowed the typhoon to intensify further on Monday and Melor reached the equivalent of a Category 4 hurricane.

The center of Typhoon Melor is making a landfall on the northeast coast of Mindoro.  Since the core of Melor will be moving over the island of Mindoro during the next few hours, the typhoon should start to weaken.  Melor will likely still be a typhoon when the center emerges over the South China Sea.  A strong surge of cold, dry air from the north will increase vertical wind shear around Typhoon Melor in 24 to 36 hours.  The dry air and increased wind shear will weaken Melor more rapidly after that occurs.

A subtropical ridge is steering Typhoon Melor toward the west and that general motion is expected to continue for another 24 to 36 hours.  After that time a weakening Melor will be steered by the flow closer to the surface, which should start to push it toward the southwest.

Typhoon Melor will bring very strong winds and heavy rain to Mindoro and southern Luzon.  The core of Melor should stay south of Manila, but locally heavy rain may be possible.  Heavy rain could also cause flooding and mudslides in areas of steep terrain.

Strong Typhoon Melor Along Coast of Samar Heading for SE Luzon

Typhoon Melor reached the Philippines on Sunday and it was moving along the north coast of Samar toward southeastern Luzon.  At 10:00 p.m. EST on Sunday the center of Typhoon Melor was located at latitude 12.6°N and longitude 125.3°E which put it about 20 miles (32 km) north of Laoang, Philippines and about 100 miles (160 km) east-southeast of Legaspi in southeastern Luzon.  Melor was moving toward the west at 13 m.p.h. (21 km/h).  The maximum sustained wind speed was 130 m.p.h. (210 km/h) and there were wind gusts to 160 m.p.h. (260 km/h).  The minimum surface pressure was 949 mb.

Typhoon Melor has been moving through an environment favorable for intensification.  The Sea Surface Temperatures were near 28°C and there has been little vertical wind shear.  However, the circulation is starting to interact with the Philippines.  The southwestern quarter of the circulation is over Samar.  However, since the core of the circulation is north of the coast of Samar, Melor has remained a strong typhoon.  The circulation of Typhoon Melor is likely to retain much of its integrity until the center makes landfall in southeastern Luzon near Sorsogon.  Melor could remain at typhoon intensity for another 24 hours.  However, eventually the increased friction will slow the portions of the circulation that move over land and Melor will weaken to a tropical storm.

A subtropical ridge is steering Typhoon Melor slightly north of due west and that general motion is expected to continue for several more days.  On its anticipated track the core of Typhoon Melor will pass north of Samar.  It will make landfall on extreme southeastern Luzon near Sorsogon in a few hours.  The center of Melor should pass south of Legaspi before moving over the Sibuyan Sea.  It could move south of Manila in about 36 hours as a tropical storm.

Melor is a strong typhoon and it could bring strong winds and heavy rain to northern Samar, southeastern Luzon, the islands around the Sibuyan Sea and Mindoro.  Heavy rain could cause flooding and trigger mudslides, especially in areas of steep terrain.

Melor Intensifies into a Typhoon and Threatens the Philippines

Tropical Storm Melor continued to intensify on Saturday and it reached typhoon status.  At 10:00 p.m. EST on Saturday the center of Typhoon Melor was located at latitude 12.0°N and longitude 129.7°E which put it about 320 miles (520 km) east of Laoang, Philippines.  Melor was moving toward the west-northwest at 13 m.p.h. (21 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 973 mb.

The structure of Typhoon Melor is well organized and an eye has appeared intermittently on satellite imagery.  Melor has a small, well developed inner core surrounded by multiple spiral rainbands.  Thunderstorms near the core are generating upper level divergence, especially to the northeast of the center of circulation.  The upper level divergence is pumping out mass and causing the surface pressure to decrease.

Typhoon Melor is in an environment that is favorable for further intensification.  It is moving over water where the Sea Surface Temperature is around 28°C.  An upper level ridge east of Melor is producing light southerly winds over the top of the typhoon, but the vertical wind shear is modest.  Melor is likely to continue to intensify on Sunday and it could become the equivalent of a major hurricane.

A subtropical ridge is steering Typhoon Melor toward the west-northwest and that general motion is expected to continue for another two or three days.  On its anticipated track Typhoon Melor could be near the northeast coast of Samar in about 24 hours.  The center of Melor could make landfall over southeast Luzon in about 36 hours.  Melor could bring strong winds and heavy rain.  The heavy rain could cause flooding and mudslides, especially in areas of steep terrain.

Tropical Storm Melor Forms West of Yap

A well defined center of circulation developed within an area of thunderstorms on Friday and the system was designated Tropical Storm Melor (28W).  At 4:00 p.m. EST on Friday the center of Tropical Storm Melor was located at latitude 10.4°N and longitude 134.9°E which put it about 210 miles (335 km) north-northeast of Koror, Palau.  Melor was moving toward the west-northwest at 17 m.p.h. (27 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 997 mb.

Tropical Storm Melor organized quickly on Friday.  A rainband wrapped about three quarters of the way around the center of circulation and an eyewall may be forming.  Outer rainbands are also rotating around the center of circulation.  Thunderstorms around the center of circulation are producing upper level divergence.

The environment around Tropical Storm Melor is favorable for further intensification.  It is over water where the Sea Surface Temperatures are warm.  An upper level ridge is producing light southerly winds over the top of Melor, but there is only modest vertical wind shear.  Once a fully developed eye forms at the center of Melor, the tropical storm could intensify rapidly.  Melor could become a typhoon on Saturday and it could become the equivalent of a major hurricane in 48 to 73 hours.

A subtropical ridge north of Melor is steering the tropical storm toward the west-northwest and that general motion is expected to continue during the next two or three days.  On its anticipated track, Melor could reach the Central Philippines within 72 hours.  It could be a strong typhoon at that time.