After intensifying rapidly into a strong but small typhoon on Monday, vertical wind shear caused Higos to begin a rapid weakening trend on Tuesday.  At 11:00 p.m. EST on Tuesday the center of Typhoon Higos was located at latitude 15.3°N and longitude 152.9°E which put it about 450 miles east of Saipan and about 880 miles west-southwest of Wake Island.  Higos was moving toward the west-northwest at 7 m.p.h.  The maximum sustained wind speed was 80 m.p.h. and there were gusts to 90 m.p.h.  The minimum surface pressure was estimated to be 974 mb.

Strong southwesterly winds in the upper levels are blowing over the top of Higos.  Those strong winds have blown the upper half of the circulation off to the northeast of the lower half of the circulation.  The lower portion of the circulation consists of a tight center with spiral bands of shallower clouds rotating around the center.  The wind shear is preventing deep thunderstorms from forming near the center and it is causing Higos to weaken rapidly.  Unless the shear lets up, which is unlikely, the lack of deep convection to remove mass will cause the surface pressure to increase and the circulation to spin down.

Since Higos consists primarily of a lower level circulation it is likely to be steered by winds in the lower portion of the atmosphere.  A subtropical ridge to the east of Higos is likely to steer it to the north-northwest until the wind shear causes it to spin down.

A center of circulation consolidated within a large area of thunderstorms centered about 900 miles east of Guam and the system was designated as Tropical Storm Higos.  At 10:00 p.m. EST on Saturday the center of Tropical Storm Higos was located at latitude 12.1°N and longitude 157.4°E which put it about 480 miles northeast of Fananu and about 850 miles east of Guam.  Higos was moving toward the north-northwest at 7 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.

Higos was moving over warm Sea Surface Temperatures.  Satellite imagery indicated that upper level divergence was well developed and there appeared to be an outflow channel to the northeast.  As the divergence pumped out mass, the surface pressure decreased and the wind speeds increased.  A spiral band of thunderstorms wrapped around the center of circulation and the system displayed increased organization.  Higos has the potential to intensify during the next 24 to 48 hours and it could possible become a typhoon.  Later in the week stronger upper level winds are expected to increase the vertical wind shear and weaken Higos.

Higos was near the western end of a subtropical ridge of high pressure which was steering it toward the northwest.  The subtropical ridge is expected to continue to steer the storm toward the northwest in the short term.  Over the longer term the track of Higos will depend to some extent on how strong it becomes.  If it intensifies more, Higos will be affected more strongly by upper level westerly winds located farther north.  Those winds would cause Higos to take a more northerly track.  If Higos remains weaker, then it could be less affected by the upper level westerlies and it might take a track farther south.  Guidance from numerical models is split between a more northerly and a more westerly track.

Tropical Storm Mekkhala is moving through the northern Philippines.  At 11:00 p.m. EST on Saturday the center of Tropical Storm Mekkhala was located at latitude 13.9°N and longitude 123.0°E which put it near Daet and about 150 miles east-southeast of Manilla.  Mekkhala was moving toward the northwest at 11 m.p.h.  The maximum sustained wind speed was 40 m.p.h. and there were gusts to 50 m.p.h.  The minimum surface pressure was 996 mb.

Mekkhala crossed over northern parts of Samar on Saturday and the center is near the southeastern portion of Luzon.  The islands disrupted parts of the circulation in the lower levels and Mekkhala weakened throughout the day.  Thunderstorms have been redeveloping in the part of the circulation over Lamon Bay and Mekkhala continues to be a tropical storm.  Divergence continues in the upper portion of the circulation and the wind shear remains at a moderate level.  While the atmospheric and oceanic environment would support intensification, if the center moves across Luzon further weakening is likely.

Mekkhala is near the western end of a subtropical ridge which has been steering the system toward the northwest.  If deep convection continues, then the ridge could continue to steer it toward the northwest.  However, if the system weakens to the point where only shallow convection exists, then it could be steered more toward the west by the lower level flow.

The relatively slow movement of Mekkhala continues the potential for locally heavy rainfall, flooding and mudslides.

Tropical Storm Mekkhala intensified rapidly on Friday and it has reached typhoon intensity.  At 3:00 p.m. EST on Friday the center of Mekkhala was located at latitude 10.9°N and longitude 127.5°E which put it about 280 miles east of Tacloban and about 500 miles east-southeast of Manila, Philippines.  Mekkhala was moving toward the west-southwest at 11 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 974 mb.

The speed of the upper level east-southeasterly winds blowing over the top of Mekkhala weakened on Friday and the vertical shear affecting the circulation decreased.  The combination of less vertical wind shear and warm Sea Surface Temperatures allowed convection to develop all around the core of the circulation.  Strong thunderstorms near the center of Mekkhala created upper level divergence and the storm intensified rapidly into a typhoon.  Mekkhala remains in a favorable environment and further intensification is possible before it reaches the Philippines.  Once the center of circulation beings to move over the islands, interaction with land will weaken it.

A strengthening subtropical ridge has been steering Mekkhala a little south of due west and that motion is expected to continue in the short term.  The typhoon could reach the Philippines in about 12 hours.  Mekkhala could turn more toward the west-northwest as it crosses the Philippines and reaches the western end of the subtropical ridge.

Since Mekkhala has intensified into a typhoon the potential risks now include wind damage, and storm surge in addition to locally heavy rainfall, flooding and mudslides.

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.