Monthly Archives: November 2018

Tropical Cyclone Alcide Rapidly Intensifies Into Equivalent of Hurricane/Typhoon

Tropical Cyclone Alcide rapidly intensified into the equivalent of a hurricane/typhoon east of northern Madagascar on Wednesday.  At 10:00 a.m. EDT on Wednesday the center of Tropical Cyclone Alcide was located at latitude 10.6°S and longitude 55.7°W which put it about 675 miles (975 km) north of Port Louis, Mauritius.  Alcide was moving toward the west-southwest at 11 m.p.h. (17 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 972 mb.

The circulation around Tropical Cyclone Alcide organized rapidly during the past 24 hours.  An eye formed at the center of circulation.  A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Several bands of showers and thunderstorms were revolving around the core of Alcide.  Storm near the core were generating upper level divergence which was pumping mass away from the tropical cyclone.

The circulation around Tropical Cyclone Alcide is relatively small.  Winds to hurricane/typhoon force extend out about 25 miles (40 km) from the center of circulation.  Winds to tropical storm force extend out about 80 miles (130 km) from the center.

Tropical Cyclone Alcide will move through an environment capable of supporting further intensification during the next 48 hours.  Alcide will move over water where the Sea Surface Temperature is near 27°C.  It will move near the western end of an upper level ridge.  The ridge will produce easterly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear, but the shear will not prevent intensification.  Tropical Cyclone Alcide could strengthen to the equivalent of a major hurricane during the next day or two.

The upper level ridge will steer Tropical Cyclone Alcide in a west-southwesterly direction.  On its anticipated track Alcide would stay north of Mauritius and La Reunion.  Tropical Cyclone Alcide could be east of northern Madagascar in a few days.

Tropical Cyclone Alcide Forms North of Mauritius

Tropical Cyclone Alcide formed north of Mauritius on Tuesday.  At 10:00 a.m. EDT on Tuesday the center of Tropical Cyclone Alcide was located at latitude 9.7°S and longitude 58.9°E which put it about 740 miles (1190 km) north of Port Louis, Mauritius.  Alcide 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 999 mb.

A distinct center of circulation consolidated in an area of thunderstorms over the South Indian Ocean and the system was designated as Tropical Cyclone Alcide.  The circulation around Alcide was slowly becoming better organized.  The inner end of a band of thunderstorms was wrapping around the western side of the center of circulation.  Several other bands were developing south and west of the center.  Bands north and east of the center consisted primarily of showers and lower clouds.  Storms near the center of circulation were starting to generate upper level divergence which was pumping mass away from the core of the tropical cyclone.

Tropical Cyclone Alcide will move through an environment that will support intensification.  Alcide will move over water where the Sea Surface Temperature is near 27.5°C.  It will move around the northwestern side of an upper level ridge.  The ridge will produce easterly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear which will slow the rate of intensification, but the winds are not likely to be strong enough to prevent intensification.  Tropical Cyclone Alcide could strengthen into the equivalent of a hurricane/typhoon during the next 48 to 72 hours.

The upper level ridge will steer Tropical Cyclone Alcide slowly toward the west-southwest during the next two or three days.  On its anticipated track Alcide could be northeast of Madagascar in a few days.  It could be the equivalent of a hurricane/typhoon at that time.

Tropical Storm Xavier Causes Warning for Coast of Mexico

Potential impacts of Tropical Storm Xavier caused the government of Mexico to issue a Tropical Storm Warning for a portion of the coast.  The Tropical Storm Warning was in effect from Punta San Telmo to Playa Perula, Mexico.  At 1:00 p.m. EST the center of Tropical Storm Xavier was located at latitude 17.8°N and longitude 105.4°W which put it about 110 miles (175 km) southwest of Manzanillo, Mexico.  Xavier was moving toward the north at 6 m.p.h. (10 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 1003 mb.

An upper level trough is producing strong southwesterly winds which are blowing toward the top of Tropical Storm Xavier.  Those winds are causing significant vertical wind shear and they blew the upper portion of Xavier northeast of the lower level circulation earlier on Sunday morning.  However, new thunderstorms formed around the center of circulation and in a rainband northeast of the center.  There are several bands of showers and thunderstorms west of the center of circulation.  The bands southeast of the center consist primarily of low clouds and showers.  The strongest winds are occurring in the northeast portion of Tropical Storm Xavier.  Winds to tropical storm force extend out about 80 miles (130 km) from the center of circulation.  Winds are blowing to tropical storm force near the coast of Mexico which is why the Tropical Storm Warning was issued.

The future intensity of Tropical Storm Xavier will be determined by the strength of the upper level winds.  Xavier will move over water where the Sea Surface Temperature is near 28°C.  So, there is plenty of energy in the upper ocean to support a tropical storm.  However, the upper level winds were almost strong enough to shear Xavier apart on Sunday morning.  If the upper level winds do not get any stronger, then Xavier could persist as a tropical storm for another day or two.  If the upper level winds do get stronger, which is the forecast of many numerical models, then Xavier will quickly weaken to a tropical depression.  The official forecast from the National Hurricane Center follows the second scenario and it weakens Xavier to a tropical depression by Monday night.

The upper level trough will also determine future track of Tropical Storm Xavier.  If the upper level winds allow Xavier to persist as a tropical storm, then the trough will steer Xavier north-northeast toward the coast of Mexico.  If the upper level winds blow the top of the circulation away from the lower level circulation, then the winds closer to the surface would turn the lower part of Xavier back toward the west.  The official forecast from the National Hurricane Center follows the second scenario.

Bands of showers and thunderstorms in the northeaster part of Tropical Storm Xavier are already dropping rain over the coastal regions of Colima and Jalisco.  Prolonged heavy rain could cause flash floods in some locations.  Winds could reach tropical storm force along the coast even if the center of Tropical Storm Xavier does not make landfall.  There could also be a minor storm surge where the wind blows water toward the coast.

Tropical Storm Xavier Forms Southwest of Manzanillo

Tropical Storm Xavier formed southwest of Manzanillo, Mexico on Friday night.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Xavier was located at latitude 14.5°N and longitude 108.2°W which put it about 405 miles (650 km) southwest of Manzanillo, Mexico.  Xavier was moving toward the east-northeast at 8 m.p.h. (13 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 1006 mb.

A center of circulation developed in an area of thunderstorms southwest of Mexico on Friday.  When more thunderstorms developed closer to the center of circulation on Friday night, the National Hurricane Center designated the system as Tropical Storm Xavier.  The core of Tropical Storm Xavier was small.  The inner part of a band of showers and thunderstorms was wrapping around the center of circulation.  Storms near the core were generating upper level divergence.  Other short bands of showers and thunderstorms were revolving around the center of Tropical Storm Xavier.  Winds to tropical storm force extended out about 70 miles (110 km) from the center of circulation, but the strongest winds were occurring primarily in the southeastern quadrant of Xavier.

Tropical Storm Xavier will move through an environment somewhat favorable for intensification during the weekend.  Xavier will move over water where the Sea Surface Temperature is near 28°C.  So, there will be plenty of energy in the upper ocean to support intensification.  However, an upper level trough west of Xavier will produce strong southwesterly winds which will blow toward the top of the tropical storm.  Those winds will cause moderate vertical wind shear and they will inhibit upper level divergence to the west of Tropical Storm Xavier.  Xavier is likely to intensify on Saturday, but its small circulation means that it could weaken if the wind shear increases.

The upper level trough will also steer Tropical Storm Xavier in a north-northeasterly direction during the next day or two.  On its anticipated track the center of Tropical Storm Xavier could approach the west coast of Mexico by Sunday night.