Tag Archives: Tropical Storm Iselle

Tropical Storm Iselle Weakens

Tropical Storm Iselle weakened on Tuesday as it moved over the Eastern North Pacific Ocean west of Baja California.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Iselle was located at latitude 21.3°N and longitude 122.5°W which put the center about 815 miles (1310 km) west of the southern tip of Baja California.  Iselle was moving toward the west-northwest at 9 m.p.h. (15 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.

Tropical Storm Iselle weakened on Tuesday.  An upper level trough west of the West Coast of the U.S. was producing southwesterly winds that were blowing toward the top of Iselle’s circulation.  Those winds were causing moderate vertical wind shear.  The vertical wind shear was causing Tropical Storm Iselle to weaken.

The vertical wind shear was also causing the distribution of thunderstorms in Tropical Storm Iselle to be asymmetrical.  Thunderstorms were occurring in bands in the eastern side of Iselle’s circulation.  Bands in the western side of Tropical Storm Iselle consisted primarily of showers and lower clouds.  Storms near the center of Iselle generated upper level divergence that pumped mass away to the northeast of the tropical storm.  The removal of mass in the upper levels was less than the convergence of mass in the lower levels of the atmosphere.  So, the surface pressure increased on Tuesday.

The effects of the vertical wind shear also caused the distribution of wind speeds in Tropical Storm Iselle to be asymmetrical.  Winds to tropical storm force extended out 230 miles (370 km) in the eastern side of Iselle’s circulation.  Winds to tropical storm force extended out 140 miles (220 km) in the western side of Tropical Storm Iselle.

Tropical Storm Iselle will move through an environment that will be unfavorable for intensification during the next 24 hours.  Iselle will move over water where the Sea Surface Temperatures are near 26°C.  It will continue to move under the southern part of an upper level trough that is west of the West Coast of the U.S.  The upper level trough will continue to produce southwesterly winds that will blow toward the top of Iselle’s circulation.  Those winds will continue to cause moderate vertical wind shear.  In addition, Iselle will move into a mass of drier air that is west of Baja California.  Tropical Storm Iselle will  continue to weaken on Wednesday because of the effects of the vertical wind shear and the drier air.

Tropical Storm Iselle will move around the southwestern part of a high pressure system that is over the Eastern North Pacific Ocean.  The high pressure system will steer Iselle toward the west-northwest during the next 24 hours.  On its anticipate track, Tropical Storm Iselle will move farther away from Baja California.

Elsewhere, Tropical Storm Lala continued to weaken slowly far to the northwest of Hawaii.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Lala was located at latitude 35.2°N and longitude 177.6°W which put the center about 470 miles (760 km) north of Kure Atoll.  Lala was moving toward the west-northwest 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 995 mb.

Tropical Storm Iselle Spins Southwest of Baja California

Tropical Storm Iselle was spinning southwest of Baja California on Monday night.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Iselle was located at latitude 20.1°N and longitude 118.6°W which put the center about 590 miles (950 km) west-southwest of the southern tip of Baja California.  Iselle was moving toward the northwest at 15 m.p.h. (24 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 988 mb.

Tropical Storm Iselle strengthened on Monday.  More thunderstorms developed near the center of Iselle’s circulation.  Bands of showers and thunderstorms were also revolving around the center of Tropical Storm Iselle.  Storms near the center of Iselle generated upper level divergence that pumped mass away from the tropical storm.  The removal of mass caused the surface pressure to decrease.

Wind to tropical storm force extended out 195 miles (315 km) from the center of Tropical Storm Iselle.

Tropical Storm Iselle will move through an environment that will become unfavorable for intensification during the next 24 hours.  Iselle will move over water where the Sea Surface Temperatures are near 27°C.  It will move under the southern part of an upper level trough that is west of the West Coast of the U.S  The upper level trough will produce southwesterly winds that will blow toward the top of Iselle’s circulation.  Those winds will cause the vertical wind shear to increase on Tuesday.  In addition, Iselle will move into a mass of drier air that is west of Baja California.  Tropical Storm Iselle is likely to start to weaken on Tuesday because of the effects of the increased vertical wind shear and the drier air.

Tropical Storm Iselle will move around the southwestern part of a high pressure system that is over the Eastern North Pacific Ocean.  The high pressure system will steer Iselle toward the west-northwest during the next 24 hours.  On its anticipate track, Tropical Storm Iselle will move farther away from Baja California.

Elsewhere, former Tropical Storm Moke weakened to a tropical depression south of Hawaii and Tropical Storm Lala weakened gradually far to the northwest of Hawaii.

At 11:00 p.m. EDT on Monday the center of Tropical Depression Moke was located at latitude 16.0°N and longitude 163.0°W which put the center about 435 miles (695 km) east of Johnston Island.  Moke was moving toward the west at 14 m.p.h. (22 km/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 1005 mb.

At 11:00 p.m. EDT on Monday the center of Tropical Storm Lala was located at latitude 34.3°N and longitude 175.6°W which put the center about 435 miles (705 km) north-northeast of Kure Atoll.  Lala was moving toward the northwest at 6 m.p.h. (10 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 992 mb.

Tropical Storm Iselle Forms South of Baja California

Tropical Storm Iselle formed over the Eastern North Pacific Ocean south of Baja California on Sunday morning.  At 11:00 a.m. EDT on Sunday the center of Tropical Storm Iselle was located at latitude 15.3°N and longitude 114.2°W which put the center about 595 miles (955 km) south-southwest of the southern tip of Baja California.  Iselle was moving toward the west-northwest at 12 m.p.h. (19 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 1003 mb.

A low pressure system over the Eastern North Pacific Ocean south of Baja California strengthened on Sunday morning and the U.S. National Hurricane Center designated the system as Tropical Storm Iselle.

The distribution of thunderstorms in Tropical Storm Iselle was asymmetrical.  Thunderstorms were occurring in bands in the southern part of Iselle’s circulation.  Bands in the northern side of Tropical Storm Iselle consisted primarily of showers and lower clouds.  Storms near the center of Iselle generated upper level divergence that pumped mass away to the south and west of the tropical storm.  The removal of mass caused the surface pressure to decrease.

Wind to tropical storm force extended out 105 miles (165 km) from the center of Tropical Storm Iselle.

Tropical Storm Iselle will move through an environment that will be somewhat favorable for intensification during the next 24 hours.  Iselle will move over water where the Sea Surface Temperatures are near 29°C  It will move under the southeastern part of an upper level ridge that is south of Baja California.  The upper level ridge will produce northeasterly winds that will blow toward the top of Iselle’s circulation.  Those winds will cause moderate vertical wind shear.  The moderate vertical wind shear will inhibit intensification, but the wind shear may not be enough to prevent intensification.  Tropical Storm Estelle could intensify during the next 24 hours.

Tropical Storm Iselle will move around the southwestern part of a high pressure system that is over the Eastern North Pacific Ocean.  The high pressure system will steer Iselle toward the northwest during the next 24 hours.  On its anticipate track, Tropical Storm Iselle will remain far to the southwest of Baja California.

Elsewhere, Tropical Storm Moke was passing south of the Big Island of Hawaii and Tropical Storm Lala was spinning far to the northwest of Hawaii.

At 11:00 a.m. EDT on Sunday the center of Tropical Storm Moke was located at latitude 15.2°N and longitude 155.0°W which put the center about 310 miles (500 km) south of Hilo, Hawaii. Moke was moving toward the west at 15 m.p.h. (24 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 1002 mb.

At 11:00 a.m. EDT on Sunday the center of Tropical Storm Lala was located at latitude 32.1°N and longitude 173.9°W which put the center about 365 miles (590 km) northeast of Kure Atoll.  Lala was moving toward the west-northwest at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 988 mb.

Tropical Storms Hernan and Iselle Form West of Mexico

Tropical Storms Hernan and Iselle formed west of Mexico.  At 11:00 a.m. EDT on Thursday the center of Tropical Storm Hernan was located at latitude 19.1°N and longitude 106.2°W which put it about 95 miles (155 km) south-southwest of Cabo Corrientes, Mexico.  Hernan was moving toward the north-northwest at 5 m.p.h. (8 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 1001 mb.

The circulation around Tropical Storm Hernan was not well organized.  An upper level ridge over the southwestern U.S. and northern Mexico was producing northeasterly winds which were blowing toward the top of Hernan.  Those winds were causing strong vertical wind shear.  As a result of the shear, the stronger thunderstorms were occurring in bands in the southern part of the circulation.  Bands in the other parts of Tropical Storm Hernan consisted primarily of showers and lower clouds.  Winds to tropical storm force extended out 100 miles in the southern half of Hernan.  Winds in the northern half of the circulation were blowing at less than tropical storm force.

Tropical Storm Hernan will move through an environment unfavorable for intensification during the next several days.  Hernan will move over water where the Sea Surface Temperature is near 29°C.  So, there will be plenty of energy in the upper ocean to support intensification.  However, the upper level ridge will continue to cause strong vertical wind shear, which will inhibit potential intensification.  Tropical Storm Hernan is likely to weaken on Friday when it moves over colder water.  Hernan could approach the southern end of Baja California on Friday.

At 11:00 a.m. EDT on Thursday the center of Tropical Storm Iselle was located at latitude 17.0°N and longitude 115.8°W which put it about 560 miles (900 km) southwest of the southern tip of Baja California.  Iselles was moving toward the northeast at 5 m.p.h. (8 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 1001 mb.

The circulation around Tropical Storm Iselle was also not well organized.  It was being sheared by the same upper level ridge that was causing strong vertical wind shear over Tropical Storm Hernan.  Most of the thunderstorms in Iselle were also occurring in the southern half of the circulation.  Tropical storm force winds extended out 100 miles from the center in the southern half of Tropical Storm Iselle.  Iselle will also move through an environment unfavorable for intensification.