Tag Archives: southwest U.S.

Tropical Storm Rosa Nears Baja California

Tropical Storm Rosa moved nearer to Baja California on Monday morning.  At 11:00 a.m. EDT on Monday the center of Tropical Storm Rosa was located at latitude 27.5°N and longitude 116.5°W which put it about 90 miles (145 km) west-southwest of Punta Eugenia, Mexico.  Rosa was moving toward the north-northeast 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 1000 mb.

A Tropical Storm Warning was in effect for the portion of the coast from Punta Abreojos to Cabo San Quintin, Mexico.  A Tropical Storm Watch was in effect for the portion of the coast from Bahia de los Angeles to San Felipe, Mexico.

Tropical Storm Rosa was weakening as it approached the coast of Baja California.  Rosa was moving over water where the Sea Surface Temperature was near 23°C.  An upper level low west of California was producing southwesterly winds which were blowing toward the top of the circulation.  Those winds were causing significant vertical wind shear.  The effects of cool water and vertical shear were causing most of the stronger thunderstorms to occur northeast of the center of circulation.  Bands south and west of the center consisted primarily of showers and lower clouds.

The center of Tropical Storm Rosa will reach northern Baja California in a few hours.  Rosa will bring some gusty winds when when it reaches the coast, but the greater risk is locally heavy rainfall.  Rosa could drop several inches of rain and flash floods could occur.  The lower level part of Rosa’s circulation will weaken when it crosses Baja California.  However, the upper low west of California will steer the middle and upper parts of Tropical Storm Rosa over the Southwestern U.S.  Rosa, or its remnants, could drop locally heavy rain over that region during the next several days.  Flash Flood Watches have been issued for southeastern California, eastern Nevada, western Arizona, and much of Utah.

Elsewhere over the Eastern North Pacific, Tropical Storm Sergio was strengthening slowly south of Baja California.  At 11:00 a.m. EDT on Monday the center of Tropical Storm Sergio was located at latitude 11.5°N and longitude 109.5°W which put it about 790 miles (1275 km) south of the southern tip of Baja California.  Sergio was moving toward the west at 14 m.p.h. (22 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 995 mb.

Hurricane Rosa Moves Toward Baja California

Hurricane Rosa moved toward Baja California on Saturday night.  At 11:00 p.m. EDT on Saturday the center of Hurricane Rosa was located at latitude 22.4°N and longitude 118.9°W which put it about 440 miles (710 km) south-southwest of Punta Eugenia, Mexico.  Rosa was moving toward the north at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 100 m.p.h. (160 km/h) and there were wind gusts to 120 m.p.h. (195 km/h).  The minimum surface pressure was 969 mb.

A Tropical Storm Warning was in effect for the portion of the coast from Punta Abreojos to Cabo San Quintin, Mexico.  A Tropical Storm Watch was in effect for the portion of the coast from Bahia de los Angeles to San Felipe, Mexico.

Hurricane Rosa will move into an environment unfavorable for hurricanes on Sunday.  Rosa will move over water where the Sea Surface Temperature is cooler than 26°C.  In addition an upper level low near the west coast of the U.S. will produce southwesterly winds which will cause vertical wind shear.  The combination of cooler water and more vertical wind shear will cause Hurricane Rosa to weaken.  Rosa could weaken to a tropical storm by Sunday night.

The upper low will steer Hurricane Rosa toward the northeast during the next several days.  On its anticipated track Rosa could reach Baja California on Monday.  It will likely be a tropical storm at that time.  Even though it will weaken, Rosa will drop heavy rain over parts northern Baja California and the southwestern U.S.  The heavy rain could cause flash floods.

Elsewhere over the Eastern North Pacific Ocean Tropical Storm Sergio formed southwest of Acapulco, Mexico.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Sergio was located at latitude 12.3°N and longitude 103.3°W which put it about 390 miles (630 km) southwest of Acapulco, Mexico.  Sergio was moving toward the west at 10 m.p.h. (16 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.

Hurricane Rosa Rapidly Intensifies Into a Major Hurricane Southwest of Baja California

Hurricane Rosa rapidly intensified into a major hurricane southwest of Baja California on Thursday.  At 5:00 p.m. EDT on Thursday the center of Hurricane Rosa was located at latitude 16.9°N and longitude 115.9°W which put it about 570 miles (915 km) southwest of the southern tip of Baja California.  Rosa was moving toward the west at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 125 m.p.h. (200 km/h) and there were wind gusts to 145 m.p.h. (240 km/h).  The minimum surface pressure was 953 mb.

Hurricane Rosa rapidly intensified into a powerful hurricane on Thursday and a circular eye developed at the center of circulation.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in the ring of storms.  The circulation around Hurricane Rosa was symmetrical.  Several bands of showers and thunderstorms were revolving around the core of the hurricane.  Storms around the core were generating strong upper level divergence which was pumping mass away from the hurricane.

The circulation around Hurricane Rosa was relatively small.  Winds to hurricane force only extended out about 35 miles (55 km) from the center of circulation.  Winds to tropical storm force extended out about 115 miles (185 km) from the center.  The Hurricane Intensity Index (HII) for Hurricane Rosa was 23.6.  The Hurricane Size Index (HSI) was 9.8 and the Hurricane Wind Intensity Size Index (HWISI) was 33.4.

Hurricane Rosa will continue to move through an environment favorable for intensification during the next 12 to 24 hours.  Rosa will move over water where the Sea Surface Temperature is near 28°C.  It will move through an area where the upper level winds are weak and there will be little vertical wind shear during the shorter term.  If a rainband wraps around the existing eye and eyewall, an eyewall replacement cycle could halt the current period of rapid intensification.  Hurricane Rosa will start to move over cooler water during the weekend.  An upper level low west of California will produce southwesterly winds which will blow toward the top of Rosa’s circulation.  Those winds will cause more vertical wind shear and they could cause Rosa to weaken more quickly.

Hurricane Rosa will move around the western end of a ridge of high pressure over northern Mexico on Friday.  Rosa will start to move more toward the north when it moves around the western end of the ridge.  The upper level trough east of California will turn Rosa more toward the northeast during the weekend.  On its anticipated track Rosa could approach Baja California early next week.  It may weaken to a tropical storm before it gets to Baja California, but it still will have the potential to drop heavy rain.

Linda Rapidly Intensifies Into a Major Hurricane

Hurricane Linda rapidly intensified on Tuesday and it now has a wind speed that qualifies it as a Category 3 Hurricane on the Saffir-Simpson Scale.  This makes Linda the fifth major hurricane in the Eastern North Pacific in 2015.  At 11:00 a.m. EDT on Tuesday the center of Hurricane Linda was located at latitude 21.3°N and longitude 113.9°W which put it about 280 miles (450 km) west-southwest of the southern tip of Baja California.  Linda was moving toward the north-northwest at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 140 m.p.h. (225 km/h).  The minimum surface pressure was 956 mb.

Upper level winds over Linda decreased and the reduction in vertical wind shear allowed it to intensify rapidly during the past 12 hours.  A visible eye and symmetrical eyewall are evidence of a well organized inner core.  Thunderstorms near the center of circulation are generating upper level divergence in all directions which is pumping out mass and causing the pressure to decrease.  Linda could intensify for a few more hours, but it will start to move over much cooler Sea Surface Temperatures (SSTs) later today.  It will be unable to extract enough energy from the cooler water to maintain its intensity and Linda will start to weaken.  As Linda moves farther north, it will also start to encounter stronger upper level winds around the southern portion of an upper level trough near the west coast of the U.S.  Increased vertical wind shear in addition to cooler SSTs will speed up the rate at which Linda weakens.  Since Linda has a large circulation, it could take longer for it to spin down.

An upper level ridge over Mexico is steering Linda toward the north-northwest and that general motion is expected to continue as long as it maintains tall thunderstorms.  When Linda weakens to a tropical storm over cooler water, the circulation will not extend as high in the atmosphere.  After that time Linda will be steered more toward the west by winds lower in the atmosphere.  On its anticipated track Linda will move parallel to the coast of Baja California for several days before turning away from the coast later this week.

Tropical Storm Linda Forms South of Baja California

A spiral band continued to wrap more tightly around the center of circulation inside a large low pressure system west of Mexico on Sunday and the National Hurricane Center designated the system as Tropical Storm Linda.  At 11:00 a.m. EDT on Sunday the center of Tropical Storm Linda was located at latitude 14.1°N and longitude 109.0°W which put it about 610 miles (980 km) south of the southern tip of Baja California.  Linda was moving toward the northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 45 m.p.h. (70 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 1000 mb.

The circulation in Tropical Storm Linda is well organized.  There is one main spiral rainband and multiple outer rainbands.  Outside of the core of the circulation there are fewer thunderstorms east of the center, which could mean that some drier air is being pulled into that part of the storm.  Thunderstorms in the core are generating upper level divergence.  Linda is over water where the Sea Surface Temperatures (SSTs) are above 29°C.  An upper level trough near the west coast of the U.S. and an upper level ridge over northern Mexico are combining to create an outflow channel to the northeast, which is enhancing the flow of mass away from the tropical storm.  There is little vertical wind shear over the top of Linda and the environment is favorable for further intensification.  A period of rapid intensification is possible and Linda is likely to become a hurricane.  Eventually, when it moves farther north, Linda will move into an area of cooler SSTs and more vertical wind shear, which will cause it to weaken.

Linda appears to be moving a little more toward the west-northwest this afternoon.  The upper level ridge over northern Mexico is expected to steer it in a generally northwesterly direction during the next few days.  On its anticipated track, Linda would move west of Baja California during the middle of next week.

Norbert Reaches Major Hurricane Status

Despite being close to land and near much cooler Sea Surface Temperatures (SSTs) Hurricane Norbert intensified rapidly during the overnight hours and it has maximum sustained winds of 120 m.p.h.  This makes Norbert a Category 3 hurricane on the Saffir-Simpson Scale and it is considered to be a Major Hurricane.  At 8:00 a.m. EDT on Saturday the center of Norbert was located at latitude 24.8°N and longitude 113.8°W which put it about 95 miles west of Cabo San Lazaro and about 220 miles south-southeast of Punta Eugenia, Mexico.  Norbert was moving toward the northwest at 8 m.p.h.  The minimum surface pressure was estimated to be 957 mb.

The government of Mexico has adjusted the warnings issued for Norbert.  The Hurricane Warning has been discontinued.  Tropical Storm Warnings are now in effect for the portion of the coast from Santa Fe to Punta Eugenia and from San Evaristo to Loreto.

Norbert is expected to continue to move toward the northwest this weekend.  It will soon move over much cooler SSTs.  Once Norbert moves into that environment it will encounter much cooler, more stable air which will begin to lessen the convection.  As Norbert extracts less energy from the ocean and convection transports less energy upward, the circulation will begin to spin down.

The remnants of Norbert’s circulation could turn northeast and cross northern Baja California into the southwestern U.S. next week.  It is also possible that as the circulation around Norbert weakens, the upper and lower portions could decouple.  The upper and middle portion of the circulation could move over the southwestern U.S. and enhance the probability for rainfall there, while the lower level circulation remains nearly stationary and dissipates west of Baja California.