Tropical Storm Rosa

Tropical Storm Rosa Forming 0300 Hours September 20 2018
Tropical Storm Rosa Forming 0300 Hours September 20 2018

NWS National Hurricane Center Miami FL 300 AM MDT Thu Sep 20 2018

A pair of ASCAT passes between 0400 and 0500 UTC indicated that the center of the depression had moved inland over the Mexican state of Sonora, with winds as high as 25 kt still occurring over the Gulf of California. The associated deep convection has taken on a more linear pattern as it has pushed farther inland across northwestern Mexico, and it is unlikely that the system still has a closed surface circulation over the rough terrain. As such, the depression is deemed to have dissipated, and this is the last advisory on this system. Winds over the Gulf of California should quickly diminish during the next 6-12 hours.

Moisture associated with the remnants of the depression will continue to pose a heavy rainfall and flooding threat over the next couple of days. Widespread amounts of 5 to 10 inches and isolated amounts up to 15 inches are forecast in the Mexican states of Sonora and northern Sinaloa. These rains could cause life-threatening flash flooding and mudslides. Heavy rains will also lead to a heightened risk of flash flooding in the southwestern United States today and in the southern Plains beginning on Friday.

This is the last advisory issued by the National Hurricane Center on this system.

NWS Weather Prediction Center College Park MD 1100 AM PDT Wed Sep 19 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on newly formed Tropical Depression Nineteen-E located over the southern Gulf of California.

(see Spanish video below)

1. An elongated area of low pressure located about 850 miles southwest of the southern tip of the Baja California peninsula has become less organized today. Environmental conditions could be conducive for some gradual development of this system during the next few days while it moves slowly west-northwestward or northwestward. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low…30 percent.

2. An area of disturbed weather is expected to form over the weekend a few hundred miles south of the Gulf of Tehuantepec. Some slow development of this system is possible early next week while the system moves nearly parallel to the southwestern coast of Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low...20 percent.

NWS Weather Prediction Center College Park MD 900 AM MDT Wed Sep 19 2018

Satellite images show that an area of low pressure has developed over the Gulf of California overnight within an inverted trough. This is also supported by 24-hour pressure falls of 3.7 mb at Loreto just west of its center at 1300 UTC. Microwave imagery shows curved convective banding features to the east and north of the center, suggesting organized convection.

Therefore the system is being declared a tropical depression with 25-kt maximum sustained winds. Infrared imagery shows minimal vertical wind shear over the system, with a slight restriction to the outflow on its western side, which is confirmed by recent SHIPS output. However, the system has only 12 hours or less over water, and it is expected to move inland without significant strengthening.

An upper-level trough moving into the western United States is expected to steer the depression north or north-northeast across the Gulf of California into northwest Mexico tonight, which is well advertised by the track guidance. The depression is expected to dissipate in the 24-36 hour time frame due to steep terrain.

The main impact with the system is expected to be heavy rainfall, with 5-10 inch areal average amounts and local amounts to 15 inches leading to life-threatening flash flooding and landslides near the track of the depression.

FORECAST POSITIONS AND MAX WINDS

INIT  19/1500Z 26.3N 110.9W   25 KT  30 MPH -(ENE Isla del Carmen, Mexico)
 12H  20/0000Z 28.0N 110.7W   25 KT  30 MPH -(San Fernando de Guaymas, Mexico)
 24H  20/1200Z 30.5N 109.5W   15 KT  15 MPH -( El Pinito, Mexico)
 36H  21/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 AM PDT Tue Sep 18 2018

For the eastern North Pacific…east of 140 degrees west longitude:

1. A broad and elongated area of low pressure extending from near the southern tip of the Baja California peninsula southwestward for a few hundred miles continues to produce widespread but disorganized showers and thunderstorms. Although environmental conditions appear conducive for tropical cyclone formation, the large size of the system and land interaction is expected to limit the development potential of this disturbance. However, this system could still become a tropical depression during the next day or two while it moves near Baja California Sur and the Gulf of California. Regardless of development, this disturbance will likely produce very heavy rainfall over Baja California Sur and other parts of northwestern mainland Mexico over the next several days. Interests in Baja California Sur and northwestern Mexico should monitor the progress of this disturbance. * Formation chance through 48 hours…medium…40 percent. * Formation chance through 5 days…medium...40 percent.

2. Another area of low pressure is located about 800 miles southwest of the southern tip of the Baja California peninsula. Environmental conditions are expected to be marginally conducive for some gradual development of this system over the next several days while it moves slowly west-northwestward or northwestward. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low...20 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Mon Sep 17 2018

For the eastern North Pacific…east of 140 degrees west longitude:

1. A broad and elongated area of low pressure located a few hundred miles south of the southern tip of the Baja California peninsula continues to produce widespread but disorganized showers and thunderstorms. Although environmental conditions appear conducive for tropical cyclone formation, the large size of the system suggests that any development should be slow to occur.

This system will likely become a tropical depression later this week while it moves generally northward at about 10 mph. Interests in Baja California Sur should monitor the progress of this disturbance.

* Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…high...70 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Sun Sep 16 2018

For the eastern North Pacific…east of 140 degrees west longitude:

1. A large area of disturbed weather centered several hundred miles southwest of Mexico is associated with a trough of low pressure. Environmental conditions appear conducive for gradual development of this system, and a tropical depression is likely to form by the middle of next week while it moves generally northwestward at about 10 mph. Interests in Baja California Sur should monitor the progress of this disturbance. * Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…high...80 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Sat Sep 15 2018

For the eastern North Pacific…east of 140 degrees west longitude:

1. A large area of disturbed weather centered several hundred miles southwest of Mexico is associated with a trough of low pressure. Environmental conditions appear conducive for gradual development of this system, and a tropical depression is likely to form by the middle of next week while it moves generally northwestward at about 10 mph. Interests in Baja California Sur should monitor the progress of this disturbance. * Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…high…80 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Sat Sep 15 2018

For the eastern North Pacific…east of 140 degrees west longitude:

A large area of disturbed weather centered several hundred miles south of the southern coast of Mexico is associated with a trough of low pressure. This system is gradually becoming better organized, and environmental conditions appear conducive for further development. A tropical depression is likely to form by Tuesday while the system moves generally west-northwestward at about 10 mph. Interests in Baja California Sur should monitor the progress of this disturbance. * Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…high…80 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Fri Sep 14 2018

For the eastern North Pacific…east of 140 degrees west longitude:

1. A large area of disturbed weather is centered several hundred miles south of the southern coast of Mexico. Environmental conditions appear conducive for gradual development, and a tropical depression could form early next week while the system moves generally westward to west-northwestward at 10 to 15 mph south of Mexico. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…medium…60 percent.

If this system is named, it will be Tropical Storm Rosa.

NWS National Hurricane Center Miami FL 500 AM PDT Thu Sep 13 2018

For the eastern North Pacific…east of 140 degrees west longitude:

An area of low pressure is expected to develop well south of the southwestern coast of Mexico over the weekend. Thereafter, environmental conditions appear conducive for gradual development, and a tropical depression could form while the system moves generally westward to west-northwestward at 10 to 15 mph south of Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…40 percent.

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