Tropical Storm Jimena

Post Tropical Jimena Track 1700 Hours August 6 2021
Post Tropical Jimena Track 1700 Hours August 6 2021

Tropical Stom Jimena Wind Speed FieldTropical Storm JimenaNWS Central Pacific Hurricane Center Honolulu HI 500 PM HST Fri Aug 06, 2021 (see NEW video below)

Deep convection near center of Jimena collapsed overnight, and Jimena consists of a low cloud swirl with shallow convection flaring along its northern and eastern flanks. Dvorak current intensity estimates varied from 1.5 at HFO to unclassifiable at SAB, while CIMSS ADT held onto a 2.0/30 kt. Jimena is moving over sub 24C sea surface temperatures as it draws in dry air from the north, and westerly vertical wind shear of more than 15 kt is increasing. Given its current structure and the hostile environment ahead, Jimena has been downgraded to a post-tropical remnant low with an initial intensity of 30 kt.

Post-Tropical Cyclone Jimena will continue to be steered toward the west-northwest (295 degrees) around 7 kt tonight by a deep subtropical ridge to the north. Under an environment of cool sea surface temperatures and continued westerly vertical wind shear, the increasingly shallow system will move toward the west this weekend until dissipation.

This is the last advisory issued by the Central Pacific Hurricane Center on Jimena.

FORECAST POSITIONS AND MAX WINDS

INIT  07/0300Z 17.9N 140.8W   30 KT  35 MPH - Post Tropical (ESE Hilo, Hawaii)
 12H  07/1200Z 18.5N 142.0W   25 KT  30 MPH - Post Tropical (ESE Hilo, Hawaii)
 24H  08/0000Z 18.9N 143.3W   25 KT  30 MPH - Post Tropical (ESE Hilo, Hawaii)
 36H  08/1200Z 19.2N 144.8W   20 KT  25 MPH - Post Tropical (ESE Hilo, Hawaii)
 48H  09/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM HST Fri Aug 06, 2021 

During the last 6 hours, deep convection associated with Jimena has waned. A recently arriving 1756 UTC ASCAT pass revealed peak believable winds of around 30 kt. The latest Dvorak T- and CI-numbers from TAFB and SAB have also decreased, and these data support lowering the initial intensity to 30 kt. Jimena is currently moving over SSTs near 24C and into a more stable air mass. In addition, westerly shear will increase along the cyclone’s path during the next 12 hours. These factors should cause continued weakening, and Jimena is expected to degenerate into a remnant low by late tonight or early Saturday.

The initial motion estimate is 295/7 kt. The west-northwestward motion is forecast to continue for another day or so, followed by a gradual bend to the west as Jimena weakens and is steered by the low-level trade wind flow. The new track forecast is slightly to the south of the previous NHC advisory, and is in best agreement with the HCCA and TVCN consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  06/2100Z 17.6N 140.0W   30 KT  35 MPH - Depression (ESE Hilo, Hawaii)
 12H  07/0600Z 18.2N 141.2W   25 KT  30 MPH - Post Tropical (ESE Hilo, Hawaii)
 24H  07/1800Z 18.8N 142.5W   25 KT  30 MPH - Post Tropical (ESE Hilo, Hawaii)
 36H  08/0600Z 19.1N 143.9W   20 KT  25 MPH - Post Tropical (ESE Hilo, Hawaii)
 48H  08/1800Z 19.2N 145.5W   20 KT  25 MPH - Post Tropical (ESE Hilo, Hawaii)
 60H  09/0600Z...DISSIPATED

NWS National Hurricane Center Miami FL  500 AM HST Fri Aug 06, 2021

A convective mass continues to persist over the center of Jimena, although coldest cloud tops have warmed over the past few hours. A fortuitous 1105 UTC AMSR-2 pass shows the center a bit west of the earlier estimates, which places it beneath the coldest remaining cloud tops. The intensity is held at 35 kt based on a blend of Final-T and CI numbers from TAFB, SAB and ADT. This intensity is also supported by overnight ASCAT data and a more recent ship observation. Jimena is currently moving over SSTs near 24C. Going forward, westerly shear will increase along the cyclone’s path during the next 12-24 hr. These factors should cause the tropical cyclone to weaken, and Jimena is expected to degenerate into a remnant low by Saturday morning. The NHC intensity forecast is in good agreement with the SHIPS and HCCA guidance.

The initial motion estimate is 300/8 kt. As Jimena weakens, the increasingly shallow system is expected to be steered by the low-level trade-wind flow, which should cause it to gradually turn toward the west in about 48 hours. The ECMWF is a little faster and lies on the southwest side of the guidance envelope, while the GFS is slower and northeast of the consensus. The NHC forecast was adjusted to the southwest of the previous forecast during the first 12-24 hours based on the farther west initial position. Thereafter, the track is close to the previous forecast, and in best agreement with the HCCA and TVCN consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  06/1500Z 17.5N 139.3W   35 KT  40 MPH - Tropical Storm (ESE Hilo, Hawaii)
 12H  07/0000Z 18.0N 140.4W   30 KT  35 MPH - Depression (ESE Hilo, Hawaii)
 24H  07/1200Z 18.7N 141.8W   25 KT  30 MPH - Post Tropical (ESE Hilo, Hawaii)
 36H  08/0000Z 19.2N 143.3W   25 KT  30 MPH - Post Tropical (ESE Hilo, Hawaii)
 48H  08/1200Z 19.5N 144.9W   20 KT  25 MPH - Post Tropical (ESE Hilo, Hawaii)
 60H  09/0000Z 19.6N 146.7W   20 KT  25 MPH - Post Tropical (ESE Hilo, Hawaii)
 72H  09/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 AM HST Thu Aug 05, 2021 

Conventional satellite imagery indicates that Jimena’s cloud pattern has changed little during the past several hours, although most recently, enhanced infrared images show some warming of the cloud tops just west of the center. Timely AMSR-2 and GMI passive microwave color composite images revealed a well-developed banding feature wrapping around the surface center from the north and west portions of the cyclone. The initial intensity is held at 35 kt and is in agreement with the Dvorak satellite intensity estimates from TAFB and SAB.

The large-scale models and the statistical-dynamical SHIPS intensity guidance (GFS/ECMWF) show that the previously noted period of conducive atmospheric and oceanic conditions should be ending soon. By the 36-hour period, sub-25C sea-surface temperatures and a gradually stabilizing/drier surrounding air mass should cause Jimena to weaken. Guidance also shows increasing west-northwesterly shear beyond 48 hours. Accordingly, the NHC forecast calls for Jimena to weaken to a depression by mid-period, and degenerate into a remnant low in 60 hours.

Based on the aforementioned microwave images, the initial motion is estimated to be northwestward, or 315/6 kt. A subtropical ridge anchored to the northeast of the cyclone is forecast to steer Jimena toward the northwest through the 48 period. Afterward, a turn toward the west-northwest is expected as the vertically shallow system is influenced more by the easterly tradewinds. The official forecast is basically an update of the previous one and lies near the multi-model consensus (TVCN) aid.

FORECAST POSITIONS AND MAX WINDS

INIT  05/1500Z 16.1N 137.2W   35 KT  40 MPH - Tropical Storm (ESE Hilo, Hawaii)
 12H  06/0000Z 16.5N 137.7W   35 KT  40 MPH - Tropical Storm (ESE Hilo, Hawaii)
 24H  06/1200Z 17.5N 138.9W   35 KT  40 MPH - Tropical Storm (ESE Hilo, Hawaii)
 36H  07/0000Z 18.5N 140.2W   30 KT  35 MPH - Depression (ESE Hilo, Hawaii)
 48H  07/1200Z 19.5N 141.5W   30 KT  35 MPH - Depression (ESE Hilo, Hawaii)
 60H  08/0000Z 20.3N 142.9W   25 KT  30 MPH - Post Tropical (ESE Hilo, Hawaii)
 72H  08/1200Z 20.9N 144.3W   20 KT  25 MPH - Post Tropical (ESE Hilo, Hawaii)
 96H  09/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 PM PDT Wed Aug 4, 2021

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

The National Hurricane Center is issuing advisories on Tropical Storm Hilda, located almost 1200 miles west of the southern tip of the Baja California peninsula, and on newly redeveloped Tropical Depression Nine-E, located more than 1700 miles west-southwest of the southern tip of the Baja California peninsula.

  • 1. A broad area of low pressure is expected to develop a few hundred miles offshore of the southwestern coast of Mexico this weekend. Environmental conditions are forecast to be conducive for some gradual development thereafter, and a tropical depression could form early next week while the system moves west-northwestward at 10 to 15 mph, parallel to and offshore of the coast of southwestern Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…40 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Wed Aug 4, 2021

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

The National Hurricane Center is issuing advisories on Tropical Storm Hilda, located more than 1100 miles west of the southern tip of the Baja California peninsula.

  • 1. Shower and thunderstorm activity associated with the remnant low-pressure system of Tropical Depression Nine-E, located more than 1600 miles west-southwest of the southern tip of the Baja California peninsula, has continued to become better organized during the past several hours. If this development trend continues, tropical cyclone advisories will be initiated on this system later today. Environmental conditions appear to be conducive for additonal development over the next few days while the system moves northwestward at 5 to 10 mph. By late Thursday, further development is not expected as the system is forecast to move over cooler waters. For additional information on this system see High Seas Forecasts issued by the National Weather Service. * Formation chance through 48 hours…high…near 100 percent. * Formation chance through 5 days…high…near 100 percent.
  • 2. An area of low pressure is expected to develop a few hundred miles south of the southern coast of Mexico late this week. Environmental conditions are forecast to be conducive for some gradual development this weekend while the system moves west-northwestward at 10 to 15 mph, parallel to and offshore the coast of southwestern Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low...30 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Wed Aug 4, 2021

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

The National Hurricane Center is issuing advisories on Tropical Storm Hilda, located more than 1000 miles west of the southern tip of the Baja California peninsula.

  • 1. Shower activity, in association with the remnants of Tropical Depression Nine-E, located more than 1600 miles west-southwest of the southern tip of the Baja California peninsula, continue to become better organized. Environmental conditions are expected to be somewhat conducive for development over the next day or so, and a tropical depression is likely to form later today or tonight while the system moves northwestward at 5 to 10 mph. By late Thursday, further development is not expected as the system is forecast to move over cooler waters. * Formation chance through 48 hours…high…80 percent. * Formation chance through 5 days…high…80 percent.
  • 2. An area of low pressure is expected to develop a few hundred miles south of the southern coast of Mexico late this week. Environmental conditions are forecast to be conducive for some gradual development this weekend while the system remains offshore and moves west-northwestward at 10 to 15 mph, parallel to and offshore the coast of southwestern Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…30 percent.

NWS National Hurricane Center Miami FL 1100 PM PDT Tue Aug 3, 2021

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

The National Hurricane Center is issuing advisories on Tropical Storm Hilda, located more than 1000 miles west-southwest of the southern tip of the Baja California peninsula, and has issued the last advisory on Post-Tropical Cyclone Ignacio, located about 400 miles west-southwest of the southern tip of the Baja California peninsula.

  • 1. Shower activity has increased near a low pressure system, associated with the remnants of Tropical Depression Nine-E, more than 1600 miles west-southwest of the southern tip of the Baja California peninsula. Environmental conditions are expected to be somewhat conducive for development over the next day or so, and a tropical depression is likely to form tonight or Wednesday while the system moves northwestward at 5 to 10 mph. By late Thursday, further development is not expected as the system is forecast to move over cooler waters. * Formation chance through 48 hours…high…80 percent. * Formation chance through 5 days…high…80 percent.
  • 2. An area of low pressure is expected to develop a few hundred miles south of the southern coast of Mexico late this week. Environmental conditions are forecast to be conducive for some gradual development this weekend while the system remains offshore and moves west-northwestward at 10 to 15 mph, roughly parallel to the coast of southwestern Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…30 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Tue Aug 3, 2021

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

The National Hurricane Center is issuing advisories on Tropical Storm Hilda, located more than 1000 miles west-southwest of the southern tip of the Baja California peninsula, and on Tropical Depression Ignacio, located about 400 miles west-southwest of the southern tip of the Baja California peninsula.

  • 1. A low-pressure system associated with the remnants of Tropical Depression Nine-E is producing limited and disorganized shower activity more than 1600 miles west-southwest of the southern tip of the Baja California peninsula. Environmental conditions are expected to be somewhat conducive for development over the next day or so, and a tropical depression is likely to form tonight or Wednesday while the system moves northwestward at 5 to 10 mph. By late Thursday, further development is not expected as the system is forecast to move over cooler waters. * Formation chance through 48 hours…high…80 percent. * Formation chance through 5 days…high…80 percent.
  • 2. An area of low pressure is expected to develop a few hundred miles south of the southern coast of Mexico late this week. Environmental conditions are forecast to be conducive for some gradual development this weekend while the system remains offshore and moves west-northwestward at 10 to 15 mph, roughly parallel to the coast of southwestern Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low...30 percent.

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Video: Weather Forecast Honolulu, Hawaii ▶ Honolulu weather Forecast 08/06/2021