Tropical Storm Alvin

Post Tropical Depression Alvin Track 0800 Hours June 29 2019
Post Tropical Depression Alvin Track 0800 Hours June 29 2019

 

Tropical Storm Alvin 0900 Hours June 27 2019Tropical Storm Alvin  –   NWS National Hurricane Center Miami FL 800 AM PDT Sat Jun 29, 2019

Alvin continues to be devoid of deep convection while moving over cooler waters with strong southwesterly shear across the system’s circulation. Due to the ongoing lack of convection, it is estimated that Alvin has degenerated into a post-tropical remnant low. The remnant low will continue to move west-northwestward to northwestward until it dissipates in 18-24 h.

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

NWS National Hurricane Center Miami FL 200 PM PDT Fri Jun 28, 2019

Alvin is rapidly weakening due to motion over sea surface temperatures of 23-24C and increasing southwesterly vertical wind shear, with the low-level center now partly exposed at the southern edge of the weakening convective mass. The initial intensity is reduced to 45 kt based on a blend of recent ASCAT data and subjective satellite intensity estimates. Continued rapid weakening is expected, and Alvin is forecast to become a remnant low in about 24 h and dissipate completely after 36 h.

The initial motion is 310/13. The cyclone should continue generally northwestward for the next 12-18 h due to flow around a mid-level ridge to the north. After that time, the weakening and the increasingly shallow system should turn west-northwestward as the low-level winds become the predominant steering mechanism.

FORECAST POSITIONS AND MAX WINDS

INIT  28/2100Z 19.7N 118.6W   45 KT  50 MPH -Tropical Storm (WNW Socorro Island, MX)
 12H  29/0600Z 20.7N 120.0W   35 KT  40 MPH -Tropical Storm (WNW Socorro Island, MX)
 24H  29/1800Z 21.5N 121.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 36H  30/0600Z 22.0N 123.1W   20 KT  25 MPH...POST-TROP/REMNT LOW
 48H  30/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 AM PDT Fri Jun 28, 2019

Alvin continues to lose organization as a steady weakening trend has commenced. The satellite presentation has become more ragged and the center is now very close to the southwestern edge of the deep convection. Satellite intensity estimates continue to decrease, with a blended average indicating a 55 kt initial intensity for this advisory. Alvin is already over SSTs of 24 C and will move over even cooler waters over the next 36 hours. In addition, the latest guidance depicts southwesterly shear of 15 to 20 kt impacting the circulation, and this is forecast to increase to over 30 kt in 24 hours. These factors, along with Alvin moving into an increasingly stable atmospheric environment, will result in continued steady weakening into this weekend. By Saturday night, Alvin is expected to become devoid of deep convection, and the cyclone is forecast to dissipate by Sunday.

Alvin accelerated slightly overnight, with an initial motion of 305/14 kt. This faster motion is expected to be only temporary and the official track forecast is near the clustering of the consensus aids. Alvin will be steered around the southwestern periphery of mid-level ridging to its north through today. Thereafter, a much weaker cyclone will become steered by the lower level environmental flow, which will result in a turn to the west-northwest and decrease in forward speed tonight into Saturday.

FORECAST POSITIONS AND MAX WINDS

INIT  28/1500Z 19.0N 117.7W   55 KT  65 MPH -Tropical Storm (WSW Socorro Island, MX)
 12H  29/0000Z 20.1N 119.3W   45 KT  50 MPH -Tropical Storm (WSW Socorro Island, MX)
 24H  29/1200Z 21.0N 121.0W   35 KT  40 MPH -Tropical Storm (WSW Socorro Island, MX)
 36H  30/0000Z 21.6N 122.4W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  30/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 PM PDT Thu Jun 27, 2019

Somewhat surprisingly, Alvin has strengthened into a hurricane this evening. The diminutive system is exhibiting a rather symmetric CDO with very deep convection bursting near the center. Microwave images show a small eye about 10 n mi in diameter. Subjective Dvorak classifications from both TAFB and SAB, along with objective intensity estimates from UW-CIMSS, support a current intensity of 65 kt. Alvin is not expected to maintain its intensity for very long. Within 12 to 24 hours, the cyclone should encounter significantly stronger southwesterly shear and SSTs below 24 deg C. These hostile environmental factors should bring about rapid weakening, as supported by essentially all of the numerical guidance. Alvin is expected to degenerate into a remnant low on Saturday.

The hurricane is moving a little to the right and slightly faster than previous estimates, with an initial motion of about 305/14 kt. Alvin should continue to move near the western periphery of a subtropical ridge for the next 48 hours, with the weakening cyclone gradually turning toward the left and decelerating. The official track forecast is very close to the latest corrected dynamical model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  28/0300Z 17.4N 115.4W   65 KT  75 MPH -Category 1 (WSW Socorro Island, MX)
 12H  28/1200Z 18.7N 117.1W   60 KT  70 MPH -Tropical Storm (WSW Socorro Island, MX)
 24H  29/0000Z 20.1N 119.1W   45 KT  50 MPH -Tropical Storm (WSW Socorro Island, MX)
 36H  29/1200Z 20.9N 120.6W   35 KT  40 MPH -Tropical Storm (WSW Socorro Island, MX)
 48H  30/0000Z 21.5N 121.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  01/0000Z...DISSIPATED

National Hurricane Center Miami FL 900 AM MDT Thu Jun 27, 2019

…ALVIN HOLDING STEADY…

DISCUSSION AND OUTLOOK

Recent microwave imagery indicates that Alvin’s convective structure has improved over the past several hours, and a 1057 UTC SSMI overpass showed a closed ring of convection around the mid-level center of the small tropical storm. However, the infrared presentation of Alvin has not changed significantly since the last advisory and satellite intensity estimates are also unchanged. The initial intensity is therefore held at 50 kt, in deference to ASCAT data from late last night.

The dynamical models (primarily the HWRF, HMON, and GFS) continue to indicate that Alvin could strengthen during the next 12 to 24 hours before it reaches much colder waters to the north. Once the tropical storm reaches those waters in a day or so, it should quickly weaken, likely becoming a remnant low around or just after 48 h. The NHC intensity forecast has not been changed substantially since the previous advisory and remains close to the intensity consensus aids. It is worth noting that the small size of Alvin could make it susceptible to short-term swings of intensity, up or down, and once weakening begins it could occur even faster than currently indicated.

Tropical Storm Alvin Earliest Reasonable Arrival Time
Tropical Storm Alvin Earliest Reasonable Arrival Time

The official track forecast has been nudged slightly northward but is otherwise unchanged. The initial motion estimate is 300/12 kt, and Alvin is expected to continue to move west-northwestward or westward at a similar forward speed for the next 24 to 36 hours. After that time, the cyclone should turn toward the west as it weakens and becomes steered by shallow easterly flow to the north before it dissipates entirely. The NHC forecast closely follows the HCCA and TVCN aids.

INIT  27/1500Z 15.8N 113.1W   50 KT  60 MPH - Tropical Storm (WSW Cabo San Lucas, MX)
 12H  28/0000Z 16.9N 114.9W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, MX)
 24H  28/1200Z 18.5N 117.0W   50 KT  60 MPH - Tropical Storm (WSW Cabo San Lucas, MX)
 36H  29/0000Z 19.7N 119.0W   35 KT  40 MPH - Tropical Storm (WSW Cabo San Lucas, MX)
 48H  29/1200Z 20.5N 120.7W   30 KT  35 MPH - Tropical Storm (WSW Cabo San Lucas, MX)
 72H  30/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 AM PDT Thu Jun 27, 2019

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

The National Hurricane Center is issuing advisories on Tropical Storm Alvin, located several hundred miles south of the southern tip of the Baja California peninsula.

NWS National Hurricane Center Miami FL 300 AM MDT Thu Jun 27, 2019

Alvin’s satellite presentation is much improved since this time yesterday, consisting of a small but distinct CDO with extremely cold overshooting cloud tops of about -90C near the well-defined center. The outflow is fairly symmetrical due to the low vertical wind shear conditions affecting the compact cyclone. A 0435Z ASCAT-A pass revealed that tropical-storm-force winds only extended 15-20 nmi away from the center in the northern semicircle along with one peak wind vector of 46 kt located in the northwestern quadrant near the overshooting cloud tops. Given Alvin’s small size and likely undersampling by the scatterometer instrument, the intensity is raised to 50 kt, which is consistent with ADT and SATCON estimates.

The initial position and motion vector of 300/11 kt are based on ASCAT-A/-C scatterometer wind data and passive microwave fixes. Although the new track has been shifted north of the previous advisory track, there otherwise are no significant changes to the previous forecast track reasoning. Alvin is expected to move steadily west-northwestward around the southwestern periphery of a deep-layer subtropical ridge that extends westward from northwestern Mexico. The latest track guidance has again shifted northward and the new NHC track has likewise been shifted northward, but not quite as far the consensus models out of the respect for the lower latitude ECMWF and FSSE models.

Additional strengthening is expected during the next 12 to 24 hours while Alvin remains over SSTs greater than 26 deg C and within a low vertical wind shear regime. By 36 hours, however, the combination of cooling SSTs and a more stable airmass is forecast to induce steady to rapid weakening. Alvin is expected to degenerate into a remnant low by late Saturday and dissipate by Monday. The NHC intensity forecast is similar to a blend of the consensus models IVCN. HCCA, and FSSE.

FORECAST POSITIONS AND MAX WINDS

INIT  27/0900Z 15.1N 111.9W   50 KT  60 MPH - Tropical Storm (WSW Cabo San Lucas, MX)
 12H  27/1800Z 15.9N 113.5W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, MX)
 24H  28/0600Z 17.3N 116.0W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, MX)
 36H  28/1800Z 18.7N 118.1W   45 KT  50 MPH - Tropical Storm (WSW Cabo San Lucas, MX)
 48H  29/0600Z 19.6N 119.9W   35 KT  40 MPH - Tropical Storm (WSW Cabo San Lucas, MX)
 72H  30/0600Z 20.7N 122.7W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  01/0600Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM PDT Wed Jun 26, 2019

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

The National Hurricane Center is issuing advisories on recently upgraded Tropical Storm Alvin, located a several hundred miles southwest of Manzanillo, Mexico.

1. An area of low pressure is expected to develop in a few days several hundred miles southwest of the southern coast of Mexico. Some slow development of this system is possible over the weekend and into early next week as it moves westward to west-northwestward.

* Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…20 percent.

NWS National Hurricane Center Miami FL 900 AM MDT Wed Jun 26, 2019

Visible and passive microwave imagery this morning indicate that the center of the tropical cyclone is located farther south than previously estimated, possibly due to a reformation of the center. The center of the cyclone is now embedded near the deepest inner- core convection and some overall improvement in the convective pattern is evident. Satellite intensity estimates indicate that the cyclone has reached tropical storm strength, and the initial intensity of 35 kt is based on the latest Dvorak estimate from SAB. Alvin’s formation marks the 3rd latest date of the development of the first named storm in the eastern Pacific basin during the satellite era (since 1966).

Alvin has turned a little south of due west and the initial motion estimate is 260/12 kt. The new NHC forecast track over the first couple of days has been adjusted southward, in large part due to the more southerly reformation of the center. Despite this, the overall track forecast philosophy has not changed. Alvin is expected to move westward and then west-northwestward with a gradual decrease in forward speed over the next few days along the southwestern periphery of a subtropical ridge.

Tropical Storm Force Winds 0600 Hours June 26 2019
Tropical Storm Force Winds 0600 Hours June 26 2019

There remains about a 24-36 hour window for some additional strengthening to occur over warm SSTs in a low-shear and sufficiently moist environment. This environment, combined with the improving structure of the storm, supports raising the intensity forecast a little in the near term. The new NHC forecast is in good agreement with the dynamical models and the intensity consensus. After 36 hours, the forecast track takes Alvin over progressively cooler waters and into a drier and higher-shear environment. This should result in steady weakening, with the cyclone likely becoming devoid of deep convection by 72 hours, and dissipating by day 5.

FORECAST POSITIONS AND MAX WINDS

INIT  26/1500Z 14.7N 109.4W   35 KT  40 MPH - Tropical Storm (WSW Acapulco, MX)
 12H  27/0000Z 14.7N 111.4W   45 KT  50 MPH - Tropical Storm (WSW Acapulco, MX)
 24H  27/1200Z 15.0N 113.7W   45 KT  50 MPH - Tropical Storm (WSW Acapulco, MX)
 36H  28/0000Z 15.7N 115.8W   45 KT  50 MPH - Tropical Storm (WSW Acapulco, MX)
 48H  28/1200Z 16.4N 117.7W   40 KT  45 MPH - Tropical Storm (WSW Acapulco, MX)
 72H  29/1200Z 17.4N 121.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  30/1200Z 18.0N 124.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  01/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 AM PDT Wed Jun 26, 2019

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

The National Hurricane Center is issuing advisories on Tropical Depression One-E, located a few hundred miles southwest of Manzanillo, Mexico.

NWS National Hurricane Center Miami FL 1100 PM PDT Tue Jun 25 2019

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

The National Hurricane Center is issuing advisories on Tropical Depression One-E, located a few hundred miles southwest of Manzanillo, Mexico.

1100 AM PDT Tue Jun 25, 2019

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

1. Showers and thunderstorms associated with a broad area of low pressure located a few hundred miles south of Manzanillo, Mexico, continue to show signs of organization. Environmental conditions appear to be conducive for some additional development and this system is likely to become a tropical depression within the next day or two while it moves west-northwestward away from the coast of Mexico.

* Formation chance through 48 hours…high…80 percent. * Formation chance through 5 days…high...80 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Tue Jun 25, 2019

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

1. Shower and thunderstorm activity associated with a broad area of low pressure located a few hundred miles south-southeast of Manzanillo, Mexico, is showing some signs of organization. Environmental conditions appear to be conducive for some additional development and this system is likely to become a tropical depression during the next couple of days while it moves west-northwestward away from the coast of Mexico. After that time, environmental conditions are forecast to become less conducive for tropical cyclone formation.

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

NWS National Hurricane Center Miami FL 500 PM PDT Mon Jun 24, 2019

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

1. Satellite imagery indicates that a broad area of low pressure has formed in association with the tropical wave located a few hundred miles south of the southern coast of Mexico and that the accompanying shower activity is showing signs of organization. Environmental conditions are expected to be conducive for the gradual development of this system, and a tropical depression is likely to form within the next few days while the system moves west-northwestward away from the coast of Mexico.

* Formation chance through 48 hours…medium…60 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Mon Jun 24, 2019

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

1. Showers and thunderstorms associated with a tropical wave located a few hundred miles south of the southern coast of Mexico have become a little better organized since yesterday. Environmental conditions are expected to be conducive for the gradual development of this system, and a tropical depression is likely to form within the next few days while the system moves west-northwestward away from the coast of Mexico.

* Formation chance through 48 hours…medium…50 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Mon Jun 24, 2019

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

1. Showers and thunderstorms associated with a tropical wave located a few hundred miles south of the southern coast of Mexico have changed little in organization overnight. Environmental conditions are expected to be conducive for the gradual development of this system, and a tropical depression is likely to form within the next few days while the system moves west-northwestward away from the coast of Mexico.

* Formation chance through 48 hours…medium…50 percent. * Formation chance through 5 days…high...70 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Sun Jun 23, 2019

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

1. Shower activity associated with a tropical wave located a few hundred miles southwest of the Gulf of Tehuantepec has become a little better organized since yesterday. Environmental conditions are expected to be conducive for the gradual development of this system during the next few days, and a tropical depression is likely to form by the middle of the week while the system moves west-northwestward away from the coast of Mexico.

* Formation chance through 48 hours…medium…50 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Sun Jun 23, 2019

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

1. A tropical wave located a few hundred miles southwest of the Gulf of Tehuantepec is producing disorganized showers and thunderstorms. Environmental conditions are expected to be conducive for a gradual development of this system during the next few days, and a tropical depression is likely to form by the middle of the week while the system moves west-northwestward away from the coast of Mexico.

* Formation chance through 48 hours…medium…50 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Sun Jun 23, 2019

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

1. Disorganized showers and thunderstorms located a few hundred miles southwest of the Gulf of Tehuantepec are associated with a tropical wave. Environmental conditions appear conducive for a gradual development of this system during the next several days, and a tropical depression is likely to form by the middle of the week while the system moves west-northwestward away from the coast of Mexico.

* Formation chance through 48 hours…medium…40 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Sat Jun 22, 2019

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

1. Disorganized showers and thunderstorms located southeast of the southern coast of Mexico are associated with a tropical wave. A low-pressure area is expected to form in association with this system in a couple of days and gradual development is possible while it moves west-northwestward away from the coast of Mexico through the middle of next week.

* Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…medium...60 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Sat Jun 22, 2019

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

1. A low-pressure system is expected to form several hundred miles south of the southwestern coast of Mexico in a couple of days. The gradual development of the low is possible thereafter and a tropical depression could form while it moves west-northwestward away from the coast of Mexico through the middle of next week.

* Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…50 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Fri Jun 21, 2019

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

1. A low-pressure system is expected to form several hundred miles south of the southwestern coast of Mexico in a few days. The gradual development of the low is possible thereafter and a tropical depression could form while it moves west-northwestward away from the coast of Mexico through the middle of next week.

* 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 Fri Jun 21, 2019

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

1. A low-pressure system is expected to form early next week a few hundred miles south of the southwestern coast of Mexico. The gradual development of the low is possible thereafter while it moves west-northwestward away from the coast of 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 Fri Jun 21, 2019

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

1. A low-pressure system is expected to form within the next few days several hundred miles south of the southwestern coast of Mexico. Environmental conditions could support the gradual development of this system while it moves west-northwestward through the middle of next week.

* 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 Thu Jun 20, 2019

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

1. An area of low pressure is expected to form a few hundred miles south of the southwestern coast of Mexico in a few days. Environmental conditions could support gradual development of this system while it moves west-northwestward through early next week.

* Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…30 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Thu Jun 20, 2019

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

1. An area of low pressure is expected to form a few hundred miles south of the southwestern coast of Mexico by early next week. Environmental conditions could support the gradual development of this system thereafter while it moves west-northwestward.

* 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 Thu Jun 20, 2019

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

1. An area of low pressure is expected to form a few hundred miles south of the southwestern coast of Mexico by early next week. Environmental conditions could support gradual development of this system thereafter while it moves west-northwestward.

* Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…30 percent.