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Tropical Storm Alvin Discussion Number 11

Wiki-Hurricanes Forecast Center

2:00 AM PDT Fri Jun 28 2019

Alvin's existence has a hurricane was short-lived. The storm's satellite appearance has deteriorated significantly since the last advisory. Hints of an eye have disappeared in infrared satellite imagery and the bulk of the convection appears to be located northeast of the low-level circulation, as indicated by two ASCAT passes from a few hours ago, and upper-level outflow appears good in the north and east quadrants but inhibited in the south and especially west. All of this is likely as a result of intensifying southwesterly shear. Dvorak intensity estimates have accordingly decreased at 06z with intensities from SAB and TAFB coming in at T3.5/55kt. As a result, it is expected that Alvin has begun to weaken and its intensity has been decreased to a 60 kt tropical storm for this advisory.

Alvin is not expected to intensify any more as shear is beginning to affect the storm and it is not expected to abate. The system is also already tracking over increasingly cooler SSTs with temperatures already estimated at 24-25C. As shear begins to decouple the system, the mid-level moisture should continue to round the ridge over northern Mexico and the southwestern United States, which will allow for dry, stable air to dominate the low-level center's environment. All of these factors combined should result in rapid weakening from here on out. The forecast has been adjusted to account for this quicker weakening trend. Given model guidance, Alvin could become a remnant low as early as 36 hours from now.

Alvin's mid-level remnant moisture should continue to advect northwestward and later turn northward which it is expected to have marginal effects in the southwestern United States this weekend. The storm's lower-level remnants are likely to turn west-southwest under the influence of a low-level ridge over the subtropical northeast Pacific in around 36 hours when the storm becomes post-tropical and completely decouples.

FORECAST MAX WINDS

INIT 28/0900Z 60 KT 70 MPH

12H 28/1800Z 50 KT 60 MPH

24H 29/0600Z 35 KT 40 MPH

36H 29/1800Z 25 KT 30 MPH...POST-TROP/REMNT LOW

48H 30/0600Z 20 KT 25 MPH...POST-TROP/REMNT LOW

72H 01/0600Z...DISSIPATED

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