Tropical Storm Alvin Discussion Number 7
Wiki-Hurricanes Forecast Center
2:00 AM PDT Thu Jun 27 2019
Alvin continues to present a similar appearance as a compact system with a small CDO and continuous bursting of strong convection near the center. The satellite presentation is characterized by a somewhat-defined central dense overcast, with a ragged spiral band extending to the west and north. Outflow continues to be adequate and symmetrical. SAB and TAFB disagree on the Dvorak front, with the former giving T2.5/35kt and the latter the stronger T3.0/45 kt. With no recent microwave passes since the last package, no further assessment can be made on the inner structure of the system. A recent ASCAT-A pass shows a very small wind field with winds of at least 35 kts (the National Hurricane Center notes a 46 kt wind barb). Given the small size of the system and the available data, Alvin's intensity has been increased to 45 kts this advisory.
Alvin is expected to remain in fairly favorable conditions overall for the next 24 hours or so. Shear is expected to remain low under the influence of an upper level anticyclone and the storm is expected to not track over cool SSTs until about 24 hours out. Mid-level relative humidity will remain adequate for the system, although Alvin has been intermittently struggling with the region of dry air to its west that it continues to move into. As a result, the storm should be able to intensify slowly for about the next day or so before succumbing to cold SSTs, being hampered mainly by dry air intrusion.
The earlier wrench in the forecast regarding the southerly shift in forecast track has passed as the storm appears to be resuming a west-northwesterly track around the ridge centered over northern Mexico this morning. Therefore there is fairly high confidence that Alvin will begin weakening significantly when it reaches a strong SST gradient around this time tomorrow. The intensity forecast has been increased slightly to account for the current intensity upgrade and further potential for strengthening throughout the day today.
FORECAST MAX WINDS
INIT 27/0900Z 45 KT 50 MPH
12H 27/1800Z 50 KT 60 MPH
24H 28/0600Z 55 KT 60 MPH
36H 28/1800Z 45 KT 50 MPH
48H 29/0600Z 35 KT 40 MPH
72H 30/0600Z 25 KT 30 MPH...POST-TROP/REMNT LOW