The first named storm of the 2018 Pacific hurricane season, Tropical Storm Aletta, was named Wednesday morning. Aletta is likely to intensify into a hurricane away from land by the weekend, although the intensity guidance has backed off on intensification a bit. To the east of Aletta is another tropical wave that has a high chance to develop into a tropical cyclone by Sunday. The Atlantic basin remains quiet for the moment, although some models are indicating the possibility of development over the Northwestern Caribbean Sea by the middle of next week.

As of 9:00 a.m. MDT (11:00 a.m. MDT), Tropical Storm Aletta was centered near 14.7°N 107.1°W and was moving westward at about 7 mph. Maximum sustained winds were 40 knots (45 mph), with an estimated minimum pressure of about 1000 mb. A recent ASCAT pass showed that maximum sustained winds are still about 40 knots and that the storm had not strengthened since this morning. Dry air appears to have become entrained into Aletta’s circulation, with the circulation located at the northwestern edge of the convective mass. Since the structure of Aletta is not very well organized at present, intensification should be fairly slow during the next 12-24 hours or so. After that time, strengthening is likely since wind shear is low and sea surface temperatures are warm, and Aletta should become a hurricane by Friday. The intensity guidance has become less bullish on intensification today, with most models predicting that Aletta will peak as a Category 1 hurricane. Aletta should reach its peak intensity around Saturday. After that time, steady weakening is expected as Aletta moves west-northwestward into cooler waters.

The average first named storm in the eastern Pacific basin forms on June 10, so Aletta is very close to the average date if not a little early. The eastern Pacific has already seen one other tropical cyclone form this year: pre-season Tropical Depression One-E in early May, which failed to strengthen into a tropical storm far from land areas.

To the east of Aletta, there is a tropical wave that is likely to become the next tropical cyclone of the Pacific hurricane season this weekend. The National Hurricane Center (NHC) gives this system a 30 percent chance of development within 48 hours, and an 80 percent chance of development within five days. The 12z ECMWF, UKMET, GFS and CMC models all predicted that this system would become a tropical depression within the next five days. This system should remain closer to the Mexican coast, and is also likely to become a hurricane by early next week as it moves west-northwestward.

The Atlantic basin remains quiet, with the NHC not expecting any development within the next five days. The 12z Wednesday GFS and CMC models both predicted that a tropical depression would form over the Northwestern Caribbean Sea by the middle of next week. However, the reliable ECMWF model continues to show no development at all, and the GEFS ensembles are not particularly excited about development either. I give a 10% chance of a tropical cyclone developing over the Northwestern Caribbean during the next 10 days.

I will be back with an update on the tropics tomorrow.