The eastern Pacific remains very active. Tropical Storm Aletta strengthened into the first hurricane of the 2018 Pacific hurricane season Thursday afternoon, and is likely to strengthen a little more as it moves west-northwestward away from land. To the east of Aletta, a tropical wave is likely to develop into a new Eastern Pacific tropical cyclone by Sunday. The Atlantic basin remains quiet for now, but the GFS, UKMET and CMC models are all indicating that the Northwestern Caribbean and Gulf of Mexico may be worth monitoring for potential development by late next week.

As of 3:00 p.m. MDT (5:00 p.m. EDT) Thursday, Hurricane Aletta was centered near 15.3°N 110.0°W, and was moving west-northwestward at about 6 mph. Maximum sustained winds were 65 knots (75 mph), with an estimated minimum pressure of 987 mb. This makes Aletta a minimal Category 1 hurricane on the Saffir Simpson Hurricane Wind Scale – the first of the 2018 Pacific season. Aletta has developed an eye-like feature on visible satellite imagery, although the infrared appearance is not very impressive.  During the next 24 hours or so, Aletta is expected to remain in a low shear and fairly moist environment while sea surface temperatures remain above 27°C (80.6°F). Some intensification is likely during this time, and Aletta is likely to strengthen into a high-end Category 1 hurricane by early Saturday. It is possible Aletta could reach Category 2 status, though this is not predicted by most of the intensity guidance. By late Saturday, Aletta will be moving over waters less than 26°C (78.8°F), and will be moving into a drier and more stable environment. Rapid weakening is likely after that time, and Aletta should degenerate into a post-tropical remnant low by the middle of next week away from land areas.

To the east of Aletta, a tropical wave is producing disorganized thunderstorm activity and is likely to develop into the next eastern Pacific tropical cyclone by Sunday. The National Hurricane Center (NHC) gives this disturbance a 40 percent chance of development within 48 hours, and a 90 percent chance within five days. This system is likely to pass much closer to the Mexican coast than Aletta, and the global models are indicating that this system could pose a threat to the Baja California Peninsula or even western Mexico by late next week. Fortunately, however, sea surface temperatures drop quickly near the southern tip of Baja California, and this should cause the potential cyclone to weaken if it nears the Baja California peninsula. The next name on the 2018 Pacific hurricane season naming list is Bud.

The Atlantic basin continues to be quiet for the time being, with the NHC not expecting any development over the next five days. The 12z Thursday GFS, UKMET and CMC models all indicated that a broad area of low pressure is likely to develop over the northwestern Caribbean Sea by the middle of next week, and this region may warrant monitoring for potential tropical development after that time. It should be noted that the 12z Thursday ECMWF model showed no development at all, and the GEFS and EPS models are not particularly enthusiastic on development either. The next name on the 2018 Atlantic hurricane season naming list is Beryl.

I will be back with another post tomorrow on the tropics.