The National Hurricane Center gives a disturbance in the eastern Pacific Ocean a 70 percent chance of developing into a tropical depression or a tropical storm this week. Models don’t do much with the storm, but the system’s development would end the unusual tropical silence coming from the eastern Pacific almost six weeks into the basin’s hurricane season.
Conditions are favorable for the slow development of a tropical disturbance located a few hundred miles off the southern coast of Mexico. The disturbance will pose no threat to land as it steadily moves west toward open waters. Even the most aggressive weather model solution on Monday night didn’t develop the system beyond a weak tropical storm, but it seems likely that the disturbance will take advantage of favorable conditions to reach tropical depression status by mid-week.
If this disturbance does indeed become a tropical depression, it would be the first tropical system in the eastern Pacific this year. The basin’s hurricane season began back on May 15. This is one of the latest starts to the eastern Pacific hurricane season on record, with no tropical depressions or named storms through June 24. Every hurricane season in the last 20 years saw at least one tropical depression form by June 18 at the latest. Tropical Storm Agatha earned its name on July 2, 2016, the latest formation of a named storm in the last couple of decades.
Why the unusual silence? While sea surface temperatures in this part of the Pacific have hovered around or slightly above normal since May, the region hasn’t seen many disturbances and the overall environment has been unfavorable for tropical development. A slow start to a hurricane season isn’t necessarily an indication that the entire season will be slow. Patterns can change in a hurry.
NOAA’s Climate Prediction Center expects that the eastern Pacific has a 70 percent chance of seeing above-normal activity this year, largely due to an El Niño the agency expects to persist through the summer months. A normal season in the eastern Pacific would see 15 named storms, eight of which would strengthen into hurricanes and four of those hurricanes reaching category three or higher on the Saffir-Simpson Hurricane Wind Scale.
The first named storm in the eastern Pacific this year will be called Alvin, followed by Barbara and Cosme. Each list of storm names in the eastern Pacific contains 24 masculine and feminine names that are recycled every six years. Names of particularly damaging or deadly storms are retired and replaced; the name Mario on this year’s list replaces Manuel, which was retired after the 2013 hurricane season.