Tropical Trouble: Eastern Pacific May Get a Record Early Season Tropical System Next Week

Jonathan Belles
Published: May 6,2017
The eastern Pacific may see its first tropical system during the middle of the upcoming week, kicking off the 2017 Pacific Hurricane Season. If a tropical depression forms before May 12, it would become the earliest tropical cyclone to form in the east Pacific in the satellite era. This record is currently held by Alma in 1990. 
An area of low pressure is expected to form in the far eastern Pacific to the south of Central America.
According to the National Hurricane Center, that area of low pressure has a 50 percent chance of developing by Thursday as it moves northwestward. Development is not currently anticipated this weekend.

Modeled precipitation and wind direction for mid next week. The orange oval represents the area in which the National Hurricane Center believes that tropical cyclone formation may occur through Thursday.

This low-pressure system is anticipated to remain just offshore from Central America while traveling parallel to the coast through the end of next week. However, there are differences regarding the track of this system among the computer models, which will make a difference in the impacts to the coast.
(MORE: 2017 Atlantic Hurricane Season Forecast Calls For a Near-Average Number of Storms, Less Active Than 2016)
Water temperatures south of El Salvador and Guatemala are in the low to mid-80s, which is favorable for thunderstorms to grow as the disturbance moves overhead early next week.
In addition, the area of disturbed weather is expected to form in an area with low wind shear, which should foster gradual development over the next few days.

Forecast wind shear for Central America. Deeper red colors represent unfavorable areas for tropical development while blue areas and areas with transparent shading represent favorable areas for tropical development.

Heavy rainfall and enhanced wave activity are the main threats to the shoreline between Costa Rica and southern Mexico.
If this system strengthens into a tropical storm, it will receive the name Adrian. It could also become the earliest named storm on record if it develops by May 14.
The eastern Pacific season begins May 15, which is about a half a month earlier than the Atlantic season. The earlier start date is due to warmer waters and typically weaker wind shear earlier in the season as compared to the Atlantic.
(MORE: El Niño May Develop in Late 2017 and Could Impact Hurricane Season)

Do Pacific Storms Threaten the United States?

This system won't have much of an impact stateside, but historically, early season tropical systems do bring moisture northward from time to time.
Tropical storms and hurricanes in the eastern Pacific typically weaken as they move north due to colder water and increased upper-level winds. Depending on the weather pattern across North America, moisture from the storm can get pulled north into the Southwest U.S.

Tropical storms and hurricanes in the eastern Pacific typically weaken as they move north due to colder water and increased upper-level winds. Depending on the weather pattern across North America, moisture from the storm can get pulled north into the Southwest U.S.

Although the majority of the hurricanes and tropical storms that form in the eastern Pacific move away from land and are only a concern to shipping interests, the weather patterns at the beginning and end of the season are more conducive to these systems potentially affecting Mexico and the southwestern United States.
Arizona is the southwestern state with the history of the most tropical storm encounters. According to the National Weather Service in Tucson, Arizona, a total of eight tropical storms or depressions have remained intact and affected Arizona directly since 1965. Five of these actually made it as tropical storms with sustained winds of 39 mph or higher.
(MORE: Hurricane Central)
Flooding rains are typically the greatest concern from any tropical systems that survive the journey into the southwestern United States. This means that the actual number of systems that have affected the Southwest throughout history is much higher since many of them dissipate before actually reaching the United States. Why is this?
While the storm may no longer be intact, the remnant tropical moisture can fuel drenching rains as it moves into the region. The 2016 eastern Pacific hurricane season provided several examples of how this can happen, including Tropical Storm Javier, Hurricane Newton and Hurricane Paine.

MORE: Hurricane Patricia, 2015

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