Eastern Pacific May Get a Record Early-Season Tropical System This Week

Jonathan Belles
Published: May 9, 2017

The eastern Pacific may see its first tropical system this week, kicking off the 2017 hurricane season in that basin. If a tropical depression forms before Friday, it would become the earliest tropical cyclone to form in the northeast Pacific in the satellite era. This record is currently held by Alma in 1990.

A broad area of low pressure has formed a few hundred miles off the coast of Central America, which has been dubbed Invest 90E by the National Hurricane Center (NHC). This is a naming convention used to identify features that have a chance of developing into a future tropical depression or storm.

(MORE: What is an Invest?)

Satellite imagery Tuesday morning showed shower and thunderstorm activity was continuing to organize in association with Invest 90E over the eastern Pacific to the west of Central America.

Enhanced Satellite

According to the NHC, Invest 90E has a high chance of developing into a tropical depression or storm in the next couple of days as it moves northwestward. If the development trend continues, then it is likely that a tropical depression will form later today.

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 this week. 

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

In addition, the broad area of low pressure is located in an area with low wind shear, which could foster gradual development over the next day or two.

This potential system is anticipated to remain just offshore from Central America while traveling parallel to the coast through the end of this week. Eventually, it may curl back toward the coastline of southern Mexico and Central America. However, there are differences regarding the track and intensity of this system among the computer models, which will make a difference in what, if any, impacts to expect on the coast.

(MORE: 2017 Atlantic Hurricane Season Forecast Calls For a Near-Average Number of Storms, Less Active Than 2016)

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.

Adrian will be the name given to the first tropical storm of the 2017 season in the eastern Pacific.

The eastern Pacific season begins May 15, which is about a half-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?

These systems 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 southwestern United States.

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 U.S.

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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