Invest 91E Likely to Become Tropical Depression Late This Week; Heavy Rain Expected in Southern Mexico

Jonathan Belles
Published: May 30,2017
A tropical disturbance located south of Mexico could develop into this season's next tropical depression by late in the week, but this particular system doesn't pose a threat to the United States.
The area of storminess, deemed Invest 91E by the National Hurricane Center, has a moderate chance to develop into a tropical depression by Thursday, and a high chance by Sunday. Heavy rainfall in southern Mexico will likely be the biggest threat.
(MORE: What Is an Invest? | Hurricane Central)
Areas of investigation, or invests, are part of a naming convention used by the NHC to identify disturbances they are watching for potential development.
Invest 91E contains a gradually tightening low-level swirl of winds and towering thunderstorms beneath light wind shear, which is favorable for the growth of a tropical system.
Water temperatures are also favorable for the birth of a tropical depression, with temperatures climbing into the mid-80s.

Current Storm Status

The disturbance is forecast to slowly shuffle northward toward the Mexican coast over the next few days, but computer models currently disagree about when, or even if, this system will reach the coast.
It will bring locally heavy rainfall and a mudslide threat to southern Mexico through the weekend. Some communities in Mexico's state of Oaxaca and surrounding states could see more than a foot of rainfall.

Forecast Rainfall

Wind gusts up to 40 mph are possible over the next couple of days – higher if the system develops faster than anticipated.
Waves of 5 to 8 feet are likely along the coast of Mexico and Guatemala through mid- to late-week, and some minor coastal inundation is possible, especially along east- or southeast-facing coasts.
(MORE: 15 Most Iconic Hurricane Images of All Time)
Early-season tropical cyclones are common in the eastern Pacific, where the first tropical storm forms, on average, about June 10.
A tropical storm forms in the first 10 days of June roughly once every five years in the East Pacific Basin, generally south of Mexico.

Points where tropical cyclones have formed in the first 10 days of June.

Although this system is not expected to directly impact the U.S., storms early in the season can bring moisture northward.
(MORE: Here's How Eastern Pacific Tropical Cyclones Can Affect the United States)
The Eastern Pacific season began May 15 – 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.
Since we've already had Tropical Storm Adrian this year, the next name on the list is Beatriz.

MORE: Hurricane Patricia – 2015

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