Gulf of Mexico System Could Impact U.S. and Mexico

Jon Erdman
Published: September 25,2015

El Niño has certainly exerted its influence on the 2015 Atlantic hurricane season.
(MORE: An Atlantic First In Over 100 Years | Early End to the Season?)
Record high vertical wind shear, which tends to rip apart developing or mature tropical cyclones, has been in place over the Caribbean Sea, according to Colorado State University's Dr. Philip Klotzbach (Wunderblog).
Despite that, it is still late September, and homegrown tropical cyclones spinning up closer to the U.S. can occur. With that in mind, we have an eye on the Gulf of Mexico in the week ahead.

Development Factors

Early next week, the upper-level wind pattern will feature a southward dip of the southern-branch jet stream centered over Texas and northern Mexico, with weak high pressure aloft centered somewhere between the Bahamas and Bermuda.
Low pressure at the surface may form somewhere near the Yucatan peninsula and get pulled north by the upper-air pattern mentioned above.

Potential Gulf Setup

That may sound ominous if you're concerned about tropical storms or hurricanes. Let's go through a checklist of ingredients to see how likely a tropical system is to form.

Favorable Factor	In the Gulf?	Comments
Warm water	Yes	Not as warm as the eastern Pacific, but near or above average, and plenty warm enough for tropical development
Moist air	Yes	Deep moisture pumped from the tropical eastern Pacific and Central America will be well above late September average over at least the central and eastern Gulf of Mexico.
Unstable for thunderstorms	Yes	Gulf water warming and adding moisture to the air above it + jet stream dip to the west mentioned above = plenty of instability.
Low/no wind shear	Likely Not	That same jet-stream dip, however, will likely create hostile wind shear over at least the western and northern Gulf of Mexico.

That one negating factor, wind shear, is why any threat of strong tropical cyclone development in the Gulf of Mexico remains very low at this time.
Computer model solutions differ with a few scenarios showing at least a weak area of low pressure approaching the Gulf Coast in the upcoming week.

Impacts, Regardless

Whether or not an area of low pressure does acquire enough organization to be designated a tropical depression or storm, there may still be impacts along the Gulf Coast early in the week ahead.

Gulf Coast Potential Impacts

• Locally heavy rain: Bands of locally heavy rain may push ashore along, particularly, the central and eastern Gulf Coast. We can't rule out a few heavy rainbands, as well, along the western Gulf Coast. 
• High surf, rip currents: Persistent southeast winds may whip up high surf and rip currents from southeast Louisiana to at least the Florida panhandle. Some elevated surf may also propagate to parts of the Texas Gulf Coast. 
• Coastal flooding: This persistent onshore flow may lead to areas of at least minor coastal flooding, particularly around high tide, from southeast Louisiana to the western Florida panhandle. The longevity and strength of onshore flow over the western Gulf (Texas), and thus, the coastal flood threat, there, remains uncertain at this time.

(FORECASTS: S. Padre Island | Biloxi | Destin)
We don't recommend canceling any Gulf Coast beach or fall festival plans right now.
However, we do recommend visitors with little experience at the beach to familiarize yourself with the dangers of rip currents.
Look for surf hazard warning flags and heed the advice of lifeguards. Even experienced swimmers should stay out of the water when rip currents are a threat.
Over 30,000 rip current rescues are performed each year in the U.S., often occurring in waves of just 2-3 feet. Rip currents claim about 100 lives each year in the U.S.
Check back with us at weather.com and The Weather Channel for updates on this Gulf of Mexico disturbance.

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