Some oil and gas companies have started evacuating nonessential personnel at facilities in the Gulf of Mexico ahead of a storm that forecasters say could develop into a tropical storm before reaching the Texas coast Tuesday.

“Shell has initiated efforts to reduce nonessential personnel on some offshore assets as a precautionary measure in addition to normal preparations for heavy weather,” Shell spokesperson Ray Fisher told Hart Energy. “No impact to operations or product is anticipated. We will continue to monitor the situation and will take further precautions as warranted.”

Likewise Chevron is also monitoring the storm, having already evacuated some nonessential personnel from its offshore GoM facilities, said Kent Robertson, upstream media relations team lead for the company.

Neither Fisher nor Robertson disclosed how many people have been evacuated or from which platforms.

Western GoM blocks include Alaminos Canyon’s Perdido area, where Shell is producing from the Tobago, Silvertip and Great White ultradeepwater fields. Chevron’s assets in the western GoM include the Gila, Gibson and Tiber prospects in the Keathley Canyon area nearby.

As of about 12:30 p.m. Monday, the system had not become a tropical storm, according to the National Hurricane Center. Aircraft data indicated the circulation was “highly elongated and lacks a well-defined center.” However, the hurricane center warned the system—which packed winds near 45 mph and is traveling northwest—had the potential to become a tropical storm before reaching the Texas coast sometime Tuesday.

An updated advisory released about 30 minutes later stated the system became better organized and was “very likely” to become a tropical storm Monday afternoon or evening.

There is a 90% chance of a cyclone formation, according to the hurricane center’s forecast.

While the weather threat prompted some to move forward with evacuations, others remained in a wait-and-see mode.

As of Monday morning, BHP Billiton had not planned any personnel evacuations from its deepwater Shenzi and Neptune platforms, said Jaryl Strong, a BHP Billiton spokesman.

“We will continue to monitor the weather and will activate our hurricane plan should the forecast change,” he said. The Shenzi development is located in the Green Canyon area, about 100 miles offshore Louisiana. Neptune is located in the Atwater Valley area, about 135 miles offshore Louisiana.

BP, which has several developments in the GoM including the Gila prospect in the Keathley Canyon area, said it is observing the disturbance and normal operations continue at its operated offshore facilities.

Hess Corp., which is producing from six GoM fields, is monitoring the storm. Tim Coffy, a spokesman for Hess, said the company stands ready to activate its response plans for severe weather conditions.

This is the first tropical development that could impact U.S. GoM operations since hurricane season started June 1.

The National Oceanic and Atmospheric Administration said there is a 70% chance that between six and 11 named storms will develop in the Atlantic Basin. Of these storms, between three and six could become hurricanes packing wind speeds of more than 74 mph with the possibility for up to two major hurricanes with winds of more than 111 mph.

The oil and gas industry has been fortunate lately, surviving hurricane seasons—which run through November 30—with few disruptions. In 2013, one hurricane and four tropical storms swept through the GoM, but only one, Tropical Storm Karen, impacted production. Just more than 3 MMbbl of crude oil and 6.7 Bcf of natural gas were shut in by the storm, according to the Interior Department. The amounts represented about 7.5% of normal monthly oil production in the GoM and 3.4% of normal gas production, the U.S. Energy Information Administration said.

Contact the author, Velda Addison, at vaddison@hartenergy.com.