Why we treat some Invest areas like tropical storms…

It’s critical that offshore operators are aware of tropical hazards well in advance of tropical storm development. 

Tropical Storm Bill, June 16 2015
Infrared Satellite of Tropical Storm Bill approaching the Texas coast.

Two years ago we were monitoring an area of disturbed weather near the Yucatan Peninsula. At the time, forecast models indicated that a trough of low pressure would move offshore the Yucatan within the next 24 hours and form a closed circulation as it tracked northwest toward the Texas coastal bend. Hurricane Carlos, off the southern coast of Mexico, was feeding in abundant tropical moisture from the Pacific, aiding thunderstorm development. Over the next few days, upper-level winds over the Gulf weakened, enhancing convection and improving the low-level circulation. Within 36 hours a tropical storm was designated over the northern Gulf of Mexico. About 15 hours later, Tropical Storm Bill made landfall over Matagorda Island, Texas with maximum sustained winds near 60 mph.

Extensive squall and thunderstorm activity, between the Invest area and an upper-level low moving across the Gulf coast, produced enhanced >27 knot winds, gale force gusts and rough sea conditions across many deep water areas several days before Invest 91L was classified as a tropical storm.

With gale warnings in place and widespread strong convection persisting across much of the region, offshore oil and gas operators were already experiencing conditions that would trigger steps in their hurricane contingency plans. One morning I briefed a customer on the deteriorating conditions. He said, “So, Tropical Storm 91L will track northwest toward Keathley Canyon”. It was quickly evident that the customer was not concerned with whether the storm was an Invest area or tropical storm. He needed to determine whether gale force winds would impact his operation and require evacuation.

Coastal and offshore operators who wait on the official tropical storm designation and storm advisories issued by the National Hurricane Center may not have adequate time to prepare for storms brewing within a close proximity to shore. It was this storm, Invest 91L/Tropical Storm Bill, that became the catalyst for us to prepare detailed track forecasts for significant tropical disturbances. These advisories give customers advanced warning for disturbances with a significant chance of developing and producing conditions above their hurricane criteria. In short, these reports include:

  • Regional tropical weather discussion
  • 5-day graphical storm projection
  • 5-day forecast of storm conditions




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