Gulf of Mexico 'Hot Tub' Could Fuel Hurricane Season Toward Peak

Jonathan Belles
Published: July 20,2016
Sea surface temperatures so far this hurricane season have busted records in the Gulf of Mexico, running just under 2 degrees Fahrenheit above average, and that could mean more fuel for tropical storms and hurricanes if the season becomes more active.
Temperatures at the Gulf of Mexico's surface from June 1 through July 17 were at their warmest for the time period since records began in 1982, according to Michael Lowry, hurricane specialist for The Weather Channel.

Oceanic heat content – a measure of how much heat is stored in the oceans – was also at record to near-record levels for mid-July in parts of the Caribbean, Gulf of Mexico and waters surrounding the Bahamas, according to Dr. Jeff Masters of Weather Underground.
Tropical storms and hurricanes can tap into this heat energy, which can help them to intensify. The warmer the water and the deeper the warm water layer goes, the ocean becomes more supportive for thunderstorm production in the atmosphere.
(MORE: Ocean Heat Content)

Sea Surface Temperatures

Why Are Ocean Temperatures So Warm?

The answer is simple: land temperatures around the Gulf brim have been running at record or near-record warmth. As of July 19, at least 18 stations were reporting their warmest July on record in Florida alone.

Ranked observed average temperature for July 1 - July 18. A station denoted as "1" is seeing its warmest July on record.
(Southeast Regional Climate Center)

Winds over the Gulf of Mexico have been primarily light and out of the warm tropics. To a large degree, there hasn't been much to remove heat from the Gulf of Mexico.
Tropical cyclones are one of the most efficient heat-movers, but there hasn't been a tropical cyclone in the Gulf since Tropical Storm Colin in early June.
This lack of movement in the Gulf has led to very warm ocean temperatures. In Tampa Bay, ocean temperatures as high as 95 degrees were observed last week. Temperatures have cooled slightly since then, following afternoon thunderstorms.

Water temperature in Old Tampa Bay, Florida in early to mid-July, 2016
(NOAA/National Ocean Service)

Sea surface temperatures have been as much as 3 to 4 degrees Fahrenheit above average in the Gulf of Mexico in the last two weeks, according to the Climate Prediction Center.

What Other Factors Are in Play and How Do They Impact Hurricanes?

Sea surface temperatures are only one of five requirements, in addition to a generally unstable atmosphere, for a tropical system to form and develop. Many of those requirements are as important as ocean temperatures.
Other factors that impact tropical systems include humidity, wind shear and instability. For example, you can have plenty of warm water, but if wind shear and dry air are abundant, a potential tropical storm may struggle to develop.

In addition to "how warm," sea surface temperatures are also a matter of "where." Remember that tropical systems building from their infancy to a hurricane usually move thousands of miles. They need warm water throughout the journey to stay healthy.
A large portion of tropical systems originate in the eastern Atlantic and cross the ocean to grow closer to the United States, so warmer waters in the eastern portion of the basin would give new disturbances a healthy start. Eastern Atlantic waters are important for busy seasons, according to Eric Blake of the National Hurricane Center.
A large swath of warm water exists in the equatorial Atlantic, but most tropical waves cross the Atlantic north of the warmest water. It is typically in August and September when these warm waters move north.
If a tropical system does get into the Gulf, it would have plentiful warm water in which to form and grow. We could potentially have stronger storms if – and that's a pretty big if – storms get into the Gulf while waters are this warm. Keep in mind, however, the other atmospheric factors that are in play, in addition to warm water, should a storm make it into the vicinity of the Gulf or Caribbean.
(MORE: Hot Temperatures This Week Could Bolster Gulf of Mexico Heat)

Why Haven't We Had Storms Recently

Saharan air has been common recently from Africa to Austin, Texas. This is the main reason for the lack of tropical activity in the last month. But keep this in mind: June and July are typically two of the least active months of the hurricane season.
Generally, dry air moistens up as it transits warm water, but this takes weeks as it crosses the Atlantic. Blasts of Saharan dust have frequently rolled from the African continent through mid-July.
That dry air has both limited thunderstorm activity across the Atlantic and reduced the amount of strong tropical waves. Tropical waves are important because they can be the precursor disturbance that allows thunderstorm activity and heat to accrue in one location.
(MORE: The Heart of the Hurricane Season is Ahead)
For these warm waters to have any impact on hurricane season, there have to be tropical systems, and without tropical waves, there are far fewer tropical systems.
Wind shear has been fairly low this month, but as always, there will be patches of higher shear around the basin.
Instability, or the ability for storms to grow vertically, can be limited during outbreaks of Saharan dust.
Saharan air typically decreases and water temperatures increase as we head into August and toward the peak of hurricane season.
MORE: Hurricane Imagery