Despite an early unofficial start to the 2015 hurricane season — with Tropical Storm Ana making landfall weeks before the official June 1 start date — scientists predict that this year’s season will see some of the lowest storm activity in nearly a decade.
Announcing the National Oceanic and Atmospheric Administration’s (NOAA) outlook for the season Wednesday, NOAA administrator Kathryn Sullivan said that the 2015 season has the highest probability of a below average season since about 1998. This year is anticipated to see six to 11 tropical storms, between three and six of which could become hurricanes (with between zero and two of those having the potential to become major storm events). Between 1981 and 2010, each season saw an average of 12 named storms, six hurricanes, and three major storm events.
“These numbers are below average for hurricane season, but below average doesn’t mean no pitches get thrown our way,” Sullivan said in a press call Wednesday. “No matter how many pitches Mother Nature throws at us, if just one of those pitches gets through the strike zone we could be in trouble.”
A strengthening El Niño is the main reason scientists predict a particularly quiet season. El Niño — characterized by unusually warm temperatures in the equatorial regions of the Pacific Ocean — changes global wind patterns, creating hostile upper-level winds in the tropical Atlantic that in turn create unfavorable conditions for the formation of hurricanes.
“In the Atlantic, El Niño brings stronger than normal winds, which creates a hostile environment for hurricanes,” James Done, a meterologist with the National Center for Atmospheric Research, told ThinkProgress. “Hurricanes generally favor calm environments, and strong winds tend to tear hurricanes apart.”
Cooler ocean temperatures in the Atlantic also lessen the chance of an intense storm season. Warm waters are the primary force behind hurricane intensity — normally, waters have to be a little over 78° F for hurricanes to form and intensify — and current ocean temperatures for the southern Atlantic Coast are just around that threshold.
But while the Atlantic might see a reprieve from an active hurricane season, El Niño will have the opposite effect for the Pacific region. Both the waters around Hawaii and those in the northeast Pacific could see a 50 percent increase in activity from average years, Jeff Masters, director of meteorology at Weather Underground, told ThinkProgress.
The northwest Pacific has already seen an incredibly active typhoon season, with seven typhoons occurring since the season began in January. Warm Pacific temperatures — driven by El Niño — are largely responsible for the increased frequency and power of the storms.
An active Pacific storm season could bring intense rains to the U.S. Southwest, with states like Arizona, New Mexico, and the western part of Texas most likely to see the remnants of hurricanes that develop off the coast of Mexico.
Unfortunately, drought-plagued California is unlikely to see those rains. “Those storms tend to track east, so it probably won’t help the drought in California,” Masters said. California has seen a few tropical storms in the past — one in the 1800s and one in 1939 — so while such an event is possible, Masters pointed out that “we have no skill to predict those kinds of things.”
Despite the potential for a quiet season in the Atlantic, Masters cautioned that the “standard disclaimer” still applies: “Even a quiet hurricane season can breed a category 5 monster. The fact that this season’s forecast is for quieter-than-average doesn’t mean people should be less prepared.”
The 1992 hurricane season was the year that, despite an El Niño pattern, saw the devastating impact of Hurricane Andrew, which killed 15 people when it made landfall and is still one of the costliest storms in U.S. history.
NOAA officials stressed that storm surge — the water level rise caused by a storm — is the greatest threat to public safety caused by a hurricane. “Storm surge is always the greater threat to life in a hurricane,” Sullivan said. “It is the water, not the wind, that kills.”
As climate change drives up sea levels, storm surge is poised to become even more dangerous. While scientists don’t yet understand how climate change will impact the frequency of hurricanes, they are confident that stronger storms will become stronger, dumping more precipitation and creating higher storm surge. Even a small rise in sea level translates to a pronounced rise in storm surge — according to a study conducted by Lloyds of London, the storm surge associated with Hurricane Sandy was 30 percent higher due to sea level rise.
“Just a few centimeters of sea level rise can make billions of dollars in additional damage due to storm surge,” Masters said.
President Obama will visit the National Hurricane Center on Thursday, May 28 to receive briefings on hurricane preparedness for the upcoming season. The visit comes during National Hurricane Preparedness Week, which runs through Friday.
But to truly prepare for hurricanes in both the present and future, Done said, scientists need to better understand how to anticipate a storm’s impacts. Done, whose work is partially funded by the re-insurance industry, has been involved in creating a hurricane scale that better correlates with potential damage by taking into account things like the area of the damaging winds and how fast a storm is moving forward.
“Where the science needs to go is to try to understand what we can say about seasonal forecast impacts,” Done said. “That’s something that researchers are engaged in to make these seasonal forecasts more useful.”