How important is the preseason hurricane outlook?

BATON ROUGE, LA (WAFB) - While hurricane season officially begins June 1, we got off to an early start. The Atlantic basin has already seen one tropical storm.

Tropical Storm Arlene formed on April 20, 2017 in the Central Atlantic. Arlene is only the third tropical or subtropical storm known to have formed in the month of April, joining Ana in 2003 and an unnamed storm in 1992.

It's important to note that early activity tells us nothing about how active or inactive the upcoming season may be.

Arlene formed a few weeks after the first hurricane preseason outlooks were released.

Preseason hurricane outlooks are still an inexact science, but forecasters are getting better.

Over 30 years ago Dr. Bill Gray, a researcher at Colorado State University, issued his first preseason hurricane outlook.

Dr. Gray passed away last year so Dr. Phil Klotzbach has taken over the reins to one of the oldest hurricane outlooks.

"Dr. Gray started this back in the early 1980's because he said 'hey we have some skill, there is a lot of curiosity, people want to know how active the season is going to be,'" Klotzbach said.

Accuracy has improved since that first forecast. Dr. Klotzbach explains that there are patterns to look for in developing a preseason outlook.

"We look at historical data and historical weather patterns and basically look and see what sets of conditions preceded an active season and alternatively what sets preceded inactive seasons," he said.

Colorado State is not the only group putting out preseason forecasts.

A number of private companies, universities, and even the National Hurricane Center (NHC) issue these forecasts. A major tool used by the National Hurricane Center is computer modeling.

They don't predict the specific storms, but they are better at predicting sea surface temperatures, predicting the upper level wind patterns that do affect tropical cyclones," James Franklin explains.

The biggest difference between Colorado State and NHC is in the numbers. NHC issues a range forecast, while Dr. Klotzbach issues specific numbers.

"It's to try and recognize that there is uncertainty in these forecasts," Franklin said. "The idea is to try and get the answer right about two thirds of the time."

"Obviously there's uncertainty in these forecasts," Klotzbach added. "You know we don't certainly expect our numbers to verify perfectly, but we find that by giving the general public one number that tends to help kind of focus in on exactly what we are thinking."

So what's the key to this hurricane season?

"One of the big things that we are looking at for 2017 is an El Nino going to develop? If an El Nino develops that would tend to lead potentially to suppressing overall Atlantic hurricane activity," Klotzbach said. "Where as if it doesn't develop we could end up with a more active hurricane season.  So that's one of the big things we are monitoring this year."

El Nino is warmer than usual waters in the central and eastern Pacific. This yields more tropical activity in the Eastern Pacific. That activity creates wind shear in the mid and upper levels of the Atlantic creating an unfavorable environment for developing Atlantic tropical systems.

This is where forecasters with Colorado State and the National Hurricane Center disagree. CSU believes some form of El Nino will occur while NHC predicts a very weak El Nino to occur.

Regardless of which forecast you believe forecasters stress don't let your guard down.

"It's not a prepardness tool.," Klotzbach noted. "People need to be prepared the same every hurricane season regardless of the seasonal forecast because it obviously just takes that one hurricane to make it an active season for you."

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