Hurricane forecast team reviews influencing factors for 2013 Atlantic season

The Tropical Meteorology Project at Colorado State University today released its initial outlook for the 2013 Atlantic basin hurricane season. For its December forecast only, the team relies on probabilities of key factors influencing the hurricane season rather than issuing a numerical forecast for the number of storms in this initial outlook.

The team will release the first forecast with predictions for the number of named storms, hurricanes and major hurricanes expected for the Atlantic basin on April 10.

"We have been in an active era for Atlantic basin tropical cyclones since 1995, and we expect positive Atlantic Multi-Decadal Oscillation (AMO) and strong thermohaline circulation (THC) conditions will continue," said Phil Klotzbach, lead author of the forecast. "One of the big challenges for 2013 is whether or not El Nino will develop for the 2013 hurricane season. Since El Nino never fully developed in 2012, and we have since returned to neutral conditions, there is the possibility that an El Nino event will develop next year."

The team predicts four scenarios:

• THC circulation becomes unusually strong in 2013 and no El Nino event occurs (resulting in a seasonal average net tropical cyclone (NTC) activity of ~ 180) – 20% chance.
• THC continues in the above-average condition it has been in since 1995 and no El Nino develops (NTC ~ 140) – 40% chance.
• THC continues in above-average condition it has been in since 1995 with the development of a significant El Nino (NTC ~ 75) – 35% chance.
• THC becomes weaker and there is the development of a significant El Nino (NTC ~ 40) – 5% chance.