FSU COAPS Atlantic Hurricane Season Forecast

On May 30, 2013, COAPS scientists released their fifth annual Atlantic hurricane season forecast. Hurricane season begins June 1 and runs through Nov. 30.

The 2013 forecast called for a 70 percent probability of 12 to 17 named storms, including 5 to 10 hurricanes. The mean forecast was for 15 named storms, including 8 hurricanes, and an average accumulated cyclone energy (a measure of the strength and duration of storms accumulated during the season) of 135. The forecast numbers were based on 50 individual seasonal atmospheric forecasts using sea surface temperatures predicted by a recently upgraded National Oceanic and Atmospheric Administration (NOAA)climate model.

The forecast mean numbers are identical to the observed 1995-2010 average named storms and hurricanes and reflect the ongoing period of heightened tropical activity in the North Atlantic. The FSU prediction was slightly less than the official NOAA forecast that predicts a 70% probability of 13 to 20 named storms and 7 to 11 hurricanes.

Dr. Tim LaRow and his colleagues at COAPS use a numerical climate model developed at Florida State to understand seasonal predictability of hurricane activity. The model is one of only a handful of numerical models in the world being used to study seasonal hurricane activity. The model is one of only a handful of numerical models in the world being used to study seasonal hurricane activity and is different from the statistical methods used by other seasonal hurricane forecasters. FSU is the only university in the United States issuing a seasonal hurricane forecast using a global numerical atmospheric model. The model uses the high performance computers at FSU to make predictions of the atmosphere six months into the future. Based on these atmospheric predictions, tropical activity is objectively determined and forecasts are issued around June 1st.

The COAPS forecast is already gaining recognition for its accuracy only four years after its launch. The 2009 forecast predicted eight named storms and four hurricanes, and there ended up being nine named storms and three hurricanes that year. The 2010 forecast predicted 17 named storms and 10 hurricanes, and there were actually 19 named storms and 12 hurricanes. The 2011 forecast predicted an average of 17 named storms and nine hurricanes, and there were actually 19 named storms and seven hurricanes. The 2012 forecast predicted an average of 13 named storms and seven hurricanes, and there ended up being 19 named storms and 10 hurricanes.

"2012 was unusual in that El Niño did not develop as the climate model expected," said Dr. LaRow. “El Niño develops when sea surface temperatures in the equatorial Pacific Ocean are warmer than normal, leading to increased wind shear in the Atlantic, which can disrupt developing tropical systems. Last year, El Niño never developed. This year El Niño is not predicted to develop."

Re-forecasts conducted using data since 1982 show that the model has a mean absolute error of 1.9 hurricanes and 2.3 named storms. Details about past forecasts are archived here.

To learn more about this forecast, contact lead scientist Tim LaRow ( This email address is being protected from spambots. You need JavaScript enabled to view it. ; (850) 644-6926) and see the following articles:


2013 Atlantic hurricane season (June 1 - November 30) predictions and observed activity.

Forecasting Group Forecasting Method Forecast Issue Date Total Named Storms (Tropical Storms + Hurricanes) Hurricanes Accumulated Cyclone Energy
FSU COAPS Dynamical  5/30/13  15 (70% chance of 12-17) 8 (70% chance of 5-10)    135
NOAA Hybrid 5/23/13  70% chance of 13-20  70% chance of 7-11   70% chance of 120%-205% of median
UK Met Office Dynamical 5/15/13 14 (70% chance of 10-18) 9 (70% chance of 4-14) 130 (70% chance of 76-184)
Colorado State University Statistical 6/3/13 18 9 165
Tropical Storm Risk Statistical 4/5/13 15 (+/-4.1) 7.5 (+/-2.8) 131 (+/-55)
Weather Services International Statistical 4/8/13 16 9 N/A
2013 Observed N/A N/A  13  2 33 
Average Observed per Season, 1981-2011 N/A N/A 12.3 6.5 104.4


*For the latest updates on hurricane activity, visit the National Hurricane Center.

The International Research Institute for Climate and Society (IRI) also releases a forecast for the abbreviated August 1 - October 31 peak Atlantic hurricane season. The IRI forecast can be found at http://iri.columbia.edu/forecast/tc_fcst/north_atlantic/.