2013 Hurricane Outlook Update (August 13)

Tuesday, August 13, 2013

In mid-August 2013, Dr. Tingzhuang Yan, Dr. Len Pietrafesa, and Dr. Paul T. Gayes updated their modeled, hurricane outlook based on changing climate factors (a common process for all hurricane outlooks).

The outlook includes common predictions, similar to those created annually by well-known atmospheric research organizations and institutions (e.g. NOAA, Colorado State University), but is the only model to attempt predicting landfalls. Many of the model predictions will be familiar to most people who live along the coasts and includes the number of named storms (TS), number of hurricanes (NH), and number of major hurricanes (MH, category 3 or higher). It also predicts the number of landfall hurricanes along the Atlantic seaboard (ECLF) and the number of landfall hurricanes along the US Gulf Coast (GMLF). The model, once it calculated these probabilities, determined the number of landfalls to be a “fraction of a storm” which simply isn’t practical (obviously you can’t have 1.11 or 0.89 storms making landfall) so the researchers have chosen to display the data as the most likely to least likely number of hurricane landfalls.  The climatology column reflects the long-term, annual average of each measure for the 63-year record.

The science of creating these outlooks is based heavily on statistics from data that is available in the historic storm records. Reliable information on the number of storms, hurricanes, landfalls and physical conditions that were present during storm formation only dates back into the 50s.  Using this information, what is produced are tables that indicate the probability of having 1 named storm, 2 named storms, 3 named storms etc… and that information is then summarized for official reporting which is why the outlooks are typically displayed as ranges or probabilities.

To initially test the model, years for which storm and climate data were available were hindcast in order to determine the model’s skill (you can see these results by clicking on each category in the table below).

Table 1: 2013 Updated North Atlantic Basin Seasonal Hurricane Forecast
Category April Forecast August Forecast Climatology
ACE 122[119~124] 124~127 103
TS 14 [13~15] 15~18 11.0
NH 7 [6~8] 7~9 6.2
MH 3 [3~4] 2~4 2.7
ECLF [1, 0, 2] 1.11 [1, 2, 0] 0.65
GMLF [1, 0, 2] 0.89 [0, 1, 2] 0.95