2013 Hurricane Outlook Update (July 26)

Friday, July 26, 2013

In late July 2013, Dr. Tingzhuang Yan, Dr. Len Pietrafesa, and Dr. Paul T. Gayes updated their hurricane outlook based on changing climate factors (a common process for all hurricane outlooks). What makes this forecast unique is that in addition to predicting the number of storms in any given season the outlook also includes the probability of hurricanes making landfall along the US Atlantic and Gulf Coasts.

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 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 0.96 storms making landfall) so the researchers have chosen to display the data as the most likely to least likely number of hurricane landfalls.

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. Sixty years of data, while not ideal, is the best the researchers have to work with. 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.

Table 1: 2013 Updated North Atlantic Basin Seasonal Hurricane Forecast in July
Category April Forecast June Forcast July Forcast Climatology
ACE 122[119~124] 138 [133 ~ 142] 137 [135~140] 103
TS 14 [13~15] 15   [13~17] 16 [14 ~ 18] 11.0
NH 7 [6~8] 8     [6~9] 8 [6 ~ 9] 6.2
MH 3 [3~4] 3     [3~5] 3 [3 ~ 4] 2.7
ECLF [1, 0, 2] [1, 2, 0] [1, 2, 0] 0.65
GMLF [1, 0, 2] [2, 1, 0] [1, 2, 0] 0.95