Rex Ross Web Site Special Weather Feature

"Looking Ahead to the 2013 Tropical Season"
May 10, 2013


2013 Hurricane Activity Outlook

Hurricane season officially gets underway on June 1.

The consensus outlook for the 2013 hurricane season activity varies a bit among several reputable forecasters, but the general level of activity being forecast is about

16-18       Named Storms
9              Hurricanes
4-5           Major Hurricanes (category 3, 4 or 5)

For the entire U.S. coastline, some predictions indicate about a 72% chance of a major hurricane making U.S. landfall in 2013.

Specifically, for the East Coast, the chance of a major hurricane strike is expected to be about 48%, while the chance of a major hurricane landfall along the Gulf Coast from the Florida Panhandle to Brownsville, Texas, is about 47%.

(A note here: the chances of landfall for a major hurricane is an interesting number, but as most of us recall from Ike, landfall of any hurricane can be a catastrophe whether or not the hurricane is classified as a Major Hurricane)

This outlook for the 2013 Atlantic Basin tropical storm season appears to point to a relatively higher than average activity. 

The long term averages from 1950-2012 are:

12             Named Storms
7               Hurricanes
3               Major Hurricanes

The averages for the more recent period of 1995-2012 are a bit higher at:

15             Named Storms
8               Hurricanes
4               Major Hurricanes

Three straight Atlantic hurricane seasons (2010-2012) have had 19 storms, and only seven Atlantic seasons have had more hurricanes than last season's 10 hurricanes. 

Among the four 2012  U.S. landfalls were the most intense tropical cyclone to make a U.S. landfall prior to June 1 (Tropical Storm Beryl), a soaking Tropical Storm Debby, a painfully slow Hurricane Isaac, and one of the most destructive storms in U.S. history, Sandy. (Sandy became a "post-tropical" system shortly before landfall.)

New Focus on How to Categorize Hurricanes

Typcially, hurricanes have been identified as Category 1, 2, 3, 4 or 5 based on their maximum sustained windspeeds.

Recent events such as Hurricane Ike in 2008 and Sandy in 2012 show the need for some assessment of storm surge as well as wind speed. In many cases, the effects of the storm surge are more devastating than the wind damage.

The National Hurricane Center is searching for ways to convey separately the storm surge threat, as opposed to only  the generic hurricane/wind warnings. They have set a 2015 date by which they hope to unveil a distinct Storm Surge Watch or Warning mode.

This means in effect, it will be possible to have both a Tropical Storm Warning, for example, and a Storm Surge Warning issued separately for the same storm. As was pointed out with Tropical Storm Debby in Florida last year and Ike in 2008, a storm doesn’t have to be major hurricane or even a hurricane in order to create a damaging storm surge. The basic issue is that some storms may pack very strong winds, but only a limited storm surge, while others may have relatively modest winds, but dangerous storm surges.

Looking at Past Forecasts Vs Actual Storm Activity

Below is a table published by Stan Blazyk in his Galveston County Daily News Weather Blog on April 13, 2013 which shows the April forecasts over the past five years with the actual number of storms for each year.

Named Storms
Major Hurricanes (cat 3, 4 or 5)
    Forecast Actual   Forecast Actual   Forecast Actual
2012   10 19   4 10   2 2
2011   16 19   9 7   5 4
2010   15 19   8 12   4 5
2009   12 9   6 3   4 2
2008   15 16   8 8   4 5

As you can see the actual number of named storms were underestimated in 4 of the 5 years and overestimated in 1 (2009).

The number of hurricanes was overestimated in 2 years, underestimated in 2 and on the mark in 1 (2008).

The number of major hurricanes, likewise, was underestimated in 2 years, overestimated in 2 and on the mark in1 (2012).

Forecasts Are Only Partially of Interest

While forecasts for the upcoming season are interesting and may give an indication of the overall expected activity, the averges don’t matter much when a storm is threatening the area in which you live.  

So, as usual, all interests near or along the U.S. Atlantic or Gulf of Mexico coasts should be alert to developing tropical storm activity and should make early preparations if forecasts indicate that any storm may head in your direction.