2011 Atlantic hurricane season forecast
01 June 2011
Today marks the first official day of the 2011 Atlantic hurricane season, which is forecast to
be a very busy one according to many popular forecasting agents such as Colorado State University
(CSU), Tropical Storm Risk (TSR), and the National Hurricane Center (NHC). I am predicting an
above-average hurricane season, with an 85% chance of this season being more active than normal,
a 10% chance of this season being normal, and only a 5% chance of this season having less activity
than the climatological mean of 1995-2010. I am predicting that the Atlantic basin will experience
15-18 named storms, 8-12 hurricanes, and 4-7 major hurricanes, 1-3 of these becoming the major
Category 5 hurricanes.
There are several factors that go into this such as Sea Surface temperatures across the
Atlantic basin as a whole. They are running 1-2 °C above average in most areas, which is more than
enough to support tropical development at any given time. Another important factor that ties in
with temperatures in the Atlantic is Ocean Heat Content (OHC). This is the amount of energy stored
in the water. This can allow for rapid and explosive intensification. Values in the Caribbean at this
time are not quite warm enough to support rapid development, but it is getting close. As we
approach the peak of the season, we can expect to see these values soar.
More important factors include wind shear, dry air, and ENSO. Because we are so early in
the season, the Subtropical Jet Stream is created high wind shear over a lot of the Atlantic right now,
with the exception of the Gulf of Mexico. However, the Subtropical Jet Stream is slowly retreating
north, and wind shear will begin to lower, especially in the Caribbean and off the East Coast of the
United States. Dry Air is not really a problem across the Atlantic basin right now, but there is quite
a bit in the Gulf of Mexico. This should reduce over the next couple of weeks as the basin becomes
As for ENSO, or the El Niño-Southern Oscillation, there are three categories: El Niño,
Neutral, and La Niña. In an El Niño season, the Pacific is more likely to see an above average season
because high wind shear and cool Sea Surface temperatures limit the number of tropical cyclones in
the Atlantic basin. An example of this would be the 2009 season, which was well below average. In
a La Niña season, the Atlantic is more likely to see the above average season, because there is low
wind shear and warm Sea Surface temperatures. An example of this would be last year (2010),
when we had 19 named storms, 12 hurricanes, and 5 major hurricanes.
Unlike last year, I am forecasting several impacts to the continental USA. This is because the
Bermuda High is expected to be set-up differently than it was last hurricane season, a set-up that
favors systems to hit the USA. Some of my analogue years are: 1951, 1989, 1996, and 2008. All
these years featured several tropical cyclone landfalls on the USA, and the pattern matched what it
is expected to look like this year. The two key areas of concern I am particularly worried about is
the coastline of Texas, and the coasts of both North Carolina and South Carolina. In most of these
seasons, a tropical cyclone made landfall on one or both of these areas. Everyone living along the
coast of the USA needs to be prepared, but these two areas in general need to really pay attention to
what is occurring in the tropics and be prepared if a system develops and heads your way.
This concludes my 2011 Atlantic hurricane season forecast. I’d appreciate comments
and/or concerns about this forecast!