Texas Emergency Management ONLINE2013 Vol. 60 No. 6

EXPERTS PREDICTING BUSY 2013 ATLANTIC HURRICANE SEASON

The National Oceanic and Atmospheric Administration released the 2013 Atlantic hurricane forecast on May 23. Falling in line with Colorado Sate forecasters Phillip J. Klotzbach and William Gray that released their forecast on April 10, NOAA also predicts an above average season.

Officially NOAA is calling for 13-20 named storms, 7-11 hurricanes and 3-6 major hurricanes. Hurricanes are consider major if categorized as a Category 3 (111 mph or higher winds) or higher on the Saffir-Simpson Scale.

Koltzbach and Gray are calling for 18 named storms, 9 hurricanes and 4 major hurricanes.

Other noteworthy forecasts are from AccuWeather and Penn State. Both predict 16 named storms. AccuWeather predicts 8 hurricanes and 4 major hurricanes.

Forecasters are on the same page this year for three main reasons.

The West African monsoon climate pattern will stay intact. This particular pattern affects hurricane formation and promotes high activity. The long-term pattern began in 1995 and the era tends to last 25-40 years.

Sea surface temperatures are warmer than average in the tropical Atlantic and Caribbean Sea. The chart below shows current SSTs  ranging from  23.9° - 28.2° Celsius for much of the mid-south Atlantic, Caribbean and Gulf of Mexico. A key ingredient for tropical systems is a warm breeding ground of water.

SST Analysis
ENSO (El Niño/La Niña–Southern Oscillation) is expected to stay neutral for the 2013 season. This means that El Niño is not expected to develop. El Niño typically suppresses hurricane activity in the Atlantic because of the wind shear the pattern creates. Wind shear is the change in wind speed and/or direction over with height or a rapid change in winds over a short horizontal distance. Given that El Niño is not forecast to develop, it makes for a nice calm atmosphere which is more favorable for hurricane development.

Forecasters Koltzbach and Gray say there is a 72 percent probability for at least one major hurricane to make landfall along the entire U.S. coastline (average for last century is 52 percent). For the East Coast including the Florida peninsula there is a 48 percent probability (average for last century is 31 percent) and for the Gulf Coast from the Florida Panhandle west to Brownsville, there is a 47 percent probability (average for last century is 30 percent).

An interesting part of the forecast is the hurricane years Koltzbach and Gray choose to compare to the current atmospheric conditions we presently see. Among the five years named in the study, the year 1915 was included. In 1915, a Category 4 hurricane struck Galveston with winds of 135 mph and left 275 people dead. This was a mere 15 years after the deadly 1900 hurricane.

Tracking Chart

The bigger question left to answer is where a tropical system will make landfall. The last hurricane to make landfall in Texas was Hurricane Ike in 2008. The last major hurricane to make landfall in Florida was Hurricane Wilma in 2005. The 2005 hurricane season also brought Louisiana and Gulf Coast states east Hurricane Katrina and Texas took a blow from Hurricane Rita. It was also the season all 21 hurricane name on the list were used. Names were added using the Greek alphabet. It’s arguable that both states are long overdue for a direct landfall from a major hurricane.

The Bermuda High is the key player in directing a tropical system. Where the Bermuda High sets up will be the next thing to watch. The feature is has not developed yet. The Bermuda High (also known as Azores High) is a semi-permanent, subtropical area of high pressure in the North Atlantic Ocean off the East Coast of North America. The high shifts east, west, north and south. During hurricane season the center is located closer to Bermuda.

The feature is extremely important to tropical cyclone development and direction. The high supports drier and sinking air over the tropics which leads to sunny days. The sunny days provide direct rays of light for heating the water.  Again, tropical systems thrive in warmer water.

Where will the Bermuda high set up?

It’s too early to say. The southeast coast of Florida and the Gulf Coast states become more vulnerable when the high sets up further west than normal. When this happens, the high tends to direct tropical systems farther south and west before the make landfall. If the high sets up more to the east, other the Atlantic coast states are more subject to a tropical cyclone making landfall. There have been some hurricane seasons such as 2000-2002 when the high was weak and positioned farther east. In this location, the majority of possible hurricanes were deflected out to sea. Another scenario is the high stretching its western edges all the way to the east coast of the U.S. When this happens, the U.S. Coast becomes an open door. The high acts as a buffer and doesn’t allow a northward turn to happen until the cyclone impacts the U.S. Coast. Or, in this case the high can be so strong that it keeps a hurricane tracking as far south and west as Central America.

The next step is watching where the Bermuda High sets up and trying to forecast how strong the high will be.

You can keep track of the latest hurricane advisories, tracking and forecasts with the National Hurricane Center.

Hurricane season runs from June 1 – November 30.


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