Above Normal Activity Forecast
June 1st officially begins this year’s tropical weather season so it is time to take a look at the tropics. This year I am forecasting a much more active tropical season compared to last year, one in which only 9 named storms occurred; the lowest number of named storms since 1997. The official Storm Force 31 Tropical Forecast calls for 14 named tropical cyclones, with 9 of those becoming a hurricane. In addition, 4 of the 9 hurricanes are forecast to become “Major”. Lastly, 3 of the named systems are forecast to make U.S. landfall.
Several factors are pointing to an increase in tropical cyclone development for 2010 and were considered for this year’s forecast.
- Sea Surface Temperatures (SSTs) across the tropical Atlantic are significantly warmer than compared to 2009. In May 2009, SSTs across the tropical Atlantic were averaging about 0.5 degree Celcius below normal.
However, currently, SSTs across this same region are averaging about 1 degree Celcius above normal. 
- The rapidly weakening El Nino in the tropical Pacific will lead to weaker trade winds across the tropics of the Atlantic favoring the development of tropical cyclones. In 2009, we were heading into a modest to strong El Nino that continued through the winter. The El Nino increased the trade winds and wind shear across the traditional tropical cyclone development regions of the Atlantic. In turn, much less activity occurred.
As mentioned above, 2009 saw the fewest Atlantic tropical cyclones since 1997, another El Nino year. For the 2010 tropical season, we will see the El Nino weaken into neutral condtions and possibly by late in the season, a weak La Nina. Neutral and especially La Nina conditions are very favorable for Atlantic tropical cyclone development. In 1998, after the 1997 El Nino, we saw a similar situation take place and 14 named storms developed with 3 becoming “Major”
What do we mean when we say a hurricane is “Major” since to most of us all hurricanes are significant? Hurricanes are classified based on the maximum wind speed of the system. This classification is known as the Saffir-Simpson Scale.
When a hurricane reaches Category 3 or higher strength it is classified a “Major”
To arrive at this year’s forecast, several previous years with similar conditions were reviewed. These include 1958, 1969, 1995 and 1998. During the tropical season in all of these years we saw a weakening of an already established El Nino; however, less so in 1958 and 1969. In these tropical season’s, most of the storm development occurred across the central Atlantic. The storms then tracked to the north-northeast and mainly affected the eastern U.S. and major shipping routes. However, it should be noted that there were a few “Major” hurricanes developed and made landfall along the Gulf Coast. One occurred in 1969, Hurricane Camille and another in 1995, Hurricane Opal.
Dale Bader / Meteorologist, Storm Force 31
