By Dale C. S. Destin |
Major Hurricane Luis, Sept 3, 1995
It is “June too soon”, the start of the Atlantic hurricane season. The predictions this year are unanimously in favour of a normal to below normal season. This is considered good news for the people of the Caribbean, Central America and North America. But, don’t be lulled into a false sense of safety; preparations for the season are still very important, regardless to the forecast.
CSU; FSU; TSR; NOAA; WSI; AccuWeather; UK Met; INSMET – Institute of Meteorology, Cuba; EUROSIP; ECMWF; NCSU
The consensus forecast calls for 10 named storms (NS) of which five are expected to become hurricanes (H) and two major hurricanes (MH) i.e. winds of 111 mph and greater. These are very normal numbers given the average season, based on the period 1950-2010, usually produces 11 named storms, 6 hurricane and 3 major hurricanes.
A better measure of the activity of a season is the accumulated cyclone energy (ACE) index. In addition to taking into account the number of named storms, the ACE index also takes into account the duration and strength of each storm. For the 2014 Atlantic hurricane season, the consensus is for an ACE of around 72, the fifth lowest since 1995. This is about 30% below the average of 103.5 (1950-2010).
There are two main reasons why the various models are predicting a normal to possibly below normal season. Firstly, an El Nino is deemed likely. El Nino is the name given to the episode of unusually warm sea surface temperatures (SSTs) in the tropical Pacific. Secondly, the tropical North Atlantic SSTs have been cooler than normal. This configuration of high and low SSTs over the tropical Pacific and Atlantic Oceans respectively is just about the perfect recipe for a quiet hurricane season.
However, it is not clear when this contrast of SSTs will become optimal. If El Nino occurs late in the year, it may not hamper the hurricane season as expected. Hence, the number of storms could be more than indicated by the consensus forecast above. On the other hand, the earlier El Nino develops, the lower the number of storms is likely to be.
There is also the issue of the eventual strength of El Nino. A strong El Nino would have a more suppressing impact on the hurricane season than a weak El Nino or no El Nino, which is probable but highly unlikely.
Additionally, there is also the unknowable of whether it will be a central Pacific or eastern Pacific El Nino. Both suppress hurricane activity but by contrast, the former tends to cause an above normal number of cyclones impacting the western Caribbean, Central America and the United States. Thus, places like Jamaica, Cayman Islands and Cuba have an elevated chance of being struck by a storm or hurricane.
Further, coupled with the inherent difficulties in predicting El Nino during this time of the year (the spring barrier), preseason hurricane forecasting skill is also still quite low. Most forecasting groups have less than 20% skill in forecasting the Atlantic hurricane season during June or before.
What It Does And Does Not Mean?
How is the forecast to be understood? It means that tropical cyclone activity in the Atlantic basin will be normal or possibly below normal with just a slight chance of the season being above normal. It means that many areas will be spared the impact of a storm. However, it does not mean that no place will be impacted. It does not mean that every place or area will be spared of above normal tropical cyclone activity. The forecast speaks to the expected cumulative conditions for the Atlantic basin (Atlantic Ocean, Caribbean Sea and the Gulf of Mexico). It does not say anything about what can be expected for a particular place, country or region.
It is quite possible for there to be a normal or below normal season and your country or region experiences above normal activity. This can happen since the forecast does not say anything about a specific point or country, so while the Atlantic Basin may have a quiet hurricane season as a whole, your country or region may not necessarily escape a disaster. It only takes one hurricane to cause a disaster, ruin your year and cause significant socio-economic setbacks.
Tropical cyclone adaptation and preparation are the only ways to minimize the impacts of tropical cyclones. Do not take any hurricane season lightly. Prepare for every season as if it is going to be the worst you will ever face, because it could well be so, regardless to the forecast.
The designated storm names for this year’s Atlantic hurricane season – June 1 to November 30, are Arthur, Bertha, Cristobal, Dolly, Edouard, Fay, Gonzalo, Hanna, Isaiah, Josephine, Kyle, Laura, Marco, Nana, Omar, Paulette, Rene, Sally, Teddy, Vicky, Wilfred.
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