The Forecast for 2012 Atlantic Hurricane Season

4 05 2012

Thus far for the year, there have been two forecasts for the North Atlantic Hurricane Season, and both have predicted below normal activity. However, when one looks at the actual forecasts, it could easily be argued that these forecasts are really predicting near normal conditions. Here are the numbers for both forecasts:

                                    Klotzbach and Gray       Saunders and Lea

                             (Colorado State University)     (Tropical Storm Risk)

Named Storms          10 (12)                                            13 (11)

Hurricanes                  4 (6)                                                  6 (6)

Major Hurricanes      2 (2)                                                  3 (3)

The numbers without brackets are the forecast values, and the numbers in brackets are the normal or average values for the season, depending on the base period. The bracketed numbers differ because of the different in base period. From their numbers, I would say near normal conditions are being predicted since this is a climatological Statistical forecast, and in climatology near normal is any value that falls within the middle tercile or 33.3% of the historical data. In this case, near normal would be the range 9 to 12 named storms, 5 to 7 hurricanes, 2 to 3 major hurricanes. Saunders and Lea’s forecast is actually forecasting above normal named storms.

Persons should not put too much confidence in these forecasts thought, as historically, the ability to produce an accurate forecast for the Atlantic Hurricane Season from April lead time is very low. In other words, the Meteorological Community has very little skill in producing an accurate forecast for the hurricane season from this early in the year; these April forecasts are often wrong. See the skills graph below:

Image

December and April’s forecasts show very little to negative skill

The figure above displays the recent 10-year (2002-2011) skill for the forecast number of North Atlantic Hurricanes issued by different organisations.  The forecast precision is assessed using the Mean Square Skill Score (MSSS), which is the percentage improvement in mean square error over a climatological forecast. Positive skill indicates that the model performs better than a climatology forecast (what obtains on average), whilst a negative skill indicates that it performs worse than climatology. Two different climatologies are used: a fixed 50-year (1950-1999) climatology and a running prior 10-year climate norm. The figure compares the forecast skill of the TSR (Tropical Storm Risk), NOAA (National Oceanic and Atmospheric Administration) and CSU (Colorado State University) seasonal hurricane outlooks 2002-2011 as a function of lead time. NOAA does not release seasonal outlooks before late May. It is clear there is little skill in forecasting the upcoming number of Atlantic hurricanes from the prior December and April. Skill climbs slowly as the hurricane season approaches. Moderate skill levels are reached by early June and good skill levels are achieved from early August.

Regardless to the forecast number of named storms and hurricanes, we should always prepare the same for every season as it only takes one hurricane to make it an active season for you and ruin your year. We have recent examples of near normal seasons being quite deadly and costly. Recall in 1992, there were 7 named storms, 4 hurricanes and 1 major hurricane – Andrew. Andrew hit the United States and at the time was the costliest hurricane causing US$26 billion dollars and killing 65 persons. Closer to home, in 1989, there were 11 named storms, 7 hurricanes and 2 major hurricanes, one of which was Hurricane Hugo. Many persons remember Hurricane Hugo; this system absolutely flattened Montserrat; it left in its wake 11 deaths, 3000 homeless  and damage of about EC$1 billion. Hugo also caused significant damage to Antigua costing about EC$200 million.

References

Colorado State University, Fort Collins, Extended Range Forecast of Atlantic Seasonal Hurricane Activity and Landfall Strike Probability for 2012  [online]. Available from: <http://hurricane.atmos.colostate.edu/forecasts/2012/apr2012/apr2012.pdf> [Accessed 26 Apr 2012].

Texas A&M University, Corpus Christi, Montserrat: Emergency Planning, Response and Recovery Related to Hurricane Hugo [online]. Available from: <http://msld.tamu.edu/hrrc/Publications/researchreports/Downloads/91-02R%2BBerke%2Band%2BWenger%2BMontserrat%2B-%2BEmergency%2BPlanning%2BResponse%2Band%2BRecovery%2BRelated%2Bto%2BHurricane%2BHugo.pdf> [Accessed 24 April 2012].

Tropical Storms Risk, London, Silver Spring, April Forecast Update for Atlantic Hurricane Activity in 2012 [online]. <http://www.tropicalstormrisk.com/docs/TSRATLForecastApr2012.pdf>[Accessed 26 Apr 2012].

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2 responses

28 04 2013
Merrill

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2 05 2013
Jame

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