Expect a busy Atlantic hurricane season this year, with sixteen named storms, say Pennsylvania State University (PSU) hurricane scientists Michael Mann and Michael Kozar. Their annual Atlantic hurricane season forecast issued on May 16 calls for 12 – 20 named storms this season, which starts June 1 and runs until November 30. An average season has 10 – 11 named storms. Their prediction was made using statistics of how past hurricane seasons have behaved in response to sea surface temperatures (SSTs), the El Niño/La Niña oscillation, the North Atlantic Oscillation (NAO), and other factors. This year’s forecast is primarily based on three factors:

1) The current above-average sea surface temperatures in the Atlantic Main Development Region (MDR) for hurricanes, from Central America to the coast of Africa between 10°C and 20°C North latitude, will continue into the main part of hurricane season;
2) The fading La Niña event in the Eastern Pacific Ocean will be replaced by neutral El Niño/La Niña conditions;
3) The North Atlantic Oscillation (NAO) will be near average during hurricane season.

Figure 1. Hurricane Igor of 2010 as seen from the International Space Station.

The PSU team will also be making a new experimental forecast based not on the absolute MDR sea surface temperatures, but on difference between the MDR SST and ocean temperatures over the rest of the globe’s tropical oceans. Some research has suggested that Atlantic hurricane activity is greater when this relative difference in SSTs is high, not necessarily when the absolute MDR SST is high (in other words, if all the world’s tropical oceans have record high SSTs, we wouldn’t get an unusually active Atlantic hurricane season, even with record warm SSTs in the Atlantic.)

The PSU team has been making Atlantic hurricane season forecasts since 2007, and these predictions have done pretty well:

2007 prediction: 15 actual: 15
2009 prediction: 12.5 actual: 9
2010 prediction: 23 actual: 19

NOAA will be issuing their annual pre-season Atlantic hurricane season forecast at 11:30am on Thursday, and I’ll make a post on that Thursday afternoon. Tropical Storm Risk, Inc. (TSR) issues their pre-season forecast on May 24, and Colorado State University issues theirs on June 1.

My next post on the Mississippi flood will be on Friday.

Links:

PSU 2011 Atlantic hurricane season forecast issued on May 16.

Jeff Masters