The folly of long-term hurricane predictions and the hurricane droughtThis ISS photo captured Hurric

The folly of long-term hurricane predictions and the hurricane droughtThis ISS photo captured Hurricane Danny, which intensified to a category 3 storm in the Atlantic Ocean last week but has dissipated and The United States is in a record-breaking period for hurricanes right now, but you may not have noticed. The record right now being extended every day is “longest gap between major hurricane strikes in the United States”.The 2005 Hurricane season was a super-season, breaking records for most named storms and for monetary damage, but since a Category 3 storm named Hurricane Wilma hit Florida late in 2005 there has not been a single major hurricane strike on the U.S. (major hurricanes defined as category 3 or stronger).There are some basic patterns that contribute to hurricane formation patterns. At the top of the list is the El Niño oscillation pattern in the Pacific Ocean; warm waters off the South American coast leads to strong winds over the Atlantic that blow circulating storms apart. This pattern lets us confidently make some predictions about low hurricane intensity years; 2015 has a strong El Niño present in the Pacific so it’s fair to expect a year with few Atlantic hurricanes. In fact, Hurricane Danny met just this fate: weakened and blown apart. On the other hand, during El Niño years, the warm water in the Pacific can feed major storms in that basin as we’re seeing this year.La Niña years, the opposite of El Niño years, have abnormally cold water in the Eastern Pacific. These years tend to be associated with weak Atlantic shearing winds and can be prime years for hurricane formation; 2005 was a weak La Niña year and it was the strongest Hurricane season on record. On the other hand, there have been several La Niña years since 2005 and no major hurricane strikes on the U.S. What’s the deal with that?The most recent weak La Niña years were 2013 and 2014, however, especially in 2014, systems that could have developed into hurricanes off of Africa were disrupted by abnormally large plumes of dust coming from the Sahara. 2010 was a La Niña year with an active hurricane season, but none of the major storms hit the U.S. – literally just a roll of the dice.That example shows to me how hard it is to predict total numbers of hurricanes or their impacts even a few months in advance. Hurricane Katrina, which provoked this series, formed when two distinct low pressure systems from Africa combined off the Cuban coast. In other words, Katrina was a very unlikely situation and an illustration of the complexity involved in hurricane generation.Hurricanes need stable conditions, lack of wind shear, warm water, and nothing in the atmosphere that disrupts them; getting the mixture just right for a strong hurricane is always going to be a roll of the dice.I write this post to illustrate some of the follies of hurricane prediction. Every year, NOAA will release an official forecast that is based mostly on historical patterns and the presence or absence of La Niña/El Niño, but even NOAA’s best estimates can be disrupted by something as unpredictable as Saharan dust storms. Other estimates based on “private prediction methods” will get publicity every year, but they’re even less accurate than NOAA’s predictions.After Katrina, there was a worry that the world was entering an era of stronger hurricanes due to warming ocean surface waters. Although the past 10 years hasn’t produced major storm impacts on the U.S., this prediction still is generally possible; warmer waters means more energy that can feed storm growth, but until we understand and can simulate hurricane formation in extreme detail it’s going to be difficult to understand how all the variables work together. Warmer waters can lead to more hurricanes but they can also lead to stronger weather systems and shearing winds that tear apart hurricanes. What the long-term trend will be is a question scientists are still working on. There’s a new tropical storm, Erika, in the Atlantic right now that has plenty of warm water to feed on and could threaten the U.S. coast, but even that would be about a week away and subject to the vagaries of the winds.Furthermore, let’s also highlight one last storm in this “major hurricane drought”; the second most destructive (monetary) hurricane in U.S. history struck in 2012, a year with a weak positive El Niño signal. That storm was hurricane Sandy. Although The U.S. has been in a drought of strong hurricanes, it hasn’t been in a drought for hurricane damage.Finally…if I’m going to write a whole piece on hurricane development and long-term predictions I might as well make one, right? Typically after strong El Niño years, the planet tends to slip into a La Niña phase with extra heat floating around the tropics from the El Niño; prime conditions for hurricane formation.If you wanted a long-term prediction, it’s entirely possible that 2016 could be a good year for hurricane formation and could produce storms that break the drought of major impacts on the U.S., but it also might not. They might just go the wrong way like 2010, they might be broken up by dust like in 2014, or we might see the pendulum swing back like we saw in 2005. Beyond that general description of what the planet tends to do, we just have to sit and watch and prepare for the future.-JBBImage credit: Scott Kelly/NASAhttps://twitter.com/StationCDRKelly/status/634386097301118976/photo/1References:http://www.livescience.com/50704-hurricane-drought.htmlhttp://slate.me/1qLakcchttp://www.hurricanescience.org/science/science/activity/http://1.usa.gov/1Efr1qThttp://ggweather.com/enso/oni.htmhttp://bit.ly/1NPDYaD -- source link

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