Many of you may not know who Arlene is. That's ok, she was overshadowed by some of her more famous sisters. She last showed up in June of 2005. She came to the Southern U.S. from Honduras and killed a person. She was the first of her kind that year, many others followed and did far worse things.
Of course I am talking about Tropical Storm Arlene. She made landfall about 6 years ago to the date. For a tropical storm, she was a large one. Just missing hurricane status. But she ushered in one of the most active and historic hurricane seasons on record! Her more famous sisters are known as Hurricane Katrina and Hurricane Rita. There were 26 named storms in 2005, so many that we ran out of names and had to use names from the Greek alphabet for the remaining storms.
2011 tropical season is underway, it began June 1st. So far, the Atlantic basin has been quiet. But forecasters have warned that it will not remain that way as the season progresses. The Climate Prediction Center says the Atlantic will see 12-18 named storms, 6-10 of which may reach hurricane status (sustained winds over 1 minuet that measure at least 74 m.p.h). Of the named storms, the CPD says that 3 to 6 of them may become major hurricanes (Cat. 3 or higher, winds at least 111 m.p.h.). This would equate to what is referred to as a "hyper-active" hurricane season. 2005 definitely qualifies as a hyper-active season, and we just endured one last year. 2010 was an active, yet rare year. 19 named storms in the Atlantic and NOT ONE of those storms made landfall in the U.S. This is very rare.
Your probably asking yourself, "How can they forecast an entire hurricane season when they can't even predict the weather 36 hours out?!". There are signs but before I talk about those that are scientific, I want to just brush over a little research I did.
The U.S. has had a wild Spring. A record amount of tornadoes and severe weather in general across much of the country has us praying for that Summer weather to give us a break. I decided to look at past Springs and the amount of severe weather and compare it to the following Hurricane Season.
Last year, we had 1,543 reported tornadoes. As I mentioned above, 2010 had 19 named storms but none made landfall. 2009 had 1,305 tornadoes and nine named storms (1 landfall). 1,685 tornadoes were reported in 2008 and we had 16 named tropical storms that Summer (3 landfalls). 1,102 tornadoes and 15 named storms (1 landfall) in 2007. 1,117 tornadoes and nine named storms for 2006. Our active hurricane season in 2005 (26 named, five landfalls!) only had 1,262 tornado reports. Finally, 1,820 tornadoes were reported in 2004 with 15 named storms (three landfalls). Breaking down the stats, it is somewhat difficult to draw correlations between active Springs and Summers. So far this year, there have been 1,482 preliminary tornado reports. Those haven't been all confirmed yet. But still a high number. What will that translate into for this Summer?
Let's talk about trends that DO correlate to an active tropical season. We will begin with sea water temperatures. Warm water is "fuel" to a hurricane so the warmer the water, the better a chance to get storms to fire up and strengthen. The Atlantic waters are impacted by what happens off of our coast here in the Pacific. Our cool Spring can be credited to the cool, La Nina conditions. The La Nina typically gives us cooler than normal ocean waters here in the Pacific. The main goal of the ocean is to balance itself out. If we have a cold Pacific, the oceans will make up for it by having a warm Atlantic. Warm waters in the Atlantic means a good amount of "fuel" for storms this Summer!
Warm surface waters mean provide the atmosphere with a lot of uplift. When the sun strikes the warm waters and warms the air around it, that air will begin to lift. And guess what lift means for storms? You got it! Rising motions in the atmosphere help aid hurricanes and all storms for that matter! Now we have warm waters in the Atlantic and that means plenty of uplift for our storms.
Here is a map of 2010 and the storm tracks of those 19 storms that Summer.
Note how many made their way into the Gulf of Mexico. As only one storm tracked into the Gulf, that could mean a lot of untapped energy will remain for this hurricane season. As a tropical storm or hurricane makes its way through the warm Gulf, it feeds off the warm waters. When that warm surface waters get used up, the ocean pulls up cooler water from below to replace that warm water. The more storms that track through the Gulf, the less fuel for the next storms to use. With only one storm moving through that area last year, that could mean plenty of leftover energy just waiting to be used this year!
So there are the "proven", scientific reasons as to why we could see a very active, fun but dangerous 2011 Atlantic Hurricane Season.