While October is just into its second day it’s worth noting that September, normally the tropics most active month, was one of the quietest on the Atlantic side of things in 14 years. You need to go back to September of 1997, to find a September with fewer storms, at only one.
Looking at the overall year, not since 1986, have we see so few named storms at this point in the season. So far in 2014, there have been only 5 named storms, the quietest the Atlantic basin has been since the mid-80s when there were also five named storms by early October.
Looking at the number of named storms is only one measure of how active the tropics are during the year. Accumulated Cyclone Energy or ACE is calculated by the National Weather Service every six hours and uses an approximation of the wind energy used by a tropical system over its lifetime. This index is running much lower than average across the Atlantic this season.
The chart below shows the current ACE values and how they compare to average. Notice while the Atlantic has experienced a significantly quieter than average season, some areas of the pacific have seen nearly one and a half times higher ACE value. Globally, the ACE values are also under average.
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Back To The Seventies
There are many different factors at play contributing to a quiet Atlantic season and a more active Pacific one. This pattern is somewhat reminiscent of the 1970s. At that time the Pacific Decadal Oscillation was in its colder mode. This is one variable that tends to push the Atlantic Hurricane season into a less active mode. Remember, less than average can still be devastating if you get one big storm.
The 1970s was also a colder and snowier period for much of New England. This is part of the reason why forecasters are leaning towards a snowy and cold winter ahead. There are many cyclical patterns in meteorology oscillating up and down, back and forth over weeks, months, years and decades. The coming 4 months finds the eastern two-thirds of the United States on the colder side of many of these equations. For us here in New England whether the core of the cold and snow is here or further west is still of course unsure.
We can also look at the instability of the atmosphere this year as compared to what would be typical to see other reasons why there have been so few storms. The two images below show instability as compared to average for the Atlantic and parts of the Pacific Ocean.
Notice how much more unstable the Pacific has been as compared to the Atlantic. This is another piece of the puzzle as to why it’s been quite off our coastline.
There are a lot of variables to review and I’m not going to throw them all out. There is another graph that I find interesting. Look at how the sea surface temperature graph shows cooler than average water in the tropical Atlantic. Warmer water contains more potential energy and thus the opposite is true.
Over the next week, there is still the opportunity for tropical storm formation. While the peaks of the hurricane season occurred during the second week of September, there is still time for development before the season comes to a close.
During the first and second week of October, you can see where storms typically will develop if they are going to on the following map. Tropical development tends to be suppressed a bit further south as the waters begin to cool.
The Pacific continues its active ways as tropical storm Simon moves north east off Baja. The current projections take it away from land in the coming days.