wxman57 wrote:I've been participating in a group discussion (via email) between a number of top researchers regarding the lack of activity across all basins this year. What we've concluded is that dry air in the mid levels dominates the deep tropics in all basins. This dry air is likely a byproduct of subsidence, which also results in a warming of the air in the mid levels. This leads to a decrease in instability, making it harder for TCs to develop and/or intensify.
Now, the big question is what is the cause of the subsidence? Can we predict it? How can we go forth with future predictions if we cannot predict such a harsh environment?
It could be a combination of cooler than normal Pacific water as it is in negative Pacific Decadal Oscillation (PDO). I also suspect droughts could play a role as there are severe droughts in Brazil and Russia. I would also look at position of monsoon and Intertropical Convergence Zone (ITCZ). There has not been an El Nino since 2010. El Nino usually makes Pacific more active. I wonder if all the dry air may have played a role in 1977 being inactive worldwide.
I notice some of the most active Atlantic seasons on record occurred with both warm Atalntic Multidecadal Oscillation (AMO) and PDO like 1933, 1995, and 2005.
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