Dr. Phil Klotzbach presented on The Madden-Julian Oscillation's Influence on Continental U.S. Hurricane Landfalls. The MJO as it is called for short, is the one climate factor that can explain most of the intra-seasonal variability in hurricane activity. The talk highlighted the different phases of MJO that are conducive for spawning/enhancing hurricanes in the Atlantic (and different phases in other basins). It can make or break a hurricane seasonal forecast because if the right phase hits at the right time (e.g., when climatological conditions are also favorable) there can be some very active weeks during the season. Interestingly, it was not a factor in 2017 for the Atlantic during September, but was in October, when an unfavorable phase essentially suspended what could have been an even more active season.

Jim Kossin has an uncanny knack for spotting something in the climatology or dynamics of hurricanes that we may have all noticed in passing and then coming up with some brand-new information or insight. He jettisoned his planned talk on ~one-year-old work on North Atlantic decadal variability in hurricane intensification (which we blogged about late last year) in favor of presenting new unpublished work entitled “A Global Slowdown of Tropical Cyclone Translation Speed.” In light of a growing body of evidence that global warming is slowing down large-scale circulation patterns, Jim dug into the historical tropical cyclone data and found support for a decline in tropical cyclone translation speeds. He pointed out that this could have profound implications for tropical cyclone–induced flooding if precipitation is dumped for longer periods of time over the same spatial locations (as played out during Harvey last year). This is an area of interest at AIR as we develop upcoming models for tropical cyclone–induced flood.

Dr. Greg Tripoli discussed the very active hurricane period over the Atlantic in 2017 from late August to late September from the perspective of features in the stratosphere that propagated westward from India and created very favorable conditions for ventilation over the Atlantic. These features were spawned during a very active Indian Monsoon last summer as La Niña was gaining strength. Importantly, it got some of us to thinking how La Niña may really influence hurricane activity over the Atlantic. It may be that La Niña enhances the India Monsoon (because all the warm water is concentrated in the western portion of the Pacific Basin and even farther west), which then generates upper atmosphere features that propagate westward across East Asia and Europe, resulting in enhanced outflow. The enhanced outflow is also manifested as reduced upper level shear, which has been the canonical explanation for why La Niña enhances hurricane activity in the Atlantic.

The Bill Gray Symposium was a series of talks spread across two conference sessions, the latter of which was very informal with someone in the audience buying a bunch of beers for anyone who wanted to partake (meteorologists ARE a fun bunch!). The talks by many were really to honor the late great Bill Gray, who made so many, many contributions to the field during his 50-plus years as a tropical meteorologist. Those who knew him and were in fact lucky enough to share floor space with him (our very own Michal!) recall him avidly debating with any visiting scientist giving a seminar on tropical cyclone activity and climate change. One of Bill’s daughters spoke last, and for those of us in the audience who did not know Bill personally, she made us feel as though we did. The program can be found online here and here.

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