Ryan N. Maue Research Meteorologist WeatherBELL Analytics October 30, 2015 Global Tropical Cyclones

Tropical Cyclone Climatology What is normal for global tropical cyclone (TC) activity? (80-90 TS per annum) How to quantify TC activity with our current best- track quality? Uncertainty. For climate (change), what is important? Ratios, counts, integrated metrics, SST impact, etc. What are the relevant metrics ? –Landfalls –Category 5s

Low confidence that any observed long-term (i.e., 40 years or more) increases in tropical cyclone activity are robust, after accounting for past changes in observing capabilities. The uncertainties in the historical tropical cyclone records, the incomplete understanding of the physical mechanisms linking tropical cyclone metrics to climate change, and the degree of tropical cyclone variability provide only low confidence for the attribution of any detectable changes in tropical cyclone activity to anthropogenic influences. There is low confidence in projections of changes in tropical cyclone genesis, location, tracks, duration, or areas of impact. Based on the level of consistency among models, and physical reasoning, it is likely that tropical cyclone related rainfall rates will increase with greenhouse warming. It is likely that the global frequency of tropical cyclones will either decrease or remain essentially unchanged. An increase in mean tropical cyclone maximum wind speed is likely, although increases may not occur in all tropical regions. IPCC, 2012: Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation. A Special Report of Working Groups I and II of the Intergovernmental Panel on Climate Change (Field et al. 2012)

Global Tropical Cyclone ACE 24-month Running Sums | January October 2015 Global NH [knots 2 ]

Daily Caller

Global Tropical Cyclone Frequency 12-month Running Sums TC (34 knots +) & HURR (64 knots +) μ = 87 | 47

Global Tropical Cyclone Frequency 12-month Running Sums HURR (64 knots +) & MAJOR HURR (96 knots +)

Historical global tropical cyclone landfalls:

Weinkle et al. (in press, J Climate) Relevant metric: global major hurricane landfall$ …this subset of storms is a function of “climate”