Author Archives: Tom Sabbatelli

About Tom Sabbatelli

Senior Product Manager, Model Product Management
Tom is a Senior Product Manager in the Model Product Management team, focusing on the North Atlantic Hurricane Model suite of products. He joined RMS in 2009 and spent several years in the Client Support Services organization, primarily providing specialist peril model support. Tom joined RMS upon completion of his B.S. and M.S. degrees in meteorology from The Pennsylvania State University, where he studied the statistical influence of climate state variables on tropical cyclone frequency. He is a member of the American Meteorological Society (AMS).

Are We Any Closer to Determining What’s Going on in the Atlantic?

It’s not often that you see an Atlantic hurricane making headlines in January. Subtropical Storm Alex was named by the National Hurricane Center on January 13, 2016 and strengthened into a hurricane one day later. Although Alex ultimately exhibited a short lifespan and caused minimal damage, the storm has the scientific and risk management communities talking about what it might mean for the 2016 hurricane season and the near-term state of the basin.

In October, we discussed the below-average rate of landfalling hurricanes in recent Atlantic seasons, the influence of the Atlantic Multidecadal Oscillation (AMO) on basin activity phase shifts, and how shifts are reflected within the RMS Medium Term Rates (MTR) methodology.

In response to recent quiet seasons, scientists hypothesized about a possible shift in Atlantic hurricane frequency, one that would end the observed active Atlantic hurricane regime that began around the mid-1990s. Central to these discussions was commentary published in the October 2015 edition of Nature Geosciences, suggesting that AMO is entering a negative phase detrimental to Atlantic cyclogenesis.

However, recent peer-reviewed research highlights how sensitive the historical record is to the precise definitions used for hurricane activity. An article soon to be published in the Bulletin of the American Meteorological Society argues that the definition of the recent “hurricane drought,” based on the number of U.S. major landfalling hurricanes, may be arbitrary. This research finds that small adjustments to intensity thresholds used to define the drought, as measured by maximum winds or minimum central pressure, would shorten the drought or eliminate it completely.

In its most recent annual review of the Atlantic basin, RMS recognized that the anticipated atmospheric conditions for the upcoming season present a unique challenge. The latest forecasts suggest that the influence of the El Niño-Southern Oscillation (ENSO), another key indicator of hurricane frequency, may oppose the influence of a negative AMO.

ENSO represents fluctuating ocean temperatures in the equatorial Pacific that influence global weather patterns. El Niño, or a warm phase of ENSO, is associated with increased Atlantic wind shear that historically inhibits tropical cyclone development in the basin. La Niña, or a cool phase of ENSO, is associated with decreased Atlantic wind shear that historically supports tropical cyclone development.

Illustrations of the three main phases of the El Niño-Southern Oscillation. Source: Reef Resilience

ENSO has played an important role in influencing tropical cyclone activity in recent Atlantic hurricane seasons, particularly in 2015. Last season, the basin experienced one of the strongest El Niño phases on record, which contributed to below-average activity and well-below normal Accumulated Cyclone Energy (ACE), an index quantifying total seasonal duration and intensity. .

Looking ahead, the latest ENSO forecasts predict a shift out of the current El Niño phase over the next few months towards a more neutral or even a La Niña phase. The extent to which these conditions impact hurricane activity for 2016 is still to be determined; however, these conditions historically support above average activity.

Mid-February 2016 observations and model forecasts of ENSO, based on the NINO3.4 index, through December 2016. Positive values correspond with El Niño, while negative values correspond with La Niña. Sharp shifts from El Niño to La Niña are not unprecedented: La Niña conditions quickly followed the very strong El Niño of 1997-98. Source: International Research Institute for Climate and Society

The concurrence of potential changes in both the AMO and ENSO represent a unique period for 2016:

  • A negative AMO phase may act to suppress Atlantic hurricane activity in 2016.
  • A neutral or La Niña ENSO phase may act to enhance Atlantic hurricane activity in 2016.

These signals also have a range of potential implications on the RMS MTR forecast. Thus, RMS will spend the upcoming months closely engaging both the scientific community and market regarding this unique state of the basin and its potential forward-looking implications on hurricane activity. Modelers will evaluate the influence and sensitivities of new data, new methods, and new science on the MTR forecast. During this time, RMS will communicate results and insights to the broader market across a variety of mediums, including at Exceedance in May.

This post was co-authored by Jeff Waters and Tom Sabbatelli. 

Jeff Waters

Meteorologist and Manager, Model Product Strategy, RMS
Jeff Waters is a meteorologist who specializes in tropical meteorology, climatology, and general atmospheric science. At RMS, Jeff is responsible for guiding the insurance market’s understanding and usage of RMS models including the North American hurricane, severe convective storm, earthquake, winter storm, and terrorism models. In his role he assists the development of RMS model release communications and strategies, and regularly interacts with rating agencies and regulators around RMS model releases, updates, and general model best practices. Jeff is a member of the American Meteorological Society, the International Society of Catastrophe Managers, and the U.S. Reinsurance Under 40s Group, and has co-authored articles for the Journal of Climate. Jeff holds a BS in geography and meteorology from Ohio University and an MS in meteorology from Penn State University. His academic achievements have been recognized by the National Oceanic and Atmospheric Administration (NOAA) and the American Meteorological Society.