65th IHC Booklet/Program (pdf - 4.9MB) - Office of the Federal ...

A New Secondary Eyewall Formation Index; Transition to Operations and Quantification
of Associated Hurricane Intensity and Structure Changes
A Joint Hurricane Testbed Project (Year 2)
Jim Kossin 1,2 , Matt Sitkowski 2,3 , and Chris Rozoff 2
(james.kossin@noaa.gov)
1 NOAA/NCDC, Asheville, NC; 2 Cooperative Institute for Meteorological Satellite Studies
(CIMSS), University of Wisconsin; 3 Department of Atmospheric and Oceanic Sciences,
University of Wisconsin
Eyewall replacement cycles in hurricanes are generally associated with rapid and dramatic
changes in wind structure and intensity. While the intensity fluctuations are usually transient and
of particular concern when storms are near land, the broadening of the wind-field tends to be a
long-lived change that has substantial impacts on shipping and marine interests because of the
associated increases in wave height, storm surge, and radius of 50 kt wind (R50). In fact, eyewall
replacement cycles represent a highly efficient (and easily identifiable) pathway to storm growth.
Despite the implications and known impacts of eyewall replacement cycles, objective tools to
forecast these events were not available prior to the 2010 hurricane season. Consequently,
forecasters have relied on subjective methods for estimating the onset of these events and
adjusting intensity forecasts accordingly.
In Year-1 of this Joint Hurricane Testbed project we transitioned a new objective model into
operations at the National Hurricane Center, and the model was run in a real-time experimental
mode during the 2010 season. The model provides probability of onset of an eyewall
replacement cycle out to 48 hours based on observed and forecast environmental features and
observed storm features (as measured with GOES infrared imagers). In the first part of this
presentation, we will verify the model performance and skill for the 2010 season.
In the ongoing Year-2 of this project, we are constructing and documenting the first general
climatology of intensity and structure changes associated with eyewall replacement cycles. This
climatology is based on low-level aircraft reconnaissance data and is being utilized to construct
additional objective forecast tools. These tools will provide prognostic information about the
most likely intensity evolution based on measured environmental and storm features with the
primary goal of reducing intensity forecast error. Recent results of this part of the project will be
introduced in the second part of this presentation.
Session 12 – Page 5