J. P. Kossin, 62 nd IHC, Charleston, SC An Objective Tool for Identifying Hurricane Secondary Eyewall Formation Jim Kossin and Matt Sitkowski Cooperative Institute for Meteorological Satellite Studies University of Wisconsin Madison, WI 62 nd Interdepartmental Hurricane Conference Charleston, SC, March 2008

J. P. Kossin, 62 nd IHC, Charleston, SC This work is supported by the National Oceanic and Atmospheric Administration under the GOES-R Risk Reduction program and the Office of Naval Research under Grant No. N

J. P. Kossin, 62 nd IHC, Charleston, SC Goal: Create a tool that uses readily available data to estimate the probability of secondary eyewall formation events in tropical cyclones Motivation: These events are generally associated with marked changes in the intensity and structure of the inner core:  rapid intensity deviations  significant broadening of the surface wind field  changes in storm surge, sea-state, radius of 50 kt wind Despite the importance of secondary eyewall formation in tropical cyclone forecasting, there is presently no objective guidance to diagnose or forecast these events.

J. P. Kossin, 62 nd IHC, Charleston, SC Data and Method: Our first step was to utilize the SHIPS developmental data.  ambient environmental features  geostationary satellite-derived features The features were then separated into 2 classes (using microwave, radar, recon reports, anything available): Classes were limited to Category 1 hurricanes or greater, with centers over water. 10 years (1997–2006). 1) a secondary eyewall formed at some time in the following 12 h 2) a secondary eyewall did not form at any time in the following 12 h

J. P. Kossin, 62 nd IHC, Charleston, SC The algorithm is based on the Bayes probabilistic model  P (C yes | F) estimates the probability of imminent secondary eyewall formation, given the set F of observed features.  P (C yes ) is the climatological probability (~10% in the North Atlantic). Based on class separation

J. P. Kossin, 62 nd IHC, Charleston, SC “Leave-one-season-out” cross validated algorithm performance 970 (984)52 (45) 20 (25)22 (15)12 (7) skill Inclusion of IR increases the confidence of the model

J. P. Kossin, 62 nd IHC, Charleston, SC Cross validation hindcast example (hits, misses, false alarms)

J. P. Kossin, 62 nd IHC, Charleston, SC Ivan, 13 Sep 2004, 06Z ~12 h later  Misses and false alarms? 13 Sep 06Z (too early)

J. P. Kossin, 62 nd IHC, Charleston, SC The algorithm has been alerting us to secondary eyewall formation events that we had previously missed

J. P. Kossin, 62 nd IHC, Charleston, SC Mitch, 27 Oct 1998, 00Z ~12 h later  False alarm? 27 Oct 1998, 00Z URNT12 KNHC DETAILED VORTEX DATA MESSAGE A. 26/0508Z B. 16 DEG 20 MIN N 81 DEG 53 MIN W C. 700 MB 2391 M D. NA E. NA F. 064 DEG 124 KT G. 342 DEG 9 NM H. 922 MB I. 14 C/ 3047 M J. 19 C/ 3024 M K. 15 C/ NA L. CLOSED WALL M. CO8-15 N. 16 DEG 20 MIN N 81 DEG 53 MIN W 26/0508Z O /7 P..25/2 NM Q. AF A MITCH OB 09 KNHC DETAILED MAX FL WIND 124 KT NW QUAD 0500Z. GOOD RADAR PRESENTATION. DOUBLE EYEWALL, WIND CENTER 3 NM DIA.;

J. P. Kossin, 62 nd IHC, Charleston, SC A miss and a false alarm

J. P. Kossin, 62 nd IHC, Charleston, SC False Alarm

J. P. Kossin, 62 nd IHC, Charleston, SC Hurricane Isabel (2003) 12 Sep 00Z  hit 17 Sep 00Z  miss

J. P. Kossin, 62 nd IHC, Charleston, SC Hurricane Rita (2005) 22 Sep 00Z  hit 23 Sep 06Z  miss

J. P. Kossin, 62 nd IHC, Charleston, SC Work in progress:  Extension beyond SHIPS features  Application to EPAC & WPAC tropical cyclones  Apply results to numerical simulations of secondary eyewall formation to better understand the physical mechanisms at work We hope to piggyback a beta-version onto SHIPS as soon as possible

J. P. Kossin, 62 nd IHC, Charleston, SC End

J. P. Kossin, 62 nd IHC, Charleston, SC