by

Lance F. Bosart1, Jason M. Cordeira1, Thomas J. Galarneau, Jr.2, Benjamin J. Moore3, and Heather M. Archambault1

1Department of Atmospheric and Environmental Sciences University at Albany/SUNY, Albany, NY

2National Center for Atmospheric Research, Boulder, CO*

3Cooperative Institute for Research in Environmental Sciences University of Colorado, and NOAA Earth Systems Research Laboratory Physical Sciences Division, Boulder, CO

Abstract

An analysis of three predecessor rain events (PREs) that occurred ahead of North Atlantic tropical cyclone (TC) Ike and East Pacific TC Lowell during 10–15 September 2008 is presented. The three PREs produced all-time 24-h record rainfall at many locations, including Lubbock, Texas (189.5 mm), Wichita, Kansas (262 mm) and Chicago-O'Hare, Illinois (169 mm) on 11–13 September, respectively. PRE #1 developed over Texas on 10 September with moisture from a stalled frontal boundary, organized with moisture from the Bay of Campeche, and matured with moisture from TC Lowell. PRE #2 developed over the Texas Panhandle on 11 September, and organized and matured over Kansas and Missouri with moisture from the Bay of Campeche and TC Lowell. PRE #3 developed over Texas on 11 September, merged with and absorbed PRE #2 over Kansas and Missouri, and matured as it ingested moisture from TC Ike. All three PREs matured in the equatorward entrance region of an intensifying subtropical jet stream (STJ). Heavy rainfall with the three PREs occurred along a plume of moist air characterized by high precipitable water values that extended poleward over the Central U.S. near the juxtaposition of the nose of a low-level jet, a region of low-level forcing for ascent along a warm front, and the STJ equatorward entrance region. The cumulative bulk upscale effect of deep convection from the three PREs enhanced and “locked in” a favorable upper-tropospheric flow pattern conducive to ridge development over the Ohio Valley and STJ intensification over the central U.S. and Great Lakes region.