Our intention was to model Allisonís erratic track, highly variable rainfall pattern, and intensity changes. Since the storm's environmental flow was weak in its initial days, small convective processes were the predominant steering influence and were responsible for Allison's erratic track. Rainfall amounts between places only a few kilometers apart varied considerably because intense rainbands would develop and remain stationary over the same area for many hours. For instance, during a 10 hour period between 2300 UTC June 8 and 0900 UTC June 9, the Green's Bayou station in Houston recorded 26.93 inches (680 mm) of rain while a station just 7 km away recorded 9.57 inches (240 mm).
The NCEP operational models generally did a poor job of predicting Allison, especially in the first days of its existence. We chose to use the ARPS (Advanced Regional Prediction System) available from CAPS (Center for Analysis and Prediction of Storms) to model Allison. The very high resolution of ARPS (1 km) and the availability of post-analysis data helped us obtain a clearer picture of Allison than can be expected of the NCEP operational models.
The latest information regarding this research can be found at http://weather.ou.edu/~bobwein/Allison.html
Supplementary URL: http://weather.ou.edu/~bobwein/Allison.html