The 9-10 November 2001 Algerian flood - A numerical study

To better understand the atmospheric evolution leading to the genesis of the Algerian storm that brought massive flooding on 9-10 November 2001, a cloud-resolving model (CRM) simulation of the event was carried out using the University of Wisconsin Nonhydrostatic Modeling System (UW-NMS). The model was initiated with the 1° National Centers for Environmental Prediction (NCEP) Aviation model (AVN) analysis at 1000 UTC 9 November and then integrated for a period of 60 h. Three two-way nested grids were employed. Evidence was obtained that the flood resulted from convective coupling of an anomalously strong upper-level tropopause fold with surface air warmed by WISHE over the warm southern waters of the Mediterranean Sea. The dynamic mechanisms leading to the genesis of the flood were similar to those suggested for the SOC that occurred over the Gulf of Mexico about a decade earlier. Furthermore, it was shown that the storm's genesis and resulting low-level warm-core structure were similar to the genesis and structure of polar lows common to the North Atlantic ice shield. Fortunately, these local flow systems are predictable given a model's ability to finely resolve topographical, sea-surface, land-use, and coastline features and skillfully simulate their interaction with the broader scale flow.