A Comparative Study Between Short Life- Cut off Low and Long Life-Cut off Low Accompanied by Heavy Precipitation Storms Over Iraq: Case Study

Abstract

A comparative study between Short Life Cut Off Low (SL-COL) extended for one day, and Long Life Cut Off Low (LL-COL) extended for ten days associated with successive rain storms over Iraq on 21 to 30 April, 2018. The study tracking the evolution stages of both COLs in different pressure surfaces at troposphere layer, and found that there are many dynamical processes effect on prolong the life of COL. These processes exchanged their roles between different pressure levels. In both cases the high potential vorticity (PV) anomaly at 315ᵒ K isentropic surface is responsible on the emergence COLs, and the convection processes at lower troposphere and latent heat at upper troposphere are responsible on COLs dissipation. The main reasons of long-life COL can be summaries as a high-pressure system below COL at the surface which preventing the convection process, the formation of Omega block that promoting the COL system and preventing its dissipation rapidly in spite of the intense convection processes due to tropical moist system at the surface.