13th Conference on Mesoscale Processes


Repeating patterns of precipitation and surface pressure evolution in midlatitude mesoscale convective vortices

Eric P. James, Colorado State University, Fort Collins, CO; and R. H. Johnson

Five repeating patterns of precipitation organization and surface pressure effects are defined based on observations of 45 midlatitude mesoscale convective vortices (MCVs) from the Next Generation Weather Radar Network, the Oklahoma Mesonet, and the NOAA Profiler Network. Eight of the 45 cases are classified as “collapsing-stratiform-region MCVs”. These MCVs arise from small asymmetric mesoscale convective systems (MCSs). As the stratiform region of the MCS weakens, a large mesolow appears beneath its dissipating remnants due to broad subsidence warming, and at the same time the midlevel vortex spins up due to column stretching. Nineteen of the 45 cases are classified as “rear-inflow-jet MCVs”, and tend to form within large and intense asymmetric MCSs. Rear inflow into the MCS, enhanced by the development of an MCV on the poleward side, produces a rear inflow notch and a distinct wake low at the back edge of the stratiform region. One of the 45 cases, called a “vertically-coherent MCV”, contains a well-defined surface mesolow and associated cyclonic circulation, apparently due to the strength of the midlevel warm core and the weakness of the low-level cold pool. Three of the 45 cases are classified as “cold-pool-dominated MCVs”; these cases contain significant precipitation but no discernable surface pressure perturbations. The remaining 14 cases are classified as “remnant-circulation MCVs” containing no significant precipitation or surface pressure effects.

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Session 1, Mesoscale precipitation systems I
Monday, 17 August 2009, 8:45 AM-10:00 AM, The Canyons

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