Ambient Conditions Associated with the Maintenance and Decay of Quasi-Linear Convective Systems Crossing the Northeastern U.S. Coast

Abstract

Quasi-linear convective systems (QLCSs) crossing the Atlantic coastline over the northeastern United States were classified into three categories based on their evolution upon encountering the coast. Composite analyses show that convective lines that decay near the Atlantic coast or slowly decay over the coastal waters are associated with 900-800-hPa frontogenesis, with greater ambient 0-3-km vertical wind shear for the slowly decaying lines. Systems that maintain their intensity over the coastal ocean are associated with 900-hPa warm air advection, but with little low-level frontogenetical forcing. Neither sea surface temperature nor ambient instability was a clear delimiter between the three evolutions. Sustaining convective lines have the strongest environmental 0-3-km shear of the three types, and this shear increases as these systems approach the coast. In contrast, the low-level shear decreases as decaying and slowly decaying convective lines move toward the Atlantic coastline. There was also a weaker mean surface cold pool for the sustaining systems than the two types of decaying QLCSs, which may favor a more long-lived system if the horizontal vorticity from this cold pool is more balanced by low-level vertical shear.

Application of a simple analytical model to severe winds produced by a bow echo like storm in northeast Italy

“…These storms typically have a length scale of 50–100 km, an aspect ratio of 5:1,and temporal duration longer than or equal to 3 hr (e.g. Bluestein and Jain, ; Parker and Johnson, ; Coniglio et al ., ; Lombardo and Colle, ; Lombardo and Colle, ). While these and other bow‐shaped systems may exhibit bookend vortices and severe surface winds, they do not exhibit an elevated rear inflow at the leading edge of the system, unlike the “true” bow echo storms (Weisman, ; George and Knievel, ).…”

Processes Controlling the Structure and Longevity of Two Quasi-Linear Convective Systems Crossing the Southern New England Coast

“…Murray and Colle (2011) found a similar trend over the northeastern United States, with convective systems moving eastward toward the coast during the late afternoon and evening, thus creating a nocturnal (0600-1200 UTC) maximum in convective activity over the coastal waters. However, the total frequency of convective storms over coastal waters is comparatively less than inland areas over the Northeast (Lombardo and Colle 2010;Murray and Colle 2011).…”

“…Numerous studies have addressed the influence of terrain on mesoscale convective systems (MCS; e.g., Carbone et al 2002;Ahijevych et al 2004;Frame and Markowski 2006;Parker and Ahijevych 2007;Reeves and Lin 2007;Miglietta and Rotunno 2009;Letkewicz andParker 2010, 2011), but fewer studies have explored the evolution of organized convective storms passing over the coastal ocean (e.g., Mapes et al 2003;Lombardo and Colle 2010;Murray and Colle 2011) and large lakes (Bosart and Sanders 1981;Bosart and Galarneau 2005;Workoff 2010;Metz 2011). A better understanding of evolving convective systems near the coast is important for severe storm forecasting, since these are often regions of relatively dense populations.…”

Mesoscale Convective Systems and Their Synoptic-Scale Environment in Finland

“…In the United States, MCS research has advanced from climatological (e.g., Maddox 1980;Bluestein and Jain 1985;Bluestein et al 1987;Geerts 1998) and structural investigations (e.g., Houze 1985, 1987;Houze et al 1990;Parker and Johnson 2000) toward studies concentrating on forecasting issues, such as MCS initiation, sustenance, longevity, and severity (e.g., Gale et al 2002;Jirak et al 2003;Coniglio et al 2004Coniglio et al , 2007Coniglio et al , 2010Kuchera and Parker 2006;Cohen et al 2007;Jirak and Cotton 2007;Lombardo and Colle 2012). For the time being, corresponding studies are unfortunately exceedingly rare in Europe.…”