Basic Convective and Mesoscale Research
NSSL Project 1 – Convective Weather Research: Discrimination of Mesoscale Convective System Environments Using Sounding Observations
Funding Type: CIMMS Task II
Objectives
Identify environmental variables that may help to determine if a given
quasi-linear mesoscale convective system (MCS) will produce widespread
severe surface winds on 3-12 h time scales, with focus on the details
of the kinematic environment and how the wind profiles may impact the
strength and motion of the systems, which will hopefully provide forecasters
with information that can be used to improve the shortterm prediction
of MCS.
Accomplishments
This study provided a description of the environments associated with
severe wind-producing MCSs based on the analysis of numerous variables
derived from observed sounding data. It is shown that the deep layer
wind shear (0-6 to 0-10 km) is a better discriminator than the low-level
shear (0-2 and 0-4 km), although the discriminatory ability of both
the low-level-only and deep-layer shear is very good once the orientation
of the convective line is known and the line-perpendicular shear component
can be used. These results suggests that a shear variable that includes
the physical benefits of low-level and upperlevel shear together, such
as the 0-10 km bulk shear, may be the best way to use the environmental
shear to assess the potential for a quasi-linear MCS to produce severe
winds.
Our results show quantitative evidence that the propagation component of system motion and the advective component are both large and additive for the long-lived severe MCSs. This shows that environmental relationships that can forecast MCS motion would be very useful in forecasting the intensity of MCSs. The present results support the notion that a configuration in which the deep-layer shear is large and in the same direction as the deep-layer mean wind (as is usually the case for a unidirectional shear profile) greatly favors a fast forward-propagating and severe MCS.
This project has been completed.
Publications
Cohen, A.E., M.C. Coniglio, S.F. Corfidi, and S.J. Corfidi, 2007: Discrimination
of mesoscale convective system environments using sounding observations.
Wea. Forecasting, in press.
Cohen, A.E., M.C. Coniglio, S.F. Corfidi, and S.J. Corfidi, 2006: Discrimination of mesoscale convective system environments using sounding observations. 23rd Conf. on Severe Local Storms, Amer. Meteor. Soc., St. Louis, MO, CD-ROM P2.4.
Box plots for the 0-2 km, 0-4 km, 0-6 km, and 0-10 km shear. Each set of three categories indicates the results for the weak MCSs (green), severe, non-derecho MCSs (yellow), and the derecho-producing MCSs. The boxes enclose the 25th and 75th percentiles. The dotted lines connect the medians for the distributions for each variable.