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Basic Understanding
Part of our mission is to improve
our basic understanding of the processes that produce severe weather.
Once we better understand how and why severe weather happens, this information
can be used to improve the forecasts and warnings of severe weather for
the public. This knowledge transfer occurs through our participation
in scientific conferences, peer-reviewed formal publications, formal
and informal interactions with forecasters, and our interactions with
the Storm
Prediction Center 
.
Our basic research program is conducted using observations, such as those
from field projects like the International H2O Project (IHOP) and the
Thunderstorm Electrification and Lightning
Experiment (TELEX), the Pan
American Climate Studies - Sounding Network (PACS-SONET), and output
from a variety of numerical models. Data from numerical models and observations
often can be used synergistically and provide information beyond that
available from either data source alone. In addition, numerical models
are not perfect and must be verified with observations to ensure that
the model is producing a behavior that is realistic.
CONVECTION INITIATION RESEARCH (IHOP)
A key focus of the International H2O Project (IHOP_2002) was the observation of the atmospheric convective boundary layer (BL) on the U.S. southern Great Plains with a dense array of mobile observing systems, with the main objective of deducing the processes governing convection initiation (CI) near surface-based boundaries. More about convection initiation research (IHOP) »
DERECHOS
NSSL has worked to understand thunderstorm complexes,
or mesoscale convective systems (MCSs), that produce widespread severe
surface winds (derechos) (Coniglio
and Stensrud 2001, Coniglio et al. 2004, Coniglio and Stensrud 2004, Stensrud
et al. 2005). This research has identified aspects of derecho climatology
and derecho environments that have not been documented in past literature,
including a warm-season zonal flow pattern and a significant reduction
in the deep-layer vertical wind shear as derechos decay
(Fig.
1).
Using NSSL's numerical modeling capabilities, it is found that the addition
of upper-level shear to a moderate low-level shear profile, and hence,
the generation of a deep shear profile, increases the lifting and deep
convective overturning of elevated inflow above the storm-generated cold
pool (Fig.
2) (Coniglio et al. 2006). The deep shear facilitates the development
of a critical level (level at which cold pool speed = environmental wind
speed along system motion), which allows mid and upper-level downshear
accelerations to maintain the deep convective overturning above the cold
pool leading edge. In addition, upper-level shear increases the size and
precipitation of the MCSs for both quasi-2D and 3D regimes. These results
show that the shear profile throughout the troposphere must be considered
to gain a more complete understanding of the structure and maintenance
of strong midlatitude MCSs. Efforts to use these findings to better
predict severe MCSs are
currently underway at the NOAA/Storm
Prediction Center.
