Dr. David M. Schultz
National Severe Storms Laboratory
CURRENT RESEARCH INTERESTS
Frontal/Cyclone Conceptual Models
While at SUNY, my Ph.D. thesis was aimed at reconciling a controversy
over the structure and evolution of midlatitude cyclones (these are
the phenomena that are commonly called "low pressure systems"). For
about seventy years, meteorologists have been using a conceptual model
of cyclone evolution proposed by the Norwegians. About eight years
ago, it became apparent that cyclones off the East Coast of the United
States (and in other areas) evolved somewhat differently (the
Shapiro-Keyser model). My research was entitled "The Effect of
Large-Scale Flow on Low-Level Frontal Structure and Evolution in
Midlatitude Oceanic Cyclones", where I show that the structure of the
cyclone and its attendant fronts is highly dependent on the shape of
the jet stream in which the cyclone is embedded. When the cyclone is
embedded in diffluent, high-amplitude flow, the structure resembles
the Norwegian cyclone model, whereas when the cyclone is embedded in
confluent, low-amplitude flow, the structure resembles the
Shapiro-Keyser model.
Two conceptual models of cyclone evolution showing
lower-tropospheric (i.e., 850 hPa) geopotential height and
conventional frontal symbols (top) and potential temperature
(bottom). (a) Norwegian cyclone model: (I) incipient frontal
cyclone, (II) and (III) narrowing warm sector, (IV) occlusion; (b)
Shapiro--Keyser cyclone model: (I) incipient frontal cyclone, (II)
frontal fracture, (III) frontal T-bone and bent-back warm front,
(IV) frontal T-bone and warm-core seclusion. The stages in the
respective cyclone evolutions are separated by approximately 12 h.
Panel (b) is adapted from Shapiro and Keyser (1990, their Fig.~10.27)
to enhance the zonal elongation of the cyclone and fronts and to
reflect the continued existence of the frontal T-bone in stage IV.
This research is published in July 1998 Monthly Weather Review.
Download an Adobe Acrobat version of this manuscript.
Idealized primitive-equation
simulations of cyclones embedded in confluence and diffluence have
been performed by Heini Wernli of ETH in Zurich, Switzerland. His
simulations support the Schultz et al. (1998) results. Here are his results.
If you have any further
questions about the research discussed here, or desire a manuscript,
please feel free to write to me: david.schultz@noaa.gov.
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