The Lemon technique is a method used by meteorologists using weather radar to determine the relative strength of
thunderstorm
A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are someti ...
cells in a vertically
sheared environment. It is named for
Leslie R. Lemon, the co-creator of the current conceptual model of a
supercell
A supercell is a thunderstorm characterized by the presence of a mesocyclone: a deep, persistently rotating updraft. Due to this, these storms are sometimes referred to as rotating thunderstorms. Of the four classifications of thunderstorms (s ...
.
The Lemon technique is largely a continuation of work by
Keith A. Browning
Keith Anthony Browning (born 31 July 1938) is a British meteorologist who worked at Imperial College London, the Met Office, and the University of Reading departments of meteorology. His work with Frank Ludlam on the supercell thunderstorm at ...
, who first identified and named the supercell.
[; ]
The method focuses on
updraft
In meteorology, an updraft is a small-scale current of rising air, often within a cloud.
Overview
Localized regions of warm or cool air will exhibit vertical movement. A mass of warm air will typically be less dense than the surrounding region, ...
s and uses
weather radar
Weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern weather radars are mostly puls ...
to measure quantities such as height (''echo tops''), reflectivity (such as morphology and gradient), and location to show features and trends described by Lemon.
These features include:
* ''Updraft tilt'' - The
tilted updraft
A tilted updraft (also known as a tilted storm) is a thunderstorm which is not vertically erect. This happens as a result of unidirectional wind shear, or a change in wind speed with height. In such an environment, the top of the updraft is pushe ...
(vertical orientation) of the main updraft is an indication of the strength of the updraft, with nearly vertical tilts indicating stronger updrafts.
* ''Echo overhang'' - In intense thunderstorms, an area of very strong reflectivity atop the weak echo region and on the low-level inflow inside side of the storm.
* ''Weak echo region'' (WER) - An area of markedly lower reflectivity, resulting from an increase in updraft strength.
* ''
Bounded weak echo region
The bounded weak echo region, also known as a BWER or a vault, is a radar signature within a thunderstorm characterized by a local minimum in radar reflectivity at low levels which extends upward into, and is surrounded by, higher reflectivities a ...
'' (BWER) - Another area of markedly lower reflectivity, now bounded by an area of high reflectivity. This is observed as a "hole" in reflectivity, and is caused by an updraft powerful enough to prevent ice and liquid from reaching the ground. This powerful updraft is often an indication of, or is facilitated by, a
mesocyclone
A mesocyclone is a meso-gamma mesoscale (or storm scale) region of rotation (vortex), typically around in diameter, most often noticed on radar within thunderstorms. In the northern hemisphere it is usually located in the right rear flank (back ...
. A mesocyclone is not strictly necessary for BWER development. Storm rotation can be reliably detected by the
Doppler velocities of a
weather radar
Weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern weather radars are mostly puls ...
.
See also
*
Convective storm detection
Convective storm detection is the meteorological observation, and short-term prediction, of deep moist convection (DMC). DMC describes atmospheric conditions producing single or clusters of large vertical extension clouds ranging from cumulus co ...
References
{{reflist, 2
External links
Paul Sirvatka and Les Lemon ''The Lemon Technique'' – College of DuPage Meteorology
The Lemon Technique (LT) to determine updraft strength
(University of Illinois
The University of Illinois Urbana-Champaign (U of I, Illinois, University of Illinois, or UIUC) is a public land-grant research university in Illinois in the twin cities of Champaign and Urbana. It is the flagship institution of the Univer ...
)
Severe weather and convection
Radar meteorology